Geology 446

Hydrology-hydrogeology

  Part I of the lecture notes.

 Lecture 1. Significance of Water and its Study.

 Significance of Water.

•      Water is such a vital and ubiquitous resource that its study and management is the principal focus of hundreds of thousands of scientists and engineers around the world and hundreds of billions of dollars in costs every year.

Water is essential to all life on earth.

•      The earth is the only planet that appears to have significant quantities of water, the earth is also the only planet that appears to have life (Mars may have had life when it was wetter).

•      More than 70% of the earth’s surface is covered by water or ice more than 70% of the human body is water.

Significance to You:

•      Death within 3 days without water, less in Desert. 

•      Average use in USA 180 Gal. per person per day.

•      A perpetual resource, but distribution & degradation is a problem.

•      Most serious natural resource challenge in Southwestern U.S.

The Environment for life. 

•      A saline solution of water bathed the environment in which life evolved, as species have evolved they have emerged from the water, but without inputs of water they can only survive for hours or days.

•      Water based fluids bathe the cells in the bodies of all living things, this solution is quite similar to that in the oceans from which cellular life evolved.

Definition of Hydrology:

•      Hydrology is the study of water and its behavior in the environment. There are several branches of hydrology:

Surface water hydrology:

•       Surface water hydrology: The study of water on the surface of the earth. (not including the Oceans).

Groundwater hydrology:

•      The study of water in the subsurface, closely related to study of the geology of unconsolidated deposits and soil physics the study of water in soils..

Water Resources Management:

•      combining hydrology with planning, law, economics, aquatic biology, chemistry, engineering and often forestry this discipline seeks to manage water resources to minimize flooding, insure water supply, maintain or improve water quality, etc.

Related disciplines include:

•      Hydraulics: The study of movement and control of water, generally by means of dams, canals, pipelines, etc.

•      Limnology: The study of Lakes.

•      Meteorology: Study of weather including precipitation and atmospheric processes.

•      Climatologic: Study of the long term climate of earth.

Water, water everywhere…

•      With increasing demands on a finite supply of clean water to supply agriculture, industrial and municipal uses, sustain natural environments and help generate electricity and disperse wastes, the importance of the study of water continues to increase.

LECTURE 2. The Properties of Water, The Hydrologic Cycle, & Evaporation..

Distribution of  Water.

•      97.3 % in oceans

•       90% of  fresh remainder is ice caps (Antarctic & Greenland).

•      Less than .3% in lakes, streams and groundwater aquifers: supports all terrestrial life.

•      Only .001% in atmosphere, but vapor & clouds have huge effect on climate.

Distribution of Surface Water in USA:

•      Abundant in southeast (except some parts of Florida).

•      and Northeast (Except major urban areas and coastal areas).

•      Less abundant in Midwest.

•      Rare in West, except Pacific Northwest.

•      Texas is marginal, except “deep east” Texas.

I. Properties of Water.

•      Water consists of two hydrogen and one oxygen molecules strongly bonded together.

•      Because of the nature of the molecular and atomic structure of water, water has a separation of charge (also called polarity). This separation of charge has several important effects:

Strange attraction:

•      Water molecules attract each other quite strongly for a liquid, this in turn cause surface tension that helps explain why water striders can walk on water.

•      More importantly this is why water tends to remain in (and to rise) in soil pores (capillarity). If water had lower surface tension all water would drain from the pores in soil and plants would not exist on land.

The “Universal solvent”:

•      Water has a negatively charged oxygen end and a positively charged hydrogen end hence many compounds such as salts (NaCl, CaS04, etc) will rapidly dissolve in water. The ability of water to dissolve most substances.

Houston, we have a solution…

•      Gold and platinum are resistant but all other minerals are soluble which accounts for the salinity of the oceans. It also accounts for the dissolved solids and substances in freshwater.

•      Since plants and single celled animals take in nutrients in a water solution, if water did not dissolve most other substances it would not support plants and cellular organisms and hence life on earth would not exist.

Weathering:

•      Water also dissolves rocks and is the single most important factor in all erosion on earth and hence the nature of the landscape (i.e. it is frequently flat and covered with soil) not composed of bare craggy rocks and meteorite craters.

Density:

•      Water also has the very unusual property that its density does not decrease continuously with decreasing temperature. Rather at 4 degrees C it reaches maximum density.

Why Margaritas are possible:

•      This means that ice is less dense than cold water and therefore ice floats. That makes frozen Margaritas possible, but it also allows life to exist in many northern lakes and oceans that would otherwise freeze from the bottom up and hence solidly.

Potholes explained:

•      Since ice expands when it freezes (density decreases) liquid water that enters cracks in rocks or pavements will expand and exert tremendous force rending rocks and causing both erosion and potholes.

Boiling and Freezing points:

•      Pure water boils at 100 degrees C (212 F) and freezes at zero (32 F) (the standard scales for temperature being based on its behavior). Water is also used as standard for mass in metric system (1 liter or cubic decimeter at 25 C weighs 1 kilogram).

Altered States:

•      Three states are: Ice (Solid), Liquid & Vapor.

•      Water is present in all three on earth, partly because some vaporization occurs at all temperatures above freezing. Therefore liquid and vapor forms of water are ubiquitous (particularly in the summer in East Texas). Ice may not be as obviously present  but clouds are generally composed of ice particles even in warm areas.

Heat capacity:

•      Water has a great capacity to store heat without a change in state. This capacity has a huge effect on global weather particularly temperature. Those areas with little water vapor undergo greater temperature seasonally & diurnally swings as do moist areas. Thus the hottest and coldest areas tend to be dry and far from the moderating influences of oceans.

“A watched pot never boils”…

•      This heat capacity explains why it takes a long time to bring a pot of water to boil.

•      The heat capacity of water also means that water can be used in heat pumps and is essential to power production which uses the heat capacity of water in cooling towers to condense steam used in turning turbines.

Other properties:

•      Viscosity: water is not as viscous (syrupy) as molasses or motor oil or chocolate syrup but is more viscous that gasoline. At higher temperatures water is less viscous.

•      Compressibility: water in a liquid or solid state is almost incompressible, but in a vapor state steam may be greatly compressed. This makes hydroelectric power plants possible.

Electrical conductivity:

•       water itself does not conduct electricity (it is an insulator) however the dissolved ions (like CA, Mg, Na, Cl, etc) in water do have the ability to conduct electricity.

A shocking experience:

•      All natural water has some ions, so water ends up being a pretty good conductor of electricity and therefore using a hair dryer in the bathtub or going wading in a lighting storm is not a great idea.

II. The Hydrologic Cycle.

Distribution:

•      97.3 % of all water on earth is in the oceans and 90% of the remainder is locked up in glaciers and ice caps largely in the Antarctic and Greenland.

•      However, the small proportion in lakes streams and groundwater aquifers is essential to all terrestrial life.

Driving Forces:

•      Since gravity drives water on land to return to the oceans, And heat from the sun evaporates water in the Oceans which returns to land as precipitation, a process is necessary to maintain availability of water in both systems and hence sustain life on terra firma and in the seas..

The hydrologic cycle:

•       The hydrologic cycle refers to the constant process of evaporation of water from the oceans (and to a lesser extent from lakes, forests and soil), its assent into the atmosphere, its condensation into clouds, its movement on the wind and its deposition as rain or snow. The rain and snow then return to the ocean via rivers and groundwater flow.

Rates:

•      The process of return of precipitated moisture to the ocean can be rapid (i.e. rainfall on the ocean itself), moderately rapid (due to stream flow), or less rapid (infiltration into the soil and recharge of groundwater aquifers). The cycle has no beginning or end.

Vaporization.

•      When water is converted from a liquid to a vapor form (usually from evaporation from the oceans) the energy that evaporated the water is neither created nor destroyed but is converted into a latent heart of evaporation.

 Condensation:

•      When the water condenses this heat is released.

•      The vapor may condense as a liquid or a solid (ice). These particles of liquid (or ice) may coalesce and form tiny droplets. These droplets form clouds that are blown about by the prevailing winds. When the size and number of these droplets exceeds the ability of a buoyant air mass to suspend them, they fall as rain or snow (precipitation).

Precipitation:

•      Various processes can cause precipitation. If warm moist air moves over land with cold air at the surface this may trigger precipitation. Also if clouds are forced up and over a mountain range by prevailing winds the cooling of the air mass as it rises can cause condensation then precipitation. This is termed an orographic effect.

Run-off and variations.

•      Once precipitation falls it may either run-off into streams and rivers, or it may land on vegetation (interception) and then evaporate or be captured in puddles which usually evaporate again (depression storage) or soak into the ground (infiltration).

•      Snowfall may also be converted back to water vapor directly in a process called sublimation.

Recharge and variations

•      The water that soaks into the ground (infiltrates) may be rapidly discharged into streams (interflow), it may remain in the soil as soil moisture and gradually evaporate, or it may be taken up by plant roots and be respired through plant leaves (a process called transpiration) or it may percolate down to the water table and recharge groundwater aquifers.

Groundwater flow:

•      Groundwater in turn may maintain the flow in creeks and springs (the base flow) or it may remain for thousands of years as fossil water  in aquifers in closed basins. It may even bubble-up from the sea floor.

Home again, home again…

•      The water on the land all eventually returns to the oceans most of it within a few weeks of falling as precipitation.

Process of Evaporation:

•      Evaporation requires an input of energy (solar) to convert liquid water into vapor. Evaporation removes heat from the liquid water and carries that energy away with the water vapor as latent heat of vaporization.

•      When water vapor condenses this latent heat is released at actual heat.

Bonding:

•      A water molecule in the liquid phase is tied to thousands of other water molecules by hydrogen bonding.

•      In the vapor phase, the molecules are separated so no hydrogen bonding takes place.

•      Thus water vapor occupies 42,000 as much space at standard temperature and pressure (STP) as liquid water.

•      Water vapor is 60% as dense as the atmosphere so it will rise.

Example: Why Gore-Tex Keeps You Dry.

]A given volume of air can only hold so much water vapor at any given temperature. The proportion of water vapor saturation of the air adjusted for temperature is called relative humidity.

Influence of temperature:

•      At low temperatures the water molecules are less active and hence hydrogen bonding will cause condensation if  much water vapor is present. At higher temperatures much more water can remain in the vapor phase.

•      That explains why it is more muggy around here when it is hotter.

Local conditions:

•      Because of the many water bodies and the extensive vegetation here, humidity is generally above 50% except when cold air with very little moisture moves in from the arctic (or Amarillo).

Frozen deserts or is that desserts?

•      The arctic and Antarctic despite the accumulation of snow and ice, are arid (they receive less than 10 inches of precipitation per year).

•      In arid areas,  humidity as low as 4-10% are common.

Urban heat island:

•      Urban areas (even in deserts) generate their own weather,  hence the humidity in Las Vegas has increased from about 5% to about 15% over the last 50 years.

Hot but not humid:

•      Of course if there is no source for water vapor such as in desert areas  it doesn’t matter how hot it gets, the humidity will not increase.

Moderating influence of moisture:

•      Since evaporating water uses up energy and since water vapor blocks solar energy (both as a vapor and as clouds) it is not surprising that it gets hotter in dry areas than areas with lots of water.

Different strokes:

•      However, I personally prefer a temperature of 118 with 10% humidity in Las Vegas  to 106 in Saint Louis with 90% humidity. 

Why the Dead Sea exists:

•      Saline water will evaporate more slowly than fresh water.

•      Evaporation will increase the salinity of water bodies such as saline lakes (the dead sea) and even portions of the oceans, like the Red Sea.

Cold waters run deep…

•      Water only evaporates from the surface of water bodies and circulation of colder, deeper water to the surface helps reduce evaporation.

•      Hence, deep lakes have less evaporation per unit of surface area and far less per unit of volume than shallow lakes.

Examples:

•      Lake Mead near Las Vegas (which is the largest reservoir in North America) has surface water temperatures in the 70's while 200 feet down the temperature is in the low 50's.... Canyon Lake is another example.

•      Temperatures in large lakes can lag air temperatures so evaporation may be maximal in the winter in lakes like Lake Superior.

Role of wind:

•      Wind also plays an important role in evaporation with windy hot and dry areas having the highest evaporation rates. For Lake Mead estimated evaporation is 800,000 acre feet per year (or 260 billion gallons). More water than the whole Dallas area is likely to use in a year.

Significance:

•      Evaporation and other losses from reservoirs can be substantial. Lake Mead losses about 6% of all the water flowing in the Colorado River (a River draining 12% of the U.S. and supplying water to 16 million people), the other 61 major dams on the Colorado and its tributaries cause losses of about 15% of all the water in the river.

Applications of evaporation:

•      Thin Films: Can cut evaporation to near zero, but get blown away by wind, so they do not work well in practice.

•      Sand Storage Dams: do work well in areas with infrequent violent storms and general aridity where normal dams do not work well.

Evaporation ponds:

•       can reduce volumes of liquid wastes from industrial and agricultural sources but have serious drawbacks.

•      Salt ponds: are major source of sea salt and certain chemicals.

Evaporative cooling:

•      is necessary for electric generation since steam cycle requires condensation which in turn requires cooling water loop at all power plants except geothermal, wind and solar.

Evaporation ponds:

•      So called evaporation ponds were often unlined in the past, thus much waste water infiltrated causing groundwater contamination:

Example:

•      Mission Olive Ponds.

Summary:

•      Water makes all life on earth possible both by its presence and by its many unique properties.

•      All water in earth is involved in different portions and moving at different rates in the hydrologic cycle

Lecture 3.  Condensation, Precipitation & Interception.

Its out there…

•      Only .001% of all water on earth is in the atmosphere, but water vapor and water in clouds have a huge effect on climate.

•      Condensed water often precipitates in many forms and has many impacts after it falls to ground.

Condensation:

•      Condensation is the conversion of a vapor (a gaseous phase) into a liquid (possibly subsequently into a solid).

Condensation Process.

 The Process:

•      In condensation the heat energy that was absorbed during evaporation is released. The condensation process therefore releases heat.

•       The heat released during condensation can cause violent convective storms (thunderstorms, hurricanes) to form particularly when condensation occurs rapidly. The process of evaporation and condensation drives much of the weather on the planet.

For water vapor to condense two factors must be present

•      - 100% relative humidity                                           

•          and

•      - A surface upon which the water can condense.

Condensation nuclei:

•      Water condenses as tiny droplets averaging .0004 in diameter.  Theses droplets  are formed around far smaller particles called condensation nuclei.

•      Condensation nuclei are tiny particles of sea salt, volcanic gases, air pollution or dust.

Sources of nuclei:

•      Volcanoes can affect climate via this mechanism.

•      Also dust storms may affect climate by a similar mechanism

The dew point:

•      The temperature at which (given the prevailing humidity) water vapor present in the atmosphere can condense.

•      Besides sufficient water vapor and sufficiently low temperature,  most condensation in the atmosphere requires condensation nuclei.

From dust storms to rain storms...

•      Dust storms may affect climate by creating condensation nuclei. Thus droughts that generates  dust storms such as those of the dust bowl may sow the seeds of their own demise.

Formation of clouds:

•      Viewed close-up condensed water is either invisible or forms mist or fog. When trillions of condensed water droplets are present light is diffused and refracted and hence clouds appear white or  with a heavy burden of water they actually block light, appearing dark.

Uplifting experience:

•      The water droplets held in clouds would fall to earth except for winds and convection (heating) of the clouds caused by the condensation process which causes the air and the suspended water droplets in the clouds to rise.

Fog drip:

•      In arid areas near cold coastal currents: Namibia, Chile, California (Baja and southern) condensation of fog can account from 30% to 100% of input of water into the ecosystem. Plants such as the Welwitchia, beetles and even eucalyptus need this input to survive. During 9 year drought in the Santa Barbara area, cool foggy summers prevented a far worse disaster.

Precipitation

•      The process whereby condensed liquids or solids suspended in the atmosphere fall (precipitate) usually striking the surface.

Critical size:

•       The droplets suspended in clouds fall to earth when they have reached such a size that their mass exceeds the ability of wind or rising air to keep them aloft.

•      Typically they fall as .004 inch droplets (100 times the typical size of water droplets suspended in clouds).

Replenishment:

•      Water can fall out of a single cloud for only a short period. Replenishment of the moisture is required for prolonged intense precipitation.

•      This requires a source of water vapor and intense solar energy to evaporate it and hence more intense storms are likely to be near oceans and in tropical or sub-tropical areas.

•      The intense storms in the equatorial areas such as the Congo or Costa Rica.

 Forms of Liquid Precipitation:

•      Drizzle A fine mist less than .1 inch per hour.

•      Rain: droplets larger than drizzle (.02-.2 inch in diameter).

•      Vega: is rain that evaporates after falling from a cloud but before hitting the ground.

Intensity

•      Rain can be light .1 inch per hour or less, moderate .1-.3 inches per hour and heavy .3 or more inches per hour. Torrential rain exceeds 1 inch per hour (4 inch per hour in S.B. probably more in Costa Rica).

                Oddities:

•      Vega: is rain that evaporates after falling from a cloud but before hitting the ground.

•      Raining fish or frogs… possible due to water spouts.

•      Watermelon snow… photosynthetic bacteria in melting snow.

Forms of solid precipitation:

•      Sleet: is formed by small pellets of ice this caused by rain drops freezing as they fall.

•      Snow: is precipitation of ice crystals and requires colder temperatures than sleet.

•      Hail:  is ice that is associated with thunderstorms. The large size of hail is due to a process of uplift and aggregation of falling rain that freezes in the clouds and is repeatedly uplifted (Human Hailstones??!).

ICE STORM:

•      In Jan. 1997 here, a warm moist front from the Gulf slid over much colder surface air  fell as rain that froze on the ground. In Dallas it fell as sleet In the Woodlands and east, it was worse, but in Galveston  there was no problem.

Hail:

•      Ice that is associated with thunderstorms. The large size of hail is due to a process of uplift and aggregation of falling rain that freezes in the clouds and is repeatedly uplifted adding new coats.

•       (Human Hailstones??!).

•      Areas with strong thunder-storms like N. Texas have heavy hail (2 lbs. or more)...

Snow:

•      Snow: Falling ice crystals, each is unique. There is a whole field of snow hydrology, mostly concerned with estimating moisture content.

•      10 inches of snow correspond to about1 inch of liquid water. ,The dryer and colder, the “dryer” the snow. Powder common in Utah and Nevada, 81 feet of snow one year in Tahoe...

Sublimation:

•      Very little fallen snow evaporates although a substantial portion can sublimate. When the snow melts gradually much infiltrates into the soil recharging shallow groundwater and maintaining flow in streams.

•       However, unusually warm weather, especially if accompanied by rain, can cause rapid melting and flooding.

Albedo:

•      Snow has a very high albedo and hence clean snow reflects light cooling the environment, however dirty snow absorbs light and melts faster.

•      Snow can have a wide range of water equivalents. Fresh now averages about 10% water equivalent. In dry areas snow has a lower water equivalent so snow in Utah or Nevada is more A powdery than snow in Ohio. Snow may be compacted over time increasing its water equivalent.

Implications of snow behavior:

•      Since many areas in the west depend on spring run-off from melting snow to water crops, generate hydroelectricity and support urban demand estimation of available water supply is important.

Weather processes:

•      There are three process that cause condensation and induce precipitation:

•      Cyclonic

•      Convective

•      Orographic.

•      All depend on the cooling of moist air as it rises but the process that cause this are different.:

Cyclonic:

•      Can be due to warm air sliding over cold air or cold air sliding under warm air.

•      Examples: In an ice storm (like those in Huntsville in 84 & 98, warm moist air from the Gulf  slides over much colder air at the surface and falls as rain that froze when on ground.

•      Farther North it falls as sleet or even snow and causes few problems.

•      Farther south no problems only rain.

Hurricanes:

•      Over tropical oceans this process can produce huge convective storms called hurricanes, cyclones or typhoons depending on what ocean is involved.

A hurricane by any other name...

•      Over tropical oceans this process can produce huge convective storms called hurricanes, cyclones or typhoons depending on what ocean is involved. Because more heat and more moisture is involved the power of these storms in proportionately greater.

 Convection:

•      The process of heat transfer. Convection begins when the sun heats moist air causing it to rise. As it rises, condensation takes place releasing heat energy this drives the process of further heating and up-lift and condensation. This “heat engine” runs as long as heat from the sun is present and a source of moist air is available.

•      Hence thunderstorms are likely in the afternoon but less likely in the early morning. (Tornado watch in Amarillo).

Lightning:

•      The process of ice falling through a cloud causes a separation of charge between the top and bottom of the cloud and this potential energy difference is released in the form of a stoke of lighting.

•      The sound produced by the rapids expansion of air induced by the heating of the air as the lighting passes through it causes thunder. Frequently thunderstorms are accompanied by hail.

Wotan’s hammer...

•      Ice falling through a cloud causes a separation of charge (voltage) between the top and bottom of the cloud and between the cloud and ground, lighting restores this voltage difference.

•      Thunder is the sound produced by the rapid expansion of air induced by the heating due to the 40,000 degree temp. of  lighting.

Convection & Tornadoes.

•      Convective storms derive their energy from the release of heat as a result of condensation.

•      This energy can have devastating impact as anyone from Jarrel, Waco, Wichita Falls or from any of the hundreds of communities that have experienced powerful tornadoes can attest.

Orographic precipitation:

•      Due to the presence of mountains.

•       Mountains force moisture laded air masses to rise, causing condensation and precipitation. The wettest places on earth are on the windward side. Mountains produce the driest areas as well on leeward side, an area called the rain shadow and the greatest contrasts in precipitation over short distances.

•      Examples include: Cascades. Hawaii and the Mt Whitney/ Death Valley area.

Orographic precipitation:

•      Mountains force moisture-laded air masses to rise, causing condensation and precipitation. The wettest places on earth are on the windward side of mountains. Mountains produce the driest areas as well on their leeward side (the rain shadow) and the greatest contrasts in precipitation over short distances.

The grass is greener on the other side of the mountain...

•      Examples: Cascades,Olympic pen/Yakima.

•      Hawaii Kona/drylands.

•      Mt. Whitney/ Death Valley area.

•      The higher the mountains and the stronger the prevailing storm patterns, the stronger will be the rain-shadow effect.

Local color:

•       Local factors such as mountains (orography), jungles (rain forest),  large lakes (“lake effect” snows) and movement of warm and cold air masses (fronts) driven by the jet stream cause local variations in precipitation.

Its wetter, if not better, in the tropics...

•      Water can fall out of a single cloud for only a short period. Replenishment of the moisture is required for prolonged, intense precipitation. This requires a source of water vapor and intense solar energy to evaporate it. Intense storms are likely to be near oceans and in tropical areas such as the Congo or Costa Rica.

Double whammy:

•      Intense weather if two or more factors exist.

•      Cheripungi, India: strong orography, convective and cyclonic.

•      Gulf coast: strong convective and cyclonic.

•      Tornado alley: very strong cyclonic and moderate convective (hail & tornados).

•      Olympic peninsula, Kona Coast: cyclonic and orographic.

•      Desert Mountains: Strong orographic and convective flash floods.

Drip, Drip, Drip...

•      Fog drip: in arid areas near cold coastal currents: Namibia, Chile, California: condensation of fog can account from 30% to 100% of input of water. Welwitchia, beetles and even eucalyptus need this input.

•       During 9-year drought in Southern California, cool foggy summers prevented a far worse disaster.

Wettest & Driest...

•      Cherrapunji in Assam (India): strong orography, convective and cyclonic factors.

•      Kona Coast & Mt. Waialeale on Kauai also.

•      Atacama Desert in Chile, no measurable rainfall in several hundred years: Strong rain shadow (Andes, strong negative effect), cold coastal current (Humbolt, no convection), Mid-latitude = no cyclonic activity.

•      Namib also...

Interception:

•       The process whereby vegetation (generally the forest canopy) intercepts rain or snow before it reaches the ground. This moisture then evaporates from the leaves. Interception can account for a loss of 10-20% of all precipitation.

Benefits & detriments of interception:

•      Interception reduces available water but it also greatly reduces the impact of raindrops on bare soil which would cause both erosion and much more rapid run-off.

•      This more rapid run-off from denuded areas in turn causes flooding.

Example:

•      Burned chaparral shows impact of vegetation loss on flooding...

•      After wildfires, floods and debris flows can occur in streams and rivers, in southern California in particular.

•      If a heavy storm event occurs within a couple of years of a wild fire a flood is a good possibility.To reduce this risk, reseeding, and catchment basins are used. Historical studies by Keller indicate that there is a strong relationship between debris flows and fires.

Precipitation Patterns

•      Regional & Global patterns are due to several influences:

•      Latitude

•      Global circulation patterns

•      Proximity to oceans

•      Orographic effects

•      Seasonal Variations: many areas have strong seasonal variations in rainfall.

Seasonality:

•      Changes in wind patterns can cause a strong rainy season such as in India and southeast Asia and northern Australia where summer monsoons are critical to the survival of more than 1 billion people.

•      Weaker seasonal patterns occur elsewhere, such as winter rains and snow in the far west and summer thunderstorms in the Midwest.

•       Other areas of the U.S. have a more uniform distribution of rainfall.

Long Term Variation in Rainfall.

•      In many areas (particularly in the western U.S.) a series of wet years alternate with a series of dry years but the lengths of these series can vary usually not exceeding 5 in a row.

•      California has one of the most variable and intensely studied long term precipitation patterns.

Stability vs. vulnerability:

•       However its very dependability in these areas makes these areas vulnerable, due to lack of alternative sources and storage capacity.

Weather Modification:

•      Silver Iodine has been used to create nucleation centers to induce condensation and formation of water droplets that will fall-out down wind as rain, Method is often called cloud seeding..

How Used:

•      Silver iodide smoke released from planes, towers or rockets is used in the western U.S. to increase local precipitation in the watersheds of power dams and areas dependent of precipitation for water supply.

•      Radar and radiosondes are used to determine appropriateness of a storm system.

Where it Can Work.

•      Silver iodide only works to wring moisture out of clouds with sufficient moisture and low (but not frigid) temperatures.

•      Possible 5%-10% increase on local precipitation.

Examples:

•      Project Skywater.

•      PGE.

•      Cuba.

•       Santa Barbara County.

Advantages and Disadvantages of Cloud Seeding:

•      Can increase precipitation with proper planning and help generate additional hydroelectric power or more water in a water supply reservoir.

•      May decease precipitation from warm storms

•      May be “robbing Peter to pay Paul”.

•      Could cause local flooding.

•      The sad story of the Harris Brothers....

HYDROLOGY LEC #4 Infiltration, Soil Moisture, Recharge & Transpiration.

Soil: A critical part of hydrology.

•      Soil properties and processes control things like run-off of rainfall and hence flooding

•      Also recharge of groundwater and in many cases its flow as well

•      Soil can be eroded by water and soil moisture supports all terrestrial plants, so hydrology is critical to soil science and agronomy as well

Composition of soils:

•      Soils are composed of various layers with differing properties. However in hydrology we are interested in the composition of soil with respect to the behavior of water in it. 

Horizons:

•      Most soils have horizons (layers) with different properties with depth, generally less organic matter and more consolidation at depth.

•      Many soils have zones of elluviation (leaching) and zones of accumulation due to water movement through soil.

Layers upon layers:

•      These layers are the unsaturated or vadose zone, the capillary fridge and the groundwater zone, the saturated zone is composed of these last two zones. See diagram...

Mineralogical properties:

•       Clays have huge impact due to mineralogy. Expansive (“fat clays”)  i.e. montmorillinite, expand to 8 times original volume when wet.

•      Fat clays cause huge problems (second most costly natural hazard in U.S.).

•      However,  “lean clays” (kaolin) do not expand.

•      Lateritic soils: Iron and aluminum oxides. Found in tropics have poor fertility, linked to destruction caused by loss of the rain forest.

Dirt is not simple:

•      Soils are principally composed of minerals that resist weathering, these minerals include silicon dioxide, and aluminum and iron oxides. These minerals carry a net negative charge. Hence soils have the ability to attract positive ions (cations) like Ca, Na, Mg , K, SO4, PO4, NO3 Etc.

Eye on Cations:

•      These cations are essential plant nutrients. In excess they can cause water quality problems.

•      The tendency of a soil to attract these cations is measured by its cation exchange capacity.

Example:

       Goleta Water District  waste-water reuse project.

•      Gypsum (calcium sulfate) can lower the pH of soil and replace sodium with calcium causing flocculation of the clays and aggregation of the soil.

Texture:

•      Can be sandy, silty or clayey. Depends on size of soil particles: Sand is more than 2mm, silt 2mm-.002 mm and clay less than .002 mm.

•      Clay or organic matter has most important effect on soil. Too little/too much clay produces poor tilth, ideal soil has peds: clumps of larger particles held together by some clay.

•       A mixed soil like this is called a loam.

 Porosity:

•      Ranges from 10% to 40%. It is the percentage of holes. If soil has too low a porosity it cannot hold water or provide air to plant roots.

•      Clays have higher porosity (but smaller pores).

•      Ideally, half of pores should hold air while half should hold water.

Examples of porosity:

•      Porosity of earth materials varies: clays can have 60% porosities , sands typically have 40% porosity, compacted  soils with an equal proportion of sand, silt and clay can have as little as 25% pore space.

Types of porosity:

•      Rocks can have primary porosity and secondary porosity consolidated rocks have less than 2% primary  porosity, however if fractured they can have higher porosities but generally less than soils.

What is in them pores…

•      Pore space can be occupied by air or water. A typical agricultural soil will have 40% porosity with 20% air and 20% water. This is ideal for growing plants.

Why worry about porosity:

•      Measuring porosity is important to estimating the volume of water in a soil.

Soil water

•      (also called soil moisture) is water that enters the soil through infiltration and either remains in the unsaturated (vadose) zone or percolates down to recharge groundwater.

Importance:

•      Soil water is important because it helps to hold soils together, supplies water to plants, supplies dissolved nutrients to plants and is the source from which groundwater aquifers are recharged.

Infiltration:

•      Infiltration occurs when water on the surface of a soil becomes deep enough to overcome surface tension and begin to move into the soil under the force of gravity and or soil suction.

•      In a soil that is not saturated, the soil particles exert an attractive force on water called soil suction.

Down the Worm hole:

•       If large gaps exist such as worm holes or cracks in the soil the water will rapidly infiltrate.

•      However if the soil is bare, then the impact of rain drops may cause small particles to block these pores and slow infiltration. Hence, more of the rainfall will run-off often leading to erosion and flooding.

Permeability:

•      Is the ability of water to enter and drain through soil:

•      Generally low for clays. Poor drainage can cause flooding and starve plant root for oxygen.

•      Sandy soils can have too high a permeability so water is lost easily.

Impermeability:

•      Soils can become impermeable due to compaction, but also due to chemical processes.

•      The molecular structure of clay minerals can be altered so that the aggregation of clays that helps permeability is reversed and the formerly flocculated clay minerals are dispersed.

Field Capacity:

•      The quantity of water that a soil can hold against the force of gravity is the field capacity of the soil.

Specific retention

•       Is the groundwater equivalent of field capacity, except that it allows for a much longer period for the soil to drain.

Specific yield

•      The quantity of water than can be produced from a given volume of an aquifer.

•      Specific retention plus specific yields equals the porosity of the aquifer.

Soil Suction:

•       Soil suction is measured in atmospheres. Soils at field capacity are at about .3 atmospheres . A soil suction of .3 atmospheres (30 centibars) is ideal for most plants.

 Range of soil suction:

•      Soil suctions between 1-15 bars are likely to exceed the point where the plant can no longer obtain water, causing it to wilt.

Forever wet…

•      Water evaporates very slowly from the subsurface. Particularly in fine grained soils.  So below the root zone water in a soil is likely to remain almost permanently.

•      Thus even in dry deserts there is water available to plants at depth.

Osmosis:

•      Plant roots can also cause water to move under the force of  osmotic pressure.

•      Capillarity accounts for the existence of the capillary fridge.

Wilting point:

•      This point is the wilting point it will vary for each type of plant.

•      Some desert plants can withstand soil suctions in excess of 100 bars.

Transpiration:

•      Plants extract water from the soil by overcoming the soil suction and the surface tension of the water. When a soil is saturated, the soil suction is nearly zero, as a soil dries the soil suction increases.

Significance of Transpiration.

•      In areas such as the Amazon Rain-forest the transpired water accounts for much of the water vapor that sustains the heavy rainfall of that region.

•      In dryer regions plants such as mesquite, salt cedar and other pheratophytes such up water that could sustain grass-lands or provide flow in what would be perennial streams

Examples:

•      Potato farmers in Idaho

•       White Rock Canyon.

Behavior of soil water.

•      Water moves through soil under the forces of gravity, and the attraction of the soil matrix for the water molecules called capillarity (or soil suction) and the attraction of the water molecules for each other (surface tension).

Water does not always flow downward.

•      Water will move either downward, upward or sideways in a soil in response to the combination of capillarity and gravity.

Applications of soil water behavior:

•      Irrigation: most irrigators use methods such as furrow irrigation and or flood irrigation.

•      More recently sprinklers have been used. Including center pivot systems.

•      All these methods cause a large proportion of the water to evaporate.

Drip irrigation:

•      A new method of irrigation uses drip or trickle methods. This approach was developed in Israel.

•      Drip irrigation applies water at a slow rate directly to each plant.

•      Advantages: of drip include less evaporation, low labor costs, less sensitivity to water quality. Works well on slopes.

Disadvantages:

•       include installation cost, clogging, uniformity of flow, build up of salts and saturation of the root zones.

Interflow:

•      Some soil moisture may enter the soil and flow out horizontally. This is interflow and is most common in areas with variable topography.

Recharge

•      The process of infiltrating soil water moving down into and replenishing groundwater aquifers.

Example: Las Vegas.

Measuring infiltration:

•      Infiltration is difficult to measure directly.

•      If one has a point measurement of precipitation and derives an area average for a basin and then measures the discharge of a river draining the basin, the difference between total precipitation and total discharge over the long term should be equal to the total of infiltration and evaporation (if groundwater storage remained constant).

Limitations:

•      However, this requires long-term measurements of precipitation and evaporation and discharge and an understanding of the recharge and discharge of the groundwater aquifers.

Floodwater diversion:

•      Frequently floodwater is diverted to recharge basins in areas with a high permeability.

Erosion:

•       Erosion and loss of top soil and flooding are among  the most serious problems facing man.

Soil conservation:

•      Many methods to reduced them have been developed.

•      In agriculture a cover crop may be grown to protect bare soil, or contour plowing or conservation tillage may be used.

•      In forestry where old methods of timber harvesting caused both striping of vegetation and compaction of the soil, new approaches are being implemented.

•      Many civil engineering projects now use either mulch or geo-textiles to reduce erosion.

Example:

•       In southern California a combination of recharge basins and debris dams is used to separate sediment from winter flood waters and then capture the less turbid water downstream and divert into shallow off-stream basins. Water soaks through the floor of these basins, gradually recharging groundwater aquifers.

Evaporation (Seepage) Ponds:

•      So called evaporation ponds were often unlined in the past, thus much waste water infiltrated causing groundwater contamination:

Example:

•      Mission Olive Ponds.

Cyanide heap leach

•      The principles of infiltration can be applied to purification of ores and is now the leading method of producing gold in the USA.

Example:

•       Bullfrog mine Nevada.

Soil Series:

•      Soil series are defined by presence of a given set of properties and are named for a typical location where this soil is found 

•      So “San Jacinto clay” or  “Amarillo silty loam”  are then mapped.

•      The Depcon soil series underlies SHSU, (thin sandy layer with organic matter overlying a thick clay with iron). Soil has poor drainage and low fertility, subject to erosion.

Lecture 5. Measuring Components of the Hydrologic Cycle.

Measuring Evaporation:

•       Since putting a lake inside a plastic bag is not feasible, various methods to estimate evaporation have been developed.

•      Some methods use climatic factors such as temperature, humidity, wind speed, etc but the best method is to use an evaporation pan.

Evaporation pans

•      Since a pan is shallow and made of metal it has a higher evaporation rate than an actual water body.

Actual studies:

•      Studies of evaporation by USBR, USGS at Lake Hefner, indicate that the water body evaporates 70% as much as a nearby pan.

•      This estimate is usually within 15% of correct.

•      Yearly estimates for pan evaporation have been developed for the world and range from 30 inches per year to 200 inches per year.

•       By coincidence Lake Mead is located in an area with 200 inches of evaporation per year.

Measuring Precipitation.

•      Measuring Snow.

•      Measuring Rain

•      Predicting weather patterns

•      Assessing long-term climate

Measuring snow.

•      Snow may be measured in a conventional gauge by melting the accumulated snow (measuring volume is not a very useful measure, why?).

•      Or a continuously weighing gauge can be used.

Measuring snow-water equivalents

•      Snow occupies considerably more volume than the liquid would.

•      A wet snow can be 7 times while a “dry” snow can be 13 times. Usually a 10X multiplier is used as a rule of thumb.

•      The better the snow is for skiing the worse it is for irrigation (why?).

Snow Course Survey:

•      This can be done by snow course surveys.

•      To perform such surveys a transect is chosen and depth of snow and density of snow are measured along this transect.

•      Also aerial surveys and telemetered stations are used.

How to measure snow:

•      The point measurements of snow-water equivalent are converted into volume estimates over entire river basins.

•      These estimates are correlated with historical information to develop better estimates of run-off.

Crystal balls may work better:

•       However, predicting timing of runoff and amount of additional snow and/or sublimation is a challenge. 

•      Remote sensing is now aiding this effort.

•       With these estimates reservoirs and irrigation districts can plan for most efficient use of an generally scare resource.

•      Especially since their needs may not coincide.

Measurement of Precipitation.

•      Precipitation is measured in inches or millimeters of water.

•       The simplest gauge is a can, a ruler can be inserted to measure the depth of water.Clear plastic rain gauges are common and cheap.To prevent evaporation or birds drinking the water, a gauge with a narrow neck and a narrower calibrated measuring tube is used by the national weather service. High wind will result in under-estimation.

Modern gauges:

•      Since recording rainfall even daily is a pain, recording rain gauges are becoming more common.

•      These typically use a bucket inside a gage and a scale or use a tipping bucket. These are often telemetered or have a ROM chip that can store precipitation minute by minute for 6 months.

Radar:

•      Radar can also be used to estimate precipitation and is particularly suitable for spotty, fast moving storms such as are common in Texas.

•      There is an evolving network of radar and Doppler radar sites used by National Weather Service.

Remote Sensing.

•      Data gathered from satellites can help create regional estimates of rainfall as well as predict major storms and hurricanes.

Applications:

•      There are many applications for rainfall and intensity data....

•      Agriculture.

•      Civil Engineering.

•      Water Supply.

•      Flood Warning.

Dendrochronology

•      Study of tree rings.

•      Can aid studies of long term precipitation.

Interpretation and Analysis of Precipitation

•      Rainfall and snowfall data are used to make decisions ranging from whether to take an umbrella to the

•      Decision to evacuate a city or release water worth millions of dollars into the sea to avoid over-topping a reservoir.

Available data:

•      Actual rainfall for various durations ranging from hourly to average for a century are maintained by the National Weather Service.

•      From this data intensity on an hourly, daily weekly etc basis is easily calculated.

Maximum Probable Storm Event:

•       By simple statistical methods the maximum probable storm for any duration of the storm event and recurrence interval can be estimated.

•      Typically the maximum hourly and maximum 24 hour storm events for recurrence intervals of 1, 10 25, 50 and 100 years are determined

Use of maximum probable storm event data:

•      This information is used in thousands of decisions every year.

•      This method depends on the rainfall events being random events. They may or may not be truly random but this is the best available assumption.

Reality vs. theory:

•      Unfortunately, rainfall is usually measured at a single point while the effects of rainfall such as flooding, stage height at a measuring station, etc are felt elsewhere and reflect the total contribution of rainfall over a large area.

Extending point data to an area:

•      In order to convert an estimate of rainfall at a point into an estimate for an area of interest such as a watershed or a river basin, a method of extrapolation of  point data to a larger spatial area must be employed.

•      This is called computing an area average. In order to develop an area average estimate there are three methods:

Methods of aerial averaging:

•      The arithmetic average method is simple, works well with even distribution of gages.

•      The Theissen polygon method is the area weighted average. It can account for uneven distribution of gages, can take into account data outside basin with appropriate weight and can be built into a GIS based system (use of a planimeter is out of date).

Examples:

•      Use by TWDB, 3D application to contaminant hydrogeology. and the Isohyetal Method: Uses contour lines of equal rainfall. Area between contours is measured and arithmetic average of the contour values is multiplied by the area between the contours and divided by the total basin area. Can be automated with GIS.

Locating Rain Gages:

•       In order to be used to determine accurate area averages of rainfall, locations of rain gages must be chosen carefully. In particular, locations in headwater areas, and urban areas is important. Also in areas of maximum, minimum and average precipitation within a basin.

Examples:

•      Ventura River Flood Warning System.

Measuring Stream-flow.

•      Stage gauges

•      Stilling well/float method

•      Pressure transducer based stream level sensors.

Measuring Current.

•      If a stage gauge, float or level sensor is used

•      To estimate stream flow the velocity of the stream must be determined.

•      This is done with either a propeller current meter or an ultrasonic current meter.

Measuring suspended sediment.

•      Use a sediment sampler attached to a wading rod or suspended from a cableway.

•      Sample is taken to lab then stirred up and a hygrometer is used to determine change in specific gravity over time. The specific gravity of water with more suspended sediment is higher.

Measuring soil properties.

•      Infiltrometer

•      Lysimeter.

•      Tensiometer

•      Neutron probe.

Infiltrometer:

•      Locally, one can use an infiltrometer to measure infiltration for small areas of the very surface of soils.

Lysimeter:

•      Experimentally, one can construct a lysimeter, essentially a container in which we place soil and grow plants in a field. This container has a drain at the bottom where the infiltrating water is collected and measured.

Difficulties:

•      Even with experimental measurements, estimating infiltration is very difficult and estimating the portion of water that enters the soil that percolates down to recharge groundwater is even harder.

Use of other factors:

•      However based of vegetation, slope, rainfall intensity, soil texture, soil thickness,  and preexisting soil moisture an approximate estimate can be obtained. This may be vital in predicting floods or designing structures.

Measuring Porosity:

•      A soil sample is taken with a hollow auger and wetted and allowed to drain. The saturated soil is then weighed. The soil is then cooked for many hours and when totally dry it is weighed again.

Knowing the weight of water, the differences in the mass of the sample and the volume of the sample, the volume of pore space and hence the porosity can be determined.

Measuring soil water.

•      The simple method is similar to method for measuring porosity.

•      The soil sample is weighed, dried and weighed again. The difference is the weight of water in the soil. That is converted into a volume equivalent and is compared to the volume of the soil sample.

The tensiometer:

•      The tensiometer is a tube with a porous ceramic tip. The tube is filled with water and the tensiometer is driven into the soil to the depth of the root zone  and soil suction draws water through the pores of the tip out of the tube. The force with which the water is drawn out is measured with a vacuum gage. The device works between the limits of .3 to .85 atmospheres, this covers the range between field capacity and the point when many crops need water.

In-place methods:

•      In-situ (ie in place measurements ) use either tensiometers or neutron probes.

The neutron probe

•      This probe uses a source of neurons. This source usually radio-active cobalt is lowered into the soil. High energy neutrons are emitted from the source and travel in a random path into the soil some neutrons hit hydrogen in water molecules and are converted to low energy neurons. These are measured by a detector. Neutron probes can be lowered into deep boreholes and can measure the porosity of saturated formations. Also it can measure soil moisture in dry soils.

Utility:

•      Hence tensiometers are very useful in scheduling irrigation since they can measure the actual availability of water to plant roots.

•      Example: Yuma orange grove.

Logging hydrologic data.

•      The days when technicians visited remote sites and daily or hourly recorded data into field notebooks are rapidly passing.

•      Instead data is recorded electronically, saved to computer memory chips in data-loggers and either accesses by lap-top computers, by phone/modem, by radio, by cell phone telemetry or by satellite.

Telemetry:

•      Rain gages can be telemetered and networked into a computerized flood warning system:

Hydrology Lecture # 6. Run-off & Hydrographs:

The run-off cycle:

•       refers to that portion of the hydrologic cycle that starts when precipitation reaches the earths surface and ends when water flows back into the sea (sink).

•      Water that infiltrates into the soil and is absorbed and transpired by plants is not part of the run-off cycle.

•      Likewise, water intercepted and evaporated is not part of the cycle.

Base Flow vs. run-off:

•      Water that recharges groundwater or is involved in interflow may be part of the cycle as groundwater discharge (base flow).

Run-0ff starts:

•      When precipitation exceeds the infiltration capacity of a soil the water ponds on the surface and when depressions are filled begins to flow overland under the force of gravity.

•      This is termed overland flow.

Factors affecting over-land flow.

•      The magnitude of overland flow depends on factors affecting infiltration capacity as well as on slope and the roughness of the terrain.

•      Landscapes that have heavy vegetation cover or many  depressions will have less rapid and less extensive overland flow than smooth and bare landscapes. Slope is a major factor in the speed of overland flow.

Interflow:

•      Inter-flow is the process of shallow saturated subsurface flow.

•      Occasionally, a tunnel will be eroded in the subsurface via interflow and the phenomena of piping may occur.

Influent vs. Exfluent streams:

•      Groundwater only discharges to maintain baseflow if the water table is above the stream bed level, this is an Influent stream. in arid areas permeable alluvial sediments in the channel, stream water will seep out of the stream into the ground.

•      A stream that recharges a water table is said to be exfluent.

Rivers that run dry:

•      Many streams and rivers are exfluent throughout most of their drainage: Example: Reese River.

•      Many streams are influent in some reaches and exfluent in others.  Example: Barley Creek.

•      Man can utilize an influent stream by diversion in a higher portion: Example Taft Creek.

Over-bank flow:

•      Over the long term the water table is generally rather flat (hence the use of the term table), however after a particularly large storm event added water will be present in a stream, it will cover the bed and lap against the banks (or even flow above the banks which is termed flooding or technically “over-bank flow”).

Flood Stages

•      This period of rising water levels in the steams is in the rising stage.

•      If the banks are earthen, then some of this water saturates the banks and is stored in soils. This water in bank storage is above the prevailing level of the water table.

•      This is only temporary as this water will seep back into the stream fairly rapidly after water levels subside during the falling stage.

Duration:

•      The duration of these stages can vary from minutes to months: depending on amount of flow added by storms and location of stream section  (reach).

•      The farther down stream a reach is, the longer duration and the smaller the amplitude of the rise and fall of the water levels are likely to be for any given size storm.

Factors affecting run-off: 1. Weather:

•      Global & local climate have a huge effect on run-off, as does timing of storm events.

•      A single “25 year storm” (a storm with a estimated recurrence interval of once in 25 years) can produce a wide range of run-off depending on antecedent precipitation patterns.

•      If the storm event follows on the heels of a series of “5 year storms” then the ground is likely to be saturated and the infiltration capacity of the soil low or nil.

Drought then flood

•      Conversely, if the “25 year storm” follows an unusually dry period the magnitude of the resulting flood may be greatly reduced.

•      However, if an extended drought has withered vegetation and baked the soil, flooding might be even worse that the first scenario. This is one reason the droughts often end with floods.

Example:

•      Great Texas drought of 1950s.

•      “The Time It Never Rained…”

Timing is everything

•      Timing is important, warm rains melting snow on frozen ground will cause spring floods.

•      Example: N. Dakota floods spring before last.

Elevation:

•      As one goes up in elevation precipitation tends to increase.

Orographic effects:

•      Increase in run-off from mountainous areas is due to: cooler temperatures induce less evapotranspiration and orographic effects produce more precipitation, more exposed bare rock. Also areas that are higher can impart more gravitational potential energy to water, more power of rushing water.

Example of Orographic Effects:

•      Big Thompson River flash flood.

Orientation & Aspect:

•      Orientation is important both with respect to prevailing storm tracks and with respect to north and south facing slopes (aspect).

•      Example: Kern River drainage. South Vs. North Forks.

•      Example: Chaparral/ grassland or ponderosa pine grassland ecosystems.

Topography:

•      Topography strongly influences run-off due to presence depression storage, steepness of slopes and influences the drainage pattern.

Vegetation:

•      Vegetation regulates the rate that precipitation reaches the ground by intercepting it. Vegetation is very effective in reducing the speed and force of overland flow and trapping sediment.

•      Vegetation also removes water from the soil and from shallow groundwater

Soils:

•      Soil type. Strongly influences run-off by affecting the infiltration capacity and infiltration rate of the soil.

•      Soil also influences vegetation and vice versa. Both soil type and vegetation influence run-off and run-off in turn can influence these two factors.

Geology:

•       Geology is the biggest single determinant of the physiography of a drainage basin as well as strongly influencing soil type, and existence and behavior of aquifers.

•      The way drainage patterns develop is a response to geologic factors.

Flashers vs. slow & steady:

•      Streams in areas that have impermeable rocks such as massive granites are likely to have a “flashy” character, streams in areas with more permeable rocks such as volcanics or limestones will have a much more even flow pattern.

Response time:

•      Response time is the time it takes for rainfall to reach a particular measuring point as streamflow.

Examples:

•       Kern River, Ca. 

•      Merrimac River, Mo.

•      Popo Agie River, Wy

•       Deschuttes River,  Ore.

Anthropogenic (man-made) factors:

•      Man can alter the local environment to change its hydrography significantly.

•      This is frequently in-advertent.

•      Agriculture & forestry creates bare soils and promotes erosion compared to natural vegetation. This promotes flooding.

Building in flood plains:

•      Building in flood plains and drainage and filling of wetlands takes advantage of flat, well watered and desirable areas (except during the floods that created such areas in the first place).

From pasture to parking lot:

•      Urban areas have a high proportion of impermeable surfaces and a large number of mechanisms for increasing the speed of runoff (rain gutters, downspouts, street gutters etc).

•      Hence the response time is lessened.

The hydrograph:

•      A hydrograph is a graph of flow or just stage (the height of water at a gauging station) on the y axis versus time on the axis

•      The time interval can be hours, days, months, or years.

•      The stage is usually in feet

•      Flow can be in CFS or possibly acre feet per year for large rivers.

The ideal hydrograph:

•      The idealized hydrograph has the following form for a upland stream responding to a single storm event:

•      See idealized hydrograph...

•      It has a rising arm,  a peak discharge,  and a falling arm.

•      The base flow is the flatter portion and reflects the inputs of groundwater discharge.

Variations:

•      Over longer periods hydrographs can have a variety of shapes. Those for streams in lowland temperate areas the hydrographs are usually are gently undulating except for small blips due to thunderstorms. They would usually be higher in the spring and summer lowest in the winter.

Flash floods:

•      Hydrographs that have the same time step would have very few but very sharp points indicating infrequent flash floods.

Up-stream vs. downstream

•      Likewise the higher in a drainage a hydrograph is measured, the sharper the peaks in the hydrograph are likely to be.

Examples:

•       Walker River,

•      Tippecanoe River,

•      Wild Water Creek,

•      Nelson Wash.

Relationship between hydrographs and precipitation:

•      Over the long term hydrographs and measured precipitation should move up and down in tandem. There should be some delay however (this is termed the lag and is an indication of the response time). The farther down stream the hydrograph is measured the longer the delay will be. Also, if the precipitation falls as snow the hydrograph will only begin to rise when the snow melts.

Lec 7. Form & Process in Streams

GENERAL POINTS

•      Flow variability and the channel.

•      Transport, erosion, and deposition.

•      Differences flow characteristics and sediment loads lead to variations in channel morphology.

SEDIMENT TRANSPORT

•      The transport of sediment by water involves two fundamental steps:

     (1) entrainment of sediment from the bed

     (2)  subsequent, sustained down current movement of the sediment

STREAM FLOWS

•      Large floods, Do they do most of the work?

•      There is no clear resolution to the issue of magnitude vs. frequency.

•      Temporal sequences in flow events.

1. Sediment transport that has been inherited from the past.

2. Better understanding of duration and inundation of flows throughout their entirety.

Big movers:

•      The sediment moving capabilities of large rivers are prodigious even the names and nick names attest to this.

•      Thus the red river, the many Colorado's and the name “big muddy” indicate that considerable quantifies of sediments are suspended in the water of many streams.

•      Generally upstream portions of rivers are actively eroding their beds while down stream sediments are being deposited.

 The stream channel or fluvial geomorphology.

•      Steam channels are both the primary conduit for terrestrial water to return to the sea and for the outputs from the process of mass wasting that is responsible for the gradual destruction of land masses and is a fundamental part of the rock cycle.

CHANNEL PATTERNS

CLASSIC DIVISION OF CHANNELS

•      Straight Channels

•      Meandering Channels

•      Braided Channels

Braided Channels

•      The factors that have been put forth are:

1. Abundant bedload

2. Banks composed of erodible sediments

3. Highly variable discharge

4. Steep Valley Slopes

Dynamics of stream channels:

•      Streams that have a variety of different sediments (clay, silt sand, pebbles, cobbles boulders, logs, mobile homes, etc) likely to form pool and riffle systems.

•      The pools form behind bars formed from coarse materials

•      Fine grained materials settle out in pools and pool-riffle systems gradually evolve and disappear and change location in a given stream.

Pool and riffle:

•       Pool & riffle systems are vital to the ability of streams to sustain life as they provide varied habitats, and help oxygenate the stream.

•      Under waterfalls scour holes are likely to form gradually undercutting the material that blocked the channel to create the fall.

The floodplain:

•      a relatively level area adjacent to the stream build up of sediments deposited in flood events when the stream cannot be contained within its banks.

•      Flood plains frequently contain wetlands and secondary channels. Also features like oxbow lakes are found in flood planes.

Meandering (like some lectures)…

•      Meanders are the other common feature of streams on the inside of the meander sediment is deposited on a point bar while water on the outside of the meander has a faster velocity and cuts into the usually steeper bank. The water can under-cut the bank causing erosion but it also provides great spot to catch a big fish.

Wiggle-waggle:

•      The continuing erosion and deposition at meander cause a lateral shift and an elongation of the meanders.

Examples:

•      Kaskaskia, Illinois.

•      Trinity River at Riverside.

Cut-off in its prime:

•      Eventually the added distance the water travels (and the sharp turns it must make) as the meander extends, causes the stream to cut through at a narrow neck. This eliminates that meander but another will form above or below.

•      The cut off section may form an ox bow lake or may provide an alternative channel during high flows or the stream may revert to this channel as it aggrades.

•      Thus streams are highly dynamic and therefore interesting.

Hydrology Lecture # 8.

Streams, Rivers & Lakes, Measurement and Characteristics.

Measuring volume of water:

•      For a lake take surface area times average depth (or use topographic data).

•      V = A*D

•      Where V = volume of water in Acre-feet

•      A = surface area of lake in acres

•      D = average depth of lake.

•      (average depth of lake may be hard to determine)

What is flow?

•      Flow is a volume per unit time such as a cubic foot per second (CFS).

•      That volume being measured is the volume of water passing through the cross section area of a stream channel per unit time.

Flow Units & Magnitudes:

•      Gallons per minute (GPM), Cubic feet per second (CFS), & Millions of gallons per day (MGD).

•      GPM for wells and domestic supply:

•      Small well 10-60 GPM.

•      Huntsville city well 1,200 GPM.

•      Catfish farm well 30,000 GPM.

Appropriate Units

•      Cubic feet per second:

•      CFS for streams and rivers:

•      Small creek 1-20 CFS, Trinity River 10,000-100,000 CFS, Mississippi 500,000 - 2 million CFS.

•      MGD for water & Sewage treatment plants: Huntsville ~ 4 MGD, Las Vegas 160 MGD.

What affects velocity of Flow?

•      Gradient (slope) of stream.

•      Roughness of stream bed.

•      Aquatic or terrestrial vegetation.

•      Shape of channel.

•      Depth of water.

•      Laminar versus turbulent flow.

Where is water flowing fastest?

•      In middle of channel, 20% of way to the bottom…

•      In deeper water (then why do still waters run deep?)

•      Where slope is steeper

•      Where water is smooth (then why is white water where rapids are).

•      Waterfall would be ultimate fast water.

Measurement of run-off.

•      Overland flow is virtually impossible to measure.

•      Rather it can be estimated by looking at other parts of the run-off cycle.

•      Thus precipitation less infiltration less evapo-transpiration should equal overland flow.

Example:

•      Ellwood Shores Study.

Water over the dam:

•      Once overland flow (along with interflow and discharge from groundwater) has entered a stream it can be more accurately measured.

Flow measurement

•      There are several methods for measuring stream flow most involve determining a cross-sectional area for the stream and measuring or estimating the velocity of water flowing through that cross-section.

Flow is area times velocity.

•      Since the cross section is an area and the velocity is a speed (distance/per unit time) the result of multiplying velocity times cross section is a volume

DISCHARGE EQUATION

Q = WDV

      

      Q = Discharge

W = width

D = Depth

                       V = velocity (f/s or m/s)

Common Units:

•      Typical units to measure cross section are square feet and velocity is typically measured in feet per second so the usual units of flow are cubic feet per second or CFS.

Example of flow measurement:

•      A stream has rectangular cross-section 20 feet wide, 5 feet deep. Multiply width times depth. 20 * 5 = 100 square foot area A.

•      If velocity V = .5 feet per second,

•      Flow F is .5 ft/sec * 100 square feet = 50 cubic feet per second....

•      Non-rectangular cross-sections require careful measurement.

Where to measure flow:

•      At point in stream with a solid bottom, single channel and uniform flow.

•      Preferably with a rectangular cross-section.

•      Avoid swamps, areas with turbulent flow.

•      Large rivers and small streams can be difficult to measure.

•      Old dam on Harmon creek or other places such as under bridges or in culverts are good locations, but watch out for floods...

Gauging Stations:

•      Once these measurements are made at a variety of different stream heights (stages) at a given point, a permanent rating curve for the sampling point is created relating stage (water height) with flow.

•      Then only height of water need be measured to estimate flow, this can be done by either a manual gage, a stilling well with a float or a pressure transducer.

Stage gauge:

•      Most measurements of the cross sectional area of a stream rely on a stream gage, a pole with graduated markings in feet and inches (or 1/10 of a foot). As water rises it wets a larger proportion of the gage.

 

Limitations:

•      If the site where flow is being measured has a vertical banks or walls and a flat bottom then measuring flow is as simple as multiplying the width of the channel times the height of water passing the gage (stage height). This rectangle represents the cross section.

Misleadingly easy:

•      A gage must be manually measured to determine stage height, although it is simple accurate and inexpensive. However, for long term or continuous measurements other technologies are employed.

Automated stage measurement:

•      One is a stilling well with a float. A stilling well is a pipe with a water intake and a float like a toilet tank float inside. Rising water in the creek enters the vertical pipe and raises the float which is recorded on a graph with a pen or saved to a ROM chip.

PT’s:

•      Alternatively a newer and better method uses a pressure transducer that can be buried in the deepest part of the channel inside a well screen. The pressure transducer records pressure (weight of water) and this is translated into depth of the water column above the measuring point.

Mother nature may not cooperate:

•      Unfortunately very few natural situations have these characteristics. The bottom is not flat and the deepest part of the bottom may shift over time, the banks are not vertical and in fact at higher flow water may enter other secondary channels complicating the estimate of cross section. Finally, the bed may not be impermeable.

Bad day on mud creek:

•      Thus defining were the ooze on the bottom becomes bed and not water is not easy.

•      For this reason hydrologists prefer to measure flow at locations like bridges, weirs or where bedrock is exposed all the way across the channel and the banks are steep. These areas are likely to have high velocity, a narrow width and deeper water than many areas.

Speedy:

•      Velocity can be even harder to measure or estimate than the cross sectional area.

•      It is better to measure velocity of faster moving water as the relative size of errors will be less, also still waters may have eddies that would make estimate of velocity even harder.

How to estimate velocity of flow:

•      Salt dilution method. Requires salt, conductivity meter and watch, can be automated. Good for small streams with good mixing, can be done by one person. Cross sectional area not needed.

•      Marshmallow method: requires two people, a marshmallow or bobber and a stop watch. Cross-sectional area needed.

•      Velocity meter method: requires special flow velocity meter and wading. Measure at several points. Cross-sectional area needed.

Velocity is estimated  not measured directly…

•      Data on roughness coefficients (.012 for smooth to .04 for torrents) for different streams is available.

•      Slope (gradient) measured as a whole number requires survey of stream.

Velocity measurement:

•      There are three methods for measuring velocity.

•      The (current) velocity meter

•      The float method

•      Manning equation

Current meter:

•      The current meter is made up of a propeller attached to fins that orient the blades to point in the direction of flow and which measures the rotation of the blades and converts that into an estimate of flow, Modern velocity meters measure flow in feet per second.

•      Velocity meters can be lowered from a boat,  from cableways or can be attached to poles and held underwater by hydrologists in hip waders in a shallow stream.

Limitations:

•      It is important that the current meter be held below the river surface (as wind and air resistance reduce velocity at the surface, but above the bottom where friction of the water against the bottom cause a substantial reduction in velocity).

80-20 rule:

•      To account for these factors, measurements at 80% of the total depth and 20% of the total depth should be made and averaged.

•      If the stream is likely to have differing velocities at different locations of a traverse then measurements can be made an several points moving across the stream and averaged. The more measurements, the more accurate the final estimate of velocity.

Beautiful Floater:

•      The float approach is much more crude but much simpler.

•      An object like a fishing float is placed in the river at a marked location and released at a set time the length of time it takes to float past another marked point down stream is measured. The distance between the points is divided by the time elapsed and that gives the velocity estimate.

Limitations of float method:

•      Due to eddies, difficulty in making the object float a strait course, difficulty in marking points in the middle of a stream, etc this approach has limited utility but is good for quick and dirty estimates.

Manning Method:

•      The manning approach is one that requires no actual field work. It is based on an equation which is designed to capture the factors that effect flow in hydraulic systems like stream channels.

 Manning's Equation.

•     

Q = (C/n) (AR0.667S0.5)

Q = Discharge

C = constant

n = hydraulic roughness

A = cross sectional area

R = hydraulic radius

S = slope or gradient of the channel

Rough and tuff…

•      The Roughness coefficient is a number between .014 and .070.

•      The number is smaller for smooth channels and larger for either boulder strewn mountain streams (.050) or weed choked channels (.070).

•      Harmon creek near the fish hatchery should be about .03-.035.

Hydraulic radius: its all wet…

•      The hydraulic radius is the wetted perimeter of the stream measured in feet .

•      The slope is the fall is stream elevation over some distance.

Last but not least, old salty…

•      The final method for estimating flow in a stream does not use an estimate of either cross sectional area or velocity.

•      It is termed the salt dilution method.

How salt dilution works:

•      A known quantity (mass) of granulated Sodium chloride (table salt) is placed in the stream at a known time. At a point far enough down stream that the dissolved salt will have had time to mix completely with the stream water, a conductivity meter is positioned. The increased in measured conductivity is measured on the meter. This is converted into an estimate of the increase in concentration of dissolved solids in the creek.

Logistics:

•      Measurements of conductivity are made at constant time intervals (every minute) and are continued until the increase in conductivity has ended (i.e. until “wave of salt water” has passed).

•      If the distance between the input point and the measuring point is known, and the time between the input of the salt into the water and the first increase in salinity is recorded the velocity can be estimated.

From velocity to flow:

•      The flow can also be estimated if the area under the curve of increase in salinity is determined, the time over which  the increase occurred is recorded and the mass of salt is known.

Benefits of salt dilution:

•      The salt dilution method dose not require a known cross-section or measurement of estimation of velocity it can be used when a estimate must be made in a hurry (a flood) or in a stream with no very good place to estimate cross section ( a mountain stream). Small turbulent streams are particularly suited  to this method.

Limitations of salt dilution method:

•      The method can be limited by the sensitivity of the conductivity meter.

Example:

•       Mission Creek California

•      Harmon Creek, Texas..

Applications of flow measurement:

•      Needed to predict floods, estimate water supply and control dams and irrigation projects:

•      Data is obtained by USGS at 3,000 locations in U.S. on daily basis

•      Examples: Lake Livingston (Flood of November 1994), South Platte River (water appropriation).

                      LEC. 9. Case Study Fort Hood Watershed Study.

Fort Hood Watershed Study, Purpose:

•    Determine impact of training activities on flooding and erosion. Study three watersheds with differing levels of disturbance using real-time monitoring.

•    Refine existing models (WMS, etc) of rainfall/run-off/stage/erosion with detailed data from 3 watersheds.

•    Install a low-water crossing flood alert system.

Background:

•    Base has several watersheds with varying levels of disturbance from training activities.

•    Streams are prone to flash floods.

•    Existing stream level & meteorological data is inadequate for detailed modeling and characterization.

Project Steps:

•    Site selection/GIS based stream mapping step.

•    Stream stage monitoring step.

•    Groundwater/soil moisture monitoring step.

•    Weather monitoring step.

•    Flood alert system installation step.

•    Data integration/modeling step.

Selection/mapping of Study Watersheds Step:

•    Select three watersheds contained in Base with varying levels of disturbance.

•    Select gauging stations on appropriate locations on each stream.

•    Obtain appropriate GIS data on watersheds and delineate watersheds in the GIS.

Bear Creek Watershed.

•    Bear Creek Watershed: smallest watershed, flows to Lake Belton.

•    Protected from disturbance, due to  endangered species & remoteness.

•    Most difficult to monitor/telemeter due to lack of access, irregular cross-section and no utilities.

•    Base-line for training impact analysis.

Owl Creek Watershed.

•    Moderate level of disturbance.

•    Limited tank training/some portions of basin in artillery impact/live fire areas.

•    Second largest watershed.

•    Intermediate flow.

•    5, sub-sheds, flows to Lake Belton.

House Creek

•    Greatest level of disturbance, tank training areas in basin.

•    Largest flow and watershed.

•    Subject to serious flooding.

•    Low-water crossing of public road (West Range Road ) is a flood hazard.

GIS based analysis:

•    GIS  will be used to examine underlying soils, geology and vegetation in each drainage basin.

•    GIS will be used to determine slope, aspect & area in  each drainage basin.

•    GIS can also create area weighted average (theisen polygon)  and isohytes from rainfall data.

Stream Stage Monitoring Step.

•    Installation of stream stage monitoring sites with bubbler/pressure transducers.

•    Real time turbidity monitoring.

•    Data logging capability.

•    Designed to resist loss in flood events.

•    All telemetered with solar power.

Weather Data Analysis and Monitoring Step:

•    Airfield has daily precipitation since 1960.

•    Maximum 24 hour storm can be calculated from this source.

•    2 telemetered weather stations on Base since 1994 provide hourly intensity data, spatial variation information.

Soil Moisture/groundwater Monitoring Step:

•    Soil moisture/groundwater monitored at each gauging station in upland, mid-slope & riparian zones using:

•    Shallow monitoring wells with PT’s.

•    Tensiometers, dielectric constant & resistively soil moisture measurement.

•    Calibrated by neutron probe and lab. soils analysis.

LEC. 10.NATURAL CONSTITUENTS OF WATER

What is water quality:

•      Besides measuring quantity of water the other water related parameters measured in the field usually involve quality measurements.

•      Quality measurements can be of the water body itself  or of a source of pollution such as a factory discharge, the run-off from a farm or sewer line.

What is in it:

•      Water naturally contains various constituents besides hydrogen and oxygen this includes dissolved solids and gasses, suspended sediments and various organisms.

•      In addition water may be contaminated with various man made substances.

Natural or not:

•      Water quality can involve natural constituents or anthropogenic contaminants...

•      Natural constituents can be of three types:

•      1) Inorganic minerals, 2)Organic substances and 3) organisms (such as microorganisms) .

Natural Constituents:

•      Water contains various dissolved solids which are derived from rocks and soils present in the drainage basin and/or aquifer from which the water originated.

•      Most dissolved substances are ions. Cations are negatively charged and include:

•      Anions are positively charged and include

•      Silicon is a non-ionic species that may be present in water.

Minerals :

•      Include salts (ionic compounds) and silica...

•      Major salts are calcium, magnesium, sodium, chloride, iron.…

•      All natural water has some dissolved minerals.

•      Example: Desani

Total Dissolved Solids

•      Measure of minerals and organic matter in solution.

•      Different than suspended particles

•      Usually measured as dissolved ions that change conductivity of water.

•      Water more than 1,000 parts per million is brackish, more than 10,000 ppm is saline.

Total dissolved solids vs. Suspended solids:

•      TDS All substances dissolved in water. Will not settle out.

•      Suspended solids are floating in water will settle-out gradually.

•      Can be filtered out, or let settle but fine grained clay will not settle so water is boiled and residue is weighed.

Hardness:

•       is a measure of the tendency of water to form scale deposits on pipes and plumbing fixtures.

•      It is the concentration of calcium and magnesium ions in the water.

•       Can cause serious problems at power plants

Water softeners:

•      Use an ion exchange resin and a saturated solution of NaCl the Na is replaced with Ca and Mg and the system is periodically back flushed.

•      Problematic dissolved solids:

•      Sodium: Causes damage to fertility of soils, can make high blood pressure worse.

Other undesirable constituents:

•      Chloride: Damages plants, imparts a nasty briny taste to water.

•      Iron: Stains plumbing fixtures, promotes formation of “black scum” (iron oxidizing bacteria)

•      Manganese: Stains plumbing may cause health problems.

•      Sulfur: Bad odor and taste

Examples:

•      Sulfur Creek...

Heavy Metals:

•      Heavy metals like lead and arsenic are less common but more of a problem since they can be toxic to people.

•      In some areas (western Colorado) radioactivity is naturally in water  as radon gas (from break-down of uranium)

•      Greatest danger is in the shower.

Dissolved gasses:

•      The important dissolved gas is oxygen...Needed by fish and to bio-degrade wastes.

•      Dissolved oxygen is introduced due to turbulence of water and from contact of water with atmosphere & from aquatic plants.

Dissolved oxygen:

•       (DO) is needed to support fish and break-down wastes, low DO is common in summer in stagnant water…

•      Measured by Winkler titration or now with electronic probes.

•      Low DO means dead fish...

D.O. characteristics of water:

•      Low in groundwater, high in mountain streams.

•      Bacteria use up DO.

•      More oxygen can be dissolved in cold water than warm water.

Radon.

•      Naturally occurring break-down product of uranium.

•      Found in groundwater in areas with uranium bearing rocks.

•      Released when groundwater is aerated, say in a shower head.

•      Causes lung cancer.

Other Parameters:

•      pH,

•      Temperature.

•      Turbidity can be estimated by sight.

Turbidity

•      cloudiness of water, can be measured with a sechi disk (a the metal disk tried to a rope and lowered until the marking can no longer be read).  This gives an indication of clarity.

Why is turbidity important.

•      Turbidity is an indication of presence of microscopic scum & clay in suspension.

•      This provides a nice hiding place for nasty microbes, so turbid water is difficult to chlorinate and disinfect.

•      Thus when it rains, Huntsville’s water treatment plant must shut down.

•      Measured by light transmission.

Temperature:

•      Temp. that is too high ,say due to discharges from a power plant is a problem (Example: Tampa, Florida), but warm water is enjoyed by some species like lobsters (Example New Hampshire).

•      Higher temperatures promote solution of more minerals, some can be toxic.

Heat: thermal pollution.

•      Usually related to power plant discharges.

•      Can be bad or beneficial to aquatic environment.

•       Examples: Tampa Bay, vs.. Clearwater River in Florida & Seabrook in New Hampshire.

pH:

•      pH is a measure of acid/base balance.

•      Either low or high pH can be bad.

•      Ranges from 0-14, 7 is neutral.\

•      0-7 is acidic, high acidity can leach toxic heavy metals.

•      7-14 is alkaline high alkalinity can hurt plants, make water hard to chlorinate.

Organisms:

•      Various organisms live in water.

•      Fish, mollusks and amphibians are an indicator of water quality but do not affect quality much.

•      Microorganisms such as algae, aerobic and anaerobic bacteria and microscopic animals like amoebas play an important role in maintaining water quality by breaking down wastes.

Too much of a good thing:

•      In excess, some micro-organisms such as the coliform bacteria or amoebas may be harmful to human health Examples: Hotel Lord and the White Rock Springs amoeba.

Microorganisms:

•      Include viruses, bacteria, animals (amoebas).

•      Some of these can be seen in the field with a hand lens, usually are viewed & cultured in lab.

•      Some micro-organisms that cause problems in U.S. are giardia, crypto-spiridium (Example: Beer City).

•      In third world countries (Mexico, Arkansas, etc) amoebas and coliform bacteria are common: don’t drink that rum and coke on the rocks…Watch out for the Hotel Lord in Merida.

Monitoring:

•      Monitoring water quality involves both monitoring sources and monitoring water bodies. Most standards are related to sources not actual quality of the receiving body (lake or river).

Typical water quality measurements include:

•      TDS

•      Turbidity

•      pH

•      Dissolved oxygen

•      Also concentration of specific contaminants

Canary in a coal mine:

•      Alternatively aquatic toxicity can be measured with fish or chemo-luminescent bacteria.

Difficulties:

•      Problems occur if there are many sources:

•      Example: Mississippi between Baton Rouge and New Orleans.

Nutrients:

•      Nitrate, Ammonia, & Phosphorus.

•      These are limiting nutrients if introduced can cause algal blooms (eutrophication).

•      Mostly from sewage and fertilizers.

•      Use of phosphates in detergents banned in 1970’s.

OVER-ENRICHMENT

•      Once in a water body, the nutrients can stimulate growth of aquatic plants that cause water quality problems (a process called eutrophication).

•      Animal wastes are less concentrated than fertilizers but large scale confined farming (pig herds, chicken sheds, cattle feed lots, emu farms (in their dreams)) generate huge volumes of waste.

Eutrophication:

•      The technical term for the over-enrichment of an aquatic environment. Due to nutrients like PO4 and NO3 that are in short supply naturally being supplied from human and animal waste, fertilizer and detergent.

Scum and more scum:

•      This causes a “bloom” of algae and bacteria that eat the algae. When these organisms die, the oxygen dissolved in the water is used up and fish and other animals die. Water is murky, stinks and is covered by dying pond scum and floating dead fish.

LEC 11.  Water quality: Anthropogenic contamination

Toxic Substances in Water:

•      Synthetic organic chemicals like PCB’s and DDT.

•      Hydrocarbons like gasoline or crude oil.

•      Solvents like TCE, PCE.

•      Heavy metals like lead, chromium, mercury and arsenic.

•      Radioactivity: usually Radon gas.

Fate of pollutants:

•      Dispersion: “Dilution is the solution to pollution”...

•      Biochemical decay: Microbes convert to CO2  use up O2.

•      Sedimentation: persistent pollutants like DDT, PCBs and heavy metals stay in sediments.

•      Example: Minimata Bay, Japan.

Is your drinking water safe? 

•      Probably yes, possibly no, but how safe is safe?

•      Many rural water systems are out of compliance with Safe Drinking Water Act standards,

•      Also many private wells.

Examples of Drinking Water Risks:

•      400,000 people sick in Milwaukee, 16 people die in Las Vegas from cryptospiridium.

•      EPA estimates 6,000 additional cancer cases per year due to chlorination of organic laden water forming THM’s.

•      Chlorine alternatives limited, standards for turbidity are being made tougher.

Water Pollution Control Methods:

•   Waste-water treatment: aerobic plants and/or anaerobic process. 

•    Industrial process controls.

•   Proper storage, & disposal of toxic wastes.

•   Pump & treat groundwater pollution.

•   Anaerobic septic systems phased out, replaced by aerobic systems (possible air quality and health hazard if improperly maintained).

Water Quality Laws: Clean Water Act:

•      Sets discharge limits and receiving water standards for point  & non-point sources

•      Regulates dredge & fill of wetlands.

•       funds construction of wastewater treatment plants.

•      Most expensive (to Feds) and successful environmental law.

Safe Drinking Water Act:

•      Sets maximum contaminant limits for priority pollutants in municipal water systems.

•      Requires testing and notification.

•      Many systems not in compliance with standards for heavy metals and turbidity and chlorine levels. 

•      Example: Huntsville.

Status of Water Quality in USA:

•      Most dramatic progress in water quality in USA in last 25 years.

•      Most towns have secondary sewage treatment.

•      Most discharges by industry have been reduced or eliminated.

•      Non-point source pollution major remaining problem.

Status of Water Quality in Other countries:

•      Water quality is improving in Canada, Japan and Western Europe

•      Going down-hill in developing countries with new industries:  Mexico, India, China, Nigeria, Indonesia.

•      Along with shortage (which makes quality poorer)  is biggest resource problem facing developing countries with the the most people.

Anthropogenic Contamination:

•      Water contamination due to man’s activities (anthropogenic) is a serious problem throughout the world, perhaps more so in the developing counties and the former socialist countries (and China) than in Western Industrialized ones.

Main Types:

The major sources of man-made contamination of surface water  are:

•      Sewage

•      Industrial wastes

•      Agricultural chemicals, fertilizers and wastes

•      Other sources: urban run-off , LUST

Sewage:

•       Human waste is a minor problem when populations are dispersed, although if the outhouse on the family farm was near the creek or well pathogenic organisms like salmonella and coliform bacteria could be a problem.

Control measures:

•      Indoor plumbing only partially alleviated the problem since wastes were accumulated in a more concentrated form and in larger volumes.

•      Septic tanks and outfalls at rivers are a first pass at using “dilution as the solution to pollution”.

Overload:

•      However, for large volumes of wastes generated by urban areas this does not work well.

Examples:

•      London in the 19th century.

Waste Water Treatment:

•      The approach today is a multistage sewage treatment process at a central plant using the activated sludge process (primary treatment) and aeration (secondary treatment) possibly also further steps (Tertiary treatment) to remove nutrients like nitrate and phosphorus from water.

Industrial wastes:

•       these wastes come in all types and all volumes.

•      Typical types include petroleum industry wastes, chemical industry wastes and metal processing industry wastes.

Hydrocarbons:

Petroleum wastes include crude hydrocarbons, oil field brines, refined products and acidic sludges.

Many of these wastes leak from underground storage tanks.

Chemical industry:

•      These wastes include the most toxic types of wastes (these are mostly no longer discharged into surface waters). Almost every known chemical currently used or in use the past has gotten into surface waters from chemical manufacturing.

Examples of Toxic chemicals :

•       DDT (Santa Monica Bay),

•      Kepone (James River),

•      Dioxin (Times Beach),

•      PCBs( Hudson River),

•      Mercury( Minemata Bay).

Metal finishing industries:

•      Generate heavy metal containing wastes 

•      Acidic and Basic wastes.

•      Sulfates.

•      Solvents

•      Cutting oils.

•      Large sources like steel mills have been controlled (or the problem has been exported) but machine shops, plating companies, etc still generate some problems.

Other industries:

•       have unique waste water problems: Paper Industry: Chlorine,

•      Tanning: heavy metals & acids,

•      Electronics: Heavy metals and chlorinated solvents.

High Tech Toxics:

•      High tech does not necessarily imply clean...

•      Examples: Silicon Valley, Lockheed skunk works.

Get the point!

•      Point source industrial pollution can be controlled and in the U.S. is largely controlled although improvements can be made.

Non-point source:

•      Agricultural chemicals, fertilizers and animal wastes tend to be non-point source:

•      With municipal and industrial sources of pollution more or less capable of being controlled with treatment technology non-point sources of pollution are the most challenging ones today.

Farming Dirty

•      Since agriculture is the human activity that occupies the most land it should not be surprising that it is a leading source of contamination.

•      Agricultural pollution is usually non-point source (unless a system of drains exist).

Types of Agricultural pollution:

•      Pesticides:

•      Herbicides

•      Herbicides and pesticides are a major ecological and frequently a human health problem.

Persistent pesticides:

•       like DDT, chlordane, eldrin, & Herbicides like 245T (agent orange) that are based on chlorinating aromatic molecules  have been replaced (in USA) by:

Still toxic:

•      less persistent but more acutely toxic compounds like carbamate & organo-phosphorus compounds.

•      Many pesticides are water soluble and those than are not end up in sediments.

•      Many aquatic species are sensitive.

 Bio-accumulation:

•      The process of build up of compounds in the bodies of plants and animals. Some pollutants including DDT, PCB, Dioxin and heavy metals bio-accumulate. The top of the food chain gets the highest concentration (Humans, eagles, marlin are at the top).

•      Examples:

•      Mercury in Tuna,

•      DDT in bald eagles.

Fertilizers and animal wastes.

•      Fertilizers contain minerals and plant nutrients like K, PO4 and NO3. These are water soluble in order to work. Unfortunately, much applied fertilizer gets into groundwater or runs-off, either as a water solution or attached to soil particles that are eroded.

Big trouble down on the farm:

•      This is a severe rural water quality problem, probably the single biggest water related problem in many states including North Carolina, Arkansas and other mostly rural states

Other sources:

•       Urban run-off ,

•      LUST,

•      small business,

•      home & garden.

Urban run-off:

•       Contains a wide variety of contaminants that get washed off streets and lawns. These include: garden chemicals (diazinon is big in Texas due to fire ants), and automotive products like motor oil, antifreeze, brake fluid etc. The total volume is huge.

LUST:

•      LUST stands for Leaking Underground Storage Tanks (also LUFT) with over 4 million tanks mostly holding fuel oil or gasoline many tanks or associated piping have leaked(estimated at 1/3). Usually LUST is first a groundwater contamination problem but due to discharge of aquifers this can get in surface water.

Toxics around town:

•      Small local businesses like dry cleaners and auto-repair shops are an on-going problem.

•      Household chemicals includes many toxic compounds that get washed down the sink (drain-o, oven cleaner, detergents) and pest control products.

Impacts of water pollution:

•      Pathogenic organisms: Mostly from sewage, cause 40,000 deaths every day worldwide. Usually amoebas, coliform bacteria and parasites are the culprits. “Don’t drink the water” doesn’t work if you are a resident and not just a tourist. Rarer in USA but giardia and crytospiridium can sicken many (400,000 in Milwaukee) and kill babies, the old and the sick.

Acute Toxicity:

•      Pesticides and high concentrations of oil and other chemicals can kill wildlife immediately, this problem is usually apparent and corrected quickly, but in the third world it happens frequently.

Chronic toxicity:

•      A long term poisoning over many years, heavy metals do this also chlorinated pesticides are suspected to produce this. Effects can be brain damage, birth defects or bone decay.

Carcinogenesis.

•      The process of induction of cancer. Various compounds are suspected. Chlorinated solvents and some pesticides (chlordane, DBCP) and chemicals (PCB) are proven in animals and suspected in humans of causing cancer.

Lake Ponchartrain:

•      The most polluted large lake in US.  Seepage of sewage from old and broken sewer system of the big easy is cause along with shallow depth and warm climate.

Cuyahoga River:

•      This Ohio river Caught on fire in 1968. Many industries dumped in this Ohio river which flows into Lake Erie. Scandal helped in passage of the clean water act of 1972. Now largely cleaned up. Flushing action of rivers speeds clean-up once source is removed.

Lake Erie:

•      This smallest of the great lakes is still is heavily polluted from past dumping, sediments contain mercury, lead, arsenic, PCBs,  DDT and many other compounds. Bottom fish and predators are still contaminated.

Hudson River:

•      This important New York River was polluted by Westinghouse PCB manufacturing facility dumped tons of PCBs into the river most is still in sediments.

Big Miami River:

•       This river in Ohio: Uranium dumped from Fernald plant still on bottom of river.

Sacramento River:

•       A train derailment in headwaters spilled pesticide in 1990 that killed all fish for many miles down stream.

Ohio River:

•       The Ohio River south of Pittsburgh: Collapse of million gallon fuel oil tank caused death of many fish and shut down of water treatment plants downstream for several weeks.

Trinity River

•      The most polluted large river: Black sludge episodes in past, now much better.

Rio Grande:

•      The Rio Grande is also polluted from sewage and agricultural and industrial chemicals (outflow from Juarez and Nuevo Laredo is the worst problem despite NAFTA promises).

Caddo Lake:

•       Lonestar steel in Marshal are other examples of surface water pollution problems.

Cases of Surface Water Pollution Around the World:

Lake Baikal:

•      In Russia (largest body liquid of fresh water on earth) has some bad pollution from paper mills and other industry. Tributary caught fire in 60's.

El Salvador:

•      Dense population, unrestricted use of banned pesticides, causes fish in lakes and coastal areas to die and become contaminated, people have high rates of cancer and birth defects.

Cairo Egypt:

•       8 million people,  No modern sewage treatment for most, Nile river is increasingly polluted.

Pollution Prevention:

•      Prevention involves identifying sources and putting treatment programs in place.

•      Usually secondary treatment of municipal sewage

•      Segregation of industrial waste water with specialized treatment as appropriate.

•      In some cases wastes cannot be treated and are disposed of by incineration, solidification and disposal in a hazardous waste landfill or deep-well injection.

Remediation:

•       Clean-up of contamination involves treating point sources.

•      Sometimes total removal is necessary.

•      Example: French Limited site, Crosby, Texas.

•      More frequently treatment & monitoring is sufficient.

Non-structural methods:

•     

•      Non-point sources may require elimination of some substances, collection of storm water or methods for reducing erosion and run-off thus allowing water to percolate into aquifers and be naturally attenuated by bacteria and by filtration as it moves through soil and aquifer materials.

Risks versus benefits:

•      If money was unlimited... all water pollution could be eliminated. As money is limited decisions need to be made as to which issues to address first and it is necessary to decide how clean is clean.

•      This involves public policy, law and economics. It also involves risk assessment.

•      Risk assessment uses statistics, environmental and biological science and economics to help decide issues.

Examples:

•     

•      Deal with sewage first, then chemical plant discharges. Then oil refineries and paper plants, then agriculture and finally urban run-off.

•      Continue to use chlorine for water purification.

Worst Offenders:

•      Cancer causing compounds and chronic poisons like heavy metals and particularly radio-active compounds have received strongest regulation.

•      Naturally occurring toxins have gotten less attention.