4/13/07

• Discuss lab exercise

• Water supply & usage (Chapter 10)

• Water Law

Groundwater Flow• Hydraulic head is potential energy in an aquifer

– The height of water in an unconfined aquifer reflects the hydraulic head

• The higher the water table the higher the head

– The higher the potentiometric surface in a confined aquifer will equate to higher hydraulic head

– Ground water flows spontaneously from areas of high hydraulic head to areas with low hydraulic head

Figure 10.6

Interactions between surface and ground waters (SW & GW)

• Overdraft of GW: – Leads to lower water levels of streams, lakes, reservoirs, etc.

• Overuse of SW: Yields lower discharge rates of GW• Effluent (Gaining) stream (in GW discharge zone):

– Tends to be Perennial (i.e., flow all year)• Influent (Losing) stream (in GW recharge zone above the

water table): – Are often above the water table, and flow in direct response

to precipitation– May be intermittent or ephemeral (flow part of the year)

Fluid Storage and Mobility• Rock type will impact porosity and permeability

– Igneous, metamorphic, and chemical sedimentary rocks have crystals that are tightly interlocked and low permeability and porosity

– Weathering, dissolution, and fracturing will increase porosity and permeability in crystalline rock

• Clastic sediments have more porosity and permeability– Sandstones are generally very porous– Clay and mud rich rocks are not porous or

permeable

Other Factors in Water Availability

• Geometry of host rock units

• Distribution of aquitard lenses may form perched water tables

• Local precipitation patterns and fluctuations

• Minerals in host rock

• Location of wells relative to recharge zones and discharge points

Figure 10.7

Consequences of Groundwater Withdrawal

• Pumping ground water will lower the water table and form a cone of depression around the well– This may impact local and regional ground water availability

• Aquifer rocks may re-adjust after ground water is withdrawn– Sediments may compaction and cause surface subsidence– An area of low elevation, relative to sea level, may be inundated

by the sea– Sinkholes may also develop depending on the host rock

• Near coastlines saltwater intrusion may occur– Freshwater is less dense than saltwater– Saltwater near a coast line may push freshwater lenses back if

recharge is not sufficient to force seawater toward the sea

Figure 10.8 a

Figure 10.9

Galveston Bay, TX

Figure 10.11b

Figure 10.12

Other Impacts of Urbanization on Groundwater Systems

• An increase in people in an area may cause ground water supplies to be exhausted or loss of recharge to occur– Pavement and parking lots reduce the effectiveness of

water infiltrating into ground water– Building on wetlands reduces recharge, water storage,

and water quality• Ground water recharge can be enhanced by

incorporating various artificial recharge strategies– Build artificial recharge basins– Employ any method to slow down run off and increases

surface water infiltration

Figure 10.13

Other Features Involving Subsurface Water

• Ground water may dissolve large volumes of rock (soluble rock)– Collapse of the surface rock may result in sinkholes– Caverns may also be enlarged

• Karst is a type of land form associated with many sink holes in soluble bedrock such as limestone, dolomite, or gypsum– Water removes the minerals of the rock and carries the ions

off in solution– Ground water flow rates will increase in karst areas

• Ground water flows faster without sediments and rock in the flow path

• Pollutants move faster through ground water systems in karst areas

Figures 10.16 a and b

Figures 10.17 a and b

Water Use and Supply

• Offstream use: Removal or diversion from its SW or GW sources temporarily– e.g., water for irrigation, thermoelectric, industrial use

• Consumptive use: Type of offstream use of water without water returning to the SW or GW– e.g., water incorporated into crops/products;

transpiration and human use

• Instream use: Water is not withdrawn from its source– e.g., water for navigation, hydroelectric power

generation, fish and wildlife habitat, recreational uses

Trends in Water Use

Figure 1120a

Public water supply

Trends in Water Use

Figure 11.20b

Billions of Gallons of Water / Day

Average Annual Precipitation

Water Withdrawal By State

Water Withdrawal By Sector

Figure 10.22

Water Use for Irrigation

Water Distribution in San Diego in San Diego County

58%25%

11%6%

residentialcommercial/industrialagriculturalother

California’s Plight

Last 5 years have used 5.2 million acre feet of waterLast 5 years have used 5.2 million acre feet of water MWD gets from other states’ surplus but growing use in MWD gets from other states’ surplus but growing use in

other states will render surplus non existentother states will render surplus non existent Single SourceSingle Source

-MWD-MWD Population Population

-1.14% growth annually-1.14% growth annually

Water Conservation and Transfer Agreement

April 28, 1998April 28, 1998 Largest agri-urban water transfer in U.S. Largest agri-urban water transfer in U.S.

history!!!history!!! Involved partiesInvolved parties

San Diego County Water AuthoritySan Diego County Water AuthorityImperial Irrigation DistrictImperial Irrigation DistrictMetropolitan Water DistrictMetropolitan Water District

Conservation: Ways to Save Indoors

check for leakscheck for leaks flush toilets less oftenflush toilets less often shorter showersshorter showers use water-saving devises use water-saving devises don’t waste waterdon’t waste water fully load appliancesfully load appliances defrost food in refrigeratordefrost food in refrigerator clean with waterless clean with waterless

Conservation: Ways to Save Outdoors

water landscape twice weeklywater landscape twice weekly don’t use sprinklersdon’t use sprinklers use a broom to clean pavementuse a broom to clean pavement wash cars with hoses with positive shut-off nozzlewash cars with hoses with positive shut-off nozzle use covers on pools and spasuse covers on pools and spas plant drought-resistant trees and plantsplant drought-resistant trees and plants Fix leaksFix leaks

Projects and Programs

Emergency Storage ProjectEmergency Storage Project a system of reservoirs, interconnected pipelines & a system of reservoirs, interconnected pipelines &

pumping stationspumping stations Agricultural Water Management ProgramAgricultural Water Management Program surveyor comes to your acreage & makes observations of surveyor comes to your acreage & makes observations of

plant material, soil, and irrigation system…..it’s freeplant material, soil, and irrigation system…..it’s free

Projects and Programs

Commercial, Industrial, Institutional Voucher ProgramCommercial, Industrial, Institutional Voucher Program vouchers for replacing inefficient equipment with vouchers for replacing inefficient equipment with

efficient equipmentefficient equipment

Residential Survey ProgramResidential Survey Program owner receives a review of indoor/outdoor water-saving owner receives a review of indoor/outdoor water-saving

opportunities &educational literatureopportunities &educational literature

Map of Emergency Storage Project

www.sdcwa.org/text/esp/esp_faq.htm

What does this mean for San Diego: Factors for the Future Growing populationGrowing population- SANDAG predicts increased - SANDAG predicts increased

population over the next several yearspopulation over the next several years Federal restrictionFederal restriction Future demand for waterFuture demand for water- increasing population - increasing population

with less allocationwith less allocation demand for water in 2000: 619,409 AF demand for water in 2000: 619,409 AF

2015: 787,000 AF 2015: 787,000 AF Located in a vulnerable areaLocated in a vulnerable area-earthquakes, drought-earthquakes, drought

Table 10.4

Case Studies in Water Consumption

• The Colorado River Basin

• The High Plains (Ogallala) Aquifer System

• The Aral Sea

Water law and legislation dealing with pollution

1) Surface water law

2) Groundwater law

Surface Water Law

• Riparian Doctrine– States in the eastern US– Owners of the land adjacent to a water

body own the water– Water rights are property that can be

bought and sold– Landowners can make “reasonable use” of

water on their land

Surface Water Law

• Prior Appropriation Doctrine– Western states– The first person to have diverted and used

the water has the primary right to it.– Water rights are separate from property

rights

Surface Water Law

• Public Trust Doctrine– It is the duty of the state to protect the

public’s common heritage• Streams, lakes, marshlands, etc.

– 1983, California Supreme Court used this doctrine to protect Mono Lake against Las Angeles, which had rights over the water

Groundwater Law

• Absolute Ownership Doctrine–(English Rule)

• A landowner owns the groundwater under his/her land

–Works fine if there is plenty of groundwater

–A problem in the western US

Groundwater Law

• Reasonable Use Doctrine–(American Rule)

• A landowner owns the groundwater under his/her land

• BUT, the amount of water withdrawn must be “reasonable” and “beneficial”.

Groundwater Law

• Correlative Rights Doctrine– California

• A landowner owns the groundwater under his/her land

• BUT, all of the landowners whose property overlies a common groundwater source also have equal rights to the water in the aquifer as long as it is “reasonable” and “beneficial”

• Requires “safe yield” be established