The Hydrologic Cycle

The Hydrologic Cycle

Salt water vs. fresh

waterIn this class, we will be mostlyConcerned with fresh water(terrestrial).

http://www.jhuccp.org/pr/m14/m14figs.stm

Less than 1% of the Earth’s freshwater is on the surface at any time.

20% of the freshwater flows through the ground – groundwater.groundwater.

Basic Cycle

Ocean

EvaporationEvaporation (ET)

runoff

Precipitation

Aquifer

Infiltration

Evaporation

PrecipitationEvaporation/ETSurface WaterGroundwater

Water Residence Times

Get this image from the mac to place here http://www.unep.org/vitalwater/05.htm

StreamStream: body of running water that is confined to a channelchannel and moves downhill due to gravity

Drainage BasinDrainage Basin: total area drained by a stream. Larger streams have larger drainage basins.

The size and composition of the sediment carried by the stream The size and composition of the sediment carried by the stream depends on the nature of the drainage basin.depends on the nature of the drainage basin.

Dissolved LoadDissolved Load Suspended LoadSuspended Load

Bed LoadBed Load

Braided Channel

Meandering Channel

Straight Channel

Fig. 10.18

Braided StreamsBraided Streams

Streams with high sediment loads deposit lots of channel bars. The stream moves around the bars, finding its way through the barriers.

Usually found near sediment source areas and/or areas with easily eroded substrate.

Braided Stream

Fig. 10.06

Meandering Meandering StreamStream

DepositionDeposition occurs on point barspoint bars, where stream velocity is low

ErosionErosion occurs on cutbankscutbanks, where stream velocity is high

Fig. 10.06

Meandering Meandering StreamStream

DepositionDeposition occurs on point barspoint bars, where stream velocity is low

ErosionErosion occurs on cutbankscutbanks, where stream velocity is high

Figure 14.14

Fig. 10.24

Meandering StreamsMeandering Streams

oxbow lakeoxbow lake

Fig. 10.27

Flood Plain:Flood Plain: area habitually flooded by a stream at high water. Contains fine-grain sediment deposited during flooding

Natural levee:Natural levee: low ridges formed along sides of main stream channel during flooding.

Fig. 10.27

Flood Plain:Flood Plain: area habitually flooded by a stream at high water. Contains fine-grain sediment deposited during flooding

Natural levee:Natural levee: low ridges formed along sides of main stream channel during flooding.

Water In (Inflow)

Surface runoff

Groundwater influx

Discharge from upstream

Direct precipitation

Water Out (Outflow)

Capacity (shape-dependent)

Rate (slope-dependent)

93 m

150 m

I <=> O normally

I > O channel fills

If channel fills completely, river can overflow banks and flood

Stream Budget

Flooding

Flooding at Flooding at River Park, River Park, Rock HillRock HillSeptember, 2004

Flooding along the Flooding along the Catawba river was Catawba river was caused by extreme caused by extreme rainfall resulting rainfall resulting from an unusual from an unusual series of powerful series of powerful hurricanes and hurricanes and tropical storms.tropical storms.

Precipitation – the basic water resource

GW

GW

GW

GW

GW

Adapted from: GWP (M. Falkenmark), 2003, Water Management and Ecosystems: Living with Change

Blue & Green Water - perspective

Why so much for agriculture?

• Most countries want/need to feed themselves.• No water = no plants = no food

Photosynthesis

6CO2 + 6H2O C6H12O6 + O2

• C3 plants – 1 gram biomass per 650-800 grams water transpired

• C4 plants – 1 gram biomass per 250-350 grams water transpired

• CAM plants – 1 gram biomass per 100-200 grams water transpired

Water use and farms• Average water needed per acre of crop

– Soybean (C3 plant) = 737,100 liters H2O– Corn (C4 plant) = 862,500 liters H2O

Considering that many farms are hundreds to thousands of acres…that’s a lot of water!!

---Note that corn is a more massive crop. ---Also note that CAM plants are primarily habit the desert and are not

irrigated.

Typical Domestic Water Use

• 10 – 40 L/person/day (water scarce)

• 50 – 100 L/person/day (low-income)

• 100 – 600 L/person/day (high-income)

– Differences in domestic freshwater use:

• Piped or carried• Number/type of• appliances and sanitation

Water Stress Index• Based on human consumption and linked to population growth• Domestic requirement:

– 3.65 - 14.6 m3/person/year (water scarce)– 36.5 - 219 m3/person/year (high-income)

• Associated agricultural, industrial & energy need:– 20 x domestic requirement– 73 – 292 m3/person/year– 730 – 4380 m3/person/year

• Total need:– 77 – 307 m3/person/year (water scarce)– 767 – 4599 m3/person/year (high-income)

Water Stress per International River Basin

http://www.transboundarywaters.orst.edu

Colorado River Basin• Colorado River water

usage– Water “rights” from river (in

million acre feet)• Colorado 3.85• New Mexico 0.84• California 4.4• Arizona 2.8• Nevada 0.3• Utah 1.7• Mexico 1.5Total 15.39

http://www.crwua.org/

Average River Flow = 15.5

• Population growth in Colorado River Basin