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Water Resources.

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Presentation on theme: "Water Resources."— Presentation transcript:

1 Water Resources

2 Hydrologic Cycle Hydrosphere: All the water at or near the surface of the earth Amount of water essentially constant and moves between different reservoirs 100 million billion gallons move through Hydrologic Cycle Oceans account for ~96%, Fresh water lakes and streams for only 0.016% of all water

3 Distribution of Water

4 Hydrologic Cycle Thousands of km3/yr - - - +

5 Ground water 22% of all fresh water occur underground
Aquifer: Underground formation that holds and yields water A good aquifer needs to be both porous and permeable

6 Porosity and Permeability
Porosity: Proportion of void space: pore space, cracks, vesicles Gravel : 25-45% (1K - 10K), Clay: 45-55%(<.01) sandstone: 5-30% ( ), Granite: <1 to 5%(.003 to ) higher porosity in well rounded, equigranular, coarse grained rocks Permeability: Measure of how readily fluid passes through a material Depends on the size of the pores and how well they are interconnected Clay has high porosity but low permeabilty

7 Less porosity porosity permeability Clay % <0.01 m/day sand 30-52% gravel % to 10,000

8 Subsurface Water Zone of Aeration or Vadose Zone or Unsaturated Zone: Overlies Phreatic Zone. Pore spaces partly filled with water. Contains soil moisture. Saturated Zone Zone of Saturation or Phreatic Zone: saturated zone overlying impermeable bed rock. Water fills all the available pore spaces Water Table: top of the zone of saturation where not confined by impermeable rock

9 Water table follows the topography but more gently
Intersection of water table and ground surface produces lakes, streams, spring, wetlands… Ground water flows from higher elevation to lower, from areas of lower use to higher use, from wet areas to dry areas.

10 Darcy’s law Hydraulic Gradient: Slope of the ground water table
Rate of flow is proportional to the hydraulic gradient

11 Aquifer Recharge: Process of replenishment of Ground Water by infiltration, migration and percolation Aquifer: A rock that holds enough water and transmits it rapidly. Porous and Permeable. Sandstone and Coarse Clastic Sedimentary rocks make good aquifers Aquitard and Aquiclude: Rocks of low and very low permeability e.g., shale, slate Perched water table: Local aquifer in Vadose Zone


13 Confined and Unconfined Aquifer
Unconfined Aquifer: open to atmosphere e.g., overlain by permeable rocks and soils Confined aquifer: sandwiched between aquitards Artesian System: Water rises above the level in aquifer because of hydrostatic pressure Potentiometric surface: Height to which water pressure would raise the water.

14 Artesian System: Water rises above the level in aquifer because of hydrostatic pressure
Potentiometric surface: Height to which water pressure would raise the water.

15 Consequences of Ground Water Withdrawal
Lowering of Water Table Cone of depression: Circular lowering of water immediately around a well

16 Consequences of Ground Water Withdrawal
overlapping cones of depression causes lowering of regional water table Water mining: rate of recharge too slow for replenishment in human life time

17 Compaction and Subsurface subsidence

18 Consequences of Ground Water Withdrawal….
Compaction and Subsurface subsidence Building damage, collapse flooding and coastal erosion e.g., Venice, Galveston/Houston (80 sq km permanently flooded), San Joaquin Valley (9m subsidence) Pumping in of water no solution

19 Land subsidence in San Joaquin Valley , California


21 The High Plains Aquifer
The High Plains is a 174,000-square-mile area of flat to gently rolling terrain that includes parts of eight States from South Dakota to Texas. moderate precipitation but in general has a low natural-recharge rate to the ground-water system. Unconsolidated alluvial deposits that form a water-table aquifer called the High Plains aquifer underlie the region. Since early 1800s, irrigation water pumped from the aquifer has made the High Plains one of the Nation’s most important agricultural areas. the intense use of ground water for irrigation has caused upto 100m decline in water-level in parts of Kansas, New Mexico, Oklahoma, and Texas.

22 Changes in ground-water levels in the High Plains aquifer from before ground-water development to (V.L. McGuire, U.S. Geological Survey, written commun., 1998.)

23 The Gulf Coastal Plain Aquifer System
The Gulf Coastal Plain aquifer system underlie about 290,000 square miles extending from Texas to westernmost Florida, including offshore areas to the edge of the Continental Shelf. Water withdrawals from the aquifer system have caused lowering of hydraulic heads at and near pumping centers; reduced discharges to streams, lakes, and wetlands; induced movement of saltwater into parts of aquifers that previously contained freshwater; and caused land subsidence in some areas as a result of the compaction of interbedded clays within aquifers.

24 Land subsidence in Houston

25 Flooding in coastal Galveston because of subsidence

26 Saltwater Intrusion Salt water incursion in caostal aquifer
upconing below cone of depression Aquifer below Brooklyn, NY destroyed Serious problem in Gulf Coast and California Salt water incursion in caostal aquifer

27 Extent of salt water incursion in Miami-Dade
Salt water intrusion in Miami-Dade

28 Sinkholes forms in areas with abundant water and soluble bedrock (gypsum or limestone) collapse follows ground water withdrawal

29 Stalagtites Stalagmites Dripstones in a cavern

30 Interfering with the flood plain
Asphalt and concrete reduces infiltration and hence the lag time Buildings in the flood plain increases flood heights (why?) Storm sewers quicken the flow to the river Exposed soils silt up the river channel

31 Reducing Flood Hazards
Avoid Flood Plains: Not practicable Risk mapping : identify areas endangered by different magnitude of flood Use higher risk areas for recreation purposes etc. Building codes e.g., on buildings on stilts

32 Reducing Flood Hazards
Retention ponds does not alter the channel, can be farmed Channelization Mississippi case history, Florida problems, Export of flooding Levees (Raised banks along the channel) Extensive damage if breached, alters sedimentation, upstream flooding Dams (irrigation, hydel, recreation) stream profile altered, habitat destroyed, seismic risk

33 Channelization of Kissimmee River

34 Kissimmee River Project
Wetlands drained Dairy Farms and Sugar Plantation moved in Fertilizers and pesticides washed into Florida Bay Algal Bloom used up dissolved oxygen in water Excessive sedimentation smothered bottom communities and blocked sunlight in deeper water Death of corals, sponges and bottom-communities Loss of habitat of fish and fowls of wetland Loss of recharge of groundwater Loss of evaporation and drop in rainfall Exotic plants moved in Now the river is being restored to original channel

35 Urbanisation and ground water
Loss of Recharge Impermeable cover retards recharge Filling of wetlands kills recharge area Well planned holding pond can help in recharging ground water

36 Water Quality Most freshwater contain dissolved substances
concentrations are described in ppm or ppb TDS=Total Dissolved Solids 500 to 1000 ppm for drinking water 2000 ppm for livestock some solids (e.g., Iron, Sulfur) more harmful than others (e.g. calcium) synthetic chemicals can be toxic at ppb level Radioactive elements pose special hazard Uranium, Radium, Radon

37 Hard water Hard Water: Common in limestone country
contains dissolved Ca and Mg; problematic if >100 ppm problem with soap leaves deposits in plumbing and in appliances can be cured with water softener typically ion exchange through zeolites

38 Water Use in US 4200 billion gallons of precipitation
2750 billion gallons lost by evaporation 1400 billion gallons available for consumption Biological need : 1 gal/person/day US consumption: 1800 gal/person/day = 400 billion gallons per day for the entire US

39 Offstream Use: water diverted from source e. g
Offstream Use: water diverted from source e.g.,for irrigation or thermal power generation Consumptive: water used up For farming, drinking or lost by evaporation Instream: water returns to flow: e.g., for hydroelectric power generation

40 Water Use …contd Main Uses: Thermoelectric Power
Surface: Ground water = 67:33 Consumed 2%, Return Flow 98% Irrigation Surface: Ground water = 63:33 Consumed 56%, Loss 20%, Return Flow 24% Industrial Surface 67% (saline 12%), Ground water 15% (1% saline), Public Supply 19% Consumption 15%, Return Flow 85% Domestic Public Supply 86%, Ground Water 13%, Surface 1% Consumption 23%, Return Flow 77%

41 Irrigation and Ground water
Thus, irrigation is the major consumer of ground water Western states are the major drawers of ground water causing serious environmental problems

42 Most of the precipitation is in the eastern states but…

43 Most of the water withdrawal is in the western states (see also the next slide)


45 Total withdrawal increased from 1950 to 1980 and has held steady since then although population has increased by 16% Withdrawal for thermoelectric power generation 190,000 Mgal/day: largest of any other category Higher water price, more public awareness, conservation, better farming and industrial techniques will keep water demand in check

46 Water Rights Riparian Rights (Eastern USA):
Every landowner can make reasonable use of lake or stream or water flowing through or bordering his property Municipalities have the right of eminent domain: at times of scarcity, cities get their requirement first Sale of riparian rights allowed in some states Practical in regions of plentiful water

47 Law of Prior Appropiation
First come, first served Settlers can lay claim to certain amount of water which will be honored for perpetuity The oldest claim are honored first and any left over goes to the next claimant and so on.. Los Angeles bought up water rights in 1900 from areas far and wide, some even from Arizona. Now people in those areas are very unhappy about the arrangement

48 Story of Colorado River
The Colorado River flows through Utah to Lake Powell, thence through the northwest corner of Arizona to Lake Mead. From Hoover Dam it flows southward to Mexico forming the border between Nevada, California and Arizona, and yielding major diversions to central Arizona and southern California. The river is the lifeblood of the southwestern US and its development and management have been the focus of attention by the member states for more than a century. Waters of the Colorado River System have been apportioned by a treaty with Mexico, compacts, and a Supreme Court decree to the seven basin states. Colorado River basin

49 Colorado River Compact
The Colorado River Compact of 1922 divided the use of waters of the Colorado River System between the Upper and Lower Colorado River Basin. It apportioned in perpetuity to the Upper and Lower Basin, respectively, the beneficial consumptive use of 7.5 million acre feet (maf) of water per annum. It also provided that the Upper Basin will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 75 maf for any period of ten consecutive years. The Mexican Treaty of 1944 allotted to Mexico a guaranteed annual quantity of 1.5 maf. These amounts, when combined, exceed the river's long-term average annual flow. These apportions were decided during a particularly wet climatic period. At present, the flow in Colorado does not add up to all the apportionments

50 Within Colorado water allocations are based on the Doctrine of Prior Appropriation or the First-in-Time, First-in-Right Doctrine. This doctrine is found in most arid states because when there is too little water to satisfy all users, sharing of the remaining water would be of little value to any user. But a large part of the Colorado river water is diverted to Los Angeles on the basis of this doctrine

51 Conservation Shift water-hungry crops to regions with more rainfall
Use drip irrigation to reduce evaporation loss Use pipes to reduce transport loss Water lawns in morning and evening or opt for no lawn Direct storm water in recharge basins

52 Interbasinal transfer
Transfer water from water-surplus regions to water-deficient regions California : Los Angeles aqueduct moves 150 million gallons/ day from east of Sierra Nevada to LA New York: Water supply to NYC from Finger Lakes region political problems Desalination Filtration, distillation Expensive, limited

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