Water Resource

Total Withdrawal: 134,000 Mgal/day Surface water : 63% Groundwater: 37% Irrigation Use: 39% of all freshwater withdrawal

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

Hydroelectric water use 3,160,000 Mgals/day 2.6 times annual run-off Same water is used several times by a series of dam on the same river Instream use: water is returned to the stream Almost all withdrawal is from fresh surface water

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. The area is characterized by 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. During the late 1800’s, settlers and speculators moved to the plains, and farming became the major land-use activity in the area. Since that time, irrigation water pumped from the aquifer has made the High Plains one of the Nation’s most important agricultural areas. Over the years, the intense use of ground water for irrigation in the High Plains has caused major water-level declines and decreased the saturated thickness of the aquifer significantly in some areas. For example, in parts of Kansas, New Mexico, Oklahoma, and Texas, ground-water levels have declined more than 100 feet

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.)

The Gulf Coastal Plain Aquifer System The Gulf Coastal Plain aquifer system consists of a large and complex system of aquifers and confining units that 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.

Land subsidence in Houston

Colorado River basin 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 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.

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

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

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