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Last modified
7/14/2009 5:02:30 PM
Creation date
5/20/2009 10:41:36 AM
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UCREFRP
UCREFRP Catalog Number
7409
Author
U.S. Department of the Interior.
Title
Quality of Water, Colorado River Basin.
USFW Year
1991.
USFW - Doc Type
Progress Report No. 15,
Copyright Material
NO
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<br />16 Chapter 4-Causes and Impacts of Salinity <br /> <br />irrigated along the Colorado River mainstream, <br />total irrigated lands for the entire Lower Basin <br />were about 1.5 million acres. <br /> <br />Irrigation in the Colorado River Basin has <br />increased the salinity in the Colorado River. <br />Return flows from the irrigated lands dissolve <br />salts from the soils and underlying aquifer <br />material and transport them to the river. <br /> <br />Municipal and Industrial <br />Sources of Salinity <br /> <br />Salt loads contributed to the Colorado River <br />system by municipal and industrial sources are <br />generally minor, totaling about 1 percent of the <br />basin salt load. Iorns[2] found that municipal <br />and industrial uses increased salinity by about <br />100 tons per 1,000 people in the basin. <br />Reclamation estimates for the Upper Colorado <br />River Basin show the popula~on increasing at a <br />rate of about 25,000 people per year. The <br />population estimate in 1980 was 575,900 people. <br />By 2010, municipal and industrial sources will <br />be increasing salinity by approximately <br />133,000 tons per year or more. <br /> <br />Most municipal wastes are relatively low in salt <br />concentration in comparison with natural, <br />industrial, and agricultural sources. Complete <br />elimination of such waste discharges would be <br />expensive when compared to other salinity <br />control methods. <br /> <br />Development of oil and gas, oil shale, and <br />mineral resources in the basin also has the <br />potential to increase salt loading. Many saline <br />aquifers are static (very little water movement) <br />until they are disturbed by drilling or mining <br />activities. An example is the Meeker Dome <br />Salinity Control Unit, described in chapter 7, <br />which came about as the result of saline ground <br />water flowing to the surface through abandoned <br />oil wells. <br /> <br />Increased Salinity <br />from Water Depletions <br /> <br />Addition of salts to the river system is not the <br />only cause of increased salinity concentrations. <br /> <br />The depletion of water of better quality water <br />reduces the dilution of saline inflow, increasing <br />the salinity of the Colorado River. <br /> <br />With the exception of the Central Arizona <br />Project (CAP), the Lower Basin has already <br />developed most of its water supply. CAP will <br />soon be responsible for the last major additional <br />depletion (approximately 1.5 million acre-feet <br />per year) in the Lower Basin. <br /> <br />Consumptive use of water for irrigation within <br />the basin is responsible for the largest <br />depletions of the Colorado River. Exports, <br />reservoir evaporation, and municipal and <br />industrial uses also account for lesser but <br />significant depletions. Table 2 summarizes both <br />the Upper and Lower Colorado River Basin uses, <br />including tributaries to the Colorado River in <br />the Lower Basin [4]. <br /> <br />Table 2.-Average water use in <br />the Colorado River Basin for 1976-80 <br />(Units-1,OOO acre-feet) <br /> <br />Type of use Upper Basin Lower Basin <br />Reservoir evaporation <br />and channel losses 758 1,682 <br />Irrigated agriculture 1,984 5.180 <br />Municipal and <br />industrial 178 453 <br />Fish. wildlife, <br />and recreation 0 50 <br />Transbasin exports 727 4,239 / <br /> ( <br /> I <br /> I <br /> <br /> <br />The major part of the transbasin depletions in i <br />the Upper Basin is made at higher elevations <br />where the salinity concentrations are very low. <br />This removal of high quality water results in 'the <br />remaining flows downstream becoming mor'J <br />concentrated even though some salts are <br />removed by the water delivered to another <br />basin. Many transbasin diversions have been <br />made over the years, and more are projected in <br />the future. <br /> <br />Water exported from the Upper Basin during <br />the period 1941-72 averaged about 360,000 acre- <br />feet per year. Completion of such large projects <br />
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