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<br />I\;) <br />.... <br />t.:> <br />o <br /> <br />systems. These changes should result in <br />reduced return flows and salt pickup. Projected <br />water depletions through the 1965.80 period <br />were largely unrealized; total depletions <br />increased by approximately 12 percent. <br /> <br />Previous Reclamation salinity projections have <br />been too high, largely because the depletion <br />projections were also too high. Transbasin <br />diversions and increased reservoir evaporation <br />account for most of the increased depletions from <br />1960-80; however, no additional salt pickup or <br />loading occurred with these depletions. <br /> <br />The large quantities of water expected to be <br />depleted for steam power generation, coal <br />gasification, oil shale, and mineral development <br />have not been realized in the past decade. Even <br />where new coal.fired powerplants have been <br />constructed, some of the water has been <br />obtained from existing agricultural rights. This <br />conversion of use reduces the salt loading to the <br />Colorado River by eliminating the pickup of salt <br />by canal seepage and deep percolation. <br /> <br />Reduced Flood Plains <br /> <br />The reservoirs have also significantly reduced <br />the peak flood flows downstream. The <br />consequent reductions in the downstream flood <br />plains result in decreased bank storage and <br />possibly reduced salt flushing. At least <br />temporarily, the area between the old and new <br />flood plains may act as a salt sink, but the <br />long-term salinity effects of the changes in the <br />flood plains are not known. <br /> <br />Energy Exploration and <br />Development <br /> <br />Many oftha geologic formations of the Colorado <br />River Basin were deposited in marine (salt <br />water) or brackish water environments. <br />Sulfates and sodium chloride are prevalent salts <br />in most of these formations. Many of the <br />sediments deposited in drier periods are capable <br />of transmitting water, but these aquifers are <br />frequently sandwiched between hundreds or <br />even thousands of feet of impermeable shales <br />(aquicludes). These aquifers are, therefore, <br /> <br />FACTORS IN SAUNlTY TRENDS 23 <br /> <br />static and often saline. Many static and saline <br />aquifers are present in the Colorado River <br />Basin. When a path of flow is provided by <br />drilling or mining, these aquifers are mobilized, <br />and brackish or saline waters flow back to the <br />surface. <br /> <br />The development of energy resources, <br />specifically coal, oil and gas, and oil shale, in the <br />Colorado River Basin may contribute significant <br />quantities of salt to the Colorado River. Salinity <br />can be increased either by dissolution of <br />minerals or consumption of good quality water, <br />The location of fossil fuels are associated with <br />marine derived formations. Any disturbance of <br />these saline materials will increase the contact <br />surfaces allowing for the dissolutions of <br />previously unavailable soluble minerals. <br /> <br />Salinity increases associated with the mining of <br />coal can be attributed to leaching of coal spoil <br />materials, discharge of saline ground waters, <br />and increased sediment yields resulting from <br />surface disturbing activities. Spoil materials <br />have a greater permeability than undisturbed <br />overburden, allOwing most of the precipitation <br />falling on the spoils to intiltrate instead of <br />running off. The water percolates through the <br />Wlconfined spoils allowing greater opportunities <br />for dissolving soluble minerals through increases <br />in both contact surfaces and residence time. The <br />water moves vertically until it encounters <br />undisturbed bedrock where new springs can be <br />created. The usual result is an increase in the <br />volume of water because of reduced <br />evapotranspiration and an increase in total <br />dissolved solids. <br /> <br />Studies[ 12,13, 141 conducted on postmining <br />spoils in northwestern Colorado indicate that <br />the resulting total dissolved solids (TDS) <br />concentration of spoil derived waters ranges <br />from approximately 3,000 mWL to 3,900 mgIL. <br />The variability in concentration depends on <br />water residence time and the chemical and <br />physical properties of the spoil. <br /> <br />Saline water is 8 byproduct of the production of <br />oil and gas in the basin. It is not uncommon to <br />produce several times the amount of saline <br />waters as oil. Oil and gas operators produced <br />approximately 25,000,000 barrels of saline <br />waters during December 1985 in Colorado. The <br /> <br />