OCR Text |
Show -14- Solution of reservoir bed and bank materials.-The presence of large quantities of soluble rock material, outcropping within the reservoir area and particularly in the Overton Arm, was recognized during the planning stages for Hoover Dam. This material consisted largely of gypsum (calcium sulfate) and some halite (sodium chloride) within the Muddy Creek formation. At one time it was suggested that the solution of these salts would increase to a serious extent the concentration of dissolved solids in the stored water. In the early studies a few samples of water were collected close to the bottom of the lake, particularly in the vicinity of the submerged Calico salt mines in the Overton Arm of the lake. These samples showed a local concentration of dissolved solids somewhat higher than was found in water at lesser depths in that area, but they failed to show for any large masses of water a marked increase in concentration which could be attributed to dissolving of the rock material. The water released from Lake Mead in almost every year has shown a higher concentration of dissolved solids than the average for the inflow. Assuming that the 24,-600,000 acre-feet of water in Lake Mead at the end of water year 1948 carried 0.91 ton of dissolved solids per acre-foot, the total solids in the lake would be about 22,-300,000 tons. About 12,000,000 tons of this is accounted for by the difference between inflow and outflow (p. VII-182), indicating an increase of more than 10,000,000 tons during the first 14 years of storage. This increase represents the net change, that is, the increases resulting from solution less the decreases due to precipitation of 10,000,000 tons of calcium carbonate and silica from the stored water. The total increase, of the order of 20,000,000 |
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Original book: [State of Arizona, complainant v. State of California, Palo Verde Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of Los Angeles, California, City of San Diego, California, and County of San Diego, California, defendants, United States of America, State of Nevada, State of New Mexico, State of Utah, interveners] : |