OCR Text |
Show {?.) Local Streams ( a) Description of the Alternative Streams entering the Salt Lake Valley from the east, including Big Cottonwood, Little Cottonwood, Mill, Parleys, Emigration, and City Creeks, have potential for development of an additional municipal water supply. Those streams entering the valley from the southwest and west are intermittent flows and are undependable. The larger and more reliable streams on the east side of the valley are Big and Little Cottonwood Creeks. Currently, portions of the direct flows of these two streams are diverted to treatment plants near the mouths of the canyons, where the water is treated for municipal use and then routed to the various city systems. Treatment plants located in Parleys Canyon and on City Creek treat water from these two creeks. Table H- 3 gives the percentage of water right owned by Salt Lake City for each creek and the diversion capacity to its treatment plant. Increased use of the frontal streams, particularly Big and Little Cottonwood Creeks, would logically occur in conjunction with an imported supply to Salt Lake Valley. By thus providing a larger base supply, as demands in the valley increase by additional population and growth, more of the direct streamflows would fall within the demand pattern and would be usable directly without storage regulation. Storage on either of these streams would be costly and would have the problems which are described in paragraph ( b) below. The available flows in the frontal streams and their uses are given in Table H-^. By construction of Argenta Reservoir on Big Cottonwood Creek, high spring flows now outside the municipal demand curve could be stored for use later in the summer. This would require enlargement of the Big Cottonwood Treatment Plant at the mouth of the canyon. No additional pipeline or diversion structures would be required for additional diversion to the treatment plant. However, a pipeline to deliver water to western Salt Lake County would be required. Likewise, construction of Little Dell Reservoir ( a Corps of Engineers project) in the Parleys Canyon drainage would, by means of a tunnel from Mill Creek to Lambs Canyon and a tunnel from Emigration Canyon to Little Dell, be able 499 |