Sustained Yield of the Provo Groundwater Basinby Carl H. Carpenter, Provo City Dep of Water Resources, Provo, United States,
Document Type: Proceeding Paper
Part of: Management of Irrigation and Drainage Systems: Integrated Perspectives
The sustained yield of the Provo Groundwater Basin has been determined by a correlation analysis of the change in groundwater levels with the April-October stream flow at the mouth of Provo Canyon and also the annual volume pumped by the City's deep wells. The Provo City Department of Water Resources obtains water from twelve deep wells which penetrate the unconsolidated pre-Lake Bonneville deposits of Pleistocene Age, underlying the City of Provo. A linear correlation exists between the accumulated changes in annual water levels in these wells and the natural flow in the Provo River at the mouth of Provo Canyon occurring between April and October of the preceding year. Regression analysis indicates that for a zero change in groundwater levels to occur, Provo River must yield about 165,000 acre feet of natural flow during the preceding April-October period. A water level change of one foot throughout in the aquifer represents 30,700 acre feet of water in the river at the canyon mouth. Regression analysis of the annual net change in water levels compared to the annual volume pumped by the Provo City wells indicates that 7,700 acre feet can be yielded by the groundwater basin for a zero change in water levels. Thus, the sustained yield of the Provo aquifer to the twelve City wells for a zero net change in water level is about 8,000 AF annually. For a net decline in water level of 25 feet, the yield is 20,000 AF. In 1981 the U.S. Geological Survey evaluated the groundwater resources of Northern Utah Valley, of which the Provo Groundwater Basin is a part. By use of a three dimensional, finite difference, digital computer model, it was determined that 25,000 to 30,000 acre feet of water withdrawals annually would result in a water level decline of 25 feet in the Provo area. This is comparable to the linear regression analysis, which indicates a yield of 20,000 acre feet, with 25 feet of water level decline.
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