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A Mathematical Model of an Existing Municipal Well Field
Author(s) -
DeVries Richard N.
Publication year - 1970
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1970.tb01305.x
Subject(s) - groundwater recharge , aquifer , water well , drawdown (hydrology) , superposition principle , hydrology (agriculture) , aquifer test , boundary value problem , injection well , well test (oil and gas) , permeability (electromagnetism) , geology , groundwater , petroleum engineering , geotechnical engineering , mathematics , mathematical analysis , genetics , membrane , biology
Increased irrigation demands on water from the Platte River in central Nebraska are causing a depletion in the flow that passes the City of Lincoln's Municipal well field, at Ashland, Nebraska. A study was made for the U. S. Army Engineers, Omaha District as to the future harmful effects of this depletion. a mathematical model using the Theis nonequilibrium equation was formulated. Drawdown computations were performed using an IBM 360 Model 65 computer. Recharging image wells were used to represent the physical boundary of the aquifer. Drawdowns in selected wells were calculated using the method of superposition by including both the real wells and the image wells. Values for permeability and the storage coefficient were computed from field pumping test data. Three different model runs were made. First, the wells were assumed to be pumped continuously at maximum output of 84 M.G.D. for periods of 10, 30, and 60 days both with and without river recharge. Next, the same time periods and recharge situations were run assuming 37 wells to be operating at their present field capacities, totaling 60 M.G.D. The third computer run was made using 39 wells. During the first 10‐day period only 27 wells were modeled to produce 51 M.G.D. In the next 10 days 31 wells were required to produce 59 M.G.D., and finally for the last 10 days 20 wells were‐used to produce 37 M.G.D. This operation duplicated the actual operation for July, 1968, when the all‐time peak production for any one month was recorded. It is concluded that the well field can be operated at high rates for periods of greater than 30 days without recharge from the river. Previous studies have indicated the river is the source of most of the water produced from the wells. The study does indicate that the well field can draw on the ground‐water reservoir for much longer periods than had been assumed in the past.