Modeling the Distinction Between Regional Flow and Flow to Drainsby G. M. Pohll, Univ of Nevada, Reno, United States,
J. C. Guitjens, Univ of Nevada, Reno, United States,
C. P. Close, Univ of Nevada, Reno, United States,
Abstract: Previous research at the Newlands Agricultural Research Center, in Fallon, Nevada, suggests that the quality of the water flowing to the 15 subsurface drain laterals in related to the chemistry of the shallow aquifer. More conclusive data on the flowpaths to the drain laterals is needed to determine the water quality implications of reapplying drainage effluent as a portion of the irrigation supply. To assess the quality of the water that flows to the drain laterals, it is first necessary to determine the sources of water. This paper describes the depth at which the flowpaths of the regional aquifer flow system and the local flow system toward 15 drain laterals separate. The finite difference groundwater computer model MODFLOW is used to create a steady-state, two-dimensional groundwater flow model. The model will calculate the hydraulic head distribution after a flood irrigation event. Eighty piezometers were installed at various depths throughout the field for use in model parameter estimation and to calibrate the model. Preliminary results confirm that the irrigation water mixes with the shallow groundwater. The shallow aquifer is the primary source of water and salts entering the drain laterals. Most drain lateral water traverses the aquifer to a depth of up to 4 meters below ground surface.
Subject Headings: Drainage | Water quality | Groundwater flow | Computer models | Aquifers | Water flow | Flow distribution | Drainage systems | Nevada | North America | United States
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