Simulating Subsurface Flow in an Irrigated Tiled Drained Watershed
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Abstract
Simulating Subsurface Flow in an Irrigated Tiled Drained Watershed
Haider Addab and Ryan Bailey
Department of Civil and Environmental Engineering, Colorado State University
Subsurface tile drains are frequently used in agricultural practice to enhance crop yield in poorly drained but highly productive soils. Tile drains increase availability of plant nutrients, improve soil aeration, and reduce crop diseases, soil erosion, and surface runoff. However, tile drains can also expedite the transport of chemical species such as salt ions and nitrate-nitrogen (NO3 –N) and pesticides such as herbicides, insecticides, and fungicides to surface waters. Hydrologic and water quality models such as DRAINMOD and the Soil and Water Assessment Tool (SWAT) are widely used to simulate water flow and chemical transport in tile drainage systems at various spatial scales. However, groundwater flow patterns associated with drainage are often unknown and their representation in these numerical models, although powerful analysis tools, is still a major challenge. An accurate water flow simulation is essential. In this study, coupled groundwater/tile drain flow is simulated for a tile-drained agricultural catchment in the Arkansas River Valley watershed using a MODFLOW model, with the Stream flow Routing (SFR) package used to simulate the flow of water in the tile drain network and the water exchange between the drains and the aquifer along the length of each drain segment. Short-term monitoring data (groundwater levels from instrumented monitoring wells, tile drain flow at the network outlet) are used to evaluate the MODFLOW model. The model can be used to explore the export of nitrate and salt from the study region, and to investigate the impact of best management practices for salt and nutrient management.
Simulating Subsurface Flow in an Irrigated Tiled Drained Watershed
Simulating Subsurface Flow in an Irrigated Tiled Drained Watershed
Haider Addab and Ryan Bailey
Department of Civil and Environmental Engineering, Colorado State University
Subsurface tile drains are frequently used in agricultural practice to enhance crop yield in poorly drained but highly productive soils. Tile drains increase availability of plant nutrients, improve soil aeration, and reduce crop diseases, soil erosion, and surface runoff. However, tile drains can also expedite the transport of chemical species such as salt ions and nitrate-nitrogen (NO3 –N) and pesticides such as herbicides, insecticides, and fungicides to surface waters. Hydrologic and water quality models such as DRAINMOD and the Soil and Water Assessment Tool (SWAT) are widely used to simulate water flow and chemical transport in tile drainage systems at various spatial scales. However, groundwater flow patterns associated with drainage are often unknown and their representation in these numerical models, although powerful analysis tools, is still a major challenge. An accurate water flow simulation is essential. In this study, coupled groundwater/tile drain flow is simulated for a tile-drained agricultural catchment in the Arkansas River Valley watershed using a MODFLOW model, with the Stream flow Routing (SFR) package used to simulate the flow of water in the tile drain network and the water exchange between the drains and the aquifer along the length of each drain segment. Short-term monitoring data (groundwater levels from instrumented monitoring wells, tile drain flow at the network outlet) are used to evaluate the MODFLOW model. The model can be used to explore the export of nitrate and salt from the study region, and to investigate the impact of best management practices for salt and nutrient management.
