A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Simulation of drainage water quality with DRAINMOD
Abstract The design and management of drainage systems should consider impacts on drainage water quality and receiving streams, as well as on agricultural productivity. Two simulation models that are being developed to predict these impacts are briefly described. DRAINMOD-N uses hydrologic predictions by DRAINMOD, including daily soil water fluxes, in numerical solutions to the advective-dispersive-reactive (ADR) equation to describe movement and fate of $ NO_{3} $-N in shallow water table soils. DRAINMOD- CREAMS links DRAINMOD hydrology with submodels in CREAMS to predict effects of drainage treatment and controlled drainage losses of sediment and agricultural chemicals via surface runoff. The models were applied to analyze effects of drainage intensity on a Portsmouth sandy loam in eastern North Carolina. Depending on surface depressional storage, agricultural production objectives could be satisfied with drain spacings of 40 m or less. Predicted effects of drainage design and management on $ NO_{3} $-N losses were substantial. Increasing drain spacing from 20 m to 40 m reduced predicted $ NO_{3} $-N losses by over 45% for both good and poor surface drainage. Controlled drainage further decreases $ NO_{3} $-N losses. For example, predicted average annual $ NO_{3} $-N losses for a 30 m spacing were reduced 50% by controlled drainage. Splitting the application of nitrogen fertilizer, so that 100 kg/ha is applied at planting and 50 kg/ha is applied 37 days later, reduced average predicted $ NO_{3} $-N losses but by only 5 to 6%. This practice was more effective in years when heavy rainfall occurred directly after planting. In contrast to effects on $ NO_{3} $-N losses, reducing drainage intensity by increasing drain spacing or use of controlled drainage increased predicted losses of sediment and phosphorus (P). These losses were small for relatively flat conditions (0.2% slope), but may be large for even moderate slopes. For example, predicted sediment losses for a 2% slope exceeded 8000 kg/ha for a poorly drained condition (drain spacing of 100 m), but were reduced to 2100 kg/ha for a 20 m spacing. Agricultural production and water quality goals are sometimes in conflict. Our results indicate that simulation modeling can be used to examine the benefits of alternative designs and management strategies, from both production and environmental points-of-view. The utility of this methodology places additional emphasis on the need for field experiments to test the validity of the models over a range of soil, site and climatological conditions.
Simulation of drainage water quality with DRAINMOD
Abstract The design and management of drainage systems should consider impacts on drainage water quality and receiving streams, as well as on agricultural productivity. Two simulation models that are being developed to predict these impacts are briefly described. DRAINMOD-N uses hydrologic predictions by DRAINMOD, including daily soil water fluxes, in numerical solutions to the advective-dispersive-reactive (ADR) equation to describe movement and fate of $ NO_{3} $-N in shallow water table soils. DRAINMOD- CREAMS links DRAINMOD hydrology with submodels in CREAMS to predict effects of drainage treatment and controlled drainage losses of sediment and agricultural chemicals via surface runoff. The models were applied to analyze effects of drainage intensity on a Portsmouth sandy loam in eastern North Carolina. Depending on surface depressional storage, agricultural production objectives could be satisfied with drain spacings of 40 m or less. Predicted effects of drainage design and management on $ NO_{3} $-N losses were substantial. Increasing drain spacing from 20 m to 40 m reduced predicted $ NO_{3} $-N losses by over 45% for both good and poor surface drainage. Controlled drainage further decreases $ NO_{3} $-N losses. For example, predicted average annual $ NO_{3} $-N losses for a 30 m spacing were reduced 50% by controlled drainage. Splitting the application of nitrogen fertilizer, so that 100 kg/ha is applied at planting and 50 kg/ha is applied 37 days later, reduced average predicted $ NO_{3} $-N losses but by only 5 to 6%. This practice was more effective in years when heavy rainfall occurred directly after planting. In contrast to effects on $ NO_{3} $-N losses, reducing drainage intensity by increasing drain spacing or use of controlled drainage increased predicted losses of sediment and phosphorus (P). These losses were small for relatively flat conditions (0.2% slope), but may be large for even moderate slopes. For example, predicted sediment losses for a 2% slope exceeded 8000 kg/ha for a poorly drained condition (drain spacing of 100 m), but were reduced to 2100 kg/ha for a 20 m spacing. Agricultural production and water quality goals are sometimes in conflict. Our results indicate that simulation modeling can be used to examine the benefits of alternative designs and management strategies, from both production and environmental points-of-view. The utility of this methodology places additional emphasis on the need for field experiments to test the validity of the models over a range of soil, site and climatological conditions.
Simulation of drainage water quality with DRAINMOD
Skaggs, R. W. (author) / Brevé, M. A. (author) / Mohammad, A. T. (author) / Parsons, J. E. (author) / Gilliam, J. W. (author)
1995
Article (Journal)
English
Simulation of drainage water quality with DRAINMOD
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