The effects of incorporating agricultural conservation practices at the farm- and management-scales in the Czech landscape

Abstract

<p>SWAT (Soil and Water Assessment Tool) is an open-access hydrologic, basin-scale model; it is the most popular hydrologic model in modern literature. SWAT contains hundreds of editable parameters making it a flexible option for nearly any basin.</p><p>There is a significant precedent for incorporating agricultural conservation practices into SWAT.  Contour farming results in a reduction of surface runoff by impounding water in small depressions as well as a reduction of sheet and rill erosion by reducing the erosive power of surface runoff and preventing or minimizing the development of rills. This practice is represented by adjusting the SCS curve number in SWAT. Residues are meant to slow down surface and peak runoff by increasing surface roughness. They also increase infiltration and reduce surface runoff by decreasing surface sealing and slowing down overland flow. Finally, residues reduce sheet and rill erosion by reducing surface flow volume. Conservation tillage and residue management are represented by adjusting the curve number and manning’s roughness coefficient for overland flow, respectively. Filter strips can be placed per HRU (so can be place only along a stream or between fields) & their trap efficiency is based on width of the strip. The equation is derived from the 1978 USDA Agricultural Handbook, but many studies have pointed out issues with this method- as the filter strip width approaches 30m, the sediment trap efficiency approaches 1. A sediment trap efficiency close to 1 is only seen in plot-scale, shallow slope, field experiments during which uniform flow (not concentrated flow) is achieved. We instead assigned a filter strip width back calculated from typical filter strip trap efficiencies calculated in field experiments locally.  </p><p>In addition to the filter strip, contour farming, reduced tillage, and residue management scenarios, we also ran field size reduction scenarios at the farm- and subbasin-scale in two Czech basins, Nučice and Vrchlice. We were able to utilize SWAT to determine the effects of various agricultural management practices on the small water cycle in two Czech basins ranging from 0.5 to 100 km<sup>2</sup>.</p><p>Acknowledgment: The presented research has been performed within project H2020 No. 773903 Shui, focused on water scarcity in European and Chinese cropping systems and the Grant Agency of Czech Technical University in Prague, No. SGS20/156/OHK1/3T/11.</p>