Simulation Of Soil Erosion In The Palouse Prairie Of The Pacific Northwest

Author : Mugal Samrat Dahal
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (124 download)

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Download or read book WEPP Simulation of Water Erosion on Cereal Ground Cropland i the Inland Pacific Northwest written by Mugal Samrat Dahal and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The inland Pacific Northwest (PNW) is characterized warm, dry summers and wet winters with three (high, intermediate, and low) precipitation zones. In the inland PNW, high erosion rates are attributed to hilly topography, highly erodible silt loam soil, rainy winter seasons with frequent freeze-thaw events, and widespread use of conventional tillage practices. A 1978 USDA study showed that annual water erosion from cropland in the region’s Palouse River basin averaged 20.6 t ha−1. A more recent 2009 study reported simulated average annual erosion rates of 10, 13, and 11 t ha−1 for the low-, intermediate-, and high-precipitation zones, with erosion in the intermediate-precipitation zone exceeding the tolerable limit of 11 t ha−1 despite increase of conservation practices. Identifying source areas for targeted, effective management requires understanding the factors affecting water erosion, especially how tillage practices and crop rotation interact in various topographic, soil, and climatic settings. The objectives of this study are to (i) understand how hillslope hydrological and water erosion processes are influenced by key environmental factors (soil, climate, topography) and management practices (tillage, crop rotation), and (ii) assess the spatial distribution of soil erosion for each county and precipitation zone over the last 30 years. I addressed these objectives by compiling various combinations of soil, climate, topography, tillage and crop rotation and simulating these combinations county by county with WEPP. WEPP simulations show that erosion rate is lowest in the low-precipitation zone and highest in the intermediate-precipitation zone, exceeding the tolerable limit in many cases. Temporally, high precipitation events and fallow periods in the rotation greatly increase erosion. Average annual erosion rates in Whitman County are 8.2, 13.8, and 9.8 t ha−1 in the low-, intermediate-, and high-precipitation zones. The intermediate-precipitation zone has the greatest total annual erosion, 3.0×106 t, despite having the smallest area. Columbia County has the highest erosion rate with 17.9 t ha−1 yr−1. GIS maps based on the simulations reveal critical-source areas (“hotspots”) where estimated erosion rates are more than five times the average rates, providing crucial information for, and advancing our understanding of, targeting management and increasing efficiency of conservation practices.