Hydrologic Evaluation of River Basin Scale Tillage Effects on Non‐Point Source Loads from Upland Crop Areas†

Abstract

AbstractThis study used the Hydrological Simulation Program—Fortran (HSPF) model to evaluate the river basin scale effects of nonpoint source (NPS) pollution loads caused by tillage and no‐tillage applications to upland crop areas. The study site was the Byulmi‐cheon river basin (1.21 km2) of South Korea. Hourly rainfall, discharge and stream water quality data for 2 years (2012–2013) were collected at the river basin outlet. The HSPF model under tillage conditions was calibrated using 23 rainfall events with an average Nash–Sutcliffe model efficiency value for runoff of 0.61 and determination coefficients for sediment, total nitrogen (T‐N) and total phosphorus (T–P) of 0.58, 0.61 and 0.62 respectively. The field experiment results from the no‐tillage plots with slopes of 3 and 8% under radish and sesame cultivation showed decreases in the runoff ratio, sediment, T‐N and T–P of 10.8, 81.7, 11.9 and 17.1% respectively. The HSPF model parameters soil bulk density (BD) and soil infiltration capacity (INFILT) were controlled for the upland crop areas during the evaluation of the no‐tillage effects. By increasing the parameter values from 1.33 Mg m−3 BD and 4.1 mm h−1 INFILT for the tillage condition to 1.90 Mg m−3 BD and 8.9 mm h−1 INFILT for the no‐tillage condition, the river basin runoff ratio and sediment, T‐N and T–P values were reduced by 10.3, 56.7, 18.3 and 35.9% respectively. Copyright © 2016 John Wiley & Sons, Ltd.