Title: | Perennial vegetation impacts on stream discharge and channel sources of sediment in the Minnesota River Basin |
Authors: | Dalzell, B.J. and D.J. Mulla |
Year: | 2018 |
Journal: | Journal of Soil and Water Conservation |
Volume (Issue): | 73(2) |
Pages: | 120-132 |
Article ID: | |
DOI: | 10.2489/jswc.73.2.120 |
URL (non-DOI journals): | |
Model: | SWAT |
Broad Application Category: | hydrologic and pollutant |
Primary Application Category: | BMP and/or cropping system assessment |
Secondary Application Category: | sediment loss and transport |
Watershed Description: | 90 km^2 Seven Mile Creek, a tributary of the Minnesota River located in south central Minnesota, U.S. |
Calibration Summary: | |
Validation Summary: | |
General Comments: | |
Abstract: | While sediment loads in streams draining agricultural landscapes have traditionally
been attributed to field sources via overland flow and surface erosion, recent research has
identified important nonfield sources of sediment in the Minnesota River Basin. We evaluate
the impacts of altered vegetation on water budget and sediment loading in Seven Mile Creek,
an agricultural watershed with important nonfield sources of sediment. Using the Soil and
Water Assessment Tool (SWAT) and monitoring data for different locations, we developed an
approach to account for different sediment sources and show that nonfield sediment export
is strongly affected by changes in stream discharge, which is affected by vegetation impacts
on water yield. This is important because many watershed-scale models are calibrated to
sediment loads at the watershed outlet based on the assumption that all sediment is derived
from field sources. This can lead to overestimation of erosion from field sources and unrealistic
expectations for watershed-scale reductions based on some conservation practices. In
Seven Mile Creek watershed under current conditions, approximately 76% of the sediment
delivered to the watershed outlet originates from nonfield sources (streambanks and ravines).
Relative to the current landscape, increases in perennial grasses or switchgrass (Panicum virgatum
L.) cause decreases in water yield owing to differences in evapotranspiration (especially
in the spring). As streamflow decreases, sediment export is disproportionately reduced from
nonfield sources. These results demonstrating an interaction between evapotranspiration and
streambank/ravine erosion are important for showing that nonfield sources of sediment can
be important in some watersheds, and that realistic approaches for improving water quality
may need to include strategies for managing water quantity. |
Language: | English |
Keywords: | perennial vegetation; sediment; streambank erosion; SWAT model; tile drainage |