Melinda K. Brown

Climate and agricultural land use change impacts on streamflow in the upper midwestern United States

Increased streamflow and its associated impacts on water quality have frequently been linked to changes in land use and land cover (LULC) such as tile drainage, cultivation of prairies, and increased adoption of soybeans (Glycine max) in modern day cropping systems. This study evaluated the relative importance of changes in precipitation and LULC on streamflow in 29 Hydrologic Unit Code 008 watersheds in the upper midwestern United States. The evaluation was done by statistically testing the changes in slope and intercept of the relationships between ln(annual streamflow) versus annual precipitation for the periods prior to 1975 (prechange period) and after 1976 (postchange period). A significant shift either in slope or intercept of these relationships was assumed to be an indication of LULC changes whereas a lack of significant shift suggested a single relationship driven by precipitation. All 29 watersheds showed no statistical difference in slope or intercept of the relationships between the two periods. However, a simpler model that kept the slope constant for the two periods showed a slight upward shift in the intercept value for 10 watersheds in the postchange period. A comparison of 5 year moving averages also revealed that the increased streamflows in the postchange period are mainly due to an increase in precipitation. Minimal or the lack of LULC change impact on streamflow results from comparable evapotranspiration in the two time periods. We also show how incorrect assumptions in previously published studies minimized precipitation change impacts and heightened the LULC change impacts on streamflows.

Reply to comment by Keith E. Schilling on “Climate and agricultural land use change impacts on streamflow in the upper Midwestern United States”

This reply addresses concerns raised by Schilling (2016, doi:10.1002/2015WR018482) on Gupta et al. (2015a, doi: 10.1002/2015WR017323, 2015b, doi:10.1002/2015WR017323). To this end, we provide additional analysis of the Raccoon River flows in Iowa and show that both annual streamflow and baseflow are mainly controlled by precipitation.

Reply to comments on “Climate and agricultural land use change impacts on streamflow in the upper Midwestern United States” by Schottler et al.

The reply addresses concerns raised by Belmont et al. [2016] on Gupta et al. [2015] through additional analysis of streamflow vs. precipitation relationships for the Whetstone and the Redwood Rivers and with data on available soil moisture in prechange and postchange periods in the Cottonwood River watershed. This article is protected by copyright. All rights reserved.

Reply to comment by Foufoula-Georgiou et al. on “Climate and agricultural land use change impacts on streamflow in the upper midwestern United States”: REPLY TO COMMENT BY FOUFOULA-GEORGIOU ET AL.

This reply addresses concerns raised by Foufoula-Georgiou et al. [2016] on Gupta et al. [2015] through additional regression analysis of streamflow and base flow and with description of the water quality conditions in the Minnesota River prior to European settlements in 1850s. This article is protected by copyright. All rights reserved.