Andrew C. Kessler

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.

Woody Invasions of Urban Trails and the Changing Face of Urban Forests in the Great Plains, USA

Abstract Corridors such as roads and trails can facilitate invasions by non-native plant species. The open, disturbed habitat associated with corridors provides favorable growing conditions for many non-native plant species. Bike trails are a corridor system common to many urban areas that have not been studied for their potential role in plant invasions. We sampled five linear segments of urban forest along bike trails in Lincoln, Nebraska to assess the invasion of woody non-native species relative to corridors and to assess the composition of these urban forests. The most abundant plant species were generally native species, but five non-native species were also present: white mulberry (Morus alba), common buckthorn (Rhamnus cathartica), tree-of-heaven (Ailanthus altissima), honeysuckle (Lonicera spp.) and elm (Ulmus spp.). The distribution of two of the woody species sampled, common buckthorn and honeysuckle, significantly decreased with increasing distance from a source patch of vegetation (P  =  0.031 and 0.030). These linear habitats are being invaded by non-native tree and shrub species, which may change the structure of these urban forest corridors. If non-native woody plant species become abundant in the future, they may homogenize the plant community and reduce native biodiversity in these areas.

Lidar quantification of bank erosion in Blue Earth County, Minnesota

Sediment and phosphorus (P) transport from the Minnesota River Basin to Lake Pepin on the upper Mississippi River has garnered much attention in recent years. However, there is lack of data on the extent of sediment and P contributions from riverbanks vis-à-vis uplands and ravines. Using two light detection and ranging (lidar) data sets taken in 2005 and 2009, a study was undertaken to quantify sediment and associated P losses from riverbanks in Blue Earth County, Minnesota. Volume change in river valleys as a result of bank erosion amounted to 1.71 million m over 4 yr. Volume change closely followed the trend: the Blue Earth River > the Minnesota River at the countys northern edge > the Le Sueur River > the Maple River > the Watonwan River > the Big Cobb River > Perch Creek > Little Cobb River. Using fine sediment content (silt + clay) and bulk density of 37 bank samples representing three parent materials, we estimate bank erosion contributions of 48 to 79% of the measured total suspended solids at the mouth of the Blue Earth and the Le Sueur rivers. Corresponding soluble P and total P contributions ranged from 0.13 to 0.20% and 40 to 49%, respectively. Although tall banks (>3 m high) accounted for 33% of the total length and 63% of the total area, they accounted for 75% of the volume change in river valleys. We conclude that multitemporal lidar data sets are useful in estimating bank erosion and associated P contributions over large scales, and for riverbanks that are not readily accessible for conventional surveying equipment.

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.