Impacts of Land Management Changes On Streamflow in the Northern Wabash River Basin.

In 2008, flooding resulted in property loss of $3.3 billion in the United States and 11 lives in Indiana.  The Wabash River contains an undammed stretch in excess of 700km—the longest east of the Mississippi River—draining an intensively managed landscape (74% cropland, 11% forest and 6% urban).  The recently glaciated landscape includes low topographic gradients and underlying dense till which restricts vertical water movement.  Agricultural production on the nutrient rich soils relies on artificial drainage, both surface ditches and sub-surface tiles.  It is currently estimated that at least 50% of all cropland in Indiana has drainage improvement and over 80% of the original wetlands in the state have been lost.  Trend analysis for the 72 USGS stream gauges in Indiana that are free from upstream regulation suggests that there are some increasing high flow statistics in the last 60 years, particularly in the northern till plains.  At the field scale, tile drains reduce peak flows by increasing water storage capacity between rain events, but the loss of depressional storage at the watershed scale is less understood.  In this study, terrain attributes, GIS techniques, and digital soil mapping are used to create spatially continuous, contemporaneous and historic soil property maps.  Extracted values from the maps along with current and historic land cover data are used as inputs to the VIC hydrologic model to simulate past and present streamflow.  Both an observational and modeling perspective will be used to quantify the anthropogenic change in water storage and residence time across the landscape and the implications for the Wabash River system.