CHANGING CLIMATE AND LAND-USE IMPACTS ON INDIANA'S STREAM BASEFLOW

Baseflow is a genetic component of stream flow that comes from groundwater storage or other delayed sources. Thus changes in baseflow can significantly impact the quantity and quality of stream flow and fluvial ecosystems. However, unlike a large number of studies that show the effects of climate and land-use changes on peak stream flow, little work to date has addressed their impacts on baseflow. A total of twenty-two urban and rural watersheds in Indiana with different sets of geology, physiography, and land-use were statistically analyzed for trends in annual stream baseflow for past thirty five years. A significant increasing trend in baseflow was found in Indiana's urban and rural watersheds. For watersheds with no significant increase in precipitation, urban watersheds showed the most striking increase in long-term baseflow. One of the important observations of this study was the increase in baseflow in Indiana's rural watersheds. The increasing trend of baseflow in rural watersheds is likely due to the increased level and efficiency of tile drainage in Indiana, and conversion of previously untilled land or perennial cover crops to row crops. Leakage from storm sewers, detention basins, wastewater treatment plants, and reduced evapotranspiration associated with urbanization are some of the causes attributed for increased baseflow in urban streams. Sources contributing to increased baseflow in urban and rural streams may also potentially pollute aquifers. Thus, a better understanding of trends in baseflow and likely sources of these changes are important for water resources management in both urban as well as rural areas.