POSITIVE AND NEGATIVE IMPACTS OF URBANIZATION ON BASEFLOW: A CASE STUDY FROM INDIANA

Baseflow is the flow in a stream or river that comes from groundwater discharge or seepage rather than direct runoff related to storm events. Land surface characteristics play an important role in recharging aquifers and hence sustaining baseflow. Thus, it is reasonable to expect that a change in land-use may affect baseflow. Urbanization is a pervasive and rapidly growing form of land-use change that increases impervious surface area which is usually thought to reduce recharge to groundwater. Decreases in baseflow due to urbanization have been widely reported, however because of the diversity of changes associated with urbanization it is unrealistic to conclude that all forms of urbanization reduce baseflow. Analyses of baseflow and urbanization trends in urban and rural watersheds in Indiana show that long-term effects of urbanization on baseflow can be highly complex. Urbanization in some cases is coincident with significant increases in baseflow. The style of development and associated hydrologic structures (water supply, retention and detention basins), as well as the location of the development with respect to recharge areas, and soil/land cover types being developed all play important roles in determining changes in the quantity of baseflow. Understanding how urbanization can in some cases increase baseflow can aid in management and decision-making related to water resources in urbanizing and urban watersheds, and can assist in the design of urban retrofit projects designed to improve urban aquatic habitat, particularly for critical low flow (baseflow) conditions.