Estimation of Groundwater Budget Components Based on 30-year (1984-2013) Direct Observations in Illinois

Abstract:

In this study I examine the terrestrial water balance in Illinois, including all the soil moisture (SM), groundwater (GW), and snow store components, using water budget computations over the Illinois based on direct observations during a 30-year (1984-2013) study period. This unique and comprehensive long-term hydroclimatic dataset, as maintained by the Illinois State Water Survey since 1980’s covering the areas for the entire state, includes daily-to-monthly observational networks of precipitation, streamflow, snow, soil moisture and the depth to water table. The focus of this talk is on characterizing the significance of (shallow) GW in terrestrial water and energy cycles. Baseflow is estimated by using multiple techniques for baseflow separation, and the results are compared in order to estimate the uncertainty involved in this study. GW recharge is then estimated from the GW budget equation. The interactions between SM and GW is investigated based on estimated GW recharge. Also, GW-supported evapotranspiration is quantified and its role in sustaining dry-season (summer) evaporation is highlighted. Due to their similar order of magnitude, the incorporation of both SM and GW storages is indispensable for regional water balance estimation in humid areas such as Illinois, since GW aquifers provide a significant portion of terrestrial water storage changes at the monthly to interannual timescale.