WCR: A New Technique for Mapping Recharge Fluxes to Groundwater at a Regional Scale

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

0225782 Szilagyi Naturally occurring long-term mean annual recharge to groundwater over a large region (i.e. the state of Nebraska) will be estimated with the help of a water balance approach coupled with an automated baseflow-separation technique. Evapotranspiration is to be calculated with the WREVAP model at the Solar and Meteorological Surface Observation Network (SAMSON) sites. Mean annual base recharge will be obtained by the product of Long-term mean annual runoff (the difference between precipitation [about 400 stations] and evapotranspiration) and the Baseflow Index using discharge data from the USGS gaging stations (about 130 stations) in Nebraska. Base recharge will be augmented by the amount of evapotranspiration that comes directly from groundwater and will be obtained by using satellite-derived multi-year Normalized Difference Vegetation Indices to locate the areas where this happens. Mapping will be achieved using Geographic Information Systems technology and geostatistics. This work builds upon recent advances in hydrology (the WREVAP model using Bouchet's complementary hypothesis which proved to be pivotal in explaining climate-induced changes in the hydrologic cycle [see this author's works on evaporation trends: http://csd.unl.edu/csd/ staff/szilagyi/szilagyi.html], and the automated baseflow separation algorithm) while making use of remote sensing and GIS. The present approach can easily be extended to continental scales to define fluxes to the groundwater which may become important in the understanding of the global hydrologic cycle as it relates to climate change. Currently there is no standard approach in estimating recharge fluxes to the groundwater, especially at a regional scale. The existing approaches generally build upon the use of complex water balance and/or hydro-geological models, with typically large number of parameters related to: soil and vegetation type and status, and diverse aquifer properties (permeability, saturated thickness, etc.), many of which must be optimized. Instead, the proposed approach utilizes measured data of streamflow, precipitation and a state-of-the-art evaporation estimation technique enhanced by satellite remote sensing images without the need of complex modeling and parameter optimization.