Impacts of watershed physical properties and land use on baseflow at regional scales

Authors: ABOELNOUR, MOHAMED - Purdue University; ENGEL, BERNARD - Purdue University; FRISBEE, MARTY - Purdue University; GITAU, MARGARET - Purdue University; Flanagan, Dennis

Submitted to: Journal of Hydrology: Regional Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2021
Publication Date: 3/21/2021
Citation: Aboelnour, M.A., Engel, B.A., Frisbee, M.D., Gitau, M.W., Flanagan, D.C. 2021. Impacts of watershed physical properties and land use on baseflow at regional scales. Journal of Hydrology: Regional Studies. 35. Article 100810. https://doi.org/10.1016/j.ejrh.2021.100810.
DOI: https://doi.org/10.1016/j.ejrh.2021.100810

Interpretive Summary: Baseflow is water that moves into streams from groundwater and other delayed sources (via subsurface soil and rock layers), providing for perennial stream and river flows (as opposed to event flows that occur immediately after rainfall events). These continuous flows of water are critical for ecosystems near and in streams. Being able to determine the amount of baseflow is important, but can be difficult to predict without on-site water flow measurements, and most streams and watersheds are not monitored. In this research we used information from 130 monitored Texas stream sites to determine the baseflow at these locations. We then utilized other information about each site, including soils, topography, land use, and climate, and conducted statistical analyses to determine relationships and predictive equations for baseflow. The equations developed predicted the observed baseflow with high accuracy, and can be applied to other locations not monitored to provide good estimates of stream baseflows. These results impact conservation resource personnel, engineers, scientists, water resource planners, and others involved in determining water availability and the capacity of streams to sustain neighboring plants and animals, and potentially serve as an irrigation water resource. The techniques developed here could also be applied to other national and international locations.

Technical Abstract: Texas is a large state in the US that experiences a diversity of climate conditions and water demands. In this study, 130 stream gauging sites and their associated watershed physical and geological properties were used to develop multiple regression models to predict the Baseflow Index (BFI) across Texas. Calculated BFI was derived from USGS daily streamflow data from 1980 to 2017 using the two-parameter recursive digital filtering approach of the Web-based Hydrograph Analysis Tool (WHAT). Three scenarios were developed and validated. The first two scenarios related BFI to topography, climate and land use. The third scenario used surface geology mapping, soil type and hydrogeology parameters. The models developed showed high performance, low bias and low relative errors to predict BFI, with R-squared values varying from 0.72 to 0.99, and strong agreement with filtered BFI values. The results further showed that there was no specific pattern for BFI variation across Texas. Outputs indicated that evapotranspiration (ET) contributed to lower model accuracy, since the ET was not categorized as proportional to the percentages of cultivated areas within each basin, but was generalized to represent the whole catchment. The findings of this study are beneficial for water resources planning and management at local and regional scales in Texas. Additionally, the developed models can be applied to other areas that have similar topographic, lithological and climatic conditions. The equations developed that are reported here can support further research in groundwater modeling, by presenting independently obtained BFI estimation for ungauged sites.