Groundwater Pumping and Stream Depletion

Stream Depletion by Ground Water Pumping: A Stream Depletion Factor for the State of Oklahoma

A research project reported on in the OWRRI 2010 Annual Report is titled Stream Depletion by Ground Water Pumping: A Stream Depletion Factor for the State of Oklahoma. The goal of this research is to develop a stream depletion factor for analyzing the impact of groundwater pumping on stream flow. Two major alluvial river systems in Oklahoma, the North Canadian and Washita Rivers, were selected as test subjects.

Tasks of the study include performing tests at sites adjacent to both rivers to estimate the degree of interaction between the stream and the alluvial groundwater, and to test various existing equations for modeling the connection between stream water and adjacent groundwater for use in Oklahoma. To gather the data needed, researchers placed a series of 25-foot-deep monitoring wells between the river and adjacent municipal extraction wells at each site. Well pumps were then shut down for a period of days so groundwater levels could reestablish non-impacted conditions.  The pumps were then restarted and data logs in each well recorded the groundwater level and water temperature for approximately 90 hours. The levels were plotted over time and compared to levels predicted by various equations.

The recently-published report contains only the results for the tests along the North Canadian River. The analytical solutions predicted that after one day of pumping, 30 to 35 percent of the flow pumping from the well was groundwater flowing from the stream. After five days, the figure rose to 60 to 70 percent. Continuing work includes a similar test along the Washita River where hydrologic and streambed conditions are more diverse.
OCC will follow this research and report findings as they become available.