Evaluation of Stream Depletion from Groundwater Pumping Using the Time-Series Thermal Method

Derrik Williams is giving a talk tomorrow at the CA-NV AWWA Spring Conference in Anaheim. The talk is at 8:30 AM in the Water Management and Efficiency committee’s joint session with the Water Well Technology committee. Here is the abstract

Evaluation of Stream Depletion from Groundwater Pumping Using the Time-Series Thermal Method

Derrik Williams, Stephen Hundt, and Georgina King

A recent study (Hydrometrics, 2013) was undertaken to estimate the impacts that a municipal supply well has on the streamflow in a nearby stream. Aquifer and streambed properties were collected from a combination of traditional and novel field techniques, including aquifer tests and the time-series thermal method of Hatch (1999). The hydraulic properties derived from these analyses were used with the analytical solution of Hunt (1999) to estimate the streamflow depletion that occurs due to the operation of a nearby pump.

The Hunt (1999) solution computes the streamflow depletion that occurs when a nearby well pumps from an unconfined aquifer that is connected to the stream through a semipervious streambed layer. The analytical solution gives an easy and flexible way of estimating the impact that a single well has on a stream – provided that appropriate values of streambed conductance and aquifer transmissivity can be found and that the assumed hydrologic conditions and field conditions closely match. All field measurements were collected from locations near the pumping well of concern, and data collection and analysis techniques were chosen that measure the aquifer and streambed parameters used by the Hunt solution as directly as possible. Streambed conductance was estimated by combining streambed seepage rates found with the time-series thermal method and vertical gradients captured from vertically separated piezometers. Aquifer transmissivity was estimated from an aquifer test that was carried out during the same period in which streambed measurements were collected. Pumping was drawn from the well of concern. A second pumping test helped corroborate the match of the hydraulic conditions with those assumed by the Hunt solution by revealing the impact of additional boundaries. The insight gain through the analytical solution, and the defensibility of the techniques used to support it, provide a valuable tool in managing for the dual goals of water supply and ecosystem protection.

References:

Hatch, C.E., A.T. Fisher, J.S. Revenaugh, J. Constantz, and C. Ruehl, C. 2005, Quantifying Surface Water – Ground Water Interactions Using Time Series Analysis of Streambed Thermal Records: Method Development, Water. Resour. Res., 42(10): 10.1029/2005WR004787.

Hunt, B. 1999. Unsteady stream depletion from ground water pumping. Ground Water, 37(1), 98-102.

HydroMetrics Water Resources Inc. 2013. Task 4.1: Technical memorandum on seasonal creek/aquifer interactions. Prepared for Squaw Creek Public Service District.

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