Research Summary — Too Many Streams and Not Enough Time or Money? Analytical Depletion Functions for Streamflow Depletion Estimates

Conducted in locations across the Americas, the paper “Too Many Streams and Not Enough Time or Money? Analytical Depletion Functions for Streamflow Depletion Estimates” synthesizes results from extensive experiments around the effectiveness of analytical depletion functions for estimating the streamflow depletion that results from pumping groundwater. For many people there’s a disconnect in the thought process that pumping groundwater from wells can have impacts on rivers, streams, lakes and wetlands. The lack of consideration for the interconnection of surface and groundwater is a growing concern in many places around the world.

The two status quo methods for predicting streamflow depletion each have their shortcomings; numerical models demand substantial data and operator skill to develop robust estimates, while analytical models, though easy to implement with smaller data and experience requirements, are limited by several simplifying assumptions. Authors Qiang Li, Tom Gleeson, Samuel C. Zipper, and Ben Kerr describe an emerging method, analytical depletion functions (ADFs), to balance the limitations of both.

Maintaining the low data requirements and ease of implementation of analytical models, ADFs have expanded capabilities to provide estimates with a better agreement to those created by numerical models. Authors conducted detailed experiments across four pilot areas: the BX Creek Watershed and the Peace Region in British Columbia, Canada, the Navarro River Watershed in California, USA, and the Republican River, spanning Colorado, Kansas, and Nebraska, USA. In each pilot area, ADFs were compared with progressively more complex and elaborate models used on the numerical side. Though this does not mean that ADFs can replace numerical models, the research suggests they can be deployed in water management as a preliminary screening tool to identify where the numerical model is needed to address the environmental issues resulting from streamflow depletion. The real value of this study lies in the assembly of the results and the provision of recommendations to practitioners looking to learn how to efficiently understand streamflow depletion.