Quantifying Streamflow Depletion from Groundwater Pumping: A Practical Review of Past and Emerging Approaches for Water Management

Abstract

Groundwater pumping can cause reductions in streamflow (“streamflow depletion”) that must be quantified for conjunctive management of groundwater and surface water resources. However, streamflow depletion cannot be measured directly and is challenging to estimate because pumping impacts are masked by streamflow variability due to other factors. Here, we conduct a management‐focused review of analytical, numerical, and statistical models for estimating streamflow depletion and highlight promising emerging approaches. Analytical models are easy to implement, but include many assumptions about the stream and aquifer. Numerical models are widely used for streamflow depletion assessment and can represent many processes affecting streamflow, but have high data, expertise, and computational needs. Statistical approaches are a historically underutilized tool due to difficulty in attributing causality, but emerging causal inference techniques merit future research and development. We propose that streamflow depletion‐related management questions can be divided into three broad categories (attribution, impacts, and mitigation) that influence which methodology is most appropriate. We then develop decision criteria for method selection based on suitability for local conditions and the management goal, actionability with current or obtainable data and resources, transparency with respect to process and uncertainties, and reproducibility.

Identifying hydrologic signatures associated with streamflow depletion caused by groundwater pumping

“…A range of approaches is used to model streamflow depletion from analytical models to statistical models and complex numerical models (Zipper et al, 2022). The most appropriate model varies depending on diverse factors including the research question of interest, data availability, and hydrological processes under investigation (Huang et al, 2018).…”

“…Reductions in streamflow caused by groundwater pumping, known as ‘streamflow depletion,’ can be considerably lagged from when pumping occurs and obscured by other causes of streamflow variability (Barlow & Leake, 2012). These confounding factors make it impossible to quantify streamflow depletion from observational streamflow data alone, presenting a major challenge to water management in settings with interacting groundwater and surface water resources (Zipper et al, 2022).…”

Overlooked risks and opportunities in groundwatersheds of the world’s protected areas

“…4a). GDEs within protected areas could be affected directly by groundwater pumping and contamination, and indirectly via climate change or land use change through their impact on groundwater recharge [39][40][41] . The timing and severity of these impacts are a function of the type, location and magnitude of the activity in conjunction with the local hydrogeological setting.…”

Groundwater depletion in California’s Central Valley accelerates during megadrought

“…In addition to a shortage of renewable freshwater, overpumping groundwater has led to falling to water tables 17 , streamflow depletion 18 , declining water quality and wells running dry 2 , as well as to environmental hazards such as land subsidence 19 , 20 , and wastewater intrusion 21 . To combat these threats, California enacted its Sustainable Groundwater Management Act (SGMA) in 2014, requiring high- and medium-priority groundwater basins (as identified based on groundwater demands by the state’s SGMA Basin Prioritization 22 ) to develop and implement management plans to achieve sustainable levels of groundwater pumping and recharge by 2042 23 , 24 .…”