Groundwater management in the prime agricultural region of California’s Central Valley is expected to benefit from a new computational approach engineered at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (BNL). High-resolution images derived by satellite are paired with advanced computer modeling to estimate aquifer volume change from observed ground deformation. The method could help streamline groundwater tracking across a region once multiple local management agencies begin submitting water management plans to comply with the 2014 Sustainable Groundwater Management Act.

The state law, enacted in response to groundwater overuse during periods of persistent drought requires water users to halt overdraft and bring critically overdrawn groundwater basins into balanced levels of pumping and recharge by 2040. Local groundwater sustainability agencies tasked with developing sustainableVolume change per well (left) obtained from satellite range change observations corresponding to the water year 2018, a year with rainfall near the historical average. Water usage for a selected set of wells (center) with measured flow meters. Estimated yearly water usage over the Tulare basin area (right) calculated from the distribution of crops and the water needs of each plant or animal. Source: Donald W. Vasco et al.Volume change per well (left) obtained from satellite range change observations corresponding to the water year 2018, a year with rainfall near the historical average. Water usage for a selected set of wells (center) with measured flow meters. Estimated yearly water usage over the Tulare basin area (right) calculated from the distribution of crops and the water needs of each plant or animal. Source: Donald W. Vasco et al. management policies for oversubscribed groundwater basins must now estimate groundwater use and aquifer storage capacity without sufficient monitoring data.

Realizing the need for a monitoring tool that can be applied at different spatial scales and resolutions, BNL scientists turned to data from Synthetic Aperture Radar satellites representing observed surface subsidence, or where land is sinking and groundwater storage capacity has shrunk. The data provide a detailed and macro-level indication of aquifer compaction, a process sensitive to groundwater levels across the Central Valley. Satellite observations were combined with a public database of wells drilled in California in order to estimate the spatial distribution of the aquifer volume that is lost each month due to pumping.

[See also: NASA maps monitor global groundwater and drought conditions]

The results published in Scientific Reports show that aquifer volume is influenced by variations in effective pressure in the ground surrounding documented wells. Spatial patterns of changes in aquifer volume varied significantly among study years representing drought (October 2015 to 2016), precipitation (2017) and near-average rainfall (2018). The trends reflect deviations in groundwater pumping, which change depending upon surface water deliveries to farmers.

These spatially explicit estimates of aquifer volume loss are relatively inexpensive to obtain and aid local agencies in estimating localized areas of intensive pumping and groundwater overconsumption.

To contact the author of this article, email shimmelstein@globalspec.com