Stanford And University Of Calgary Researchers Map Saltwater Intrusion In California Coast

Stanford University and University of Calgary researchers were able to transform pulses of electrical current sent 1,000 feet below ground into an image of where seawater has infiltrated freshwater aquifers. The scientists have mapped saltwater intrusion along the Monterey Bay coastline.

The study will help explain factors controlling the saltwater phenomenon. This is also expected to help improve the groundwater models that local water managers utilize in making decisions about pumping groundwater to meet the need for drinking or farming, Phys.org reported.

Meredith Goebel, a PhD candidate at Stanford's School of Earth, Energy & Environmental Sciences, said that they hope the local managers can use their findings to better spot regions that are most affected by saltwater intrusion. She added that the study can help targeted management practices be more effective.

Rosemary Knight, Goebel's graduate advisor and he George L. Harrington Professor at Stanford, admitted that she believes Earth imaging using geophysical methods can help manage the health of groundwater systems in the same way as medical imaging has played a significant role in the management of human health. Knight specializes in using geophysical imaging tools to monitor and manage freshwater resources.

The researchers used a geophysical imaging technique named electrical resistivity tomography (ERT) to map the salinity of groundwater along the stretch of the California Central coast. Seawater is said to be electrically conductive because of its high salt content while freshwater is electrically resistive.

According to Stanford's official website, ERT is a better and cheaper alternative to the current method used to monitor saltwater intrusion. The method done today involves drilling "sentinel" wells at specific locations.

Knight noted that this only provides information on one location. The ERT, on the other hand, can give scientists a full 2D slice with spatial coverage which cannot be done with sentinel wells. These wells are also expensive and it cost nearly $1 million to drill four of the wells along Monterey Bay.