PCC June July 2021 e

Identifying the Potential
and Impacts of On-Farm
Groundwater Recharge
Scientists explore agronomic impacts and best scenarios for success
of winter-time flooding to recharge depleted groundwater tables.
By JEANETTE WARNERT | Communications Specialist, UC ANR
On-farm recharge has the potential to clean up groundwater that has been contaminated with nitrogen and/or pesticides (photo by H.
Dahlke.)
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Aquifers have become depleted from decades of
overuse. Drilling deeper is an option for farmers, but
prohibitively expensive for low-income residents in
disadvantaged communities in the San Joaquin Valley.
A UC scientist believes managed aquifer recharge on agricultural
lands close to populations with parched wells is a
hopeful solution.
Helen Dahlke, professor in integrated hydrologic sciences
at UC Davis, has been evaluating scenarios for flooding
agricultural land when excess water is available during
the winter in order to recharge groundwater. If relatively
clean mountain runoff is used, the water filtering down
to the aquifer will address another major groundwater
concern: nitrogen and pesticide contamination.
“The recharge has the potential to clean up groundwater,”
she said.
Five years ago, UCCE Specialist Toby O’Geen developed
an interactive map (casoilresource.lawr.ucdavis.edu/sagbi/)
that identifies 3.6 million acres of California farmland
with the best potential for replenishing the aquifer
based on soil type, land use, topography and other factors.
Dahlke and her colleagues analyzed the map and identified
nearly 3,000 locations where flooding suitable ag land
will recharge water for 288 rural communities, half of
which rely mainly on groundwater for drinking water. The
research was published by Advancing Earth and Space
Science in February 2021.
Continued on Page 32
30 Progressive Crop Consultant July / August 2021