2 research outputs found
Implications of Using On-Farm Flood Flow Capture To Recharge Groundwater and Mitigate Flood Risks Along the Kings River, CA
The agriculturally productive San
Joaquin Valley faces two severe
hydrologic issues: persistent groundwater overdraft and flooding risks.
Capturing flood flows for groundwater recharge could help address
both of these issues, yet flood flow frequency, duration, and magnitude
vary greatly as upstream reservoir releases are affected by snowpack,
precipitation type, reservoir volume, and flood risks. This variability
makes dedicated, engineered recharge approaches expensive. Our work
evaluates leveraging private farmlands in the Kings River Basin to
capture flood flows for direct and <i>in lieu</i> recharge,
calculates on-farm infiltration rates, assesses logistics, and considers
potential water quality issues. The Natural Resources Conservation
Service (NRCS) soil series suggested that a cementing layer would
hinder recharge. The standard practice of deep ripping fractured the
layer, resulting in infiltration rates averaging 2.5 in d<sup>–1</sup> (6 cm d<sup>–1</sup>) throughout the farm. Based on these
rates 10 acres are needed to infiltrate 1 cfs (100 m<sup>3</sup> h<sup>–1</sup>) of flood flows. Our conceptual model predicts that
salinity and nitrate pulses flush initially to the groundwater but
that groundwater quality improves in the long term due to pristine
flood flows low in salts or nitrate. Flood flow capture, when integrated
with irrigation, is more cost-effective than groundwater pumping
Experimental Dosing of Wetlands with Coagulants Removes Mercury from Surface Water and Decreases Mercury Bioaccumulation in Fish
Mercury
pollution is widespread globally, and strategies for managing
mercury contamination in aquatic environments are necessary. We tested
whether coagulation with metal-based salts could remove mercury from
wetland surface waters and decrease mercury bioaccumulation in fish.
In a complete randomized block design, we constructed nine experimental
wetlands in California’s Sacramento–San Joaquin Delta,
stocked them with mosquitofish (Gambusia affinis), and then continuously applied agricultural drainage water that
was either untreated (control), or treated with polyaluminum chloride
or ferric sulfate coagulants. Total mercury and methylmercury concentrations
in surface waters were decreased by 62% and 63% in polyaluminum chloride
treated wetlands and 50% and 76% in ferric sulfate treated wetlands
compared to control wetlands. Specifically, following coagulation,
mercury was transferred from the filtered fraction of water into the
particulate fraction of water which then settled within the wetland.
Mosquitofish mercury concentrations were decreased by 35% in ferric
sulfate treated wetlands compared to control wetlands. There was no
reduction in mosquitofish mercury concentrations within the polyaluminum
chloride treated wetlands, which may have been caused by production
of bioavailable methylmercury within those wetlands. Coagulation may
be an effective management strategy for reducing mercury contamination
within wetlands, but further studies should explore potential effects
on wetland ecosystems