By Erica Gies | Scientific American
Pajaro Valley on the coast of central California has little surface water, so its farmers depend on extracting groundwater to grow leafy greens and berries for the global market. But as in many places around the world, these farmers have been pumping the water out faster than nature can replenish it. In different places, groundwater decline can cause various impacts: it can make land sink, streams, wetlands, and wells dry up and seawater creep inland under the ground. And because most pumped groundwater irrigates crops, major declines in availability could lead to a global food crisis.
In some places, water managers actively refill groundwater to ameliorate this tragedy of the commons. One method of doing so is to divert stormwater runoff into scooped basins that have been built over porous ground into which the water quickly sinks. An initiative in Pajaro Valley has been working to show how to make this vision a reality for more than a decade. Called recharge net metering (ReNeM), the idea is similar in some ways to rooftop solar net metering, which compensates homeowners for any excess energy they generate and feed into the grid. Using ReNeM, the Pajaro Valley Water Management Agency compensates landowners for a percentage of the amount of water they infiltrate underground.
