Putting Stormwater to Work: Recharge Pilots Underway

When it rains, where does the water go? In many cases, it runs off the land before it has a chance to soak into the ground and replenish our aquifers. The Sonoma County GSAs are working on several pilot projects to test whether improving land management practices can help change that — by slowing the flow of stormwater and directing it back into the ground.

The first pilot site is in the Santa Rosa Plain near Mark West Creek. Following the December rains, staff began applying water to both vineyard and fallow fields to recharge the groundwater below, a practice termed “On-Farm Recharge”. The project is comparing results on fields with cover crops versus those without, and is collecting data on groundwater levels, soil moisture, and underground conditions to understand what’s working and why.

Four additional pilot projects are currently in the planning and outreach stage and will focus on increasing stormwater recharge in upland areas.  Recharging water in upland areas can help reduce stormwater flood risks in lower, more urban areas and support groundwater sustainability throughout Sonoma County.

In the Santa Rosa Plain, a pilot is being planned for Crane Creek Regional Park.  Site investigations and modeling efforts have helped narrow down the best approaches for recharge. A primary goal of the Crane Creek pilot will be to slow down water flow; this will increase the time available for water to infiltrate to the groundwater and will allow sediment to deposit and fill in the incised channel.

In addition, three pilot projects are being planned on sites yet to be determined based on stakeholder and landowner meetings and feedback.

• Upland Stream Restoration to Reconnect Streams to Shallow Groundwater;
• Upland Vineyard Cover Cropping and Compost Applications to Increase Groundwater Storage;
• Swales on Contours to Increase Groundwater Storage on Upland Pasture and Rangeland.

The pilot projects are designed to answer practical questions such as: How quickly does water soak into the ground, and what factors — like soil type and cover crops — affect that rate?  The pilots hope to lay the groundwork for future projects by figuring out what it takes to run programs like these, from working with willing landowners to managing the day-to-day logistics.

Staff will use what they’ve learned from these pilots to estimate the costs and potential benefits of expanding on-farm and other stormwater recharge to a larger scale — an important step toward building a more resilient local water supply.

Pictured: (above) A vineyard field infiltrating on-farm Recharge water applied with a drip irrigation system. (below) Measuring the water application rate from drip irrigation used for on-farm recharge. Photos by Bachand & Associates.