Water Harvesting for Water Supply Security and Salmonid Recovery in a Coastal California Community

Summer 2014 Ecesis, Volume 24, Issue 2

In the hamlet of Bodega, in western Sonoma County, a program to develop alternative water supplies for residents and restore streamflows is being implemented. Water is a scarce resource in the predominantly rural coastal region of central California, especially during our dry season. The springs and streams along the coast must support a dispersed and growing population, as well as the wildlife dependent on the critical habitat they provide. Reducing summer water demands from these small creeks may be as important as implementing physical habitat restoration projects for coho salmon and steelhead population recovery. Roofwater harvesting systems and large-scale storage projects have been constructed in Bodega to provide local water security and improve streamflows for threatened and endangered salmonid species and other aquatic organisms.

In Bodega, as in much of the coastal California region, groundwater supplies are limited or non-existent. Bodega Water Company (BWC) is dependent upon a shallow well that draws from the water table adjacent to Salmon Creek. Several agricultural producers have similar shallow wells that supply their dairy and cattle operations. Rural residents along the creek use their riparian rights to provide non-potable water for landscaping and livestock watering. In drought years, sections of Salmon Creek in the Bodega Valley have gone dry.

Coastal streams in Central and Northern California commonly undergo a seasonal imbalance between water demands and instream flows. The Mediterranean climate, with its annual cycle of flooding and drought, is one of the most challenging environments for water management. Winter storms deliver several orders of magnitude more water than there is demand, and in most drainages even winter baseflows are an order of magnitude greater than daily demand. As streamflows decrease in the summer and fall, demand remains steady or increases due to irrigation needs. By the middle of summer there is more demand than the streams can sustainably supply in many areas. What we have is storage scarcity, not water scarcity.

The concept of using Bodega as a pilot community to test the viability of systematically replacing instream diversions with alternative water harvesting and storage systems to restore streamflow for salmonids and provide community water security was initiated in the mid-2000s by the Salmon Creek Watershed Council, Prunuske Chatham, Inc., and Occidental Arts and Ecology Center. A science-based watershed assessment process indicated that streamflow was limiting salmonid success in the watershed and that diversions were negatively impacting streamflows. Bodega had qualified as a disadvantaged community, the water rates are some of the highest in the state, and the residents had already implemented extensive water conservation practices. When federal (American Recovery and Reinvestment Act) and state (Integrated Regional Water Management Plan) funding programs were announced, the pieces were in place to move this multi-benefit project from planning to implementation. 

Prunuske Chatham, Inc., teamed with Gold Ridge Resource Conservation District (RCD) to secure design and construction funding for a suite of alternative water storage projects in the Bodega Valley. Gold Ridge RCD has managed implementation of the following projects to harvest the winter rains and runoff for use in the dry summer months:

  • In 2010, a total of nine rainwater catchment projects were installed: one underground, large-scale agricultural system (235,000 gallons); a catchment for the Bodega Volunteer Fire Department (35,000 gallons); and seven residential systems ranging in volume from 9,000 to 39,000 gallons. One agricultural pond was redeveloped for storage. The total rainwater storage capacity constructed was 490,000 gallons. 
  • In 2014, another seven rainwater catchment systems will be installed in Bodega for an additional total storage capacity of approximately 120,000 gallons.
  • A 1.4 million gallon roofwater catchment system for a dairy has been designed and will likely be constructed in 2015.
  • A 1.5 million gallon storage tank to replace dry season direct diversions is under design for Bodega Water Company and will likely be constructed in 2015 or 2016.

When completed, the total rainwater harvesting and alternative storage projects in the Bodega Valley will total over 3.5 million gallons (10.7 acre feet), and will replace the majority of the direct diversions along a 2-mile stretch of Salmon Creek. The average daily diversion reduction from this pilot program will be almost 20,000 gallons per day, or 0.03 cubic feet per second. While this is only a fraction of the volume needed to ensure stream riffle connectivity in very dry summers, it will reduce premature riffle desiccation and will prevent the wholesale drying of stream reaches adjacent to the larger diversions. Once all projects are constructed, the residents of Bodega will feel comforted knowing that their water supply is maintained and that their water use is not impairing salmon survival. — by Lauren Hammack, Principal Restoration Scientist, Prunuske Chatham, Inc.