Drought Mitigation Through Riparian Restoration
By Irv Schiffman, Board Chair
California is presently experiencing one of the most severe droughts on record. The extreme drought and heat have depleted reservoirs and caused unsustainable pumping of groundwater. As a consequence the state legislature is considering a historic change that would regulate water drawn from the ground.
A drought in California has most serious effects on the Central Valley, California’s agricultural heartland, and the region of the state where many of River Partner’s restoration activities take place. The rivers and groundwater of the Central Valley provide irrigation for thousands of acres of farmland and drinking water for millions of Valley residents. In addition, a sufficient supply of river water keeps aquatic wildlife from going extinct. A continued drought has the consequence of reducing the volume of water in both the region’s rivers and underground reservoirs.
A drought is a natural phenomenon caused by changes in weather patterns resulting in less than normal rainfall. While we cannot easily manufacture more rain, we can manage our floodplains to help mitigate some of the consequences of drought.
Such mitigation includes maintaining the cleanliness of waterways and groundwater. Our restoration areas are frequently adjacent to working farmlands and the vegetation that we plant forms a natural buffer that filters agricultural runoff and keeps non-point source pollutants, particularly nitrogen, out of the river and the subsurface water supply.
One of the more important drought mitigation measure provided through riparian restoration is an increase in groundwater. According to the California Department of Water Resources groundwater provides close to 40 percent of the state’s water supply in an average year and during extensive dry or drought years, groundwater can provide close to 60 percent of the state’s water supply. An increased recharge of subsurface water takes place when levees are moved back from the river, thus enlarging the flood plain and allowing floodwaters to wash over the newly restored acreage. River Partners fully supports levee setbacks and levee breaching as a means to reduce flood dangers and to reinstate the natural functions of the floodplain. We have restored hundreds of acres of floodplain land at the confluence of the Feather and Bear Rivers and along the Feather River south of Marysville where levees have been set back 600 feet in the first instance and almost a half-mile in the second.
Water conservation is, of course, essential during drought periods (and otherwise) and the replacement of flood threatened agricultural fields and orchards with riparian vegetation reduces the need for pumping groundwater. By retiring such crop or orchard land we are retiring agricultural irrigation on that property.
For example, on the 2,000 acres of property River Partners owns in the San Joaquin Valley, we will retire 10,000 acre-feet of water per year. This is a net water saving of 3,258,510,000 gallons per year! We irrigate our own plantings only in the first three years and then they are on their own.
California is expected to suffer more frequent floods and droughts in the future, a likely consequence of climate change. As seen above, the science of riparian restoration can serve to mitigate some of the problems brought on by these weather conditions, contributing to the sustainability of groundwater resources and the overall protection and conservation of water.
The above article originally appeared in the August 2014 issue of the River Partners Journal.