By Scott Hamilton, President, Hamilton Resource Economics
Roughly every two years, the California Department of Water Resources issues its “Delivery Capability Report” for the State Water Project (SWP). Those studies estimate the amount of SWP water that can be delivered each year, based on simulations of current facilities and regulations applied to over 70 years of historic hydrology. The first study conducted in 2001, indicated that on average, 72% of contracted water entitlements could be delivered annually. During a 6-year drought, average deliveries would drop to 41% of the contracted amount. Since then, regulations to protect endangered fish have reduced exports. DWR just released its 2023 Delivery Capability Report. Average annual deliveries are now estimated at 55% of contracted entitlement with deliveries through a six-year drought now expected to be 23%.
Usually, the Department will also provide forecasts which consider predictable future changes in supply. In the 2023 report, they considered the consequences of different levels of climate change. Climate change is expected to affect project yield in two ways. First, more precipitation is expected to come as rain rather than snow. Reservoirs that are being operated for flood protection have to release that runoff to preserve capacity for future flood events. Those releases do not often result in an increase in exports because there is no additional capacity available downstream to store that water. Second, with sea level rise, additional freshwater releases are needed to push salinity intrusions to maintain water quality for in-Delta uses. In the 2023 report, the Department considered three climate change scenarios (50%, 75%, and 95% level of concern). The middle one suggested average SWP deliveries would be 44% of contracted entitlement and the six-year drought would be 15%. Compared to the studies in the 2021 report, that is a loss of 28% of contract entitlement — around 280,000-acre feet per year for Kern County. The losses through a six-year drought are lower but similar.
The declines in SWP deliveries not only impact deliveries of regulated supplies for irrigation, but they also affect the quantity of water available for recharge – the “Article 21” water from the SWP. In 2001, the annual average was 130,000 af/year. That’s down to 86,000-acre feet per in the 2023 study, factoring in climate change. That water, stored in wet years, is recovered in dry years and is desperately needed in Kern County to endure droughts.
Unlike some of the more northern rivers, Kern County has very little unused local water. In the very wet year of 2023, Kern County beneficially used or stored almost all of the Kern River runoff. That is, there is very little additional Kern River water to capture. Years wetter than 2023 occur an average of once in 25 years. While more recharge capacity could be built to capture water in those wet years, it is generally not economical to build facilities that will be used so infrequently.
Historically, Kern County has recharged surplus water from the Friant system. But as water districts on the east side of the Valley also struggle to achieve groundwater sustainability and prevent further subsidence on the Friant-Kern Canal, it is unlikely that surplus Friant water will be available for much longer. Kern’s CVP contractors (Southern San Joaquin Municipal Water District, Shafter-Wasco Irrigation District, and Arvin-Edison Water Storage District) will be able to increase their deliveries for recharge from the Friant-Kern Canal and all have plans to do so. That may increase supplies to those districts by around 40,000 af/year in total, but the opportunity is limited currently by upstream subsidence in a long stretch of the Canal north of the county line.
These are foreboding projections for Kern County. With only relatively small increases in deliveries from the Friant as well as a need to reduce groundwater pumping to achieve groundwater sustainability under SGMA, it is likely to result in a loss of around 150,000 acres – 20% of the irrigated acreage in Ken County. Values for farmland with limited water resources are expected to continue to decline. Property tax revenues will decline but will likely be mitigated by increasing tax revenues for property owners with water supplies. The decline in water supplies will also result in the loss of jobs both on the farms and in the industries that support agriculture.
The options for improving supplies are few but deserve attention – removal of Delta regulations that cost water but are not effective in protecting endangered fish, and new infrastructure in the Delta that allow for increased diversions in the winter and spring without harming fish.
