Analysis shows climate-caused decreases in Scott River fall flows

Abstract

Because of declining anadromous fisheries, resource managers are concerned about the timing and quantity of water flows in Northern California's Scott River. We analyzed 48 years of flow and precipitation data to improve our collective understanding of the Scott River fall flow regime and to provide information for current and future fisheries-restoration efforts. Fall flows are primarily controlled by the water content of snow and precipitation during the previous 12 months. These two factors account for nearly 80% of the variation in fall flows. Our analysis shows that downward trends in fall flows appear to be explained by a decrease in the water content of the snow falling on the Scott River watershed. This information will be useful in assessing the relative benefits of conservation and restoration strategies against the larger background of climate-caused changes in river flow.

Relative Effects of Climate and Water Use on Base‐Flow Trends in the Lower Klamath Basin1

“…The difference between this component and the total decline in base flow is attributable to local‐scale factors, which we discuss. We also compare our results with those of Drake et al. (2000) and discuss implications for fisheries management.…”

“…We begin with the operating hypothesis that declines in base flow that have been observed in the Scott River are caused primarily by climate trends, as expected based on the large body of climate literature cited above and on the results of Drake et al. (2000), the only published study we could find that has addressed this problem.…”

“…, 1994; NRC, 2003; CDFG, 2004). If reduction in Scott River base‐flow has been caused primarily by climatic factors, as has been proposed by Drake et al. (2000), then flow objectives for coho salmon recovery may not be attainable through local management, and the success of other recovery objectives (e.g., habitat restoration) may be limited by continued low base flows.…”

Skeptical about soil quality

“…In Scott Valley, groundwater-surface water interactions are analyzed as part of an action plan to meet temperature TMDL (Total Maximum Daily Load) requirements for the Scott River. Climate change and groundwater pumping for irrigation in the valley have impacted late-summer and early fall stream flows in the Scott River (Drake et al 2000;Kirk and Naman 2008). The local groundwater advisory committee is developing potential groundwater management scenarios that would increase summer and early fall stream flows.…”

Modeling guides groundwater management in a basin with river–aquifer interactions

“…In Scott Valley, groundwater-surface water interactions are analyzed as part of an action plan to meet temperature TMDL (Total Maximum Daily Load) requirements for the Scott River. Climate change and groundwater pumping for irrigation in the valley have impacted late-summer and early fall stream flows in the Scott River (Drake et al 2000). The local groundwater advisory committee is developing potential groundwater management scenarios that would increase summer and early fall stream flows.…”