Water temperatures in the lower Sacramento River over the past month have often exceeded water quality standards that protect salmon and other beneficial uses (Figures 1 and 2). Water temperatures at or above the standard of 68oF adversely affect adult and juvenile salmon. Water temperatures can meet the standard if the Bureau of Reclamation maintains flow in the Sacramento at Wilkins Slough at 6000-8000 cfs, depending on air temperature. The Bureau of Reclamation has maintained such flows in the past to meet water quality standards and terms in its water rights permits (Figure 3). Shasta Reservoir water storage is 102% of normal as of June 18, 2018. Water diversions from the Sacramento River upstream of Wilkins Slough are approximately 6,000 cfs, with 100% allocation to CVP contractors under water right permits. For more on the effects on salmon, see past posts.
Figure 1. Sacramento River flow and water temperature at Wilkins Slough in lower Sacramento River: mid-May to mid-June 2018. Red line denotes water quality standard. Source: CDEC.
Figure 2. Sacramento River water temperature at Verona in lower Sacramento River: mid-May to mid-June 2018. Red line denotes water quality standard. Source: CDEC.
Figure 3. Historical and recent flow at Wilkins Slough. Source: USGS.