June Delta Exports<\/h2>\n
June exports in recent wet years (2011, 2017, and 2019) have averaged 9000-11,000 cfs under the State\u2019s current State D-1641 standards. \u00a0This is a new impact (since 1995) that has manifested itself in a decreased proportion of wild fish in the salmon runs, thus threatening the very integrity of the populations and commercial and sport fisheries.\u00a0 Under the previous D-1485 standards, south Delta project exports in June were limited to 6000 cfs in all year types.<\/p>\n
June River Flows and Water Temperatures<\/h2>\n
June river flows should be sustained to help move smolts downstream and maintain water temperatures below stressful levels (less than 68\u00b0F\/20\u00b0C).\u00a0 River flows need to be adequate to keep water temperatures in the lower sections of the Sacramento River below 68\u00b0F\/20\u00b0C, as recognized in the Central Valley Basin Plan\u2019s water quality standard.\u00a0 The flows needed to maintain water temperatures depend on air temperatures.\u00a0 Over the past decade, water temperatures have exceeded the target in June in the lower Sacramento River even in wet years 2011, 2017, and 2019 (Figures 3 and 4).<\/p>\n
June Delta Inflow<\/h2>\n
June Delta inflows need to be of sufficient magnitude to help salmon smolts pass through the Delta in a timely fashion, and not get diverted off-course toward the south Delta export pumps or succumb to huge numbers of predator fishes. \u00a0June flow entering the north Delta at Freeport needs to be maintained near 20,000 cfs to maintain water temperatures near 68\u00b0F\/20\u00b0C (Figure 5).<\/p>\n
June Delta Outflow<\/h2>\n
With 20,000+ cfs inflow and south Delta exports limited to 6,000 cfs, Delta outflow will be 10,000+ cfs (the other 4,000 cfs is from within-Delta diversions).\u00a0 This is sufficient to keep the Low Salinity Zone west of the Delta and salmon smolts moving toward the Bay and Ocean.<\/p>\n
Summary<\/h2>\n
In conclusion, the present year-round water temperature standard for the lower Sacramento River, 68\u00b0F\/20\u00b0C, should be sustained through June.\u00a0 New State Board standards should limit south Delta exports in June to 6,000 cfs to protect wild salmon smolts that are emigrating from Central Valley rivers.<\/p>\n
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Figure 1. Water temperature in the Sacramento River in the north Delta in spring 2020, along with recent 22-year median daily average. Water temperatures above 68\u00b0F\/20\u00b0C severely stress emigrating salmon smolts. Water temperatures above 75\u00b0F\/24\u00b0C are lethal to salmon. Water temperatures above 70\u00b0F\/21\u00b0C hinder or block the migration of adult winter-run and spring-run salmon as they move upstream in spring.<\/p><\/div>\n
![\"\"](\"http:\/\/calsport.org\/fisheriesblog\/wp-content\/uploads\/2020\/06\/image2.jpeg\")
Figure 2. \u201cTiming of ocean entry of fish released from the Feather River hatchery (blue) and wild out-migrating (red) from 2002 to 2010. The area of each violin represents the proportion of fish out-migrating at that Julian day and is normalized to the total abundance of outmigrants for that year. The black lines represent the interquartile range (first to third quantiles). Hatchery release data for the Feather River Hatchery (FRH) are from Huber and Carlson (2015). Data for \u2019wild\u2019 (unmarked) fall-run sized outmigrants are from the USFWS Chipps Island Midwater Trawl.\u201d Source: https:\/\/www.nrcresearchpress.com\/doi\/10.1139\/cjfas-2017-0273#.XuY87C0idvJ<\/a><\/p><\/div>\n Figure 3. Sacramento River flow and water temperature at the Verona gage just downstream of the mouth of the Feather River, 2008-2017. July 1 for each year is equidistant between the vertical lines.<\/p><\/div>\n Figure 4. Sacramento River flow and water temperature at the Wilkins Slough gage upstream of the mouth of the Feather River, 2008-2020. July 1 is one-quarter and three-quarters distance between each of the two-year period vertical lines.<\/p><\/div>\n Figure 5. Sacramento River flow and water temperature at the Freeport gage in the north Delta downstream of the mouth of the American River, 2016-2020. June flows (immediately to left of July 1 lines) of 20,000 cfs maintain water temperatures near 20\u00b0C.<\/p><\/div>\n <\/p>\n","protected":false},"excerpt":{"rendered":" When the State Water Board gets around to finally updating decades-old Central Valley water quality standards, it should bring back some old spring standards, keep some good ones, and add some new ones to provide essential protection to salmon, steelhead, … Continue reading ![\"\"](\"http:\/\/calsport.org\/fisheriesblog\/wp-content\/uploads\/2020\/06\/image4.jpeg\")
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