{"id":4186,"date":"2022-07-20T19:21:59","date_gmt":"2022-07-21T02:21:59","guid":{"rendered":"https:\/\/calsport.org\/fisheriesblog\/?p=4186"},"modified":"2022-07-20T19:21:59","modified_gmt":"2022-07-21T02:21:59","slug":"the-delta-in-april-june-2022-under-tucp","status":"publish","type":"post","link":"https:\/\/calsport.org\/fisheriesblog\/?p=4186","title":{"rendered":"The Delta in April-June 2022 under TUCP"},"content":{"rendered":"

A lot has been said about the drought\u2019s effect on water supplies for cities and farms, but little is said about how Delta fish are faring.\u00a0 Freshwater inflow to the Delta was about half of normal in April through June 2022 because of the State Water Board Order<\/a> approving the Department of Water Resources (DWR) and the Bureau of Reclamation\u2019s Temporary Urgency Change Petition<\/a> \u00a0(TUCP) for Delta operations.\u00a0 With some of this limited Delta inflow going to water users during April, May and June, little was going to the fish.<\/p>\n

The State Water Board granted the TUCP because Central Valley reservoir storage was so low at the end of winter in this third year of drought.\u00a0 During drought, most of the Delta\u2019s late spring and summer inflow comes from releases from storage in Shasta, Oroville, and Folsom reservoirs.<\/p>\n

The TUCP has ended, and the normal operating rules for the Delta under Water Rights Decision 1641 have gone back into effect as of July 1.\u00a0 It is now a good moment to review the effects of this most recent TUCP.<\/p>\n

Conditions Under TUCP (April-June 2022)<\/strong><\/p>\n

Delta inflow from the Sacramento River and tributaries averaged about 7500 cfs while the TUCP was in effect (Figure 1).\u00a0 Releases from Folsom Reservoir averaged 1000-2000 cfs of this inflow.\u00a0 Releases from Oroville Reservoir varied widely, but averaged about 2500 cfs over the period.\u00a0 Other inflow came from the Sacramento River (Shasta Reservoir) and its tributaries, which during the TUCP period averaged about 3000-4000 cfs.\u00a0 The San Joaquin River and its tributaries contributed on average another 1000 cfs to Delta inflow.<\/p>\n

There are three main uses of Delta inflow when inflow is low: repelling salt water, south Delta exports, and in-Delta use.\u00a0 South Delta exports were about 1300 cfs while the TUCP was in effect.\u00a0 Delta outflow, holding back the salt water, required roughly 4000 or more depending on tides.\u00a0 Net in-delta use (water diversions other than south Delta exports) accounted for the rest.<\/p>\n

Salinity (EC, mS\/cm) at Emmaton (west Delta Figure 2) , normally kept near 500 per the state standard for agriculture, increased to levels ranging from 500 to 8000 (Figure 2), with daily average of 2000 to 4000, four to eight times the standard.<\/p>\n

At Jersey Point, where the standard is 450-750 EC, salinity ranged from 1200 to 2300 in June (Figure 3).<\/p>\n

Conditions After TUCP (Early July 2022)<\/strong><\/p>\n

After the TUCP expired, conditions changed as regulatory requirements returned requirements under Decision 1641.\u00a0 Delta inflow increased to 12,500 cfs (Figure 1).\u00a0 At this date, salinity has fallen toward the appropriate salinity standards (Figures 3 and 4).<\/p>\n

What does this mean for the Delta and its Fish?\u00a0 <\/strong><\/p>\n

    \n
  1. The agricultural salinity standard of 500 mmhos at Emmaton near Sherman Island in the Sacramento River channel was \u201crelaxed\u201d under the TUCP (Figure 3). Salt water was able to push further upstream and mix to a further extent with inflow.\u00a0 The daily salinity (EC) range of approximately 500-8500 mmhos, an increased level of spring salinity not seen since the 2014 and 2015 drought under earlier TUCPs.<\/li>\n
  2. Likewise, the average daily salinity (EC) standard at Jersey Point near Sherman Island in the San Joaquin River channel (Figure 4) was also not being met.<\/li>\n
  3. Salinity was managed under the TUCP to meet the minimum drinking water standards (<800 mmhos) near municipal water supply diversions in the central Delta (Figure 5). (I would not drink this water or put it on plants.)<\/li>\n
  4. Throughout June, net flows in the Old and Middle River channels in the central Delta were southward toward the South Delta export pumps (Figures 2 and 6).<\/li>\n
  5. While the TUCP was in effect, salt water moved upstream in the Sacramento River channel near Rio Vista and into Cache Slough (Figure 7). Within the Cache Slough Complex, water moved upstream (Figure 8) in part due to water diversions in the north Delta.<\/li>\n
  6. Delta inflows from the Sacramento River at Freeport fell below 10,000 cfs from April through June 2022 as allowed under the TUCP (Figure 1). This drop led to the increases in salinity noted in Figures 2-8.<\/li>\n
  7. Low Delta inflows also contributed to higher water temperatures throughout the Delta during and after the TUCP period (Figures 9 and 10). Water temperatures above 72 degrees are detrimental to most of the native Delta fish.<\/li>\n<\/ol>\n

    Conclusions:<\/p>\n