New contract allows UC Davis to continue cache slough study

SOLANO COUNTY WATER AGENCY / COURTESY

Solano County Water Agency taking over state contract to fund research

In early December of 2017, it was announced that the Solano County Water Agency agreed to a $1.2 million three-year contract with UC Davis to study the Cache Slough Complex, a network of sloughs and creeks in the North San Joaquin River Delta. This replaces the previous state contract with UC Davis that began in 2012.

“SCWA has been keeping millions of dollars in reserves for many years,” said SCWA Board Chair and Mayor of Suisun City Pete Sanchez. “SCWA must invest some of those reserve monies in ventures like this UC Davis study. The bigger chunk must be devoted to levee management, flood control projects, habitat conservation and whatever other projects that will ultimately result in fulfilling SCWA’s declared goals.”

Since the Cache Slough Complex is crucial to the urban and agricultural water supply of Solano County, gaining a stronger understanding of the hydrodynamics and biodiversity of the Complex is an important goal. However, it is difficult to draw more meaningful conclusions if the research cannot be continuously conducted over longer periods of time.

“It is important to continue funding this research so we can have a longer time series,” said Dr. John Durand, a researcher for UC Davis’s Center for Watershed Sciences and the principal investigator of the study. “We want to continue monitoring this area because of the high level of primary productivity from zooplankton and phytoplankton [and because] it was surprising to discover that there was such a high proportion of native fishes here.”

The Cache Slough Complex’s high productivity has helped it to be identified as an ideal location for conserving and restoring habitats.

“There is great interest in this region because these waterways [in the North Delta] are remnants of historic slough networks that have largely been leveed and bypassed,” Durand said. “Compared to areas of the South Delta, the Cache Slough Complex is very productive [and] alien fishes have become naturalized and are able to coexist with native fishes.”

Roland Sanford, a general manager at the SCWA, also noted the historic significance of the Complex and explained other factors that make it unique to other areas of the Delta.

“The Cache Slough Complex is evidently one of the last large areas with significant ecological and physical remnants of the historic delta,” Sanford said. “Furthermore, much of the topography is gently sloping, which better accommodates sea level rise vis-à-vis creation of tidal wetlands.”

This is in contrast with areas of the southern portion of the Delta that are complicated by more extreme land subsidence. Fish in the South Delta also face the challenge of getting pulled into the pumps that bring water from the Delta into the California Aqueduct. According to Durand, much of the South Delta is considered to be “lost,” but both he and Sanford are optimistic about the potential opportunities in the north.

“From our perspective, the fact that the results of the state sponsored study and others indicate that the Cache Slough Complex has significant ecological value and potential for restoration/enhancement is important, simply because so much of Solano County’s water is in some way connected to the Cache Slough Complex — either the water comes directly from the Cache Slough Complex or flows through it,” Sanford said. “Through the continuing work of Dr. Durand and others, I am hopeful that we will identify actions that can be taken to preserve if not enhance the ecological value of the Cache Slough Complex while meeting critical water supply needs.”

The North Bay Aqueduct is responsible for transporting water from the Complex to urban and agricultural water users in Solano County. Unfortunately, this water is high in organics and has poor quality, and therefore must be treated more heavily than the cleaner water of the Sacramento River, but Sanford said that the study will do more water quality and biological sampling near the NBA’s intake at Barker Slough.

“At the moment it remains unclear what can be done to improve the NBA’s source water quality and more specifically, the degree to which ongoing and future habitat restoration efforts may or may not impact NBA source water quality,” Sanford said. “Hopefully Dr. Durand’s work will provide some insight to those questions.”

With the threat of climate change, there is more uncertainty about water levels in the Delta as well as water availability because of different patterns of severe wet and dry years. The researchers and stakeholders like Dr. Durand and water users served by the SCWA hope that this study will help reveal the best ways for agricultural operations and cities to sustainably coexist with healthy, productive ecosystems in the future.

 

Written by: Benjamin Porter — features@theaggie.org