California state water regulators poised to boost instream flows to the Sacramento-San Joaquin Delta acknowledged the difficulty in finding the right measure of applied science to benefit the ecosystem.

“We need to look at multiple stressors,” said Dorene D’Adamo, one of five members of the State Water Resources Control Board who convened for a public meeting last Wednesday on the science behind the proposed update of the Bay-Delta Water Quality Control Plan. “The one knob we are looking at is flows and I’d like to see a way to integrate those other stressors in the discussion.”

Against the backdrop of an ailing Delta ecosystem and declining fish populations, the State Water Board is working on a plan to bring more water to the estuary from the Sacramento and San Joaquin rivers and their tributaries in an attempt to protect and restore several fish species of fish on the verge of extinction.  

The idea of boosting flows has unleashed a storm of criticism from water rights holders, who argue that the updated water quality plan amounts to a water grab. But those involved with the science behind the water quality plan say leaving more water in tributaries and the rivers is directly beneficial.

“There is robust science that shows that inflow drives estuary function,” said Matt Holland, senior environmental scientist with the State Water Board.

The water quality plan contemplates a January through June outflow with a 35 percent to 75 percent range of unimpaired inflow, with a possible summer increase to help Delta smelt. A course of adaptive management is key because it allows inflow and outflow to work together, said Holland, adding “we are still looking how to represent that in a regulatory framework.” 

Because the Delta faces stressors such as water quality, loss of habitat and invasive species, “we need to focus on flow without overly muddying it up,” said Felicia Marcus, chair of the State Water Board. “It’s not the only variable and we need to articulate that and make it clearer.”

Marcus’ colleague Steven Moore said leaving more water in tributaries is a “quantum jump” from the 1995 water quality plan, which placed the burden on the state and federal water projects. The flow discussion “is very weighty” and there needs to be a “robust connection” between a “more sophisticated” flow regime and other stressors, he said.

Deliberation on the updated water plan will continue well into next year and the science behind it is likely to be revised through the peer-review process. Then the State Water Board will embark on establishing a balance between water users and the environment.