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Silver Creek Selenium Surge
Too much water coming too fast is the reason given for a controversial commingling of selenium-laced flood flows and agricultural irrigation drainage in San Joaquin Valley channels often used to serve wildlife refuges this January.
The event originated in the Silver-Panoche Creeks watershed where high runoff forced San Joaquin drainers to route both storm flows and their drainage through refuge channels instead of a bypass - largely due to the limited capacity of a newly built connector to the bypass in the San Luis Drain. The event stepped over the limit lines of a hard-won 1996 drainage management agreement for the selenium-plagued region in two ways. Under the agreement, agricultural drainage cannot be discharged into Salt Slough and other channels serving local wetland and wildlife refuges, and certain selenium load restrictions must be met.
Load restrictions were exceeded by 10% and a 2 ppb state selenium standard for Salt Slough and other channels was also exceeded. Drainers argue that a 10% stretch is a considerable achievement given such record rains, and point out that during the preceding first four months of the agreement, they succeeded in reducing selenium loads. "They're claiming an 'act of God' and saying they aren't responsible for any of this, when we've watched Silver Creek overflow year after year," says the Environmental Defense Fund's Terry Young. "It's bad planning on their part. They built that connecting channel too small."
But drainers say the connector was sized to carry problem agricultural drainage not to "solve all the flood control problems on the West side of the valley," according to Dan Nelson of the San Luis & Delta-Mendota Water Authority. Nelson says the agreement even cites Silver Creek as an example of an "unforeseen circumstance" beyond the control of drainers. "Now we need to have a discussion about how Silver Creek and stormwater fit into the discharge accounting in the agreement," says Nelson, who recently made an informal proposal to BurRec that rainfall-induced drainage not be counted in the load restrictions. (BurRec owns the San Luis Drain, a section of which the agreement allows San Joaquin drainers to use as a bypass).
Young describes herself as "ballistic" about the proposal. "After five years of negotiation on the agreement and just four months of implementation, the drainers are angling to change the deal. It's a bad faith effort in my book," she says.
But BurRec's Penny Howard sees the fact that the drainers haven't made any more formal proposals as a willingness on the part of the farming community to learn from experience and explore other drainage management options.
At the very least, Young thinks drainers should have more aggressively tried to minimize the drainage flows through the sloughs, which row crop farmer David Cory insists that they did. Cory says drainers carefully coordinated with the downstream water district and refuge managers to uphold the environmental commitments of the agreement. "No water deliveries to the refuges were taking place when the overflow went through," he says.
What the actual environmental impacts of the discharge were won't be known for a couple of months, when all the monitoring data has been analyzed. Preliminary results show no short-term toxicity to aquatic organisms, perhaps due to dilution by high flows, according to Howard. Any revaluation of the project is premature until all the data is in, says Howard, adding that the first part of the agreement only lasts for two years, during which time a long-term plan must be developed. "We're in learning mode, and this is in effect a field laboratory with certain controls," she says. "As long as we honor the process, and learn lessons, the agreement can still succeed."
Contact: Penny Howard (916)979-2476
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