Salmon spared by full reservoirs

03/06/2014

February’s 21 inches of rain ended discussions between Marin Municipal Water District and state agencies over a temporary reduction of mandatory releases to Walker and Lagunitas Creeks. The dry fall and early winter had depleted reservoirs so dramatically that the district was planning on drawing from their two emergency reservoirs; without more rain, they might have completely drained Soulajule Reservoir, which feeds Walker Creek, by the summer. Reducing flows could have threatened the ability of endangered coho salmon and steelhead trout to journey between the streams and the ocean, since streams typically alternate between deeper pools and shallow riffles, where the adults lay their eggs. Without enough flow, the riffles could become so shallow that fish would be either stranded in the stream or unable to get there in the first place. Although the release reduction is now unnecessary, the district will probably move forward with a “critical riffle analysis” to evaluate the potential impacts of reduced flows in preparation of future droughts. The district’s reservoirs now hold 83 percent of water typical for this time of year: between Feb. 4 and March 4, their volume increased from 42,000 to 59,000 acre feet of water.