PORTOLA VALLEY -- Two environmental organizations filed a lawsuit Tuesday against Stanford University, claiming the school's management of Searsville Dam and Reservoir harms steelhead trout and violates the Endangered Species Act.

The suit alleges the dam prevents steelhead, a federally threatened species, from migrating farther up the San Francisquito Creek watershed, while Stanford's use of water from the reservoir for irrigation degrades habitat downstream of the dam by reducing water levels.

Our Children's Earth Foundation and the Ecological Rights Foundation want to force Stanford to curb its use of water from the reservoir and implement a plan to allow the fish to get past the dam, either by creating a bypass or removing the entire structure. They also want Stanford to obtain an Endangered Species Act permit, which is required for any activity that harms a threatened or endangered species.

Christopher Sproul, attorney for the two environmental groups, said Stanford has been dragging its feet in addressing the problem of the dam and reservoir, situated west of the main campus in the school's 1,189-acre Jasper Ridge Biological Preserve. The goal of the suit, filed in federal court in San Francisco, is to spur Stanford to action.

"This remnant population of steelhead trout is really a marvel to preserve," said Sproul. "And it's really sad that Stanford is dewatering this creek and maintaining the dam without any changes or improvements."

University spokeswoman Lisa Lapin said the lawsuit is unnecessary, since the school is already in the midst of a comprehensive study of Searsville, which the school acquired in 1919. A committee formed in 2011 to analyze the issue is expected to make recommendations by 2014.

Lapin also asserted that the university doesn't need an Endangered Species Act permit because it isn't harming steelhead.

"Stanford is definitively not in violation of the Endangered Species Act in its operation of Searsville Dam -- in fact, the creek is a thriving steelhead habitat," Lapin said.

The National Marine Fisheries Service is in the early stages of an investigation into whether any violations have taken place. Stanford has dismissed the inquiry as a routine response to a citizens complaint.

There many issues to consider besides the steelhead, Lapin noted. Since the dam was built in 1892, the reservoir has created wetland habitat that would disappear if the dam is removed. And the land beneath the dam has been developed, leading to concerns about flooding.

Federal law requires that an Endangered Species Act permit be accompanied by a planning document known as a Habitat Conservation Plan. Stanford completed such a plan late last year, but only after removing Searsville from consideration in order to study it further.

Contact Aaron Kinney at 650-348-4357. Follow him at Twitter.com/kinneytimes.