MMWD enhancement projects improve Lagunitas Creek habitat conditions
As the 2011 Lagunitas Creek stewardship plan comes to an end, Marin Municipal Water District begins to make watershed enhancement plans for the 2021 stewardship plan.
One of the responsibilities of the Marin Municipal Water District is diverting water from the Lagunitas Creek basin to provide a water supply for over 190,000 residents throughout southern and central Marin County. Within the county, the district operates seven water supply reservoirs, five of which are within the Lagunitas Creek watershed. These diversions are regulated by the State Water Resources Control Board, which set order WR95-17 requiring MMWD to implement mitigation measures addressing the impact of water diversions at Kent Lake and the effects on the creek’s fishery resources.
These mitigation measures and requirements make up many of the watershed enhancement projects seen in the last 10 years of the 2011 plan. MMWD has set up instream flows, upstream migration flows, water year classifications, special circumstances, ramping, stream gages, reporting and temperature projects, which help to both enhance the watershed and meet the ongoing requirements of the order.
In 1997, habitat enhancements were completed and monitoring was conducted to measure the status, trends and habitat conditions of fish and shrimp populations. The stewardship plan in 2011 addressed actions that needed to be taken to benefit aquatic resource populations in Lagunitas Creek, specficially coho salmon, steelhead and California freshwater shrimp.
Gregory Andrew, recently retired MMWD fishery program manager, explained the district’s work with instream flows: “MMWD releases water from Kent Lake as needed to maintain the minimum instream flows stipulated in order WR95-17. The flows are intended to benefit the life stages of coho, steelhead and the freshwater shrimp.”
Upstream migration flows are completed four times a year between Nov. 1 and Feb. 3. These upstream flows involve a continuous flow of at least 35 cubic feet per second for three consecutive days. This ensures there is sufficient water for adults to swim upstream to spawn.
Water classification is done twice a year by Jan. 1 and April 1, and labels the time period as either normal or dry, depending on precipitation levels. Normal levels require 48 inches at the Jan. 1 reading and at least 28 inches at the April 1 reading. Any levels under this are considered dry. The water classification is important because it affects the instream flows.
Water temperature is closely monitored to try to keep it near the optimal temperature for coho and steelhead. This optimal temperature is 58 degrees between May 1 and Oct. 31, and 56 degrees from Nov. 1 to April 30. “We have found that water temperatures exceed the summertime temperature of 58 degrees during the hottest days of the summer,” Andrew described. “We release the coldest water available from the bottom of Kent Lake, and it enters the creek at about 50-52 degrees, but water temperatures become driven by ambient air temperature.” He added, “The district is currently conducting an analysis of water temperatures and evaluating effects on fish.”
The goal of ramping is to minimize rapid changes in flow in Lagunitas Creek through releases from Kent Lake. “The November upstream migration flow has been the largest change in flow,” Andrew said. “In some years resulting in the flow increasing from 8 cfs to 35 cfs.” This transition takes place over a four-hour time period.
The MMWD is responsible for keeping the United States Geological Survey stream gage at Samuel P. Taylor State Park in operation with continuous monitoring and recording of the daily stream flow. The district also contributes to the continued operation of the USGS Point Reyes station gage and operates the San Geronimo Creek stream gage.
Additionally, the district is responsible for submitting an annual report to the SWRCB describing its activities and compliance.
“The most beneficial restoration work has been the treatment of unpaved roads for sediment reduction, the roughly 70 installations of large woody debris structures and the recently completed winter habitat and floodplain restoration project,” Andrew emphasized.
A large amount of fine sediment discharge can come from roads, particularly unpaved roads, making treatment of the roads vitally important. Without treatment, the sediment can fill in pool habitats occupied by juvenile fish and shrimp or smother the gravel adults use for spawning. The treatment and drainage improvements greatly reduce sediment discharge and create better water quality and habitats.
Installing large woody debris structures, also known as an engineered log structure, helps to deepen pool habitats, “collecting other woody debris, creating cover and hiding spaces for both juvenile and adult coho and steelhead to avoid predation and far feeding sites for fish and shrimp,” Andrew illustrated. The structures also enhance the gravel habitats for spawning and provide calm backwater eddies where fish can find flow refuge during a storm.
“The winter habitat and floodplain enhancement project has installed larger LWD structures that help to reconnect Lagunitas Creek to its floodplain channel by impeding the flow in the mainstem, raising the water surface elevation and shunting water into adjacent floodplain channels,” Andrew explained. This provides refuge in calmer waters, additional feeding sites and helps to sort and store fine sediments so they do not negatively impact habitats.
When it comes to tracking efforts, Andrew continued, “The extensive monitoring of fish, shrimp and habitat has been invaluable at not only tracking population status and trends but also, and more importantly, in helping to understand the driving forces and limiting factors to the population dynamics of coho, steelhead, shrimp and other aquatic resources. This information, in turn, helps to focus where habitat restoration efforts should be directed.”
The MMWD has maintained one of the longest data sets in California, making its monitoring results invaluable and used for recovery efforts regionally.
The creation of the Lagunitas Creek Technical Advisory Committee has helped to create a fairly unified approach to watershed management and increased both data sharing and collaboration efforts. When it comes to watershed efforts, all stakeholders have remained engaged on TAC and continue to work as a collaborative, multiparty forum on fisheries, water quality and ecosystem restoration.
“The MMWD continues to recognize its responsibilities and intends to continue to remain a leader in the aquatic resource stewardship of the watershed within the district’s sphere of influence,” Andrew stated.
The district also worked on implementing a fisheries program, seeking grant money for habitat enhancement projects. For the program, MMWD staff and maintenance crews conducted their own studies, planning and implementing the majority of the habitat enhancement work, including LWD structures, road drainage improvements and sediment reduction projects. The MMWD successfully secured $4.8 million for enhancement projects in its grant funding search, with $4.2 million in funding being secured just since the 2011 stewardship plan. This funding has taken care of 38% of the total costs since 2011. These grants show the commitment of other agencies and the importance of Lagunitas Creek and Walker Creek resources statewide.
“As we work to develop the specific actions for the 2021 stewardship plan, we will, of course, continue with the ongoing requirements of order WR95-17,” Andrew said. “And we will define the elements for monitoring, habitat restoration and collaboration, including continuing with the TAC.” However, it is currently too early to tell what specific projects will be developed.
“Simultaneous with developing the 2021 stewardship plan, the district is beginning a habitat enhancement planning effort with a Prop 68 grant from the California Department of Fish and Wildlife,” Andrew said. “So that will undoubtedly inform and provide the basis for some site specific enhancement projects. For monitoring, we will be reviewing our sediment and streambed monitoring program, and we will likely incorporate new technologies into some of our fish monitoring surveys.”
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