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DWP annual compliance report available online

August 5th, 2011 by Greg, Information & Restoration Specialist

Now available to download from the Mono Basin Clearinghouse is the Los Angeles Department of Water & Power’s May 2011 Mono Basin compliance report. This annual report discusses previous year and current year operations and monitoring for the State Water Board-ordered requirements of the city of Los Angeles’ water rights licenses. Highlights are below.

The operations plan for 2011–2012 outlines the temporary operations for the officially “wet” 2011–2012 runoff year (April 1 to March 31) that have been approved by the State Water Board for the first half of the year. The intent is to test the new flow recommendations outlined in the Synthesis Report. This section also provides a review of the 2010–2011 “normal” runoff year operations.

During the 2010 field season (the 14th year of fish population monitoring) there were 33% to over 100% increases in young of the year brown trout in all reaches of Rush Creek since 2009, yet it was the third year in a row of decreases in young of the year in Walker Creek, and there were none in Lee Vining Creek. The brown trout sampled in Lee Vining Creek were in good condition while in Rush Creek trout condition was below average. More large fish were sampled in Lee Vining Creek than ever before. The report concludes that “at least several additional years of fisheries data will be required to document if the winter baseflow recommendations continue to increase the proportion of older and larger trout….” in Rush Creek. The scarcity of pools in Lee Vining Creek is constraining the production of older and larger trout there.

A creek-ice survey was conducted for the second winter in a row, and a report is included in the fisheries section. It provides an excellent overview of the winter weather during the last two years, and clearly shows how Mono Lake moderates the local climate. Lee Vining and Paoha Island air temperatures typically fluctuated 20 degrees F less than at Cain Ranch—the maximums were on average 10 F cooler and the minimums 10 F warmer near Mono Lake. During the last decade winters were milder than during the previous decade. Last winter, ice fluctuation in the creeks was very severe, and during freeze-ups fish would be forced into faster-moving ice-free parts of the channels for up to a week at a time. Relatively warm water released to Rush Creek from Grant Lake Reservoir kept the upper part of Rush Creek relatively ice-free.

This section reports geomorphology, hydrology, and vegetation aspects of the creek monitoring efforts. Highlights include a cottonwood vigor assessment based on measuring shoot lengths that grew each year and relating that growth to the streamflow and groundwater conditions that year. Results from groundwater and stream temperature monitoring are also reported.

Waterfowl and limnology
This annual report is Mono Lake-focused, reporting the mixing and plankton dynamics in Mono Lake as well as the results from waterfowl surveys. Data from “the last six years confirm that there has been a significant increase in the size of the first generation of adult Artemia and a more rapid autumn decline in Artemia accompanying the general decrease in salinity from 1982 to present.” 2010 had the lowest annual brine shrimp cyst production since monitoring began in 1982 due to low late-season adult abundance. “There is no significant long term trend in mean annual Artemia abundance;” however, there is a long-term trend of increased algal chlorophyll. A nine-year trend shows that summer waterfowl diversity and brood production are higher when Mono Lake is higher, however there have been no trends seen during the fall migration.


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