Petition Requesting Approval of Temporary Urgency Change in Water Rights Permits 5633, 9390, and 18546 in Marin County
Marin Municipal Water District (Marin Water) controls and coordinates water supply releases from Peters Dam in accordance with the provisions of State Water Board Order 95-17, which the State Water Resources Control Board (SWRCB) adopted on October 26, 1995. Order 95-17 specifies the minimum instream flow requirements for Lagunitas Creek, which vary based on hydrologic conditions of Lagunitas Creek watershed. Based on these conditions, there are two main water year classifications, Normal year and Dry year, which are based on the amount of rainfall received at the Kent Lake rain gage. The January 1 water year classification is based on the total rainfall measured during the preceding 15-month period. If the total rainfall during this period is less than 48 inches, Dry year flow requirements are maintained from January 1 through March 31. The April 1 water year classification is based on the total rainfall during the preceding 6-month period. If the total rainfall during this 6- month period is less than 28 inches, Dry year flow requirements are maintained from April 1 to the first upstream migration flow in November. Normal water year requirements exist whenever Dry year conditions are not present. Water Rights Permits 5633, 9390, and 19546 require a minimum flow of 6 cubic feet per second (cfs) in Lagunitas Creek at the USGS gage located at Samuel P. Taylor state park under all water supply conditions. Throughout the year, Order 95-17 required minimum flows at this location are: November 1st or 15th through December 31, 20 cfs; from January 1st to March 15th, 25 cfs for Normal water supply conditions, 20 cfs for Dry conditions; March 15th to March 31st 20 cfs; April 1st through April 30th 16 cfs for Normal conditions, 14 cfs for Dry conditions; May 1st through June 15th 12 cfs for Normal conditions, 10 cfs for Dry conditions; June 16th through November 1st or 15th 8 cfs for Normal conditions, 6 cfs for Dry conditions. Order 95-17 has variation between November 1st or 15th for the minimum flow of 20 cfs in that it shall begin following the first storm that produces a “trigger” flow of 25 cfs as measured at the USGS gage. In the absence of a storm causing a “trigger” flow, the 20 cfs flow requirement shall begin on November 15th of each year. Additionally, there are four upstream migration flows required at a minimum flow of 35 cfs that are to occur between November 1st and February 3rd at roughly the beginning of each month. Marin Water is requesting that the SWRCB make the following temporary urgency change to Water Rights Permits 5633, 9390, and 18546 to preserve Marin Water’s water supply in case below-normal rainfall and hydrologic conditions continue. Starting November 1, 2021, Marin Water is proposing the following minimum instream flows schedule for the 180 day period: November 1st to November 15th, 6 cfs; November 15th to November 30th, 6 cfs unless a storm above 25 cfs occurs; December 1st or December 15th to March 31st, 16 cfs; April 1st to April 30th, 14 cfs. Between November 15th and November 30th, flows would remain at 6 cfs unless a flow event greater than 25 cfs occurs as measured at the USGS gage. If this happens, flows would increase to 10 cfs and monitoring for coho spawning would take place for one week following the event. If no coho spawning is observed within the one-week period, flows would return to 6 cfs until December 1st unless a subsequent storm event occurs. If coho spawning is observed within the one-week period, flows would increase to 16 cfs and remain there until March 31st. The proposal has variation between December 1st or 15th for the minimum flow of 16 cfs in that it shall begin following the first storm that produces a trigger flow of 25 cfs as measured at the USGS gage. In the absence of a storm causing a trigger flow, the 16 cfs flow requirement shall begin on December 15th. Additionally, the other three upstream migration flows required at a minimum flow of 35 cfs would occur between December 1st and February 3rd at roughly the beginning of each month.