Mono Basin Clearinghouse
Real-time Data Companion Page: 
Explanations and links to additional resources in this frame (load only this frame/pop up this frame) courtesy of the Mono Lake Committee.

EXPLANATIONS:
(counter-clockwise on map)

SETTLEMENT AGREEMENT
The Water Board is expected to revise the required stream flows this year. The information below reflects the former rules, with some mention of the new rules, and will be revised to reflect the new rules when they are ordered.

MONO LAKE ELEVATION
The date when it was read is not shown (it is usually read twice a month). The reading (as of10/6/15) is correct. More information can be found on the Mono Lake Website. The State Water Resources Control Board intended that the lake reach 6,391 by 2014. If the lake doesn't reach that level by 2020, it will hold a hearing to review the status.

LEE VINING CREEK
Second largest creek in the Mono Basin. More background here. "Above" the diversion is controlled mostly by what SCE releases from upstream reservoirs. This year, April 1 through September 30 minimum flow "below" is 37 cfs (or "above" flow, whichever is less), and October 1 through March 31 minimum flow is 25 cfs (or "above" flow). In Dry years Stream Restoration Flows (SRFs) are not required--the peak flow does not need to pass undiverted downstream as it does in other year-types, however in a second consecutive dry year (2013 & 2015) a Channel Maintenance Flow of 75 cfs for 5 days is required. This was not released in 2015 in order to retain cold water in Grant Lake Reservoir. New Stream Ecosystem Flow (SEF) prescriptions found in the Synthesis Report are on hold pending Water Board approval of a settlement, but would require a dry year wintertime minimum flow of 16 cfs, a summertime minimum flow of 30 cfs, a bypass flow of 53-100% between 30 cfs and 250 cfs, and no diversions would be allowed when the creek is above 250 cfs. Note: The flows "below" are sometimes incorrect--on 10/6/15 the below station plus the conduit is 2.2 cfs lower than the above station.

AQUEDUCT CONDUIT
This is the route by which water is diverted to Grant Lake Reservoir from Lee Vining Creek, Walker Creek, and Parker Creek. Diversions are not allowed when the creeks are at or below their minimum flows. Normally, augmentation of Rush Creek SRFs with Lee Vining Creek water is only allowed when runoff is greater than 107% of average (up to 50 cfs in Wet-Normal years, 100 cfs in Wet, and 150 cfs in Extreme Wet years) and 7 days after Lee Vining Creek peaks. In Extreme Wet and Wet years augmentation is allowed for a maximum of 15 days, in Wet/Normal years a maximum of 5 days. New Stream Ecosystem Flow (SEF) prescriptions found in the Synthesis Report that would prohibit augmentation are on hold pending Water Board approval of a settlement. Note: "Aqueduct Conduit" plus "Lee Vining Creek below" should equal "Lee Vining Creek above," within about 1 cfs.

WALKER CREEK
Smallest of the four diverted streams. More background here. In all years, April 1 through September 30 minimum flow "below" is 6.0 cfs (or "above" flow), and October 1 through March 31 minimum flow is 4.5 cfs (or "above" flow). Flow through conditions are required during Rush Creek SRFs and anticipated Walker Creek SRFs and when Mono Lake is below 6380. There are no plans to divert Walker Creek until the diversion facility is upgraded (despite the approved plan to divert in dry years), however it was diverted in 2012 and 2013 and 2014, and minimum flows were violated due to the antiquated infrastructure. The Synthesis Report calls for the entire flow to be released in all years, and implementation of this recommendation is currently pending before the Water Board. Currently a sediment bypass procedure is being tested that drains the ponds at the diversion dams during the peak flow, however there is no required peak flow release in dry years. On 10/6/15 the displayed flows were incorrectly showing 2 cfs above and 1 cfs below when in reality all the flow was passing downstream.

PARKER CREEK
Second smallest of the four diverted streams. More background here. In all years, April 1 through September 30 minimum flow "below" is 9.0 cfs (or "above" flow), and October 1 through March 31 minimum flow is 6.0 cfs (or "above" flow). Flow through conditions are required during Rush Creek SRFs and anticipated Parker Creek SRFs and when Mono Lake is below 6380. There are no plans to divert Parker Creek until the diversion facility is upgraded (despite the approved plan to divert in dry years), however it was diverted in 2012 and 2013 and 2014, and minimum flows were violated due to the antiquated infrastructure. The Synthesis Report calls for the entire flow to be released in all years, and implementation of this recommendation is currently pending before the Water Board. Currently a sediment bypass procedure is being tested that drains the ponds at the diversion dams during the peak flow, however there is no required peak flow release in dry years. On 10/6/15 the below flow was 1 cfs lower than the above flow, which is incorrect since the entire flow is passing downstream.

GRANT SPILL
The only time this will show a flow is when Grant Lake Reservoir is spilling (at or above 7130.0 elevation). The reservoir has not spilled since 2011. In 2011 the reservoir spilled from March 29th until August 16th. The minimum combined spill plus release peak for 2011 prescribed by the Synthesis Report was 650 cfs for 5 days (total Rush Creek flow below the reservoir), and an attempt made by LADWP and SCE to test this failed, only reaching 468 cfs despite the occurrence of a (calculated) unimpaired natural peak flow of nearly 800 cfs. The settlement agreement pending before the Water Board calls for construction of a new outlet capable of reliably releasing the peak flows.

RUSH CREEK
Largest creek in the Mono Basin. This is the flow "at damsite," or what is coming into Grant Reservoir. It is usually controlled by SCE's releases from upstream reservoirs. In most years SCE must maintain its reservoirs near spill from July 1 to September 1, causing low flows during the spring, near-natural flows while they are full, and relatively high flows in the fall and winter when the reservoirs are drained. In 2014 SCE began a peaking operation causing at-times dramatic daily and week-to-week fluctuations (click on the number to see the last 5 days). In 2012-2017 seismic safety drawdown orders required Waugh Reservoir to be kept less than half full and Gem Lake Reservoir to be kept 10 feet below the spillway and Agnew Lake Reservoir to be kept empty. Seismic retrofit work is expected to be finished in time for the 2017 recreation season. More background here.

GRANT LAKE RES. ELEVATION
The "full" level of the reservoir is 7130.0 feet, equivalent to 47,171 acre-feet of storage. In non-dry years DWP is required to seek to keep Grant between 30,000 (7113.2') and 35,000 acre-feet (7118.4') on April 1, and above 40,000 acre-feet (7123.4') in wet years. Below 26,200 acre-feet (7108.9') the marina has difficulty operating (no safe harbor), below 25,000 acre-feet warm water releases become a significant problem for the fishery below the dam, and below 22,800 acre-feet (7105') the boat ramp is out of the water. Below 20,000 acre-feet the outflow in the Rush Creek Return Ditch can be noticeably turbid. Below 15,000 acre-feet (7094.5') high levels of turbidity are released from the reservoir that sometimes violate water quality rules, and dust storms rise from the back bay. DWP is never required to reduce storage below 11,500 acre-feet (7089.3') in order to provide instream flows higher than inflow. The bottom of the 7' 8" outlet pipe is 0 acre-feet (7066.8'). The Water Board-approved GLOMP specifies 12,000 acre-feet as the minimum operating level below which exports are curtailed (in 2008-2009 those guidelines were not followed and exports continued), although when below this level, the inflow must be passed downstream or the dry year minimum, whichever is less. Click here to see Grant Lake Res. storage at the end of the previous month.

GRANT LAKE RES. OUTFLOW
The outflow is equal to the "Rush Creek Return Ditch" (measured at the lower end of the ditch) plus "West Portal" plus the losses in the Mono Gate One Return Ditch. On 10/6/15 an incorrect flow of 53.2 cfs is displayed.

RUSH CREEK RETURN DITCH
This ditch is currently the only reliable route through which a controlled release of water can be sent down Rush Creek. It was upgraded in 2003 to carry a maximum capacity of 380 cfs and was tested to this capacity in 2004. In prior years the low capacity limited Stream Restoration Flows (SRF) and Channel Maintenance and Flushing Flows (CMF) below those ordered by the Water Board. In 2009 Mono Gate One at the head of the ditch was rebuilt so that flows exceeding 350 cfs can be safely delivered, however the ditch was no longer operated above 350 cfs because the lack of maintenance increased the risk of levee failure. It was tested to capacity in 2011 under close watch and with frequent patrols, and DWP identified solutions to the maintenance problems and currently claims the capacity is 380 cfs when 24-hour patrols are available. It will be upgraded further during construction of the new outlet in 2017-2018. In Dry years, April 1 through September 30 minimum flow is 31 cfs, and October 1 through March 31 minimum flow is 36 cfs. If the inflow is less than wetter year minimums, minimum flow is inflow, and minimum (Oct-Mar) is 36 cfs when inflow is less than 36 cfs. In a Dry year, no SRF is required, however in a second consecutive dry year (2013 & 2015) a Channel Maintenance Flow of 100 cfs for 5 days is required. This was not released in 2015 in order to retain cold water in Grant Lake Reservoir for release to Rush Creek in summer. New Stream Ecosystem Flow (SEF) prescriptions found in the Synthesis Report are pending Water Board approval of the 2013 settlement, and will require in dry years a minimum flow of 30 cfs April 1-30, rising to 70 cfs May 17-July 6, dropping to 45 cfs July 12th and then 27 cfs July 30, with a winter baseflow of 27 cfs. Lower winter baseflows are expected to reduce high water velocities that are believed to negatively affect German Brown Trout. On 10/6/15 the flow appears to be correct.

WEST PORTAL
West Portal flow is what is flowing from Grant Lake Res. into the Mono Craters Tunnel. East Portal, the outlet of the tunnel at the Upper Owens River, will usually be about 13-15 cfs higher due to groundwater seepage (about 60% of this "Tunnel Make" comes from the Mono Basin aquifer). The amount of annual surface water export is limited by Mono Lake level and minimum flows (not by SRFs). When Mono Lake is at or above 6380 feet above sea level on April 1st, a maximum of 16,000 acre-feet (22 cfs on average) of export is allowed until the next April 1. A maximum of 4,500 acre-feet of export is permitted between May and the following March when Mono Lake is between 6377 and 6380 on April 1st and Mono Lake is expected to remain above 6377 based on the May 1 projection and subsequent projections. No export is allowed when the lake is predicted to drop below 6377.). Note: the flow shown for West Portal is sometimes incorrect. To check this number, subtract "Rush Creek Return Ditch" from "Grant Lake Res. Outflow", however keep in mind that the return ditch value is measured at the lower end of the mile-long ditch and there are water losses in the ditch. On 10/6/15 the flow appears to be correct.

Explanation provided by the Mono Lake Committee. Last updated 10/6/15.