Mono Basin Clearinghouse
Real-time Data Companion Page: 
Explanations and additional resources.

EXPLANATIONS:
(counter-clockwise on map)

MONO LAKE ELEVATION
The date when it was read is not shown (it is usually read weekly). The reading (as of 10/10/11) is correct. The more information can be found on the Mono Lake Website. The transition to 6,391 feet asl is forecasted to take until 2021 with average past climate.

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" would normally be 54 cfs (or "above" flow, whichever is less), and October 1 through March 31 minimum flow is 40 cfs (or "above" flow). In Wet years Stream Restoration Flows (SRFs) would normally be required--the peak flow must pass undiverted downstream. In October 2010-October 2011 the Water Board allowed a temporary change to test new Stream Ecosystem Flow (SEF) prescriptions found in the Synthesis Report, with a summertime minimum flow of 30 cfs and no diversions allowed above 250 cfs. October-March minimum flow below is 40 cfs or above, whichever is less. Note: The flows below are sometimes incorrect (on 10/10/11 below plus conduit should equal above, yet it is 4.7 cfs off).

AQUEDUCT CONDUIT
This is the route by which water is diverted to Grant Lake Reservoir from Lee Vining, Walker, and Parker Creeks. Diversions are not allowed when the creeks are 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. In October 2010-October 2011 the Water Board allowed a temporary change to test new Stream Ecosystem Flow (SEF) prescriptions found in the Synthesis Report. The being diverted from Lee Vining Creek was contributing to the Grant Lake Reservoir (GLR) spill to Rush Creek (GLR began spilling in March 2011) because the test of the Lee Vining Creek SEFs had been prioritized over the Rush Creek flows (which can't be controlled while GLR is spilling).

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. There are no plans to divert Walker Creek until the diversion facility is upgraded, and the Synthesis Report calls for the entire flow to be released. Currently a sediment bypass procedure is being tested that drains the ponds at the diversion dams during the peak flow. In September 2011 Walker Creek was diverted in order to lower the flow in Rush Creek during fisheries monitoring.

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. There are no plans to divert Parker Creek until the diversion facility is upgraded, and the Synthesis Report calls for the entire flow to be released. Currently a sediment bypass procedure is being tested that drains the ponds at the diversion dams during the peak flow. In September 2011 Parker Creek was diverted in order to lower the flow in Rush Creek during fisheries monitoring.

GRANT SPILL
The only time this will show a flow is when Grant Lake Reservoir is spilling (at or above 7130.0 elevation). In 2011 the reservoir spilled from March 29th until August 16th. On August 11th DWP began releasing and exporting water out of GLR in order to lower the level and allow lower flows to be released in September during the annual fisheries monitoring. The minimum spill peak for this year prescribed by the Synthesis Report is 650 cfs for 5 days, and an attempt made by LADWP and SCE to test this failed.

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, and relatively high flows in the fall when the reservoirs are drained. 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. 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), and below 22,800 acre-feet (7105') the boat ramp is out of the water and warm water releases become a problem. 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, although when below this level due to water exports, 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" plus "West Portal" plus the losses in the Mono Gate One Return Ditch.

RUSH CREEK RETURN DITCH
This ditch is 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 due to lack of maintenance increasing 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 is now saying the capacity is 380 cfs when 24-hour patrols are available. Normally in Wet years, April 1 through September 30 minimum flow is 68 cfs, and October 1 through March 31 minimum flow is 52 cfs. If the inflow is less than this, minimum flow is inflow, and minimum (Apr-Sept) is 31 cfs when inflow is less than 31 cfs. Normally in a Wet year, an SRF of 450 cfs for 5 days followed by 400 cfs for 10 days would be required. In 2010-2011 the Water Board allowed a temporary change to test new Stream Ecosystem Flow (SEF) prescriptions found in the Synthesis Report, with the minimum flow 40 cfs April 1-30, rising to 80 cfs May 14-June 11, rising to 170 cfs June 19-August 1, dropping to 70 cfs August 15th and then 27 cfs September 11, with a winter baseflow of 27 cfs. The minimum spill peak for this year is 650 cfs, timed if possible to coincide with Parker and Walker Creek peaks. In October a pulse flow will be released in order to drain more water out of GLR with hopes that it will prevent a winter spill, which would be detrimental to the German Brown Trout fishery. Minimum winter flows would be 52 cfs from October 1 to March 31 under D1631, however the new lower SEF flows may be implemented as hoped for by all the parties.

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 15 cfs higher due to groundwater seepage. The amount of annual surface water export is limited by Mono Lake level and minimum flows (not by SRFs). Normally every year 16,000 acre-feet (22 cfs) of export is allowed, however in order to delay the GLR spill the Water Board allowed the 2010 and 2011 limits to be combined into a 32,000 acre-foot limit over two years. This allowed additional water to be diverted during the 2010 runoff year, which delayed the spill of GLR until the end of March. About 23,000 acre-feet has been exported so far, leaving 9,000 acre-feet for the rest of the 2011 runoff year (after Rush Creek peak flow operations). All but 1,500 acre-feet was exported in August and September. Note: this flow is sometimes incorrect. To check this number, subtract "Rush Creek Return Ditch" from "Grant Lake Res. Outflow".

Explanation provided by the Mono Lake Committee. Last updated 10/10/11.