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 not real-time), and 0.37 should be added for the USGS datum (used by the SWRCB). The corrected level can be found on the Mono Lake Website. The transition to 6,391 feet asl is expected to take as long as 15 years.

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. The gates on the diversion usually seep about 1 cfs into the conduit. This year, April 1 through September 30 minimum flow "below" is 54 cfs (or "above" flow, whichever is less), and October 1 through March 31 minimum flow is 40 cfs (or "above" flow). In Normal years Stream Restoration Flows are required--the peak flow must pass undiverted downstream. Note: The flows below are often incorrect, but can sometimes be calculated by subtracting "conduit" from "above".

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. 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. If the water is available, the augmentation will be tested at 150 cfs this year.

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 Stream Restoration Flows and anticipated Walker Creek SRFs. There are no plans to divert Walker Creek until the diversion facility is upgraded.

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 Stream Restoration Flows and anticipated Parker Creek SRFs. There are no plans to divert Parker Creek until the diversion facility is upgraded.

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 is not expected to spill in 2008.

RUSH CREEK
Largest Creek in the Mono Basin. This is the flow "at damsite," or what is coming into Grant Reservoir. It is controlled mostly 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 (7118.4) acre-feet 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 dock is out of the water. DWP is never required to reduce storage below 11,500 acre-feet, although below this level the inflow must be passed downstream. In 2008, DWP predicts the reservoir will be very low during peak flow operations until SCE releases more water (by July 1st). 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". There have been problems with this gauge recently.

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. In prior years the low capacity limited Stream Restoration Flows (SRF) below those ordered by the Water Board. This year, April 1 through September 30 minimum flow is 47 cfs, and October 1 through March 31 minimum flow is 44 cfs. If the inflow is less than this, minimum flow is inflow, and minimum is 31 cfs when inflow is less than 31 cfs. In 2008, an SRF of 380 cfs for 5 days followed by 300 cfs for 7 days is required. This is the first time a Normal year SRF will be tested. DWP is not required to release an SRF if it projects that the reservoir will drop below 11,500 acre-feet by the end of the runoff year.

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 export is limited by Mono Lake level and minimum flows (not by SRFs). This year, 16,000 acre-feet of export is allowed. 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 5/1/08.