43 C.F.R. § 418.20 – Diversions from the Truckee River to Lahontan Reservoir, January through June.

(a) Truckee River diversions through the Truckee Canal will be made to meet Lahontan Reservoir end-of-month storage objectives for the months of January through June. The current month storage objective will be based, in part, on the monthly Natural Resources Conservation Service (NRCS) April through July runoff forecast for the Carson River near Fort Churchill. The forecast will be used to determine the target storage for Lahontan Reservoir and anticipated diversion requirements for the Carson Division. The Bureau, in consultation with the District, Federal Water Master, Fish and Wildlife Service, the Pyramid Lake Paiute Tribe, and other affected parties, will determine the exceedance levels and predicted Carson River inflows based on the reliability of the NRCS forecast and other available information such as river forecasts from other sources. The end-of-month storage objectives may be adjusted any time during the month as new forecasts or other information become available.

(b) The January through June storage objective will be calculated using the following formula:

LSOCM = TSM/J−(C1* AJ) + L + (C2* CDT)

Where: (1) LSOCM = current end-of-month storage objectives for Lahontan Reservoir. (2) TSM/J = current end-of-month May/June Lahontan Reservoir target storage. (3) C1* AJ = forecasted Carson River inflow for the period from the end of the current month through May or June, with AJ being the Bureau's April through July runoff forecast for the Carson River at Fort Churchill and C1 being an adjustment coefficient. (4) L = an average Lahontan Reservoir seepage and evaporation loss from the end of the current month through May or June. (5) C2* CDT = projected Carson Division demand from the end of the current month through May or June, with CDT being the total Carson Division diversion requirement (based on eligible acres anticipated to be irrigated times the appropriate duty times a 95 percent usage rate), and C2 being the estimate of the portion of the total diversion requirement to be delivered during this period. (6) Values for TSM/J will vary with the Carson Division water demand as shown in § 418.22 and the Adjustments to Lahontan Reservoir Storage Targets table. Values C1, L and C2 are defined in the following table along with an example of TSM/J for Carson River water demand of 271,000 acre-feet.

Monthly Values for Lahontan Storage Computations
	January	February	March	April	May	June
TSM/J	174.0	174.0	174.0	174.0	174.0	190.0
C1/MAY	0.863	0.734	0.591	0.394
C1/JUNE	1.190	1.061	0.918	0.721	0.327
L/MAY	13.9	12.5	9.9	7.1
L/JUNE	18.2	16.8	14.2	11.4	4.3
C2/MAY	0.30	0.30	0.28	0.18
C2/JUNE	0.47	0.47	0.45	0.35	0.17

Lahontan Reservoir Storage Objectives
Period	Monthly storage objective
January through April	Lowest of the May calculation, the June calculation, or full reservoir.
May	Lower of the June calculation or full reservoir.
June	June storage target.

(d) Once the monthly Lahontan Reservoir storage objective has been determined, the monthly diversion to the Project from the Truckee River will be based upon water availability and Project demand as expressed in the following relationship:
TRD = TDD + TCL + CDD + LRL + LSOCM−ALRS−CRI
Where: (1) TRD = current month Truckee River diversion in acre-feet to the Project. (2) TDD = current month Truckee Division demand. (3) TCL = current month Truckee Canal conveyance loss. (4) CDD = current month Carson Division demand. (5) LRL = current month Lahontan Reservoir seepage and evaporation losses. (6) LSOCM = current month end-of-month storage objective for Lahontan Reservoir. (7) ALRS = current month beginning-of-month storage in Lahontan Reservoir. (Includes accumulated Stampede credit described below and further adjusted for the net efficiency penalty or efficiency credit described in §§ 418.12, 418.36, and 418.37). (8) CRI = current month anticipated Carson River inflow to Lahontan Reservoir (as determined by Reclamation in consultation with other interested parties).
(e) The following procedure is intended to ensure that monthly storage objectives are not exceeded. It may be implemented only if the following conditions are met:
1. (1) Diversions from the Truckee River are required to achieve the current month Lahontan Reservoir storage objective (LSOCM);
2. (2) Truckee River runoff above Derby Dam is available for diversion to Lahontan Reservoir;
3. (3) Sufficient Stampede Reservoir storage capacity is available.
(f) The Bureau, in consultation with the Federal Water Master, the District, Fish and Wildlife Service, the Bureau of Indian Affairs, and the Pyramid Lake Paiute Tribe will determine whether the calculated current month Truckee River diversion to Lahontan Reservoir (TRD-TDD-TCL) may be reduced during that month and the amount of reduction credit stored in Stampede Reservoir.
1. (1) Reductions in diversions may begin in November and continue until the end of June.
2. (2) Reductions in diversions to Lahontan Reservoir with credit storage in Stampede Reservoir may be implemented to the extent that:
  1. (i) The reduction is in lieu of a scheduled release from Stampede Reservoir for the purpose of supplementing flows to Pyramid Lake; and/or
  2. (ii) Water is captured in Stampede Reservoir that is scheduled to be passed through and diverted to the Truckee Canal.
3. (3) The Fish and Wildlife Service must approve any proposal to reduce diversions to Lahontan Reservoir for Newlands Project credit purposes without a comparable reduction in release from Stampede Reservoir or any conversion of Stampede Reservoir project water to Newlands Project credit water.
4. (4) The diversion to Lahontan Reservoir may be adjusted any time during the month as revised runoff forecasts become available. The accumulated credit will be added to current Lahontan Reservoir storage (ALRS) in calculating TRD. If the sum of accumulated credit and Lahontan Reservoir storage exceeds 295,000 acre-feet, credit will be reduced by the amount in excess of 295,000 acre-feet. Credit will also be reduced by the amount of precautionary drawdown or spills in that month. If the end-of-month storage in Lahontan Reservoir plus the accumulated credit in Stampede Reservoir at the end of June exceeds the end-of-month storage objective for Lahontan, the credit will be reduced by the amount exceeding the end-of-month storage objective.
5. (5) Following consultation with the District, the Federal Water Master, and other interested parties as appropriate, the Bureau will release credit water as needed for Project purposes from July 1 through the end of the irrigation season in which the credit accrues with timing priority given to meeting current year Project irrigation demands.
6. (6) Conveyance of credit water in the Truckee Canal must be in addition to regularly scheduled diversions for the Project and will be measured at the USGS gauge number 10351300 near Wadsworth.
7. (7) Newlands credit water in Stampede Reservoir storage will be subject to spill and will not carry over to subsequent years. Newlands credit water in Stampede can be exchanged to other reservoirs and retain its priority. The credit must be reduced to the extent that Lahontan Reservoir storage plus accumulated credit at the end of the previous month exceeds the storage objectives for that month. If Newlands credit water is spilled, it may be diverted to Lahontan Reservoir subject to applicable storage targets.
  1. (i) The Bureau, in consultation with the District, the Federal Water Master, and other interested parties, may release Newlands Project credit water before July 1.
  2. (ii) If any Newlands credit water remains in Stampede Reservoir storage after the end of the current irrigation season in which it accumulated, it will convert to water for cui-ui recovery and will no longer be available for Newlands credit water.
  3. (iii) Newlands credit water stored in Stampede Reservoir will be available for use only on the Carson Division of the Newlands Project.
(g) Subject to the provisions of § 418.20 (b), LSOCM may be adjusted as frequently as necessary when new information indicates the need and diversions from the Truckee River to the Truckee Canal must be adjusted daily or otherwise as frequently as necessary to meet the monthly storage objective.