Notes: The water year spans Oct. 1 to Sept. 30.
A. The forecasted full natural flow volume is published in the April 1st B-120 Forecast of annual Unimpaired Runoff (50% exceedance) at Lewiston by the California Department of Water Resources at https://cdec.water.ca.gov/snow/bulletin120/. An acre-foot (ac-ft) of water is the volume that covers an acre in one foot of water. This forecast volume determines the volume of water allotted to the Trinity River for restoration as prescribed in the Trinity River Mainstem Fishery Restoration 2000 Record of Decision. B-120 forecasts were not issued for 2001-03.
B. Full Natural Flow is the inflow to Trinity Reservoir multiplied by 1.04 to account for the watershed area between the reservoir and Lewiston. Inflows to the Reservoir are computed by the U.S. Bureau of Reclamation (USBR) from changes in reservoir storage, evaporation, and dam releases. Uncertainty in water storage and evaporation can result in negative inflows that are included in the calculations as reported.
C. Restoration water volume prescribed in the Trinity River Mainstem Fishery Restoration 2000 Record of Decision. Court-ordered restrictions in flow for 2001-2004 resulted in a cumulative reduction of 540,600 ac-ft in this period compared to Record of Decision flows released thereafter.
D. Restoration release volumes are computed from the final daily average flow record published by USGS for the Trinity River at Lewiston after subtracting flows that are released for non-restoration purposes (see E, F, and G).
E. Ceremonial releases occur in odd-numbered years for the Hoopa Boat Dance Festival except a ceremonial release was not made in 2003 because Klamath River augmentation flows satisfied water requirements for the Festival in this year.
F. Flows are released by the U.S. Bureau of Reclamation from Lewiston Dam to augment discharges in the lower Klamath River when needed to aide juvenile salmon rearing and adult migration to spawning grounds.
G. Reservoir management releases occur when necessary to protect against over-filling Trinity Reservoir.
H. “Other releases” include flow events that occur for other than river restoration and can include emergency flows related to dam and flow diversion infrastructures and water temperature management in the Trinity River.
I. The total release to the Trinity River is the sum of columns with notes D through H.
J. The peak flow release is the highest discharge recorded from measurements at 15-minute intervals throughout the water year at the USGS gage at Lewiston. The acronym “cfs” refers to the flow discharge in cubic feet per second.
K. Reported in USBR monthly reports for Lewiston Reservoir.
TBD = To Be Determined