Biological Opinions - Bureau of Reclamation

4.2 Element Two
Operate the Project, or direct the operation of the Project, for the delivery of water
for irrigation purposes, subject to water availability, while maintaining lake and
river hydrologic conditions that avoid jeopardizing the continued existence of listed
species and adverse modification of designated critical habitat.
4.2.1 General Description
The Klamath Project has two distinct service areas: the east side and the west side. The east side
of the Project includes lands served primarily by water from the Lost River, and Clear Lake and
Gerber Reservoirs. The west side of the Project includes lands that are served primarily by water
from UKL and the Klamath River. The west side also may use return flows from the east side.
The Project is operated so that flows from the Lost River and Klamath River are controlled,
except during high inflow periods. The Project was designed based on reuse of water.
Therefore, water diverted from UKL and the Klamath River for use within the west side is
reused several times before it discharges back into the Klamath River via the Klamath Straits
Drain. Return flows from water delivered from the reservoirs on the east side are also reused
several times.
Water management relies heavily on seasonal water supply forecasts provided by NRCS for the
Williamson River, UKL, Clear Lake, and Gerber Reservoir. The water supply forecasts are
developed based on antecedent streamflow conditions, precipitation, snowpack, current
hydrologic conditions, a climatological index, and historical streamflow patterns (Risley et al.
2005). NRCS updates the forecasts for the season early each month from January to June, with
mid-month updates through June. The forecasts are used to estimate seasonal net inflow to these
bodies of water and in models used to simulate water management scenarios for the Project,
UKL, Klamath River, and refuges. The inflow forecasts are estimates; observed inflows
typically vary substantially from forecasted inflows. Variation in the forecasts ranges from 1 or 2
percent to over 100 percent, depending on the timeframe of the forecast (March through
September for example) and the month in which it was issued.
A detailed description of the NRCS inflow forecasting procedures is located at the following
NRCS web sites: http://www.wcc.nrcs.usda.gov/factpub/wsf_primer.html and
http://www.wcc.nrcs.usda.gov/factpub/intrpret.html
For the purpose of estimating future Project needs, yearly demands for irrigation supply and
refuge deliveries are assumed to be similar to those that have occurred in the period of record
(POR). The irrigation demand is the amount of water required to fully satisfy the irrigation
needs of the Project. Historical demands during the POR result from a large range of hydrologic
and meteorological conditions, and are expected to be a reasonable representation of future
demand during the 10-year period of this proposed action.
4.2.2 Operation of the East Side of the Klamath Project
The east side of the Project consists of approximately 37,000 acres (ac) (15,000 hectares [ha]) of
irrigable land and reservoirs, dams, canals, laterals, drains, and pumping plants. The east side
diverts water from Clear Lake and Gerber Reservoirs. Although the water year is October 1 to
12