(1) For a discussion of mass curves for selection of reservoir capacity, see Water-Resources Engineering, Linsley, Franzini, Freyberg and Tchobanoglous, Fourth Edition, McGraw-Hill, 1992, pp. 190-192.
(2) Figure 1 can be plotted for the historic period of record for reservoir inflows.
(3) Safe yield is a "worst historic" condition. Given the length
of the instrumental record in most of the
(4) Some of the relevant variables may be measured (reservoir levels, streamflows), while others may be calculated using simulation modeling (snowpacks, soil moistures).
(5) Watershed area is a factor. Streamflow in the
(6) The gage (40.7 square miles) is 2 miles upstream from
(7) Runoff from the winter storm in Nobember 1989 is undersimulated with both 1989 and 1941, June 1, initial conditions.
(8) 1941 initial conditions were used: Watershed conditions in June of 1941 were drier than average. If watershed conditions from a historic year that was much wetter than average were used, future simulated flows would exceed historic flows.
(9) Re: Figure 1. The yield of a reservoir is a maximum if future drawdown period reservoir inflows are known. If forecasts were ideal, if future weather and streamflows were precisely known at now, the forecast pdfs in Figures 5 and 6 would be single valued.
(10) Fortunately, the hydrologic initial conditions used in watershed modeling, unlike atmospheric initial conditions that are used in General Circulation Models (GCMs), are dissipative.
(11) Moore, R.L., D.A. Jones, and K.B. Black, Risk Assessment and Drought Management in the Thames Basin, Hydrological Sciences Journal, 34, 6, 12/1989, Institute of Hydrology, Wallingford, Oxon UK.
(12) An exact match of deficit frequencies on different dates within one
drawdown period will rarely occur due to watershed/reservoir dynamics. To
create Figure 7, the reservoir storage on September 1, 1940 was increased by
10,000 acre-feet relative to the actual simulated reservoir storage for that
day.
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