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(a)
Month of the year
(b)
Month of the year
(c)
Month of the year
(d)
Month of the year
(e)
Month of the year
(f )
Month of the year
(g and h)
Month of the year
FIGURE 10.6
(a-h) Idealized guide or rule curves for U.S. Army Corps of Engineers reservoirs. (From
Kennedy, R., Clarke, J., Boyd, W., and Cole, T., Characterization of U.S. Army Corps of Engineers reservoirs:
Design and operational considerations, U.S. Army Engineers Engineering Research and Development Center,
Vicksburg, MS, 2000.)
accommodate looding where for (g) only a small minimum pool is maintained for much of the year
(e.g., for ish and wildlife), while for (h) there may not be a permanent pool.
Reservoirs may be designed for a single purpose, such as those illustrated in Figure 10.7. More
commonly, reservoirs are operated for multiple purposes. For such cases, the conservation pool
(Figure 10.3) is shared and subdivided based on the allocation of water. The conservation pool is
allocated in such a way that competing water users are able to get their equitable share based on an
agreed policy, such as the amount allocated to each user. This sharing is then incorporated into the
rule or guide curve, used for the operation of reservoirs.
One dificulty is that the rule curve is derived from historical data on river lows and water
demands (USACE 1987). Usually, the rule curve is followed at all times except in cases of extreme
drought or for public safety. However, changes in climate and hydrology can impact those lows
and water demands, which, in turn, can impact reservoir operations. For example, in June 2006,
the Western Governors Association (WGA 2006) released a report titled “Water needs and strat-
egies for a sustainable future,” in which they listed climate change as one of the challenges
facing the western states, such as through potential reductions in snowpack, which makes up a
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