Download KModSim: River Basin Management Decision Support System User

priorities. This is useful for mutual irrigation companies, or other mechanisms for
apportioning flow in a river basin. Flow-through demands are also valuable for model
calibration purposes, where a flow-through demand is located at a streamflow gaging
station site, and the demands assigned to the flow-through demand node correspond to
historical measured flows, which are assigned as the highest priority in the basin.
KModSim parameters and unknown system gains and losses can then be adjusted until
measured flows at the gaging station are reasonably matched.
Demand Di t
Shortage Rules. During higher than normal flow conditions in a river basin, all
demands are generally satisfied, whereas during low flow and drought conditions, severe
shortages may occur. The priority structure embodied in KModSim distributes available
water supply to high priority uses first. In some river basin systems, the administrative
goals are to produce a more equitable sharing of available water during drought. Simply
assigning the same priorities to all demands in the basin will not necessarily result in an
equitable distribution in a KModSim solution. Rather, without any priority guidance,
KModSim will produce inconsistent solutions and random distribution of available water.
However, similar to use of
Hydrologic State tables for
Wet
defining conditional reservoir
Ave.
operating rules, demands can also
be conditioned on Hydrologic
State
information,
allowing
Dry
development of shortage rules that
attempt to equitably share flow
deficiencies among water users
during periods of extended
drought or low-flow conditions.
As seen in Fig. 15, basin-wide
demands can be reduced by certain
B1τm Bi-1,τm Biτm Bn-1,τm
percentages as conditioned on the
Hydrologic State, allowing more
Hydrologic State Rtm
equitable sharing of available
Fig. 15. Shortage rules conditioned on Hydrologic
water resources during dry periods.
state.
Shortage rules are defined in KModSim by selecting a Hydrologic Table name in the
General form within the Demand Node Properties form, as in Fig. 16. Click Apply
and OK after selection of the Hydrologic Table, reopen the Demand Node Properties
form, uncheck the Varies by Year box, and specify the shortage rule for each period, as
seen in Fig. 17.
Conditional Reservoir Release Rules. In some cases, it is desirable to specify
conditional release rules for reservoir operations rather than conditional storage target
rules for each time period. This is easily accomplished by specifying an additional flowthrough demand node downstream of a reservoir with the desired release levels
designated as flow-through demands. These releases can be dependent on storage levels
by using the Hydrologic State option for flow-through demands.
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