How to Model Alternate Points/Exchanges
In general, StateMod uses operating rules to simulate the operation of alternate points and exchanges of water rights to meet demands. The Type 39 operating rule, discussed in Section 4.13.39, was designed to operate alternate points of diversions for diversion and well structures. This operating rule includes the source alternate point water right and options as to where the water right will be administered and whether the supply is limited to water availability at the source water right location. Note that an alternative to using the Type 39 operating rule, which has not been thoroughly tested, is to assign the alternate point water right to the destination in the diversion right (*.ddr) and/or well right (*.wer) file. This work-around does not check for whether water is physically and legally available at the source water right location, but does allow the destination to divert in-priority under the alternate point water right.
The exchange of a water right can be accomplished in StateMod using two approaches: through a direct exchange of the water right (Type 24 operating rule) or the “temporary” diversion of a water right into a changed water rights plan and subsequent exchange of the released water (Type 26, 27/28). See Section 4.13.24 for more information on the Type 24 operating rule, and see Sections 4 and Section 7.11 for information on changed water rights operations.
Some exchanges have a decreed exchange priority. If there is limited exchange potential on the specific reach where the decreed exchanges are modeled, it is recommended that the priorities of the modeled exchanges be reflective of the decreed order. Use the changed water rights approach (Type 26, 27/28) to manage the priority and order of the exchanges.