System operations describe how direct, instream, well and storage rights interact with a water right owner's preferences. Reservoirs store water based on physically available river flow, legally available flow (priority), decreed right, storage capacity, demand, and operating rules. A balance is computed which accounts for the inflows and outflows from a reservoir including natural inflow, pumped inflow, controlled releases, spills, net evaporation and seepage. Downstream river flows associated with a reservoir storage or release are adjusted using the same water allocation procedure outlined in the previous section.
Water is released from a reservoir to satisfy an owner's demand, exchange agreement, augmentation requirement, hydropower goals, or target storage values. Reservoirs may have one or more ownership accounts and may be located on the main channel or off-channel. Standard operating policies associated with most river basins have been implemented in StateMod, as described in Section 4 and Section 7.
System operations, diversion return flows to non-downstream river nodes, and well pumping return flows have the potential to add additional water to a river which might be available to a senior water right. For example, when a reservoir releases water to meet a target storage level, additional water may become available to a senior downstream right. Similarly, if a ditch returns water to a neighboring non-downstream tributary, those return flows may be used by a senior ditch on that tributary. Finally when the return flow associated with well pumping exceeds its depletion to the river, additional water may become available to a senior downstream right. When such a system operation, non-downstream return flow or net accretion occurs, the model automatically re-evaluates (re-operates) all water rights in priority in order that senior rights may benefit from the additional water supply. The following are noted:
When "new water" becomes available because of a system operation, non-downstream return flow or net accretion, the model automatically re-operates all water rights in priority in order that senior rights may benefit from the additional water supply.
The user can control the number of iterations by adjusting the control (*.ctl) file reoperation variable (
ireopx). This variable allows the user to turn off the reoperation capability or specify a volume before reoperation occurs. Both of these activities can impact results but may be an efficient method of operation if the user is interested in testing a new structure or feature and performance is an issue.
If the user wants to force a reoperation at a specific administration date, a type 12 operating rule can be specified.