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How to Model Changed Water Rights and Return Flow Obligations

Changed water rights, or water transfers, are represented in StateMod by “temporarily” diverting and storing the water right into a Changed Water Right Plan when in priority, then releasing the water from the plan to meet a demand at a priority determined by the user, often junior to the original right. Water diverted into the Changed Water Right Plan to temporarily store a diversion may or may not be used depending on other water supplies and/or operations. The correct implementation of a Changed Water Right plan and associated operating rules will account for:

  • Administration of the changed water right at the correct location and at the correct priority
  • Sharing shortages between all users, including any un-changed portion of the water right
  • Use of the changed water right at priority different to the water right and relative to other operations in the model
  • Capacity limitations of the existing headgate
  • Decreed monthly and annual volumetrics and/or associated terms and conditions
  • Availability of any unused changed water rights to other users in the system

The following schematic provides an example of Changed Water Rights operations; the plan structures and operating rules used to represent these operations are discussed in more detail below.


Figure 9 - Changed Water Rights Example Operations (see also the full-size image)