A Simple Analytical Method to Assess Multiple‐Priority Water Rights in Carryover Systems

Simple analytical storage–reliability–yield relationships have traditionally only considered a single reliability for a single yield, yet many reservoirs supply water of different priorities. Simulation models may be used to handle such multiple‐priority water rights but these models are complex and usually system specific. Here we propose a simple analytical method based on Gould‐Dincer to estimate yields in dual and triple priority allocation systems from a carryover storage. This allows rapid assessment of changes in water resource availability for different water priorities, potentially over large spatial scales. We use a dam simulation model to assess this method at 15 sites across six continents and find that the “dual‐priority” and “triple‐priority” G‐D methods can reproduce the results of the dam simulation model. Thus, the method could be generalized for multiple priority allocation systems use. We demonstrate the potential utility of the “dual‐priority” G‐D method through an evaluation of the optimum yield between high and low‐priority water rights (HPWR and LPWR) from hypothetical (but realistic) carryover systems. It confirms the possibility that “dual‐priority” water allocation may be beneficial overall compared to a single‐priority water right. By balancing the yield of HPWR and LPWR, the optimum marginal value of available water (i.e., sum of high‐ and low‐priority water) can be achieved. Overall, the method provides a simple way for rapid assessment across multiple sites allowing insights into optimal allocation practices and the interacting driving factors that affect them at a regional‐to‐global scale.