Evaluation of a tool for investigating water allocation scenarios: A test case for the Piako catchment
Author: Paul Franklin, Jani Diettrich and Doug Booker (NIWA)
The Waikato Regional Council (WRC) is responsible for managing the status of water resources in the Waikato Region. WRC’s approach to the protection, allocation and use of water resources is set out in the Waikato Regional Plan: Variation No. 6 – Water Allocation (the Plan), which became operative on 10 April 2012. As required by the National Policy Statement for Freshwater Management (NPSFM), the Plan defines minimum flows and allocation limits for all catchments in the region. As a precursor to the review of flow and allocation limits set in the Plan for the Piako catchment scheduled for 1 July 2014, WRC have initiated investigations in the catchment to support and inform the Plan review process.
The purpose of this project is to evaluate the use of the Environmental Flow Strategic Allocation Platform (EFSAP) to simulate the consequences of water quantity limit scenarios, using the Piako catchment as a case study. The aim is to help WRC understand how EFSAP can be used to characterise the instream and out-of-stream effects of different rules, and how this might be useful in the limit setting process, including managing over-allocation. In this project, EFSAP was used to simulate the spatially explicit consequences for reliability of supply and instream physical habitat of a range of water allocation limits in the Piako catchment. The scenarios developed in consultation with WRC included:
- the Plan water allocation rules for the Piako catchment excluding water harvesting
- current actual allocation (including estimated permitted takes)
- current actual allocation (including estimated permitted takes), excluding takes for irrigation.