1 Introduction
1.1 Background
The Resource Management (Waitaki Catchment) Amendment Act provides for the establishment of the Waitaki Catchment Water Allocation Board who will develop a regional plan to address water allocation in the Waitaki Catchment. The regional plan will be prepared, submissions received and heard, and approved within 12 months of the board being established.
The board will be serviced by the Ministry for the Environment, who are initiating projects to provide the board with relevant information for policy development. The resulting reports will become public documents.
In October 2004, Tonkin & Taylor was commissioned by the Ministry for the Environment to provide an independent overview of the hydrology of the Waitaki Catchment.
1.2 Project brief
The deliverables under the project brief were:
- a graphical presentation of the flow regimes in the Waitaki Catchment, supported with tabular data, which illustrates the relative size of the various flows at critical times and seasons, and the effect of infrastructure operation
- a method, likely to be spreadsheet-based, that can be used to assess the reliability of supply to run-of-river users within the tributaries based on daily time-series flows
- a method, also likely to be spreadsheet-based, that can be used to assess river flows and resource availability to all users within the main stem of the river under various allocation options.
The project brief is focused on existing hydrological information on the Waitaki Catchment, specifically historical flow data. Data is to be presented to provide a clear understanding of the magnitude and variability of flows within the catchment, including the influence of existing infrastructure on natural flows. In addition, this project provides a means to broadly assess river flows and resource availability under various potential allocation options.
This report is a collation of the hydrological information and spreadsheet models furnished to the board via the Ministry for the Environment in fulfilment of the project brief.
1.3 Scope
The following aspects are excluded from this project brief:
- effects on flows in rivers potentially receiving Waitaki water
- the recommendation of allocation options for tributaries and the Waitaki main stem
- an assessment of the water requirements of individual resource consent applications
- system modelling to replicate Meridian Energy's operation of its power infrastructure
- modelling of historical and projected irrigation and other water demands within the Waitaki Catchment
- checking and auditing of the historical hydrological records which this report relies on.
1.4 Acknowledgements
Hydrological databases and other relevant data for this project were kindly provided by the following agencies:
- Meridian Energy Ltd:
- TIDEDA flow and water level records from their Power Archive for the Waitaki
- lake level and flood operation guidelines, and storage tables for the hydro lakes
- Environment Canterbury:
- TIDEDA flow databases, including ratings, gaugings and comments, for their recording stations in the Waitaki
- naturalised flow records for the Hakataramea and Omarama Rivers
- mean annual low flow (MALF) and five-year seven-day low flow estimates for gauged tributaries in the Waitaki, including mean flow estimates for some sites
- irrigation flow records for the irrigation schemes in the lower Waitaki
- NIWA:
- TIDEDA flow databases, including ratings, gaugings and comments for their recording stations in the Waitaki, including stations operated on behalf of other agencies
- index of water level and flow recording sites in New Zealand
- Ministry for the Environment:
- GIS coverage of the location of existing and proposed resource consents
- various reference documents.
