1 Introduction
This study was commissioned by the Ministry for the Environment (MfE) to update information on water allocation in New Zealand. It follows on from an earlier survey (1999) of allocations which showed that less than 3 percent of New Zealand's freshwater was allocated at that time. In the intervening years, demand for water has grown to meet an expansion in irrigated area and population growth.
1.1 Project scope
The general purpose of the project is to update estimates of water allocation regionally and nationally from those published in the report prepared by Lincoln Environmental in 2000. The earlier study, in addition to determining the then levels of allocation, also included elements looking at economic returns to irrigation water and allocation policy. This current study is focused specifically on the quantities of water allocated and looks more closely at the allocation of surface-water resources. It has the advantage of work in the intervening years on surface-water catchments and national water accounts.
The project scope included the following elements:
- compilation of consent records for water takes for all regions
- development of a consent database incorporating the above records
- determination of allocations as a percent of water availability by region
- comparison of current allocations with those reported in the 1999 survey
- determination by catchment of surface-water allocation as a percent of water availability
- determination of irrigated area and comparison with estimates from previous studies and agricultural census
- analysis and presentation of actual water use versus allocation for a series of case examples and indicator catchments.
1.2 Related work
Related work to this study includes the following:
a) Information on water allocation in New Zealand (LE, 2000)
The report presented the results of the 1999 survey of both regional and national water allocations and forms a reference point for current and future studies into water allocation in New Zealand. In addition to allocations, it also included elements evaluating returns to irrigation water and regional allocation policy.
The analysis of consumptive water use allocation showed that:
- 70 percent of water allocations were from surface water
- 77 percent of allocations were for irrigation, and 16 percent and 7 percent for public supply and industry respectively
- 58 percent of allocations were in the Canterbury region
- consented irrigated area [The term consented irrigated area refers to the irrigated area for water has been allocated. As discussed in the latter sections of this report, there may be cases where the actual area of irrigation development is less than the consented area.] of 600,000 hectares of which 400,000 and 84,000 hectares were in Canterbury and Otago respectively
- irrigated area had increased 55 percent per decade for the past 30 years.
b) National water accounts (Stats, 2003)
The national water accounts are published by Statistics New Zealand. They present a summary water balance regionally and nationally and are composed of surface and groundwater elements. The approach is based on calculation of physical stock accounts for water based on inflows from precipitation and snow, and outflows to evapotranspiration, other regions and to the sea, as well as change in storage. The national water accounts present annual accounts for the seven-year period 1995 to 2001. The average annual water balance for this period is approximately 230 billion cubic metres (Bm3) but ranged from 198 to 263 Bm3/year. Per capita, this is equivalent to 60,000 cubic metres.
c) Identifying freshwater ecosystems of national importance for biodiversity (Chadderton et al, 2004)
Previous work by central government to assess nationally important values for water bodies developed national catchment coverage. These units were defined by NIWA and included all units with an area greater than 100 hectares. Based on this criterion, there was a total 4,711 units of which 4,427 are classified as parent catchments and 284 as sub-catchments. The same catchment coverage has been used for catchment-level analysis in this report and is referred to as the Ncc (national catchment coverage).
d) Agricultural census (Stats, 2002)
The 2002 agricultural census presented irrigated area by territorial authority. It lists the total area of land under irrigation as 467,731 hectares of which 384,227 hectares were irrigated in the year ending 30 June 2002. It should be noted that the assessment of irrigated area varies between the agricultural census and consented allocations. The former is based on reported area where as the latter is based on the area listed on the consent or, if not listed, calculated from allocation and peak demand. The difference in approach is important as there are significant differences between the two for some regions, a point further discussed in relevant sections of this report.
1.3 Outline of this report
The report includes the following:
- Section 2: Methodology; summarises the study approach and methods.
- Section 3: Consent Database; presents an overview of the consent database development, structure and summary of number of consents.
- Section 4: Allocations and Areas; presents the results of analysis of consumptive water use allocation by region, source and use, and consented irrigated area.
- Section 5: Comparisons and Trends; presents the comparison of current allocations and consented areas with the 1999 survey, national water availability (from national water accounts) and the 2002 agricultural census.
- Section 6: Surface-water Allocations; presents the results of analysis of surface-water allocations as percent of mean annual and mean annual low flow by National catchment coverage (Ncc).
- Section 7: Water Use; presents case study examples of water use versus allocations for selected locations and catchments.
- Section 8: Recommendations; lists key study recommendations for future analysis and updating of national water allocation information.
- Appendices: presents supporting information and details of analysis including; database structure, parameters and assumptions, and national and regional summaries.
