Report: TR05/10

Author: Aqualinc Research Ltd

Abstract

The purpose of this project is to identify and determine options for improvement of water allocation processes and procedures in the Waikato Region. It is part of an on-going commitment by Environment Waikato to the development of water resource management. It follows on from earlier work that determined irrigation requirements, productivity and efficiency.

Management context

The management context for water allocation is that established under the Act, Regional Policy Statement and Regional Plans (Transitional and Proposed). The principal allocation outcomes are those associated with priority water uses: reasonable use for livestock, domestic and fire-fighting, efficient water use and protection of in-stream values (environmental and cultural). The water module of the plan establishes surface water classes and associated criteria for allocation limits for all uses. The plan rules define categories of water use (authorised, permitted, controlled and discretionary), and in the cases of permitted takes, levels of use from surface water and groundwater.

Waihou catchment

The project is based on a case study of the Waihou catchment as an example of the allocation issues and options facing the Region. Land use within the catchment is typical of much of the Region, being a combination of dairy farming (40 percent) and forestry (production (8 percent) and native (34 percent)). The cumulative water availability is estimated to be approximately 240 Mm3/yr, of which two thirds is groundwater and one third surface water. The surface water resources have been the most heavily developed, due to ready access and suitable water quality. The cumulative allocation of surface water is approaching the upper allocation limit of 10 percent of Q5, and there is concern regarding allocation to meet future growth in demand. The principal uses of consented takes within the catchment are for irrigation (54 percent), supply networks (town and rural schemes) (29 percent) and industry (16 percent). In addition to consented takes, non-consented takes for livestock and non-reticulated domestic use (authorised under the RMA) and permitted takes are estimated to be equivalent to 8 Mm3/yr (20 percent of total annual water use of 40 Mm3/yr).

Allocation issues and options

The study identified a number of issues and constraints to water allocation. These can be grouped according to the principal water management objectives as listed below:

• Allocation efficiency is constrained by current consent and water management procedures:
  - High takes rate (greater than the equivalent 24 hour rate) that lock-up allocable surface water. This is the equivalent of more than 700 l/s or 30 percent of allocable resources.
  - Variability of seasonal demand within and between seasons. Irrigation demand is low on the season margins and at times when there may be alternative demand e.g. frost-protection. During low demand in the Waihou for the periods Nov-Dec and Mar-Apr, allocated resources are under-utilised by at least 15 percent, the equivalent of 350 l/s.
  - Water use lower than consented take rates and volumes. Comparison of consents and water use records indicated that actual use is approximately 80 percent of the consented take (based on records for supply networks). This effectively reduced allocation efficiency by at least 10 percent.
  - Accounting for discharges. Under-accounting for discharges to surface water (of comparable or higher quality water) leads to under-estimation of allocable surface water.
  
  
• Economic efficiency of water use is constrained by:
  - Consent duration. Consent durations vary from 3 to 30 years. Short durations while adopted as part of the management process (for synchronising review period etc), can increase supply risk and therefore limit investment in water infrastructure e.g. irrigation, supply systems.
  - Allocable resources. Surface water availability is limited by current allocation criteria (percent of Q5). This could be increased with the allocation of a proportion of resources above Q5. An allocation of 30 percent of median winter flow would yield 100 Mm3/yr (though it is acknowledged that the cost of development is higher due to storage requirements).
  - High priority use. As demonstrated in the Waihou, there is a need to protect high priority use such as community supply networks (Hauraki Plains Scheme) during low flow periods. This is currently achieved through consent conditions restricting water take when king tides coincide with low flows. However it may be better achieved through the establishment of minimum flow and restriction mechanisms within the Regional Plan.
  
  
• Protection of in-stream values could be improved by:
  - Accounting for authorised and permitted use based on water demand per land use type, as part of the determination of cumulative demand.
  - Formalisation of restrictions on takes with establishment of minimum flows, threshold allocation level (75 percent) for review of allocation criteria and in-stream values, and establishment of restriction regimes for water use categories.
  - Integration of water use records in consent processes to provide estimates of actual demand in the assessment of cumulative demand levels.
  
  

Implementation options

The study identified a range of potential improvements to current allocation methods and management. These improvements are a combination of changes to consent processes, institutional procedures and additions to Plan rules. These are:

• Defining daily take period for high take rates (greater than a nominal daily rate).
• Defining the irrigation season (Nov-Apr) within which takes are operative (and within specified number of take days, generally 120 days per season).
• Specification of maximum daily take rate (m3/d) for irrigation season margins Nov-Dec and Mar-Apr.
• Logging of takes greater than 10 l/s to verify: daily take period (where relevant), seasonal daily take and to provide accurate water use records for assessment of cumulative demand.
• Consent processes (cumulative demand) amended to include estimation of recharge from discharges and actual water use reviews.
• Establishment of additional surface water allocation tiers, (B and C), for allocations above Q5 and from winter median flow.
• Establishment of allocation threshold(s) for review of in-stream values and allocation limits.
• Establishment of rules on restriction of takes during periods of low flow for principal water use categories.
• Definition of minimum flow levels at which water takes cease or is severely limited.

Assessment of Improvements to Environment Waikato's Water Allocation Processes and Procedures [PDF, 524 KB]