A Model for Assessing the Magnitude of Unconsented Surface Water Use in the Waikato Region
Report: TR 2007/47
Author: Edmund Brown (Environment Waikato), Bryan Clements (Environment Waikato) and Andy Haigh (GIServices)
Abstract
The Waikato Regional Council has developed a model for predicting the peak summer permitted and s14(3)(b) surface water use. The Waikato Regional Council needs this model to effectively manage water allocation and establish whether there are, or are likely to be adverse effects on the environment. The model takes the number of animals and people within a catchment and multiplies these figures by determined rates of use for key animal types and individual's domestic needs based on water use estimates from published information, commonly used estimates or local information. The model's accuracy was tested against measured water use data from seven rural water supply schemes in the region.
Water use for dairy farming was found to have the most influence on model predictions. This was not surprising due to the high density of dairy cows in the region and the large volumes of drinking water required by lactating cows and the large volumes of water required for dairy shed operations.
The relative water demand from permitted and s14(3)(b) activities in relation to the allocable flow was assessed in 202 catchments. In 35 of the catchments more than 50 percent of the allocable flow is taken for these activities alone, and in 16 of these the use exceeds the allocable flow. When consented authorised water takes are included with the permitted and s14(3)(b) takes, there are 77 catchments with more than 50 percent of the allocable taken and of these, in 41 catchments the use exceeds the allocable flow.
If intensification of dairying continues, the amount of animal drinking water required will for the most part increase without restrictions due to the high priority it is afforded by s14(3)(b) of the RMA. In many catchments this may result in nearly all the allocable flow being utilised solely for s14(3)(b) animal drinking water purposes. In these catchments capping the permitted use at 15 m3/d as required by the Waikato Regional Plan will do little to relieve the situation where water use exceeds the allocable flow. Additional policy would be needed to control water take effects.
The high level of permitted and s14(3)(b) water use in a number of catchments in the region exposes a limitation in the manner the RMA provides animal drinking water as right via s14(3)(b) and s30(4)(f) without consideration of the directly linked activities such as dairy shed operations. A solution may be to constrain the number of animals per catchment that can receive water as of right. The number of animals and the water demand for associated activities such as shed operations should not be allowed to exceed the available supply of suitable freshwater. A policy of this nature will, as a consequence, limit the ability for animal intensification in large parts of the region where the permitted and s14(3)(b) use including water allocated by resource consent is close to, or exceeds, the allocable flow. This will provide a better balance between the number of animals in each catchment and the availability of water to help secure supply and protect minimum flows.