Damming and/or diverting of water undertaken in a manner that:
- Does not have adverse effects that are inconsistent with the water management objectives in Section 3.1.2.
- Does not have adverse effects that are inconsistent with the river and lake bed structures objectives in Section 4.2.2.
- Does not obstruct fish passage where it would otherwise occur in the absence of unnatural barriers, so that trout or indigenous fish can complete their lifecycle.
- Results in no increase in the adverse effects of flooding or land instability hazards.
- Results in no loss of existing aquatic habitats as a consequence of channelisation of rivers.
- Increases the use of off-stream dams for water supply purposes as an alternative to dams in perennial streams.
- ensures that decisions regarding the damming and diverting of water take account of the consequent loss of water quality and any associated reduction in contaminant assimilative capacity, minimum flows and allocable flows for out of stream uses as provided by Section 3.3.3 Policy 1 and Table 3-5 of Chapter 3.3.
Principal Reasons for Adopting the Objectives
The objective acknowledges that the objectives for water management in Section 3.1.2 and for the management of structures on the beds of rivers and lakes in Section 4.2.2 need to be applied to the effects of damming and diverting of water where they are relevant to the effects of the activity. In addition to these objectives, there are a number of effects of damming and diverting of water that are different from the other issues addressed in the Plan.
Part c) identifies that a major consequence of damming and diverting of water is the blocking of fish passage. For a number of indigenous fish species and trout in some areas such as Lake Taupo, the ability to migrate is a critical component in their lifecycle. If they cannot migrate to spawning areas or to adult habitat, the fishery will become unsustainable. Dams and diversions in water bodies that are important for fish spawning or habitat must provide means by which fish can pass the structure if it is necessary for them to do so.
Part d) identifies that the damming and diverting of water can cause flooding or erosion effects on neighbouring properties. This is due to the inevitable changes in water levels and velocities as a consequence of the damming and diversion of water. The objective identifies that no increase in the adverse effects should be allowed to occur as a consequence of damming and diverting of water. It should be noted that where a neighbour consents to the effect of flooding on their property the effect should no longer be considered to be adverse.
Part e) addresses effects of channelisation of rivers through stopbanks, drainage and flood control schemes. These schemes have sometimes been installed with little consideration of their effects on habitat. These schemes can have the effect of denying access of indigenous fish to important spawning habitat. The objective acknowledges that restoration of the habitat to the former state is not an option. Existing damage to habitat cannot be remedied as the schemes provide important community benefits. However, if new works are undertaken they will need to mitigate their adverse effects on habitat by enhancing currently degraded habitat or creating new habitat.
Part f) acknowledges that off-stream damming, an activity increasingly occurring in the Region, can have a range of positive outcomes that Council wishes to encourage. In particular, off-stream damming can mitigate the effects of flood flows and reduce the need for damming of perennial waterways and the associated adverse effects. The increase use offstream dams to store water in the wet seasons will also reduce reliance on surface water takes and lead to more efficient use of water.
Part g) and the parallel objectives in Chapters 3.3 and 3.5 ensures that when allocating water or considering discharges to water or the damming and diverting of water, both the effects on contaminant assimilative capacity and allocable flow are accounted for.