Options to minimise the effects of water abstraction activities on water quality and mahinga kai.
When natural seasonal flow variations are interrupted by taking water extreme care must be taken to maintain the amount of water needed to support healthy ecosystems. The amount of water needed is called environmental flow, which considers maximum and minimum flow levels to support a healthy ecosystem. Failure to provide an environmental flow can have serious consequences for water quality and mahinga kai.
When there is very high demand to take water from a particular waterway the following options should be considered:
- Identify minimum flows that can be sustained by a waterway.
- Calculate the maximum amount of water that can be taken from a waterway based on minimum flows.
- Allocate only a proportion of this amount to account for and ensure against overallocation.
- Review and adjust allocations when needed.
The following need to be considered as minimum requirements to maintain natural water flows:
- Regulate minimum and maximum flow levels in waterways so that there is sufficient habitat for fish and invertebrate life.
- Maintain natural channels and depth - create natural meanders, low flow channels and rest areas for mahinga kai species.
- Prevent temperatures from reaching lethal or extreme levels due to low flow or water levels.
- Facilitate up and downstream passage for fish migration where these may be blocked at the water intake - using ramps, ladders and spillways.
- Divert fish away from intake screens and outlet pipes.
Riparian vegetation - maintaining fish habitat
- Maintain, restore, and enhance riparian vegetation and wetland areas, which serve as spawning grounds and shoaling habitats for mahinga kai. Wetland areas and native planting also create refuge areas, lower water temperatures, and provide a food source of invertebrates for mahinga kai species.
- Fence waterways.
Water reuse and reduce for industry
- Minimise the use of water in any existing plant.
- Reuse water where possible without treating first.
- Design or select a plant that uses less water.
Application criteria for irrigation
- Improve irrigation practices - low flow and application options.
- Avoid excess water applications that could lead to surface runoff.
- Apply water at times and at rates equal to a particular crops needs.