Impacts of water take

Taking water from a stream or river reduces water levels and changes natural flow patterns.

When natural seasonal flow variations are interrupted by taking water from streams, rivers, and lakes 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. 

Taking water for industry or agriculture reduces the natural flow of a river or stream, or reduces water levels in a lake. This impacts on mahinga kai by changing and reducing available habitat and food supply. The taking of water for irrigation increases farm productivity but also reduces water flow and has the added potential to increase both point and non-point sources of pollution into surface waters.

Find out more about water resources and agriculture

Water is used variously for cooling, heating, cleaning machinery and manufactured products, and as part of the manufacturing process itself. Water is used in many industrial processes as a cooling agent. Cooling systems are used to remove heat from various sources such as machinery or heated processed material. Water is circulated to absorb the heat. The water can then be either returned to the water body from where it was extracted, or cooled using air contact and evaporation in a cooling tower.

Impacts of water take on water quality and mahinga kai include:

  • Changes in flow - changes in water levels and flow variability alters available mahinga kai habitat and the invertebrates they feed on.
  • Reduction in habitat - a decrease in water levels reduces habitat for fish and can impact feeding and spawning success.
  • Reduction in specialist habitats - a decrease in water levels reduces flow to riparian wetlands, backwaters, and intermittent streams.
  • Decreases in species abundance and diversity - aquatic species have developed life history strategies in direct response to natural flows, for example, diadromous fish species migrate up and down the river at various times of the year and rely on preferred velocities and depths.
  • Changes in sediment accumulation - flow reduction effects movement and deposition of sediments in streams and rivers.
  • Changes in water quality parameters - turbidity, temperature, and oxygen levels can increase with reduced flows in rivers. 
  • Increases in algae accumulation - algae respond to changes in temperature and nutrients which are likely to increase with reduction of flow especially during summer months.

Find out more about specific impacts of water abstraction for irrigation


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