Water resources and mining
How may the activities of the mining industry influence water resources?
During some mining activities, particularly gold mining and dredging, water is used for sluicing and flushing out minerals. In most mining operations the majority of this water is recycled, so water loss from rivers and streams is minimised. Water take (abstraction) can be more pronounced where dredging occurs near the riverbed. Loss of water may reduce instream habitat, elevate water temperatures, and increase summer algal blooms, which may affect invertebrate and mahinga kai communities.
Impacts of water take (abstraction) on water quality and mahinga kai
- Changes in flow - changes in water levels and flow variability alter 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 affects movement and deposition of sediments in streams and rivers.
- Changes in water quality parameters - for example, turbidity and temperature 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.
