Our land use and freshwater
Our land use affects the quality of our freshwater and the species living in it.
As urban areas in Aotearoa New Zealand expand and agriculture becomes more intensive a larger volume of water is taken out of rivers, lakes, and groundwater.
Taking water from rivers alters the volume and flow of water. This can degrade freshwater ecosystems and reduce freshwater quality.
Five per cent of agricultural land is irrigated. The amount of irrigated land is increasing especially land irrigated for dairy farming.
Irrigation uses large amounts of water. Scientific models predicted that irrigation had the greatest potential to reduce river flows across the country compared to other water uses.
Excess sediment and pollutants can cause poor ecological health and reduce biodiversity in rivers and lakes near urban, farmed and forestry lands.
Applying nitrogen or phosphorus fertilisers to the soil continuously can increase the risk of these elements moving into freshwater and leaching into groundwater.
Nitrogen and phosphorus can cause algal blooms in rivers and lakes. This reduces the amount of oxygen in the water for plants and for fish to breathe. Too much nitrate-nitrogen (one form of nitrogen) in groundwater used for drinking water is also a potential human health concern.
Fencing streams and timing irrigation are some ways to reduce the amount of nitrogen that ends up in our freshwater.
Urban and agricultural land-uses produce waste which can also pollute waterways.
This can happen when rural waste (eg, agricultural plastics, and agrochemicals and their containers) blows into waterways or when contaminants soak into groundwater.
Pollutants from cities and towns (eg, heavy metals from vehicles, plastic litter and garden fertilisers) can enter rivers, lakes, estuaries, and beaches through stormwater networks.