Rainfall and snowmelt replenish our freshwater systems, and help determine natural river and groundwater flows. New Zealand receives a plentiful supply of fresh water but it is not uniform across the country, with rainfall generally much higher on the western side of both the North and South islands. Climate change is predicted to affect rainfall patterns, which may exacerbate pressures on freshwater quantity and flows in some areas of the country. Dams, diversions, and water takes have changed the natural patterns of water flow.
Our reliance on irrigation, especially in drier regions, to support our economy, has the greatest potential of all uses to cause altered flows downstream. Unnatural flow patterns can affect the biodiversity, health, and mauri of freshwater ecosystems and many of the services they provide (Booker et al, 2016b).