The Council's hydrological network provides a continuous record of data on river and stream flows at a number of sites throughout the region.
The recording station measures the river's water level (stage height) every 15 minutes and the data is relayed back to the Council's computer system.
A rating curve is used for each recorder site to calculate the flow (litres per second) from the water level. Council staff manually carry out flow gaugings at different heights of the river to build up the relationship between water level and flow, which is then plotted as the rating curve for that site. Gaugings are carried out by wading, using a boat, bridge or cableway.
Flow gaugings are also carried out at particular monitoring sites to measure the flow. Information about river flows is used to set abstraction rates (water taken) for resource consents, to ensure that sufficient flow is left in the stream for fish health, during low flows. Flow gaugings are also used to calculate dilution rates for discharges, to avoid harmful effects of too much pollutants.