Managing the water

By Stu Kneebone, Waipā-King Country councillor

The rain events we’ve experienced this summer have been hugely challenging for some parts of the country. Acknowledging that the Coromandel has suffered significant landslip damage due to saturated catchments, creating major issues with the roading network, with significant impacts on the local community, the Waikato as a whole has escaped relatively unscathed.

Many will have observed that discharges from the Karapiro dam have been significant at times during the summer months. This is because the Waikato river is managed as part of an integrated whole of catchment approach to ensure as far as is practicable, flooding risks are minimised for those in more vulnerable parts of the catchment that have flood risk.

The Waikato River is New Zealand’s longest at 425km. Overall, it drains water from 12 per cent of the North Island. In addition, water is also contributed via the Tongariro scheme, diverting water from outside the Waikato catchment, and through three hydro-electric dams before entering Lake Taupo and the Waikato system. There are a further eight hydro-electric dams on the Waikato River.

When significant rain events are forecast, Waikato Regional Council (WRC) and Mercury (operators of the hydro dams) work closely together to manage various risks to the wider catchment from the river system.

The Waipā River can have a significant effect on the Waikato River system when it is in flood. While the Waipā catchment is only 20 per cent of that of the Waikato, it can contribute between half to two thirds of the flow in the lower Waikato river during peak discharges.

When necessary, the management of outflows from the Tongariro diversion, Taupō