Rainfall

Waiheke residents depend on the rain harvesting as there is no water reticulation on the island. Water is collected off the roof and stored in tanks. These range in size but a typical modern house would have at least on 5000 gallon (22500 litre) tanks.

NIWA and the NZ Meteorological Service have a long-term rainfall monitoring site at Awaroa on Waiheke Island. Mean annual rainfall in the Awaroa Valley, Waiheke Island, is approximately 1,280mm Source Auckland Water Resource Quantity Statement 2002

For every square metre of roof each millimeter of rain will equate to 1 litre of water. Hence withan annual rainfall of 1,280 mm and assuming a 100sqm roof an average house will expect to collect 128,000 lires of water in a year. This allows 350 litres per day. The average houshold usage in the Metrowater catchment area is 501 litres per day. Source Local Government andEnvironment Committee submission on water charges

Th flaw in this calculation is that during winter months a lot of the collected water is lost as the tanks overflow. Many Waiheke residents have to buy in water from one the water delivery companies on the island. These companies draw water from bores drawing water from the Waiheke aquifer.

It is believed that Waiheke water usage is as low as 100 litres per day per person.

Rain this year Rain this month Rain today

Source Waiheke Weather Network rain gauge Onetangi