The only source of new water in the Wairarapa is through storage
The Tararua mountain range west of the Wairarapa valley captures an annual rainfall of 5-6 metres. However, comparatively little of it falls on the good soils of the flat valley floor that are potentially suitable for high-value production.
There is often surplus water for towns and farms in winter and not enough in summer. This problem can be solved by harvesting water during the wet periods and then storing it for use when it is needed most.
Current resource consents to take surface water account for nearly all of the available core allocation from rivers in the Wairarapa valley and limited additional groundwater is available. This means the only sustainable way of meeting any increased demand for water would be from storage.
Compared with pumping water from rivers and ground water during summer when water levels are at their lowest, harvesting and storing water during wet periods has the potential to supplement river and stream flows at critical times. It also allows for active management of the overall catchment, and can provide water for a wide range of uses including economic, recreational and social.