The Waimea Plains and surrounding towns draw their water from the Waimea River and its associated aquifers. Since the 1980s, water in the Waimea Plains has been over-allocated (i.e. there is not enough water for all the people who have consents to take water, including urban water supplies, rural irrigators, commercial and industrial water users). Extended periods of dry weather or droughts have meant Council has had to impose water restrictions nearly every summer since 2001. These water restrictions affect the lives of everyone living and working in the Waimea Plains and the viability of businesses which rely on a secure water source.
If there is no Dam and river flows are low, all water take permits from the Waimea aquifers and river system could be cutback by as much as 100%, depending on the severity of the drought. This includes urban water supply permits also, but by a lesser amount. These cutbacks are required in order to protect the health of the Waimea River and avoid saltwater contamination of groundwater.
Water cutbacks would have a large impact on Waimea Plains urban, rural restricted and industrial water users in Richmond, Brightwater, Redwood Valley, Mapua and Nelson South; on commercial water users in the surrounding area; and on horticultural and agricultural water users.
Security of water supply, particularly over the summer period with peak water demands, is essential for the local economy. A third of all employment in the Tasman District is in the primary industries and manufacturing sectors. 50% of Council’s urban water supply for the areas is used by businesses.
There is a strong belief within sections of the community that there is plenty of water in the aquifers and therefore abstraction restrictions are not necessary. It is true that there are large volumes of water in the aquifers, however the volume of water is not the issue. The issue is the water level in those aquifers. Abstraction will draw the water level down to a point where it detrimentally affects the flow in both the Wairoa and Waimea Rivers. The rivers dry up as the water naturally wants to drain into the aquifers to restore their water levels. The lower water level in the aquifers would also encourage salt water to drain into them from the Waimea Estuary thereby increasing the risk of salt water intrusion. It is therefore critical that the flow is maintained in the river to retain water levels in the aquifers as abstraction occurs.
Our Region is projected to experience more extreme and more frequent drought conditions. Without a dam or other water augmentation project, we would currently have some form of water rationing for nine out of ten years. NIWA predicts that due to changing climatic conditions, parts of the Tasman Region, including the Waimea Plains, will by the year 2070 -2090, experience a 10% increase in the frequency of droughts that it currently experiences.
Statistics New Zealand’s medium series of population projections show Tasman’s population growth is projected to be 9% between 2018 and 2038, with growth in the Waimea catchment area expected to be higher. However, recent population and dwelling growth rates indicate that growth is likely to be higher than the Statistics New Zealand medium growth scenario. Due to the combination of population growth and a trend for smaller households, we expect that housing demand will grow at a higher rate over this period, placing more pressure on our water supply.
Since 1991, Council has been involved in the investigation of water supply augmentation options for the Waimea Basin.
The Waimea Water Augmentation Committee was established, which was an innovative approach for its time. It was made up of both councils, DOC, iwi, Fish & Game and irrigators and they looked at the options for augmenting water flow in the Waimea River to provide both extractive use, town and business supply irrigation and in-stream values.
18 different sites were looked at, with several re-assessed and presented to Council in various forms. This included examining the potential for Nelson City Council to supply Tasman. We have also considered options to reduce demand by water harvesting (e.g. rain water tanks).
The presentation outlining the options, assessment and analysis can be found here: Alternatives Waimea Water Augmentation Project (2017) Presentation (pdf 2.3 MB)
Eventually the eastern hills option was chosen over the western hills as the most viable, and Lee Valley was chosen over Wairoa Gorge.
Provision has been made for installation of hydroelectricity generation to utilise the stored energy in the water as it is released into the Lee River.
For information on water management and changes to the Tasman Resource Management Plan see: Dam or no-dam scenarios
If the Dam does not proceed, the Nelson-Tasman economy would be $20 million smaller each year on average with water allocation cuts of 20%, and $49 million smaller with cuts of 35%[1].
The potential financial and economic loss from a no dam option is estimated at $932m assuming a 20% water take cut, or $1,205m assuming a 35% water take cut. Of this total, an estimated $29m was the lost opportunity cost of environmental improvement in the river system[2].
[1] The New Zealand Institute of Economic Research (2017) report
Last modified:
