Alternatives

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The work leading up to the selection of the Waimea Community Dam as the preferred augmentation option canvassed many different possibilities for a secure water supply.

These focussed on supplementing the urban supply to avoid Stage 3 rationing (which sees residents reduce water usage by 25% per day).

In July 2017, Tasman District Council revisited the work on alternatives, and combined the findings into a single review for the first time.

July 2017 review of options

The assessment examined all the water augmentation options identified since a 1991 Agriculture New Zealand report, including small dams, deep bores, a pipeline from Rotoiti/Buller River to Wakefield and pumping from the Motueka Aquifer. Household rainwater harvesting was also considered.

There are four options that would provide enough water to meet current and future urban demand:

  • the Waimea Community Dam
  • a high dam on the Roding River
  • transfer of water from the Motueka aquifer
  • storage ponds beside the Waimea River

The option of a dam at Teapot Valley was also included in a cost and capacity review for comparison of the costs of a smaller dam.

Water augmentation options chart
Comparison of options

The assessment showed that the Waimea Community Dam is by far the cheapest and most effective option for meeting the urban water supply needs today and in the future.

Capital cost for extractive capacity

It is also the only option that:

  • increases flows in the Waimea River to improve ecosystem health and meets new national freshwater standards
  • holds enough capacity for current and future primary production needs
  • secures the regional economy, and
  • leverages funding from partners – Waimea Plains water users, central Government (via the Freshwater Improvement Fund), and Nelson City Council (TBC).
  Waimea Community Dam Roding High Dam Pumping from Motueka Aquifer Waimea Storage Ponds Teapot Valley Dam
Capital cost to Council - urban supply $9m $95m - $145m $35m - $40m $24.6m $46.1m
Capital cost to Council - environmental flows $16m n/a n/a n/a n/a
Notes on capital cost   Includes dam, piping and treatment plant Serving Mapua only New ponds needed every 15 years  
Annual operating cost for Council - urban supply $300,000 $3.4m - $3.8m (includes dam and treatment) $750,000 $788,000 $1.1m
Water stored 13,000,000m³ 1,200,000 – 5,100,000m³ n/a 500,000m³ (More ponds needed for future demand) 500,000m³
Daily supply potential 31,000m³ (could supply up to 60,000m³) 30,000m³ 5900m³ (serving Mapua only) 4000m³ 4000m³
Capital cost per cubic metre per day - urban supply $290 $4000 $6356 $6150 $11,525
Waimea Community Dam
Capital cost to council - urban supply: $9m

Capital cost to council - environmental flows: $16m

Annual operating cost for Council - urban supply: $300,000

Water stored: 13,000,000m³

Daily supply potential: 31,000m³ (could supply up to 60,000m³)

Capital cost per cubic metre per day - urban supply: $290

Roding High Dam
Capital cost to council - urban supply: $95m - $145m

Capital cost to council - environmental flows: n/a

Notes on capital cost: Includes dam, piping and treatment plant

Annual operating cost for Council - urban supply: $3.4m - $3.8m (includes dam and treatment)

Water stored: 1,200,000 - 5,100,000m³

Daily supply potential: 30,000m³

Capital cost per cubic metre per day - urban supply: $4000

Pumping from Motueka Aquifer
Capital cost to council - urban supply: $35m - $40m

Capital cost to council - environmental flows: n/a

Notes on capital cost: Serving Mapua only

Annual operating cost for Council - urban supply: $750,000

Water stored: n/a

Daily supply potential: 5900m³ (serving Mapua only)

Capital cost per cubic metre per day - urban supply: $6356

Waimea Storage Ponds
Capital cost to council - urban supply: $24.6m

Capital cost to council - environmental flows: n/a

Notes on capital cost: New ponds needed every 15 years

Annual operating cost for Council - urban supply: $788,000

Water stored: 500,000m³ (More ponds needed for future demand)

Daily supply potential: 4000m³

Capital cost per cubic metre per day - urban supply: $6150

Teapot Valley Dam
Capital cost to council - urban supply: $46.1m

Capital cost to council - environmental flows: n/a

Annual operating cost for Council - urban supply: $1.1m

Water stored: 500,000m³

Daily supply potential: 4000m³

Capital cost per cubic metre per day - urban supply: $11,525