Picton Water Supply

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Managing Picton's water use this summer

While the Speeds Road water treatment plant is being built and local stream water levels remain high, the Essons Valley dam provides 45% of Picton's water supply.

However, when local stream water flows reduce in summer and the water depth in the dam drops, algae growth can occur. This means the water is much more difficult to treat and we lose that source of supply.

If everyone plays their part by conserving water, we can extend the period in which the Essons Valley dam water can be treated and supplied to Picton's homes and businesses.

The graph below shows that if the water depth at the Essons Valley dam reaches zero, further water restrictions may be necessary for Picton.

Last week Picton's water demand crept above the current network's capacity. We managed to meet demand through this period because the Essons Valley treatment plant was able to produce more water than is normal. However, as the summer progresses and the water in the Essons Valley dam becomes warmer and algal growth greater, these volumes will not be able to be produced. The Picton community are urged to conserve water as much as they can to enable the network to meet demand.

While the Speeds Road wells are being upgraded, the water supply available to Picton and Waikawa water users will be 20% to 25% less than usual. This means careful water use is required so that the town does not run short of water. All residents are asked to think twice about the water they use - if everyone takes care not to waste water, restrictions may not be necessary.

If water demand continues at the level it has been over the last 10 days, water restrictions will be required during commissioning of the new water treatment plant.

Picton Water Demand Graph

Picton Water Supply Daily Average Demand versus Water Available (PDF, 37.8KB)

A similar graph helped Renwick residents to successfully manage their water use last summer.

The blue line on the graph depicts the weekly average water use over summer last year and the green line shows the weekly average water use in the corresponding week this year. The red line shows the total daily water volume available to the Picton water supply while the Speeds Road treatment plant upgrades are taking place. If water demand were to reach the red line, water restrictions will be necessary to enable the supply to meet demand.

Thank you for helping to conserve water - we're all hoping to avoid water restrictions this summer.

What can you do?

The biggest draw on Picton's water supply is garden irrigation. Sprinklers can use hundreds of litres of water each day. One sprinkler can use more than 900 litres an hour.

We encourage all residents to adopt these water saving methods:

Gardens and lawns need only half an hour of watering two or three times a week
Use efficient watering systems rather than sprinklers with sprays or wands
If using sprinklers with sprays or wands, make sure they are not watering the concrete
Mulching helps retain soil moisture. Lay soak hoses under the mulch
Water in the early morning or evening to get maximum benefit
Use a timer on your garden irrigation system - they're available from the hardware shop
Don't cut lawns too short; longer grass helps slow down evapotranspiration and the lawn will need less irrigation
Opt for more drought-tolerant plants where possible
Fix dripping taps

What Council does to help

The irrigation regime for Picton sports grounds will be reduced over the summer. However, a certain level of irrigation is required to ensure surfaces remain safe for play.

Council has asked Port Marlborough to manage water use and wastage in the marinas, and to encourage marina users to avoid wastage. Water meters are already in place measuring all Port Marlborough's water use.

Picton's water supply

Picton's main water supply is bore water drawn from an aquifer at Speeds Road.

In summer, this supply is supplemented by treated water from the Essons Valley.

Water use is measured in cubic metres. Over the last eight summers, average daily water use in Picton has been 4,450 m per day, with peak use of 5,770 m on one day. Last year the daily average was 3,800 m per day.

Restrictions have been required in past years when issues have arisen with the quality of the water in the Essons Valley dam; when at times it has become untreatable and when upgrade work has been underway.

Speeds Road

Speeds Road water treatment plant has been upgraded and was commissioned in April 2017 and now provides potable drinking water.

Essons Valley

The Essons Valley water supply comes from a stream-fed source so the water has a discernibly different taste. Some people notice the change in taste but can be assured that the water quality is maintained.

The Essons Valley supply was upgraded in 2011 and its water supply fully complies with National Drinking-water Standards.

History of Picton Water Supply

Picton's water supply was first developed in 1891 when a dam was installed in the Waitohi Stream catchment. Water was delivered into the town via 225 mm trunk main, installed in 1907 from the dam to Oxford Street. In the 1920s, Humphreys Dam was added to the system.

By the 1950s, a new source of water was needed to meet the demand of a local freezing works and the growing demands of Picton town. A new impounding dam and reservoir were constructed in the Essons Valley. A 225 mm cast iron watermain providing a direct supply from the new Barnes Dam to the freezing works was completed in 1952. The freezing works had paid the cost of the development and were given priority use of the water. However, a 1958 agreement between the freezing works and Picton Borough Council allowed a public supply from Barnes Dam whilst there was sufficient water for both. When water levels dropped below a pre-determined level, the borough supply was cut off and the public reverted to water from the Humphries and Williams Dams. In 1984, the freezing works closed and Barnes Dam became available exclusively for the municipal supply.

In 1975, the Borough developed a new bore water source at Speeds Road, Koromiko, 8 km south of Picton. Three bores abstract water from a shallow aquifer. It was decided the most cost-effective water supply for Picton would be utilising Barnes Dam with Speeds Road supply as a backup.

Today, the early dams are no longer used and the Speeds Road bores and the Essons Valley water treatment plant (Barnes Dam) supply Picton's water. Both supplies are required to meet demand during the summer peak. However, the impounded water in Essons Valley can suffer from quality problems during the summer if the stored water stratifies and algal growths are allowed to bloom. In these circumstances, the Speeds Road bores becomes the sole source for the peak demand period. The Speeds Road supply has proved a very reliable source of water. The only exception was the prolonged dry spell of 2000/01 when water abstraction was reduced. Speeds Road wells are now more drought resilient. The wells have been re-drilled and deep sumps provided to house the submersible bore pumps deep below the water level.

The water from the Speeds Road bores is disinfected with chlorine and the pH is raised by lime dosing before being pumped to the main Elevation Reservoir on the southern edge of Picton. Dual raw water mains feed water from the Barnes Dam by gravity to the Essons Valley treatment works. During 2011, the Essons Valley WTP was upgraded to improve the coagulation and flocculation of the raw water to enhance the filtration, the addition of ultraviolet disinfection and improved monitoring of chlorine levels. The output of the plant now meets the requirements of the DWSNZ. Further upgrade work is underway at the Speeds Road Water Treatment Plant to provide protozoal compliance with Drinking-water Standards NZ.