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Restrictions expected soon for river irrigation users in Marlborough

Contributor:
Fuseworks Media
Fuseworks Media

Restrictions are looming for irrigators on several Marlborough rivers as flows drop in response to the warm summer weather. All Marlborough’s rivers have minimum flow levels at which consent holders are required to shut them off. Several rivers are rapidly approaching those thresholds. River water irrigation users are advised to monitor their usage and river levels closely over the coming days.

Council’s Environmental Scientist - Hydrology, Val Wadsworth says the forecast is for continued settled weather until the end of next week, apart from some possible brief showers tonight in the ranges.

"One of the first river takes likely to be affected soon is the Wairau. Our site measurements show that bed level changes mean the flow rating has changed. The actual flow is now below 13 m3/s, not the 20 m3/s shown earlier this week.

"All irrigation takes from the Wairau River will stop when the flow reaches 8 m3/s, so a shutoff next week looks likely."

The Council will start to ramp down environmental flows into Gibsons Creek later this week. The Southern Valleys Irrigation Scheme availability will not be affected at this stage, but it will be shut off at the same time as the other Wairau Class B takes.

Other rivers

Rai - flow is currently about 1.1 m3/s with shut-off for irrigators at 1.0 m3/s. The Rai river low flow recession is often quite gradual, so consents may remain available into early next week.

Waihopai - flows about 2.3 m3/s, approaching the Class B shut off. Normally once the Waihopai reaches this level flows tend to drop off quite quickly, so the shut off of Class A consents may follow quite quickly after the Class B shut offs.

Awatere - flows still quite healthy at about 4.7 m3/s, still above the mean annual low flow, and the Class B shut off.

Irrigation status and river flow graphs can be found here:

http://hydro.marlborough.govt.nz/environmental

https://www.marlborough.govt.nz/services/irrigation/southern-valleys-irrigation

"Our aquifer levels remain healthy at this stage of the season, especially at Rarangi, the Southern Valleys and Woodbourne. The recharge sector of the Wairau Aquifer is reflecting the low flows in the Wairau River, while demand at Riverlands is causing levels to decline below the seasonal average for late January," says Val.

"Overall there is no reason for concern yet in terms of very low levels or high salinity. The Council’s hydrology staff are monitoring the indicator wells closely."

Stephen Rooney, Council’s Operations and Maintenance Engineer, says that almost all of our water supply networks are coping.

"Renwick residents, who are to be congratulated, have continued to voluntarily keep demand down but the aquifer there is starting to deplete because of the low river flow."

Everyone, including Blenheim residents, should avoid irrigating their gardens or crops during the day.

"The best time to water plants is early in the morning or late in the evening."

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