Above Dam Users Update - 06/03/2015 - Opuha Water Limited

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  • March 06, 2015

“Above Dam” irrigators (Nth Opuha, Sth Opuha, upper Opihi and Te Ngawai irrigators)

Here’s a quick update on the situation as it now sites (I have just got off the phone from ECan to get them to delay the update of their Restriction for tomorrow to give the tribs time to pick up a bit more hopefully)

The rain has been heaviest in the north of the catchment so the North Opuha is well up, Sth Opuha is starting to respond now and should sneak through 500 l/s by 5pm (ECan’s Restriction had locked in 495!). It doesn’t look like the Opihi and Te Ngawai are going to get above their trigger (today at least).

The slight problem we have is that the flow at Saleyards Bridge (SYB) is still below our agreed minimum of 2.5 cumecs (it is currently 2.2 cumecs) I cannot release anything from the dam to supplement this (and the way the river is behaving it would take 24 hours to affect SYB) I do expect SYB to pick up over the next 10-12 hours since it will be influenced by the slight increase in the Opihi, Te Ngawai and the Opuha itself has also picked up inflows below the dam.

The lake is currently at 370.05m – i.e. only 50mm above the floor where there would be no irrigation. That represents less than one more days operation at our current minimal discharge. The high inflows from the North Opuha at least should assist in bringing that back up to give us a few days more of operating volume.

So for the irrigators above the dam (Nth and Sth Opuha) we have two out of three:
Your tribs – yes

Lake level – yes (but skin of our teeth)
Saleyards Bridge – not yet

As I mentioned in the email last night (below) the Restriction page refers to tomorrow so that starting tomorrow, you can irrigate for 24 hours as long as we get sufficient flow at Saleyards Bridge.

My recommendation is that you need to wait until tomorrow morning when I hope that SYB flow has climbed +300 l/s to 2.5 cumecs and then be prepared to irrigate for 24 hours. The latest 24 hour window is 9am Sat to 9am Sun. Of course if the river flows all remain above their trigger, then there will be another day available Sunday. It looks like there may be some more rain late Saturday so it might be a two bite process depending on how the rivers hold up over the next 36 – 48 hours.

You can monitor the SYB at http://ecan.govt.nz/services/online-services/monitoring/river-flows/Pages/river-flow-chart.aspx?SiteNo=696501 but I will update you from 7am in the morning.

I know you will be desperate to get irrigating but the best option and this all probably seems awfully complicated but I do stress that we have been doing our best to enable you all the opportunity and we have a lot of eyes on us since we have required a number of dispensations for this scenario and the lake and the lower Opihi River have NEVER been as low as they are at present since the dam was commissioned.

I will keep you updated as best I can.

Regards, Tony McCormick