A series of very hot days in the last week has dropped many streams to critical levels.The Taieri at Outram reached a temperature of 26.4degC with a flow of less than two cumecs.
I wonder if minimum flows are calculated taking temperature into account?
The lower the flow, the more rapidly the water warms up during the day. The warmer the water the less oxygen it will carry — but reduced flow exacerbates this drop in oxygen. Streams can warm up by more than 8degC on very hot days.
Lack of oxygen causes fish kills if it is prolonged as well as increased levels of bacteria and algae.
Some time ago, the Otago Regional Council admitted the irrigation rights on the Taieri exceeded the total flow of the river, I wonder if that still is the case?
The Waipahi dropped to the third-lowest flow recorded recently. There is no temperature given for the water on the website but I suspect it would have been very high, not helped by the destruction of wetlands in the catchment.
Everyone complains about the extremes of climate — be it flood, drought or storm — but quickly forget about them when things return to normal, a normal that is now changing rapidly.
I fished the lower Taieri the other day. The water was flowing at just over two cumecs and clear. I caught a couple of fish in fast water which is not surprising.
I only saw one fish rising but caught several fishing with a weighted nymph in deep water. I also caught some perch that were feeding happily as they tolerate higher temperatures than trout.
My other outing was to Strath Taieri on a cold, blustery and sometimes wet day. I was glad to feel the coolness of the water compared to my previous outings in the last month. Even a few mayflies were hatching.
I started at a favourite ripple and immediately saw a rise. I had a few casts with a weighted nymph but replaced with a lighter one to fish to the rise. It took after a cast or two and was closely followed by another fish.
A good start I was thinking before the next two fish dropped off.
Just above the ripple there was a run beneath the willows. It looked rather shallow with the water at a low level but an exploratory cast produced what turned out to be the best fish of the day.
On the flat water above there were one or two fish rising — one of them took while I was just casting blind waiting for it to rise again. But the other followed the correct protocol when it rose and then took my nymph when it was dropped skilfully in front of it.
Twice I resorted to sheltering under the trees in chilly downpours that reminded me of the Waipahi in October. At one point when the sun came out I spotted a lamprey which from memory is a first for me on the Taieri.
Long may the cooler weather last.
