The week has been dominated by persistent rainfall. Genesis Energy posts rainfall information and we have the link on our website, front page. A good look at the graph reveals much about what is happening here as does the Weather url for the NZ met service. Taupo and Taumarunui have data recorded and we are in between. The Biches weather information is accurate for Turangi but small print. (A job to be done here)
Turangi – Rainfall
From this graph you can see that it has been wet. There has been a lot of rain some of the showers being quite heavy. There has been some lightning. The forecast is looking good this weekend. At last a chance to get the washing dry on the line.
Normal river flow is around 22 cumecs through Turangi. Because of the rain the river has run higher than normal and dirty for much of the week. The floods are insignificant in terms of size when against the 1958 and 2004 floods which ran around 1400 cumecs. The dirty water makes wading unsafe. I tested the water on Monday. It was high. It was dirty. With my wet line I tried the water from the beach at the Lower Island Pool. I had one good bite for my efforts.
You can see from this graph that the river has run higher than normal and in the process it has affected the fishing. This graph is on the front page of our website and is useful in determining the state of the river in bad weather events. If you check the river-flow over three months you can see that this is a small flow but is none the less a nuisance.
Tongariro at Turangi – River-flow
Like wise Mighty River Power produces a graph showing the level of Lake Taupo.
Mighty River Power control the water levels in Lake Taupo.
They must operate this control so that the level does not exceed 357.9m above sea level nor go below 355.85m while at the same time accommodating the vagaries of weather. The only outlet from the lake is the Waikato River at Taupo. The control gates can release only 200 cumecs which at times is not balanced by the inflow in bad weather events. The management dilemma in a bad weather event is whether flooding should occur downstream at the confluence of the Waipa river with the Waikato near Hamilton or the level of Lake Taupo be allowed to rise causing problems around the lake.
The operating levels are :
“Management of Lake Taupo
2.1 The consent holder may at any time operate the Taupo gates
to manage the level of Lake Taupo, for the purpose of water
storage for hydro electricity generation, between the following
357.25 masl (maximum control level), and
355.85 masl (minimum control level)”
We think a modified operating regime within these levels could reduce the problem. Our argument can be seen in our 2008 annual report which is found on our website in our archives.
This continues and willows to the rivers edge have now been cleared. Waikato Regional Council staff would have had some apprehension with rising river levels that the river did not rise to a level which would have washed the willow piles downstream and into the lake.
Silt and sand
I reported that the rver bottom was clearing last week. The sediments will have changed the river bottom again and take a little while to settle when the weather clears and the river level drops. My concern is that the “plug” at the delta mouth does not seem to be monitored and I question what is happening at the delta as a result of the silt that has gone down stream. I could be wrong but I see the plug blocking the silt making it into the lake.
I think that the first week of the school holidays is looking good on the river.