Last Friday Steve and myself went up the Dalwhinnie to record some transects (cross sections) of the Truim. The purpose was to collect baseline data for the Truim in advance of the SEPA decision on the Scottish and Southern application to remove the compensation flow in the river. The transects involved measuring the depth, substrate and flow velocity every 50cm across the width of the river. All transects were marked with wooded stakes so that they could be repeated in future.
Before establishing the transects we recorded the water level at the compensation flow gauge. It was 0.44m, slightly above the compensation flow level, but as good as we could expect at this time of year.
When selecting our transects we were looking for sites exhibiting a range of characteristics, e.g. width, depth, flow etc so that the impacts of any future changes in river flows would be apparent across a range of habitats.
The results from each transect are displayed below in a graph showing the depth and water velocity. Unfortunately it is not possible to present wide images on the blog so apologies if they are difficult to read. The depths at this transect were relatively consistent.
The second site was the widest at 17.6m. An electricity power pole was used as the reference point on the left hand bank. All measurements were taken from the left bank.
The third transect was established opposite Dalwhinnie Distillery, close to one of our electrofishing sites.
The Truim in the vicinity of Dalwhinnie had been dredged in the not too distant past and as a result has become highly mobile upstream of the distillery.
Transect 4 was a short drive downstream of Dalwhinnie in a typical part of the river with pool and riffle sequences. The transect was established close to the tail of one pool.
The last site was downstream of a concrete bridge just above the Cuaich confluence. We completed an electrofishing survey here last summer.
We had intended to do another transect downstream of the Cuaich but there was a much higher flow in the Truim compared to normal so we left it for another day.
The heck gates were secured in a lifted position, presumably because no salmon would be expected to run up the Cuaich so early in the year.
The data collected during these transects may prove to be very useful when decisions affecting the quality and quantity of juvenile salmonid habitat in the Truim are discussed.
It was good to get out of the office again although the weather at Dalwhinnie was quite different to the mild sunny conditions that we left behind at Knockando. It really has a been a remarkably good winter in Morayshire; dry almost every day, mild and no lying snow this year. Thankfully in the upper catchment things are quite different with the snow lying thick on the hills.