We thought the river was low in July but with the odd short lived rise the levels have got lower and lower. In the mainstem the low water is probably good for juvenile production, as a greater area becomes suitable habitat for fry. The advantage of this possibly outweighing the loss of the usual marginal habitat and most of the remaining side channels. Old maps of the river provide an insight as to how the river used to look with braided sections and side channels common wherever there was a floodplain. Many of these side channels have been lost for a variety of reasons but those that remain provide important habitat for a variety of species, not the least of which is the salmon with good spawning beds often found in the side channels away from the power of the main river.
The photo below shows an important spawning side channel where the flow has all but disappeared apart from some seepage through the gravel. There were about 15 redds in this channel last December.
Most of the fry and parr that use these side channels will have moved into the mainstem as the flow dropped but there were still a few trapped. As well as the salmon, pearl mussels also frequent these shady side channels. They don’t have the same ability to move as the salmon and there were many stuck in the pools between the gravel bars.
However the mussels may survive through the dry spell; it looks as if salvation may be on its way as the forecast for the next few days is the most promising for a while. The flows will surely be high enough by spawning time for the fish to use the channel again as they always do.
In the same vein and perhaps providing a portent of things to come it would appear that SSE are unable to fulfil their compensation flow obligations in the Truim and Tromie. The Tromie compensation flow has been cut and the Truim was about 50% of its normal level yesterday.
The reduced compensation flow is part of the reason for the low flows in the river at present. I often thought our forefathers generally did a good job when flows were negotiated during the development of the big hydro schemes in the 40s and 50s. However now we are faced with the distinct possibility that careful balance between abstraction and compensation will be lost – sadly it may be take take from now on!