Low water takes its toll

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.

Dried up spawning channel. The transverse gravel beds are the result of annual salmon spawning. These gravel bars provide ideal incubation conditions for salmon eggs.

Dried up spawning channel. The transverse gravel beds are created by salmon spawning in the same areas year on year. The gravel bars provide ideal incubation conditions for salmon eggs.

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.

Stranded pearl mussels in a silty pool. Surprisingly many were still alive although they must be under tremendous stress.

Stranded pearl mussels in a silty pool. Surprisingly many were still alive although they must be under tremendous stress in these conditions.

This one wasn't so lucky and it wasn't alone, the margins of the river are strewn with dead shells at the moment

This one wasn’t so lucky and it wasn’t alone, the margins of the river are strewn with dead shells at the moment. Some would have dried out but others would have been predated by birds or mammals.

Dried out caddis cases, will this impact next years hatch?

Dried out caddis cases, will this impact next years hatch?

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.

This is the level the Truim should be at, about 0.3 on the gauge with the water level at the marker.

This is the level the Truim should be at, about 0.3 on the gauge with the water level at the marker.

 

The Truim gauge yesterday. Surely it is not asking too mucb for SSE to advise the fishery board, and SEPA for that matter, that there was a problem with the compensation flow? Our calculation show that the Truim compensation flow equates to 3.3% of the low water flow at Boat o'Brig.

The Truim gauge yesterday. Surely it is not asking too much for SSE to advise the fishery board, and SEPA for that matter, that there was a problem with the compensation flow? Our calculation show that the Truim compensation flow equates to 3.3% of the low water flow at Boat o Brig. 

 

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!

 

 

 

There are 2 comments for this article
  1. Bryan Herbert at 10:40 pm

    Hi Brian

    Surely you have enough evidence there with the gauge and the mussels nearly high and dry to get Europe involved as from what I remember reading they the hydro electric have a legal obligation to maintain 60-70% flow at all times and also that the spey is an SSI. It sound like you have thrown in the towel in the second or third round of the fight instead of going the full twelve rounds remember it’s better fight and loose than not to fight in this case.

    Bryan

    • Brian Shaw Author at 9:03 am

      Hi Bryan,

      I think in this case the mussels would have been stranded even with the compensation flow operating as it was designed but for sure it will happen more frequently if the compensation flow is removed. Mussels are very demanding as far as water quality is concerned and my concern is that in 20, 30 or 50 years time when the mussels have stopped breeding people will be asking what went wrong with the Spey; it used to have the best freshwater pearl mussel population in the world. Abstraction tends to be a one way process; is removing even more from the Spey for hydro generation really the best use of that water? I very much doubt it, the sustainability of Strathspey depends on it.
      Brian

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