For many years now the impact of heavy and poorly timed water abstraction from the river Usk has had a detrimental effect on the river and its environment in a number of ways.
Welsh Water pump water from the river (close to the estuary) in large amounts to feed the reservoirs of south Wales that supply water for the population of the South Wales Valleys and Newport. This can effect the height of the river by six inches within hours. One of the effects is that salmon waiting in the estuary for spate water in which to swim upstream to spawn never get it and thus never leave the estuary and eventually die. It is estimated that stopping this practice will mean a thousand or more fish returning to spawn.
The heavy pumping from the river negates the effects of spates which is what encourages salmon migration. Agreement has now been reached to release water in a timely fashion from the Usk reservoir at the top of the system so the effects of the spates can be mimicked and the period of the spate extended.
In the spring, higher flows will aid the migration of a greater numbers of smolts down river and out to sea, hopefully to return in years to come as adult fish.
The second big abstraction takes places upstream of Gliffaes at Brecon weir. It’s here that upwards of 30 million litres a day are taken from the river to supply the Monmouthshire and Brecon Canal. Although much of this water is returned to the river at the end of the canal it means that a large section of the river suffers very low flows particular during summer. This obviously affects trout fishing during the summer.
The above is a very simple summary of the work undertaken by the Usk and Wye Abstraction group to improve understanding of how abstraction effects river flows and how this impacts on salmon, other fish and the habitats of both rivers. The studies have identified ways to modify water abstraction and reservoir operation to improve the river environment, while still ensuring water is available for public supply and for the canal.
The important news is that after some years of study Welsh Water has put its money where its mouth is and has agreed to pay for the large engineering works to make the improvements and to use the reservoirs to mimic the natural flow of the river.
More information can be found on the Wye and Usk Foundation website