Hundreds of fish died after Warnham Mill Pond reservoir was accidentally emptied on Monday (October 6).
An ecological survey took place yesterday (Tuesday October 7) to determine the extent of damage caused to the aquatic ecology at Mill Pond, following the failure of a sluice gate to close at a planned operation by the Environment Agency to lower water levels.
The sluice gate suffered a mechanical failure yesterday, causing the Mill Pond to empty.
As a result some fish and silt were washed downstream into the Boldings Brook, a tributary of the River Arun.
The river downstream has been inspected and a number of fish have died. It is also possible that there has been some damage to aquatic ecology due to the siltation of the river bed.
Cllr Jonathan Chowen, Cabinet Member for Arts, Heritage and Leisure, said: “The Mill Pond is an important and popular nature reserve and we are seriously concerned about the potential impact this incident has had on the ecology of the lake.
“It is too early to know the extent of the damage until the ecological assessment has been carried out. Once we have the results, we will be able to discuss appropriate remedies with the Environment Agency.
“In the meantime, I would like to thank our council officers who worked tirelessly to support the Environment Agency following the incident. The rescue operation that was mounted saved many fish that had got caught downstream. They did an excellent job in very difficult circumstances.”
David Willis, the Environment Agency’s area duty manager, said: “During a planned Environment Agency operation to lower water levels at Warnham Mill Pond Reservoir, near Horsham on Monday (6 October) the main sluice gate was opened to allow water to drain out but couldn’t be closed properly afterwards.
“Our officers managed to manually close the sluice gate, but while it was open water drained out of the mill pond resulting in some fish and silt being washed downstream into the Boldings Brook, a tributary of the River Arun.
“This resulted in approximately 250 adult fish and many smaller fish being killed.
“Our ecological surveys today (Tuesday 7 October) show that apart from this initial fish kill, there has been no impact on nature conservation downstream of the sluice.
“We are also investigating why the sluice gate did not operate as planned.
“Our initial investigations have shown that this was because an alarm sensor prevented the gate from closing in the normal manner and manual over-rides did not function properly.
“The water levels were being lowered to allow essential construction works to the reservoir in order to ensure its safety during extreme flood conditions.”
For the full story and reaction see this Thursday’s County Times. What do you think? Comment below or email the newsdesk.