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Information about hydro stoppage on 10 December

We are most upset to learn that misinformation regarding a recent stoppage at Osney Lock Hydro has been circulated to local residents. We would like to reassure residents that the hydro poses no additional risk to flooding, and that our operation is fully integrated into the local waterways management system.

On the evening of Thursday 10 December Osney Lock Hydro stopped generating because of a fault with a component called an encoder.  This was fixed the next day and we are now operating as normal.

Under the condition of our abstraction licence we are able to divert up to 4 cubic meters per second of flow through the hydro.  This represents around 10% of the flow through the adjacent weir. When we don’t operate this water continues to flow through the main channel, and over weirs A, B and C depending on the total flow being passed down the river system.

We notified the Environment Agency of the fact that we were not operating. As a result they decided to increase the flow over Weir B as part of their fine tuning of the local flow management.  During the time we ceased to operate, an increase in river level was recorded. The fluctuation was insufficient to trigger the EA’s early warning system.

Fluctuations in river level are caused by many factors such as recent rainfall, the percentage of the weir gates open and how much water is extracted from the river at Farmoor.  The fluctuation on Thursday night was within the normal range at Osney. It is typical for levels to initially rise quickly in response to changes in flow, weir overspill then comes into play which slows the rate of rise. This allows time for action to be taken at the weir to adjust a gate opening to increase flow. The Environment Agency plan to automate Weir B in 2016 which will reduce the effect of changing flows on the river levels.

Stephen Naylor from the Environment Agency said, “We are working with OLH and our Waterways staff to manage flows as effectively as possible. We have an operating agreement that sets out the rules for operation of the hydropower scheme to maintain river levels for navigation. We are also looking at options to improve monitoring of river levels and automation of Weir B is an important part of that.”

Osney Lock Hydro, along with Osney Mill Hydro and the local weir system forms one part of our local river network, which is managed by, and under the control of, the Environment Agency.  This autumn, Environment Agency staff carried out scenario testing to ensure that they are satisfied their protocols are up to date with the changes to the weirs and addition of a second hydro.

Under the conditions of our abstraction licence during periods of abnormally high flow, the hydro will be switched off, and Environment Agency staff have direct control over the operation of the hydro to enable this to happen as and when they see fit.

We would like to reassure local residents that throughout the development of the hydro we have worked closely with the Environment Agency to ensure the addition of the hydro poses no additional risk to flooding, and that our operation is fully integrated into the local waterways management system.

If any local resident has questions about the hydro we would be very happy to chat to you.  You can reach us via the contact page. We would also love to hear from any local resident who would like to join us for a guided tour of the hydro, to learn more about the project and the benefits it will generate for the local community and environment.

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