The Project Manager Reports – Risks of Flooding after Abstraction Ends?

The following Report was prepared by Sandra Kyriakides, WPAG Project Manager and former Welwyn Hatfield Borough Councillor.

As you may know, Affinity Water will cease abstraction from the River Mimram this April and the Fulling Mill Pumping Stations will close.  This came about through pressure to preserve the rare chalk aquifer stream that is the Mimram, together with the fact that the Affinity licenses were due to expire.  It was not in the water company’s interest to reduce or partially abstract water and their need was greatest at a time when most damage by abstraction would be caused to the river, i.e. summertime.

During my time as a Borough Councillor, and since, I have been deeply concerned that WHBC appeared to have no contingency plan for what may happen after the closure, particularly with regard to flood risk.

Because of that, I have continued to liaise closely with the Environment Agency, Affinity Water, Herts County Council and Welwyn Parish Council to raise awareness of the need to do extensive risk assessments before the planned closure date.

I am very pleased to be able to report that the outcome of this has been to find what appears to be a workable and satisfactory solution.

The update received from the Environment Agency about Affinity Water and the Environment Agency’s plans for the abstraction from the chalk aquifer near Welwyn Village confirms that Affinity Water plan to cease abstraction at the start of April 2017.

They have worked together to come up with an interim solution to address flood risk concerns when the abstraction is ceased and have confirmed that they have an agreement in principle to keep the pumping station in operational condition after the abstraction reduction.

In order to maintain operability of the pumping station, a regular small abstraction will be necessary. This regular small abstraction is planned to begin in May 2017. This means that the EA will have the option to instruct Affinity Water to increase pumping if required for flood risk mitigation.

It is important to note that this option won’t remove the risk of flooding, but aims to keep the same level of flood risk as before the change.  In other words, the River may still flood on occasion as it has in the past, but the cessation of abstraction will not cause additional flooding.

The EA promises to continue to improve the accuracy of their flood risk modelling and to investigate alternative options to manage flood risk in the Mimram catchment. This work aims to provide a permanent way of mitigating any potential increase in flood risk, enabling the EA to fulfil the longer term ambition of permanently closing the pumping station.

Residents living near to Singlers Marsh should have no longer have cause to worry as the modelling does appear to have been both thorough and extensive.

Reducing abstraction in April 2017 is one year earlier than originally planned. This is possible because of the excellent work Affinity Water have done to put the required infrastructure in place one year early.

Due to the recent long spell of dry weather, groundwater levels are below normal for the time of year. It is therefore good that the reduction is happening this year to help protect the river if the dry weather continues over the summer.  It can take a while, however, for groundwater levels to recover so we may not see a significant improvement in the short term depending on weather conditions.  Forecasts indicate that it is unlikely that the Mimram will experience sustained high flows this year, and it is far more likely that there will be very low flows.