Ardingly Reservoir moves deeper into drought

(by Karma Loveday)

Ardingly Reservoir, which serves 228,000 customers in Haywards Heath and the surrounding areas in Sussex, has moved further into drought, triggering the next level of response in South East Water’s Drought Plan. At the end of last week, it was only 22.8% full, but not all of that is usable due to sediment and the location of the draw-off tower.

The Environment Agency granted the drought permit South East Water applied for on 28 August on 29 September. But it said this alone will not be enough to secure supplies. In parallel, the company will from 9 October remove all exemptions from the Temporary Use Ban that has been in place since July (except for health, safety or welfare purposes), and has applied to Defra to be able to impose a Non-Essential Use Ban (NEUB).

The drought permit reduces the minimum flow that must remain in the River Ouse at Barcombe Mills after abstraction. It also allows South East Water to reduce from 4Ml/d a day to 1Ml/d a day the compensatory release of water from Ardingly to the Shell Brook tributary of the River Ouse. The permit will remain in effect for six months, until 29 March 2027, unless South East Water withdraws it before then.

The NEUB affects non-household use. If granted, it would restrict businesses from using mains water for the following purposes (unless an exemption applies): 

• Watering outdoor plants on commercial premises

• Filling or maintaining a non-domestic swimming pool, paddling pool or hot tub

• Filling or maintaining a pond

• Operating a mechanical vehicle washer

• Cleaning any vehicle, boat, aircraft or railway rolling stock 

• Cleaning non-domestic premises 

• Cleaning windows on non-domestic buildings 

• Cleaning an industrial plant

• Suppressing dust

• Operating cisterns in unoccupied buildings.

South East Water said it is also operationally responding to the situation. It is managing network pressure and has prioritised the Ardingly area for leak repairs by doubling the number of teams operating there. However, it pointed out that prolonged dry weather had caused significant ground movement, leading to a 20% increase in reported bursts. It has also fast-tracked several engineering projects to ease demand on the reservoir. A new pipeline to connect Bewl Water in Kent to the East Sussex network is transferring 0.9Ml.d and a treatment facility has been brought back online to produce 1.4Ml.d.

Rainfall over the coming weeks will be critical for supplies in Sussex. And at least average winter rainfall will be needed to refill Ardingly and move Sussex out of drought by spring. 

The wider picture:

The wider national picture is also challenging. Most reservoirs are less than half full, which compares to an expectation of 74.3% at this time of year. Like Ardingly, Wimbleball Reservoir in Somerset is concerningly low at 21%.

September became the sixth month this year that has recorded less than average rainfall, averaging 65% across the country (but with significant regional variation). Cooler temperatures have seen demand for water reduce, but usage is still higher than expected for this time of year.

Defra and the Environment Agency (EA) hinted more NEUBs are in the pipeline: “Depending on rainfall and demand by consumers and businesses, reservoir storage is set to continue to decline throughout the rest of the year without major interventions – such as NEUBs.” The EA is working on nine drought permit applications in addition to that granted to South East Water.

At last week’s National Drought Group meeting, the EA announced two changes to abstraction licensing rules to help farmers: to allow them to start filling up their water storage reservoirs now rather than waiting until 1 November (except for from principal salmon rivers); and to make it simpler for them to apply for longer-term abstraction licences.

• Affinity Water has completed the £10m Chaul End Reservoir which will store treated drinking water, doubling capacity across Luton, Hemel Hempstead and St Albans from 21Ml to 42Ml. The reservoir was constructed using a standardised system of precast concrete components manufactured away from the site, reducing the amount of construction activity required on site. Lessons from Chaul End and the recently completed Preston reservoir are now being used to help deliver future strategic storage projects at Hadham Mill in East Hertfordshire and Hills Reservoir in Kent.