Bristol Water is starting work on the first section of the Harry Stoke to Clifton part of the £22 million Bristol Resilience Scheme which is due for completion in the spring of 2013.

The project will lay a new network that will allow the company to move water from its northern sources into the heart of Bristol in the event of a loss of supply from its southern, Mendip based sources. The scheme will also ensure that Bristol Water has an increased water supply available to meet the growth of residential and commercial developments in the North Bristol area.

Known as the Durdham Down scheme, the latest phase will see a 10km, 700mm pipe being laid from Harry Stoke to Clifton via the Durdham Down tower. Bristol Water's contracting partner May Gurney Ltd will be carrying out the work.

Reservoir levels ongoing source for concern

Although Bristol Water is not totally reliant on the Mendip reservoirs for its resources, current reservoir levels are an ongoing cause of concern.

Reservoir levels have now dropped to an average of 56% full -- Chew Lake, the company's largest reservoir is only 52% full, 5% lower than at this time last year.

Year to date rainfall tin the Mendip catchment which feeds Bristol Water's reservoirs totals 382.5 mm against the standard average of 487 mm. Although the region had higher than average rainfall in both June and July, and close to the average in August,  these followed an exceptionally dry Spring.

In addition, last year, Mendip rainfall was persistently -- and, at times, significantly -- below average for month after month after month. There were seven months of significantly below average rainfall locally. 

The real issue for Bristol Water's reservoir storage was annual rainfall for January to December 2010 which was exceptionally low - the third lowest in the last 100 years with only 1921 and 1933 being lower (both famous drought years). 

Net reservoir inflow this May was effectively zero --the lowest inflow for May in the past 50 years. The July inflow of about 300 million litres (representing just over one day's supply) was about 30% of the average, showing that the dry conditions still persist on the catchment. Net reservoir inflow in August was 100 million litres, about 10% of average for the month. In September it was 50% of the average.

Typically, around 50% of Bristol Water's supply comes from the reservoirs with the other 50% coming from a combination of the Sharpness Canal and groundwater sources, such as springs and boreholes. 

Earlier last summer, as part of its strategy, the company reduced the amount of water taken from the Mendip sources as much as practicable, replacing it with pumped transfers of River Severn water from Sharpness. At the moment groundwater is contributing 15% of what Bristol Water needs; surface water (i.e. reservoirs), 35%; and the River Severn (via the Sharpness Canal) 50% 

Since January, the firm has been transferring northern water into the southern zone at over 1,000 million litres a month on average. 

Bristol water is now awaiting the normal refilling of the reservoirs with autumn and winter rains, while continuing to support the lakes by transfer from the Severn source.