Summary of Supply Sources
South Staffs Water obtains its water resources from three sources: Blithfield Reservoir, the River Severn and groundwater from 25 sites across the Company’s area of supply. Approximately 40% of the total water available to the Company is taken from groundwater sources and the remaining 60% from the two surface water sources.
Groundwater is abstracted from around 62 boreholes in the Triassic Sandstone aquifer. On average there are three boreholes at each groundwater site. Triassic sandstone has large water storage capacity within the structure of the strata and it does not tend to react rapidly to periods of low rainfall. Therefore, it gives a relatively reliable and constant supply of water.
Blithfield Reservoir is an impoundment reservoir with a capacity of approximately 18,224 megalitres of water. It was formed in 1953 by the construction of a dam across the River Blithe. The raw water is taken out of the reservoir by pipeline to the treatment works at Seedy Mill near Lichfield before going into the distribution network. (for further information on Blithfield reservoir, its construction and history, visit our Blithfield Website.)
The River Severn is a regulated river i.e. flows in the river are augmented by inputs from both groundwater and reservoirs at its head at times of low flows. The regulation of the River Severn is controlled and operated by the Environment Agency who monitor and report on the situation regularly. The Company take water from the River Severn at Hampton Loade where it is stored in Chelmarsh Reservoir before being treated and distributed.
Current Water Resources Position as of April 2008
Throughout the winter and spring months the Company has had no concerns over the resource position, given the higher than average rainfall. Details of the current resource position and recent rainfall are included below. However, in general, the water resource situation for South Staffordshire Water remains very healthy and at the moment the Company has no concerns over the supply situation.
Reservoir Levels
The Company uses the level in Blithfield Reservoir as the main indicator of resource availability. Regular analysis of refill scenarios for Blithfield Reservoir is routinely undertaken during the refill season and the levels are monitored continuously. Following the high rainfall in the winter of 2007/8 and the average spring rainfall, Blithfield reservoir was at 97% full at the end of April 2008.
River Severn
The surface water reservoirs used to support flows in the River Severn (Clywedog and Vyrnwy) are also close to full and therefore there are no concerns over availability of resources for river support.
Groundwater
Groundwater levels in the Sherwood Sanstone aquifer do not tend to react rapidly to short periods of high rainfall. However after several months of above average rainfall in the summer of 2007 and the winter of 2007/8 groundwater levels are rising. In general the reliable yield of the Companies groundater sources is unaffected by groundwater levels, and therefore the Company does not use groundwater levels as a means of assessing the water resources situation.
Rainfall
Average rainfall totals for the period Jan-Apr 2008 were approx. 120% above the long term average, with January and March being particularly wet.