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 over 60 boreholes (2-3 per source), all of which allow water to be pumped from the Triassic Sandstone aquifer. This aquifer is very porous (like a sponge) which means that it can hold large quantities of water in between the sand grains and in cracks in the rock. Because the sandstone can hold large volumes of water the water levels within the sandstone do not fall very far in dry periods. This makes the groundwater sources a very reliable supply of water
Blithfield Reservoir is an impoundment reservoir with a capacity of approximately 18,224 millions of litres 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 at the end of March 2009
Throughout the winter months and into March, the Company has had no significant concerns over the resource position, given the relatively wet autumn, and wet December. February and March have been very dry resulting in a Blithfield Reservoir storage level of 92%, and flows on the River Severn approaching the point where River Regulation (by the Environment Agency) may be considered. There are no groundwater resources issues. The Company has no concerns over the water resources 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 are routinely undertaken during the refill season and the levels are monitored continuously. Blithfield reservoir is currently at 92%, this is slightly below average for the time of year, however rain is forecast over the next two weeks.
River Severn
The surface water reservoirs used to support flows in the River Severn (Clywedog and Vyrnwy) are both at 94% 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 or low rainfall. Current groundwater levels are within the normal range. In general the reliable yield of the Company’s groundwater soures is unaffected by groundwater levels, and therefore the Company does not use groundwater levels as a means of assessing the water resources situation.
Rainfall
Rainfall totals for January were close to the long term average, but rainfall in February and March was 50-60% below the long term average.