KR Rollinson (Letters 13 July) asks why Thames Water doesn't abstract non-tidal water from the Thames above Teddington Weir rather than seeking to abstract water from the tidal reaches and desalinating.
Thames Water and its predecessors have been abstracting above Teddington for over 100 years. Indeed some 80% of London water is derived from the non-tidal reaches of the rivers Thames and Lea, the remainder being derived from wells, mainly in the south east.
For environmental reasons, a statutory minimum flow must be maintained over Teddington Weir, hence the amount that can be abstracted above Teddington is limited.
Mr Rollinson suggests that the aquifer might be replenished with the same quantity of tidal water that would otherwise be desalinated by pumping it into the wells.
Since well water within the aquifer is derived from pure rainwater falling over the North Downs requiring minimal treatment, I wonder if Mr Rollinson would choose to drink the water derived from his proposed new source?
Peter Shephard (M), 35 Hazell Way, Stoke Poges, Slough, SL2 4DD