The Water Resources Board, in its role as advisor to the United Kingdom government on water resources development in England and Wales, prepared regional planning studies setting out the alternative strategies, costs, and consequences for 3 regions covering most of the country. More recently a National Planning Study for all of England and Wales has been completed. The program of research and development includes such subjects as water resources instrumentation, mathematical modeling, desalination, combined use of surface and groundwater, artificial recharge, and ecologic problems.

In England and Wales, about 25% of all public water supplies are taken from groundwater which is recharged naturally by percolating rainfall. In many places groundwater levels have been lowered extensively causing saline intrusion and other problems. In recent years there has been much increased interest in the development potential of groundwater, with the result that some schemes for the combined use of naturally recharged underground resources and rivers are under construction and others are under investigation.

Artificial recharge, considered in the United Kingdom to be the final stage of groundwater development, is not yet used, but it is considered to have major potential both for using underground storage to supplement surface storage and for the partial purification of polluted surface water where suitable aquifers crop out at the surface. The Board's artificial recharge program includes hydrogeologic, engineering and economic analogue and digital model studies and field experiments in most of the techniques of artificial recharge.

One important example, the London basin, is taken as an illustration. A hydrogeologic study has been carried out to assess the potential for recharge beneath London. The aquifers are the Chalk overlain by the lower London Tertiary strata which comprise the fine-grained Thanet Sands and the sands, gravels, and clays of the Woolwich and Reading Beds. These strata form an asymmetric syncline with an axis striking east-west through London's center. The Chalk crops out in the Chilterns of Oxfordshire and Buckinghamshire in the north, and the North Downs of Kent and Surrey in the south. Over the last 170 years, groundwater levels have fallen, in some areas more than 250 ft, creating a storage volume exceeding 200 billion gal--about 5 times the total surface storage available in the Thames b sin. Three areas were identified where hydrogeologic conditions are suitable for recharge.

During the hydrogeologic study, an electrical analogue was constructed to assist in proving the transmissivity and storativity maps calculated from pumping test data obtained during the last 100 years. The model highlighted problems of saline intrusion from the Thames and has been used to illustrate the effectiveness of proposed control measures.

More recently an engineering and economic investigation has been undertaken using 2 main techniques: (1) digital groundwater models of the selected recharge areas, and (2) a digital simulation, using the 84 years' records of daily flows in the Thames. This work has shown that additional yields of more than 70 million gal/day could be made available at low cost without the need of further surface storage.

To substantiate this work further, 2 field experiments have been carried out. One involved the recharge of an existing Chalk well and adit system; in the other, water was injected into a pair of new wells, one open only to the Chalk and one open only to the Thanet Sands. There was a comprehensive program of recharge and water-quality sampling and analysis.

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