15. Water-Supply.

Water is not usually called a mineral but in this county it is a very important product of the underlying rocks. For man’s well-being and for household purposes a good supply of it is just as essential as a good supply of coal. From the standpoints of sanitation and general health there is a growing feeling that even agricultural districts should no longer rely for their supply upon surface wells.

At present the needs of the city and many country places are amply satisfied from what we may describe as a gigantic subterranean reservoir in the Bunter sandstone. It has been already noticed that the outcrop of this rock is characterised by the fewness of the streams upon it. This is associated with the fact that here the rain water, instead of flowing off soaks immediately into the ground. Much of it is taken up by vegetation or evaporates from the surface. It is probable that, at the most, only one-third percolates downwards. The outcrop of the sandstone covers an area of 183 square miles. The layer is of course thinnest along its western margin: elsewhere it varies in thickness up to as much as 750 feet in the north. The whole of this mass is saturated with water to within 20 feet of the surface on the eastern side. It is not difficult to sink an ordinary well to that depth. This fact accounts for the presence of a string of villages, viz. Arnold, Calverton, Farnsfield, Oxton, and Retford, along this edge of the Bunter.

It is natural to ask, “If the rock is so absorbent, why are not the streams which run over it absorbed?” There can be no doubt that in some cases the floor of the valley lies below the saturation level of the rock.

Map showing the Distribution of Deep Wells in Nottinghamshire (the wells practically all in the Bunter Sandstone, the outcrop of which is indicated by the dotted line. The lines show the water mains from the wells, and the dots the towns and villages at present derive their supply from deep wells in Bunter).
Map showing the Distribution of Deep Wells in Nottinghamshire (the wells practically all in the Bunter Sandstone, the outcrop of which is indicated by the dotted line. The lines show the water mains from the wells, and the dots the towns and villages at present derive their supply from deep wells in Bunter).

During the last forty years this reservoir has been drawn upon more and more by the sinking of deep wells. One of the largest of these is about 30 feet by 12 feet in cross section and goes down 150 feet. From the bottom tunnels are run into the surrounding rock. From the roofs and walls of the tunnels water pours like a concentrated thunder-shower and runs in a torrent along the floors to the bottom of the well. Thence it is raised to the surface by powerful pumps kept constantly at work, some of them being capable of delivering between two and three millions of gallons per day. From the pumping station the water is forced up to reservoirs situated at a height sufficient to secure their being above the highest point which requires a supply.

The accompanying map shows the position of most of the deep wells in the Bunter and the places supplied by them. Thus though the soil which the rock produces is poor and the surface-water is limited yet it is a valuable asset not only to this county but also to the adjoining ones. Our forefathers avoided its outcrop as a place for settlements. We now go to it for the water required by the settlements they established.

It must not be supposed that this reservoir is inexhaustible. Several pumping stations now yield only half the supply they yielded at first. This is partly due to the fact that they have pumped the water away more quickly than it has percolated from above. Nevertheless it will always be a valuable and economical source of supply even though the increasing demands of a growing population may render it necessary to augment this from other counties in the years to come.