The water supply to the rural districts of Essex. : Report presented to the county council, April 4th, 1905 / by John C. Thresh.

  • Thresh, John C.
Date:
1905
Catalogue details

Licence: In copyright

Credit: The water supply to the rural districts of Essex. : Report presented to the county council, April 4th, 1905 / by John C. Thresh. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    Salisbury to Dover. The width of this outcrop often ex- ceeds 20 miles. All this area is absorbing a certain portion of the rainfall, some of which it transmits directly into the sea, some into the rivers, and an unknown quantity travels eastwards and downw ards through the chalk where this passes under the London Clay. Where the chalk outcrops under the sea (if such outcrop occurs) or under the Thames (as is known to be the case), doubtless the water finds an outlet as the flow must be from the high level collecting areas towards these lower points. Where the water gets out under the surface of the sea, or a tidal river, it is obvious that water can get in if for any reason, such as excessive pumping, the level of the water in the chalk be depressed below that of the sea or river. This has frequently occurred near the coast and near the Thames. The chalk outcrop in this county is very limited in area, and probably most of the water it collects flows southward into the Lea Valley, or northwards into the valley of the Cam. In the latter case it is lost to the county. For further details concerning the chalk as a water- bearing stratum my large Report on Essex Water Supplies may be consulted. The w^ater from the chalk where it is covered by the London Clay is usually of the highest degree of organic purity, but near the coast the deep wells are liable to the infiltration of tidal water rendering the whole supply brackish. This deep chalk water in central and south-east Essex is peculiar inasmuch as it is usually very soft and in this respect quite unlike chalk waters generally. Water is obtainable in a moderate amount, from the chalk in any part of Essex by sinking a well or by boring where the chalk lies deep beneath the surface. The cost of boring varies wdth the depth