58 SCIENTIFIC SURVEY OF NORWICH AND DISTRICT 
up of lake-like areas. ‘Thus the main streams were induced to build up 
levees of mud on their flanks and, by damming up their tributaries, to 
form the Broads which are laterally placed with respect to the main streams. 
Mr. R. C. S. Walters has kindly contributed to this chapter the 
following note on underground water levels, with map. 
THE UNDERGROUND WATER SUPPLY 
OF NORFOLK 
BY 
R. C. S. WALTERS 
THE underground sources of water supply of Norfolk are derived from 
the Chalk overlain by other strata for the most part permeable, such as 
beaches, alluvial and glacial sands and gravels, together with the ‘ Crag’ 
series inthe east. In parts of the county there are considerable thicknesses 
of Boulder Clay under which water is often obtained. 
From the work of Baldwin Latham, who published a report to the 
British Association in 1887, and from the Norfolk Water Supply Memoir 
of H.M. Geological Survey, by William Whitaker, it is possible to show 
diagrammatically the underground water levels throughout the county 
by means of contours. The diagram shows the author’s interpretation 
of these records. 
The underground water level is governed largely by the surface con- 
figuration of the chalk, part of the flow being in a westerly direction 
towards the valley of the Ouse, and part being in a northerly and easterly 
direction to the sea. 
The highest underground water levels met with are in the high ground 
to the south of East Dereham and Holt, where they are about 200 ft. above 
Ordnance Datum. From these high points the underground water 
flows in all directions, giving rise to numerous rivers which generally flow 
in the same direction. Just as most of the country between Hunstanton 
and Thetford on the west, and between Stalham, Norwich, and Lowestoft 
on the east, is low-lying, so also are the underground water levels generally 
less than 50 ft. above sea-level. 
