UK ECN site. Cringle Brook (a small stream) is a tributary of the River Witham, south of Grantham. It is a spring-fed limestone stream, 12km in length. It has one small tributary, Wyville Brook, flowing into an impounded section comprising two small ornamental lakes of around 750 m2 total area. The ECN sampling site (National Grid ref: 4921 3289) is situated in the lower reaches of the Cringle, downstream of the impounded section, where the Brook is 5-7metres wide and 10-50 centimetres deep, flowing over a sand/gravel substratum with a small content of cobbles and infrequent sections of limestone pavement. This stretch is surrounded by a private golf-course, the river channel and adjacent river corridor being generally unmanaged, with extensive bankside tree-cover and no engineering works (e.g. weed-cutting, dredging or reprofiling) undertaken. The upstream impoundment maintains a year-round flow of little variation, and also buffers the downstream section against mild enrichment by a village sewage treatment works at Skillington and a sewage pumping station at Stoke Rochford. The Brook consequently supports a stream fauna of very high diversity, including a resident population of Native Crayfish (Austropotamobius pallipes) and also sustains a rich aquatic flora.