THE EFFECTS OF WATERCRESS GROWING ON CHALK HEADWATER STREAMS IN DORSET AND HAMPSHIRE

Chalk stream headwaters are of high value for water supply, amenity, g ame fishing and fish farming The water quality implications of modern watercress growing have been investigated. Addition of fertilisers to the watercress beds are reflected in increasing concentrations of phos phorus and potassium downstream of the beds. Zinc concentrations in bo th suspended solids emanating from the beds and in sediments downstrea m of the watercress farms reach high levels in some cases. Ranunculus plants downstream of the watercress farms show elevated levels of zinc . Large amounts of suspended solids enter the receiving streams from w atercress beds and in many cases the stream bed directly downstream of the farms has a high proportion of fine organic sediments derived fro m the watercress farms.