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Title: Ecological effects of discharges from watercress farms on the chalk-streams of the NRA Wessex Region
Author: P.D. Smith
Document Type: Monograph
Discharges from watercress farms are of considerable concern to the Wessex Region of the NRA, relating principally to excessive siltation and an absence of the freshwater shrimp (Gammarus pulex) below effluent discharge points. This investigation was carried out in order to assess the severity and extent of these problems, and to identify any further impacts from watercress cultivation. Fifteen working watercress farms were identified in the Wessex Region; all were located in the Avon and Dorset Area. Macroinvertebrate samples were taken and macrophyte surveys undertaken, at points above and below each watercress farm. Where watercress farms were located at the source or perennial head of a stream, control samples were taken on an adjacent tributary, if one existed. The resulting data were analysed using biotic indices, the RIVPACS predictive model, and the multivariate statistical technique TWINSPAN. In most cases, observed biotic scores exceeded RIVPACS predictions and indicated high environmental quality. ASPT and EQI (ASPT) values were, however, lower downstream of watercress farm discharges. This generally corresponded with an increase in the number of scoring taxa, BMWP score and their EQIs. These changes were attributed to the effects of siltation downstream of watercress farm discharges.
Publisher: National Rivers Authority
Publication Date: 1992
Publication Place: [Exeter]
Subject Keywords: Discharge (hydrology)EffluentsAquatic plantsWater pollutionPollution controlWater qualityRIVPACSEnvironmental qualityBiotic index
Geographic Keywords: Dorset
Taxonomic Keywords: Gammarus pulex
Extent: 22; + figures and tables
Total file downloads: 57

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