Estimating Contaminant Loads In Rivers

Report No. 117 Estimating contaminant loads in rivers: a review Naa awmet3aech C Estimating contaminant loads in rivers: a review Ian G. Littlewood Report No. 117 Institute of Hydrology Crowmarsh Gifford Walliingford Oxfordshire OX1O 8BB o Copy,right Institute of Hydrology 1992 ISBN 0 948540 38 9 IH Report No. 117 Published by the Institute of Hydrology January 1992 A catalogue record for this book is available from the British Library Executive summary As the debate on probable and possible anthropogenic impacts on the natural environment becomes more scientific and intemational, the need has increased for reliable information concerning the magnitude and trends of mass loads carried by rivers through estuaries to the sea. River load information is also required to assist with the management of inland waters, environmental investigations and research into hydrochemical processes. This report reviews river mass load estimaton procedures with partcular reference to UK conditions. According to the sampling strategy and calculation method employed, river load estimates can be highly variable in terms of their accuracy and precision. Low frequency sampling at regular intervals, combined with simplistic computational algorithms, can result in heavily biased and imprecise load estmates. Often, significant improvements can be obtained by exploiting 'continuous' flow records in the computational algorithm. At sites with a flashy hydrological response, and for determinands with a high coefficient of variation for concentration (e.g. suspended sediment), there may still be large errors if the sampling frequency is low (e.g. once or twice per month). Levels of bias and precision in mass load estimates depend on many factors: the hydrological and hydrochemical dynamic responses at the site and for the determinan