1.   Purpose and objectives

     To ascertain the key processes by which faecal coliforms are transported through river catchments, to suggest land-use impacts on stream faecal coliform concentrations, and to develop an integrated predictive model of faecal coliform concentration from point and non-point sources.

2.   Description

     This report examines the mechanisms of faecal coliform transport and die-off on the land and in the acquatic environment. Equations derived from these investigations are used to develop a mathematical model of faecal coliform dynamics in streams and rivers.

     The model uses a mass balance structure to reproduce faecal coliform time series in a river network on both seasonal and storm-event time- scales. Published data is used to derive process equations for die-off due to environmental factors such as sunlight, turbidity, temperature and pH. A new approach, based on field observations during flow releases from reservoirs, is used to describe entrainment of organisms which have settled to the river bed.

     Potential applications include: contributing to the assessment of the health impacts of changes in land-use or effluent discharge on a section of river; estimating marine contamination loading for assessing the safety of bathing waters; predicting the timing, duration and magnitude of peak bacteria concentrations to assist water abstractors.

     The work described has relevance for other research on bacterial water quality, and can help assess the risks of exposure to water containing faecal contamination.

3.   Input

     N/A

4.   Output

     N/A

5.   Operational requirement and restrictions

     N/A

6.   Form of presentation

     Report of 64 pages, with 39 figures and 21 Tables.

7.   Operational experience

     The model described in the report was successfully applied to a reach of the River Exe, Devon, UK for the years 1990-1991 and gave a good fit to the observed data.

8.   Originator and technical support
        
     Institute of Hydrology, Crowmarsh Gifford, Wallingford, Oxfordshire OX1O 8BB.

9.   Availability

     From the UK HOMS Office, Centre for Ecology and Hydrology, formerly the Institute of Hydrology, Crowmarsh Gifford, Wallingford, Oxfordshire  OX10 8BB.

10.  Conditions on use

     N/A