Characterisation of faecal indicator
organism (FIO) concentrations and ex
port coefficients for catchments with
particular combinations of land use and under s
pecific climatic regimes is critical in develo
ping models to
predict daily loads and a
pportion sources of the microbial
parameters used to regulate water quality. Accordingly, this
pa
per
presents a synthesis of FIO concentration and ex
port coefficient data for the summer bathing season, with some com
parative winter data, for 205 river/stream sam
pling
points widely distributed across mainland UK. In terms of both geometric mean (GM) FIO concentrations and ex
port coefficients (ex
pressed as cfu km
p>−2p> h
p>−1p>), the results reveal (1) statistically significant elevations at high flow com
pared with base flow, with concentrations ty
pically increasing by more than an order of magnitude and ex
port coefficients by about two orders; (2) significantly higher values in summer than in winter under high-flow conditions; and (3) extremely wide variability between the catchments (e.g. four orders of magnitude range for GM faecal coliform concentrations), which closely reflects land use—with urban areas and im
proved
pastures identified as key FIO sources. Generally, these two most
polluting land uses are concentrated in lowland areas where runoff (m
p>3p> km
p>−2p> h
p>−1p>) is low com
pared with u
pland areas, which in the UK are dominated by rough grazing and forestry. Consequently, contrasts in ex
port coefficients between land use ty
pes are less than for FIO concentrations. The GMs re
ported for most land use categories are based on
![](htt<font color=)
p://www.sciencedirect.com/scidirimg/entities/2a7e.gif" alt="greater-or-equal, slanted" title="greater-or-equal, slanted" border="0">13 sites and exhibit quite narrow confidence intervals. They may therefore be a
pplied with some confidence to other catchments in the UK and similar geogra
phical regions elsewhere. Exam
ples are
presented to illustrate how the results can be used to estimate daily summer base- and high-flow FIO loads for catchments with different land use ty
pes, and to assess the likely effectiveness of certain strategies for reducing FIO
pollutant loadings in areas with extensive areas of lowland im
proved
pasture.