Manual - International Environmental Technology Centre

IDENTIFICATION OF POTENTIAL IMPACTS
ON FRESHWATER QUALITY
The first step in the assessment of human impacts
on freshwater resources requires identification and
quantification of the impacts of major past, ongoing
and planned projects (activities) in a catchment.
This allows for the recognition of potential
pollutants in the basin.
Table 4.1 helps to check the potential risks in a
catchment. The following three steps are proposed
to
optimize the evaluation procedure for pollution
risk assessment at a catchment scale:
screening – identification of hot spots (mapstudy
& questionnaires);
direct assessment of impacts (field study); and
quantification of problems (laboratory assessment
and timing of monitoring).
SCREENING
The screening for identification of „hot spots” can
be done based on map information, statistical
analysis and the use of a questionnaire.
What are the main objectives of screening?
analysis of the distribution of activities that
affect water quantity and quality at the
catchment scale;
identification of potential pressures;
identification of „hot spots” and elaboration
of guidelines for further assessment; and
integration of the information at the catchment
level.
What issues should be identified?
water demand by agriculture, municipal
and industrial users:
daily uptake (m3 day-1 ) can be estimated
using information from the water supply
system or surface/groundwater usage;
if there is no water supply system -
water demand should be calculated by multiplying
the number of people and animals
by average consumption values;
Potential impacts on water quality:
information about sewage outflow and
sewage treatment in a catchment should
be collected;
if there is no quantitative data, it can be
assumed that sewage outflow equals
water use in a catchment,
collect information about local industries,
including planned and implemented projects
and estimate their impact (Table 4.1);
collect information about large farms
and aquaculture farms;
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Surveys & Assessments: Landscape