Geography Reference
In-Depth Information
Water quality evaluations require a broad range of environmental and
administrative data and one of the major categories of data include pollutant
sources. Pollution may result from point sources or non-point sources (diffuse
sources). Point sources are clearly identified at a single or multiple locations
such as wastewater flow in conduits from municipalities and industries.
However, nonpoint sources are diffuse and may not be defined by certain point
locations for pollution such as urban runoff, erosion from agricultural and
deforested lands. In other words, non-point sources include everything else
that is not a point source. Sometimes, it is difficult to distinguish between both
the point and non-point sources of pollution because a diffuse source on a
regional or local scale may result from a large number of individual point
sources, such as automobile exhausts.
An important difference between a point and a diffuse source is that a
point source is amenable to control through collection and treatment processes
while a non-point source is difficult to control with engineered facilities, e.g.
collection and treatment, because of diffuse character of this source.
A diffuse pollution source consisting of several point sources may also be
controlled provided all point sources can exactly be identified. Most common
point and non-point sources of pollution are listed in Table 1.
3.
W
ATER
Q
UALITY
E
VALUATION
Water quality evaluation is an overall process of evaluating physical,
chemical and biological nature of water in relation to natural quality, human
effects and intended uses particularly uses which may affect human health and
the health of the aquatic system itself (Bartram and Ballance, 1996). Water
quality evaluation includes the use of monitoring data to define the condition
of water, to provide a basis for detecting trends and to provide information
enabling the establishment of cause-effect relationships. Thus, important
aspects of water quality assessment are:
interpretation
of water quality data,
reporting
of results, and
recommendations
for future actions. Three important
components of water quality evaluation in a logical sequence are monitoring,
followed by assessment, followed by management (Meybeck et al., 1992).
The process of water quality evaluation involves many complex
operations, which are linked together forming a chain of about twelve links
where every link is important as its failure will weaken the entire evaluation.
Elements of various water quality evaluation programmes may differ
depending upon the objectives of the programme.
