WATER QUALITY MANAGEMENT IN CONNECTED CATCHMENT- SHALLOW LAKE SYSTEMS - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 16

to the regulatory requirements and appropriate evaluation of water quality. Therefore it is important to
understand and agree definitions and terms when dealing with water quality management. In view of
the complexity of factors determining water quality, and the large choice of variables used to describe
the status of water bodies in quantitative terms, it is difficult to provide a simple definition of water
quality (Chapman, 1996).

A very general and brief definition could be: Water quality is a term used to describe the chemical,
physical, and biological characteristics of water, usually in respect to its beneficial use and suitability
for a particular purpose. So in assessing water quality, it is not just a list of chemical constituents to be
investigated but the assessment should be linked to the water uses and there should be a targeted
objective behind the assessment. Water quality assessment includes the use of monitoring to define the
condition of the water, to provide the basis for detecting trends and to provide the information
enabling the establishment of cause-effect relationships. Thus there is a logical sequence consisting of
three components: monitoring, followed by assessment, followed by management.

Another important term to define is pollution. This can be defined briefly as an impairment of the
beneficial use(s) of a water body. Finding chemical constituents in high concentrations in the water
column or sediments is not pollution unless these constituents are impairing the beneficial uses of the
water body. Therefore it is important to identify the uses of water body in order to comply with the
permissible limits on the pollutants in it. However, the concept of pollution is relative, in that it
reflects a change from some reference value to a value that causes problems for human use. A
worldwide reference value is difficult to establish because insufficient monitoring has occurred prior
to changes in water quality due to human activities. Furthermore, there is no universal reference of
natural water quality because of the high variability in the chemical quality of natural waters
(Meybeck et al., 1996). Before we seek to understand the water quality or pollution of a certain water
body as explained in these definitions, it is important to understand the following issues:

The water or hydrologic cycle;

The human interventions within the hydrologic cycle;

The effect of these interventions on the hydrologic paths, and the water quality based on
different uses.

The following section gives a brief explanation of these issues.

Water Cycle and Impacts of Anthropogenic Activities on Water Quality

The continuing growth in the global population is increasing the demand for freshwater. One
important factor affecting freshwater availability is socioeconomic development, and another factor is
the general lack of sanitation and waste treatment facilities in highly-populated and poor areas of
developing countries. A principal cause of water scarcity is water quality degradation, which can
critically reduce the amount of freshwater available for potable, agricultural, and industrial use,
particularly in semi-arid and arid regions. Thus, the quantity of available freshwater is closely linked
to the quality of the water, which may limit its use. Human activities and interventions related to the
water resources within a watershed have a direct impact on altering the characteristics and the quality
of the existing water bodies.

The quality of freshwater at any point in the watershed reflects the combined effects of many
processes along water pathways. Human activities on all spatial scales affect both water quality and
quantity. Alteration of the land use and associated vegetation not only changes the water balance, but
typically alters the processes that control water quality. The effects of human activities on a small
scale are relevant to an entire drainage basin. Furthermore, local, regional, and global differences in
climate and water flow are considerable, implying various effects due to human activities on the land
and on water quality and quantity, depending on the location within a watershed, geology, biology,
physiographic characteristics, and climate. These natural characteristics also greatly control human