WATER QUALITY MANAGEMENT IN CONNECTED CATCHMENT- SHALLOW LAKE SYSTEMS - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 19

risk. Figure (2-2) shows the surface water body and all the principle factors and their component
parameters that form its integrity.

Figure (2-2): Five principal factors and their components that comprise the integrity of surface waters.
(Adapted from Karr et al, 1986)

Sources or causes of water pollution can be classified into two types:

Human alteration of the status of the water body and its inhabitants that downgrades its integrity
and creates pollution

Addition of allochthonous pollutant loads to the water body originating from outside of it.
The first cause of pollution may include a hydraulic modification of water bodies (channel lining and
straightening that downgrade habitat, building dams and impoundments, flow diversion from streams,
drainage of riparian wetlands, urban development that changes stream hydrology and cause stream
bank erosion, in situ sediment contamination by human activities). The second cause, allochthonous
sources of pollution (discharged from outside the water body), are identified as point and nonpoint
sources.
The term point source means any discernible, confined and discrete conveyance, including but not
limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock,
concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or
may be discharged. This term does not include agricultural storm water discharges and return flows
from irrigated agriculture. Major point sources under this definition include sewered municipal and
industrial wastewater sources and effluents from solid waste disposal sites.
Non-point source water pollution arises from a broad group of human activities for which the
pollutants have no obvious point of entry into receiving watercourses. They include everything else
rather than point sources and include diffuse, difficult to identify, intermittent sources of pollutants
usually associated with land use. A major example of nonpoint sources is the agricultural wastewater
runoff and infiltration. In contrast, point source pollution represents those activities where wastewater
is routed directly into receiving water bodies by, for example, discharge pipes, where they can be
easily measured and controlled. Obviously, non-point source pollution is much more difficult to
identify, measure and control than point sources. The non-point sources pollutants ultimately find their
way into groundwater, wetlands, rivers and lakes and, finally, to oceans in the form of sediment and
chemical loads carried by rivers. The ecological impact of these pollutants ranges from simple