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What do you understand by the term water quality, and what factors control its variation in time and space?

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What do you understand by the term water quality, and what factors control its variation in time and space? Water quality can be described as the physical, chemical and biological characteristics of water, and is a broad term encompassing the quality of water held within river channels and lakes, but also groundwater, water held in sol, rainwater, and water in the oceans. As far as humans are concerned water quality is of primary importance in the freshwater resources which make up only a small percentage of the Earth's water resources, and therefore I shall focus primarily on water quality in river channels and lakes for the purpose of this essay. Water quality is controlled by a multitude of factors which are clearly variable over time and space and which can be grouped into natural and man-made influences. Whether the source of water is underground (groundwater) or directly from rain washing over the land is obviously a major factor determining water quality in rivers and lakes; also of great influence will be the effects of catchment characteristics, inputs to the hydrological system including pollutant sources, and mans treatment of contaminated water. The term water quality can be broken down further into natural water quality, defined as the physical, chemical and biological characteristics of water unaffected by human activity. ...read more.


Spatial variations will therefore obviously occur between geologically different catchment areas and along a river's course if the rock type changes. Spatial and temporal variations in water quality are also determined by groundwater flows into a rivers catchment system. This is largely dependent on the nature of precipitation into the catchment, the nature of the soil through which the water will percolate, the geology of the aquifer and the quality of the existing groundwater, which may be thousands of years old. This demonstrates the importance of temporal variations in groundwater quality which may be very long term. Spatial variations occur as solute concentrations in groundwater tend to increase with depth due to a lack of flushing soluble compounds by new water in deep groundwater stores. Large surface water storage (e.g. lakes and reservoirs) can also determine variations in water quality through time and space. As the water remains stationary fro long periods at a time bacterial activity helps to remove organic matter and flocculation and settlement of small particles are more likely to occur. This can therefore improve water quality. This is further helped by the reduction in turbidity which has been known to promote toxicity in water. ...read more.


These use processes such as chlorination, flocculation, decantation, absorption by activated carbon and disinfection to remove large amounts of soluble chemical compounds, organics materials and particulates found in water. Careful land management and the modified/controlled use of agricultural chemicals is also human action which can help to improve the quality of our water resources, and naturally these will vary both spatially and temporally, being more likely to occur in more technologically advanced regions of the developed world. It is clear, therefore, that many factors control the variation of water quality through time and space. Many of these are natural factors resulting from changes in the geological location of the water resources or climatic alterations in precipitation. However, man induced effects on water quality through the use of agriculture and industry, most usually in a negative sense with the associated increased chemical concentrations into water sources, also play a major role. Large scale water treatment programmes to improve the quality of our drinking water must also not be forgotten., in conclusion therefore it seems fair to say that water quality will vary greatly both spatially and temporally in both short and long-term scales due to a variety of natural and human controlling factors. ...read more.

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