Water has two closely linked dimensions: quantity and quality. Water quality is an important concept related to all aspects of ecosystems and human well-being such as the health of a community, food to be produced, economic activities, ecosystem health and biodiversity.
The quality of an aquatic environment can be defined as the set of concentrations, speciations, and physical partitions of inorganic or organic substances, the composition and state of aquatic biota in the water body and the description of temporal and spatial variations due to factors internal and external to the water body (http://www.who.int).
In other words; water quality refers to the condition of the water, including chemical, physical, and biological characteristics, usually relative to the requirements of one or more biotic species and/or to beneficiary use of water to any human need or purposes. Water quality helps ecological processes to sustain. Good water quality supports native fish populations, vegetation, wetlands and birdlife and poor water quality can pose health risk for people and for ecosystems. Besides, many human uses depend on water quality that is suitable for drinking, irrigation, recreation (swimming, boating), industrial processes, navigation and shipping, production of edible fish, shellfish and crustaceans, scientific study and education, etc.
Each freshwater body has an individual pattern of physical and chemical characteristics largely determined by the climatic, geomorphological and geochemical conditions of its drainage basin and the underlying aquifer. It should to be noted that water usually returns back to the hydrological system after its use and if discharged untreated, it can severely affect the environment. Thus, water quality is closely linked to the surrounding environment and land use. Water is affected by human uses such as agriculture, urban and industrial use, and recreation. Changes in water quality, including increases in levels of specific nutrients, can have serious adverse effects on aquatic life, thus in wildlife and eventually on human nature. Aquatic ecosystems play a crucial role in maintaining water quality. They are valuable indicators of water quality. If water quality is not maintained, the environment will suffer and the commercial and recreational value of our water resources will diminish, as well. Research studies indicate that worldwide water quality is declining mainly due to human activities. Increasing population growth, rapid urbanization, discharge of new pathogens and new chemicals from industries and invasive species are the main factors that contribute to the deterioration of water quality. In addition, climate change will further affect water quality.
From a management point of view, water quality is defined by its desired end use. Water for recreation, fishing, drinking, and habitat for aquatic organisms require higher levels of purity, whereas for hydropower, quality standards are much less important. It is important to know that different beneficial uses have different needs and thus, there is no single measure that constitutes good water quality. For example, while water that is suitable for drinking purpose can be used for irrigation, water used for irrigation may not meet drinking water standards. However, fish and wildlife have other requirements. Fish need water that contains enough oxygen and nutrients since they get all of their oxygen and food from water.
Therefore depending on the beneficiary use, we use guidelines, and standards must be met accordingly. For instance, the first edition of guidelines for drinking water quality was published by World Health Organisation (WHO) in 1984-1985 and was intended to supersede earlier European and international standards.
The standards are also set by the national agencies based on their political and technical/scientific decisions about how the water will be used and referred to their international commitments where exist. There are also international standards such as regulations of International Organization for Standardization (ISO) which is covered in the section of ICS 13.060. The European Union has established a framework for Community Action in the field of water policy in the EU Water Framework Directive (Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000). The primary objective of the directive is to prevent further water deterioration and to implement the necessary measures to achieve “good water status” in all EU waters by 2015.
Water quality guidelines and standards provide basic scientific information about water quality parameters and ecologically relevant toxicological threshold values to protect specific water uses. The most common standards used to assess water quality are related to health of ecosystems, safety of human contact and drinking water. Drinking Water Regulations are health-related standards that establish the Maximum Contaminant Levels. Drinking water should not present a risk of infection, or contain unacceptable concentrations of chemicals hazardous to health and should be aesthetically acceptable to consumer. The control of the feacal pollution depends on being able to access the risk from any water source and to apply suitable treatment to eliminate the identified risks.
In order to describe and access water quality of a river, stream, lake, groundwater or marine environment, we need to have parameters that can be measured. Measurements of these parameters can be used to determine and monitor changes in water quality, and determine whether it is suitable for the health of the natural environment and the required uses. Water quality is measured by several factors, such as the concentration of dissolved oxygen, bacteria levels, the amount of salt (or salinity), or the amount of material suspended in the water (turbidity). In some water bodies, the concentration of microscopic algae and quantities of pesticides, herbicides, heavy metals, and other contaminants may also be measured to determine water quality. These parameters are mainly categorized under physical, chemical, and biological properties of water.
Water quality is determined by measurements on site and by in situ examination of water samples or in the laboratory. Thus, on-site measurements, the collection and analysis of water samples, the study and evaluation of the analytical results, and the reporting of the findings are the main elements of water quality monitoring. The results of analyses conducted on a single water body are only valid for the particular location and time at which that sample was taken.
To gather sufficient data (by means of regular or intensive sampling and analysis) to assess spatial and/or temporal variations in water quality is therefore one of the purposes of a monitoring programme.
Physical measurements are those that include water temperature, depth, flow velocity and turbidity. These are all useful in analysing how pollutants are transported and mixed in the water environment, and can be related to habitat requirements for fish and other aquatic wildlife. For example, many fish have very specific temperature requirements, and cannot tolerate water that is either too cold or too hot.
With chemical measurements we measure concentrations of wide range of chemicals and chemical properties. Test results are defined as milligrams of chemical per liter of water (mg/l). Chemical water quality studies focus on the chemicals that are most important for the problem at stake, since even the purest water contains countless chemicals and it would be impossible to measure all of them. Therefore; while in agricultural areas, studies measure chemicals found in manure, fertilizers, and pesticides, in an industrial area studies focus on measuring chemicals used by the nearby industries.
With bacteriological analysis we measure the hygienic quality of water. The bacteriological quality of a water body is very important especially when we use the water body for drinking purposes.
To assess a water body in terms of quality, it is essential to gain a water quality data obtained in several intervals (monthly, seasonally, and annually) and monitor the changes of parameter values to point out the variations immediately after a specific intervention. The lack of water quality data and monitoring worldwide as well as lack of knowledge about the potential impact of natural and anthropogenic pollutants on the environment and on water quality is one of the major problems to define and solve water pollution problem. In many countries, the lack of prioritization of water quality has resulted in decreased allocation of resources, weak institutions and lack of coordination in addressing water quality challenges. Considering approximately 25% of the world’s population has no access to potable water, water quality is at most importance in human health.
Monitoring the water bodies is particularly important to point out the reliability of source accessed for public use especially for drinking purposes. Water quality measurements for drinking purposes generally focus on health of the community and aestethic aspects. It should be ensured that the water intended for human consumption can be consumed safely on a life-long basis, and this represents a high level of health protection. Monitoring and control technologies provide the surveillance of source water quality and the detection of biological and chemical threats. They lead us to define the boundary conditions for the subsequent treatment and provide early warning in case of unexpected contaminations. They are mandatory for the high quality of finished water in treatment processes. Moreover, detection of changes in water quality during distribution and monitoring drinking water quality at consumers’ tap is essential. Water quality deterioration in distribution systems, mainly caused by inappropriate planning, design and construction or inadequate operation and maintenance and water quality control, may be the cause of waterborne and water-related illness. Rapid urbanization, population growth and aging of infrastructure stress the distribution sysytems.
To ensure the water quality, the standards should be based on the latest scientific evidence and efficient and effective monitoring, assessment and enforcement of drinking water quality should be secured.