www.infonet-biovision.org - Water quality and protection

Water quality and protection - DROP

Short description:

The quality of water is crutial to ensure the health of the people consuming it. There are three main criteria for water quality: firstly its natural co-compounds like calcium or magnesium, secondly pollution by chemicals like pesticides or fuels, and thirdly biological contamination by bacteria or other microorganisms. Biologically contaminated water can be treated and made palatable. Treatment of chemically polluted water is extremely complex and costly, so the best way is to protect the watersources from chemicall pollution.

Hide: Water an its co-compounds

Water an its co-compounds

Chemically pure water is a molecule that consist of two hydrogen atoms bonded to a single oxygen atom. Water is a tasteless, odourless liquid at ambient temperature and pressure, and appears colourless in small quantities, although it has its own intrinsic very light blue hue. Nevertheless, according to experience, water has often a quiet distinct taste. This taste is caused by numerous co-compounds that are soluted in the water. The most common compounds of groundwater are calcium and magnesium that are soluted from the rock the water flow through. The concentration of these elements depends on the composition of the respective rock-underground. Calcium and magnesium give the water a special taste and are at the same time essential elements of the human diet. Rainwater lacks of those elements, which has to be considered when consuming only rainwater.

Spring or well water can also contain elements that are toxic when consumed, such as arsene. There are various methods to tread the water. For more information see below the section "Further reading".

Hide: Chemically polluted water

Chemically polluted water

Chemically polluted water
There are various sources of chemical pollution such as for example spilled fuels, pesicides used on crop fields or in house gardens, or heavy metalls leached from rainwater harvesting installations. Generally, chemical pollution of water can not be undone and the water can be rendered unpalatable by chemical pollution. Hence, it is very important to protect water sources from chemical pollution. For more details see protecting water sources in the document water harvesting.

Hide: Biologically polluted water

Biologically polluted water

Biologically polluted water
Besides chemical pollution by fuels, pesticides, etc., water can also be polluted by microorganisms. Microorganisms can cause -- depending on the type and concentration -- light to very heavy illness. Deseases such as Amebiasis, Schistosomiasis, Cholera and many others are waterborne. Generally, biologically contaminated water can be treated by different methods. For more information see water treatment.

Hide: Protecting water sources

Protecting water sources

Protecting ground water from contamination

Especially when ground water is near to the surface, i.e. in an uncofied aquifer, it needs to be protected from contamination. There are several causes for pollution of the ground water:

Drainage of fertilizers and agrochemicals (e.g. herbizides) from fields
Seepage of faeces from a latrin pit
Seepage from waste deponies
Contamination with soluble pollutants from the air
Seepage of hazardeous pollutants from accidents (e.g. of a petrol truck)

Water infiltrating from the surface, e.g. after a heavy rain, can carry microorganisms from a latrine pit through the soil to the ground water. Thus, when finding a suitable place for a latrine, the ground water flow has to be taken into account. Latrines should always be build downstream to wells or sources. Also other possible sources of contamination should have a minimum distance from wells, sources or surface water. If the watershed of a groundwater flow is known, it should be specially protected, e.g. hazardeous transports should not be allowed to pass through the area.

Latrines positioned upstream and downstream of a well (Wagner and Lanoix 1958).

Protecting watersheds

A watershed is defined as any surface area from which all rainwater is drained into the same water catchment. This does not only include surface water streams but also groundwater streams. Ground water id usually built by different layers as shown in the figure below.

Groundwater conservation area (according to BUWAL 2004)

Protecting wells

Wells should be constructed according to certain rules: the well should be protected by a concrete apron with high walls from run-off or spilled water. The concrete for the apron should be of good quality and should not have any cracks, allowing waste water from the surface to return to the source.

Example of a well protected by an apron (Vukasin et al. 1995).

Protecting springs

In areas where springs occur, the spring an its surroundings need to be protected from contamination. The area directly around the spring should be fenced to exclude animals and humans. Also the upstream area should be fenced to avoid contamination of the source. The spring chamber should be lined and covered and pipes should be layed to access the water. The access point should be at a safe distance downstream from the spring site.

Preventing loss of water

Water can be lost in different ways: it can run-off, evaporate or being contaminated an not usable any more. How to prevent contamination of the water was discussed above. Evaporation and evapotranspiration (or simply transpiration) gets stronger, the warmer the climate is. Evaporation means the loss of water from the soil surface, transpiration means the loss of water through the leafs of plants. Measures to counter this loss of water include firstly the increase of vegetation, preferably multi storage vegetation, to create shadow and, thus, reducing direct sun; and secondly by reducing the wind speed with hedges and shelter belts. Leaving the soil undisturbed by practising no or only a minimal tillage also reduces evaporation.

An increased soil cover also increases the infiltration of the water into the soil and, thus, minimizes water run-off. During the raining season, the surface run-off can be spread by different measures to improve the infiltration of the water. One possible method is to build terraces by constructing barriers. Because of the reduced slope and the spreding of the water, it has more time and a bigger surface area to infiltrate and the terraces at the same time protect the soil from eroding and reduce the damage caused by flash floods.

Barriers can also be build in a way that the caught water is diverted to cultivated fields or single trees, providing them with an extra amount of water.

Hide: Information sources

Information sources

BUWAL (2004). Wegleitung Grundwasserschutz. Vollzug Umwelt. Bundesamt für Umwelt, Wald und Landschaft, Bern.

Hide: Further reading