SOURCES OF DRINKING WATER
Alternatives for Community Decision Making
By Phil Bartle, PhD
Dedicated to Andrew Livingstone
A community should have several sources of potable water, and manage its water supply on the basis of choices
A Matter of Choice:
Almost every community has a range of sources of clean water. The many sources vary in the kinds of technology needed to bring the water to the people, and those technology alternatives have different costs associated with each of them. The optimum situation for which the mobilizer can work, is that a community, through its executive, is fully aware of the options, knows the relative costs and benefits, and will manage its drinking water resources.
Too often we assume that there is only one good way to obtain potable water. This will be true for most communities where you work. It is your job, as mobilizer, to be aware of the range of alternatives, and to be able to present these to community members so they can make decisions and choose the various sources that make a package most appropriate to their situation.
For the community members to be informed about alternative sources, they should undertake an appraisal. Here is a job for you, participatory appraisal, where you stimulate and guide them to produce an accurate inventory. As managers, the community members must look at all the potential sources, review the costs and benefits of all the available technological alternatives, assess all available (financial and non financial) resources, and make management decisions that balance the costs and benefits of the various strategies.
What, then, are the kinds of water sources to expect to be listed in an appraisal?
The Three Main Categories of Sources:
For any community, its potential sources of drinking water are usually found in three categories: (1) water that is in the air, (2) water that is on the surface, and (3) water that is underground. When making a participatory appraisal, prepare a checklist and consider sources that belong to each of those three categories.
Let us look at these three in turn.
Water from Air:
Most water that is in the air has been vaporized. Water vapour itself is a gas rather than a liquid. When we see clouds, however, we are not looking at a gas, but at water that has condensed, sometimes onto dust particles. Those tiny micro droplets are liquid, but are so small that they stay up in the air (together as clouds) until they join together, then drop to earth.
Precipitation (water falling to earth) can happen while the water is in various forms. If liquid, it is called rain. If it has been crystallized, it then falls as snow. If it freezes into droplets, it is called hail.
Hail sometimes falls, then is lifted up again, attracting more water which freezes at the high cold altitudes, getting bigger. This can happen several times so the hail stones can become as big as one, two or three centimetres in diameter. Snow falls in the tropics very seldom, usually only at high altitudes on mountains. Hail does fall, even in the tropics, on rare occasions, because the freezing temperature is at high altitudes, not near the surface, even in hot climes.
For most intents and purposes, when we talk about getting drinkable water from the air, we are talking about rain. As soon as it hits the earth, then we can talk about getting water from the surface.
When water is heated and vaporizes, any pollutants, including dirt and micro-organisms, are usually left behind. If it simply condenses back into a liquid, that water is as pure as it can get, like distilled water. Unfortunately, its condensation is not so simple, as dirt and micro-organisms are in the air, and the water can pick and combine with those. In most cases, however, the pollutants are not enough to cause diarrhoea, so we can usually consider rain water to be very clean and safe to drink.
The technology for harvesting rainwater is considered in the companion document: Water Technology for the Mobilizer. In general, that document should be studied along side this one.
Water from the Surface:
Water on the surface is either moving or still. Moving water can range in size from small rivulets through medium sized streams to large rivers. Still water can range from temporary puddles through lakes to the oceans.
Small puddles, common in the rainy season, are most likely to be contaminated with water-borne diseases, while oceans have too much salt to be drinkable, and need special technology to remove the salts. Other things being equal, in general, if the water is moving it is more likely to be safe than if it is still. Water that is too still for too long can become stagnant and polluted, as in a swamp, full of many life forms, some of which are not friendly to the health of human beings.
If it smells bad, it is probably not safe to drink.
Various kinds of technology are used to take water from the surface and send it to the home to be consumed. They are in the same companion document.
Water from Under the Ground:
When it rains, not all the water stays on the surface and ends up in the rivers, lakes and eventually the ocean. Some of that water gets absorbed by the earth.
Under the ground, water flows, in a manner similar to that on the surface, in rivers and lakes. An underground stream is called an "aquifer." Water flows through porous earth, usually gravel and sometimes sand. It is contained by non-porous earth, usually by solid rock or clay.
There is no guarantee that under any given area of land that there is an aquifer running. Some areas simply do not have groundwater.
An aquifer may be shallow (close to the surface) or deep. An aquifer may be shallow (close to the surface) or deep. Although there are many variations, generally a shallow aquifer will have sweet (uncontaminated) water while a deep aquifer, which has flowed underground for a longer time, will be full of minerals, sometimes being too salty to drink.
For the most part, underground water is available by digging a well to it, and the water being brought up from there to the surface by bucket or pump. More details are in the companion document, Water Technology. Sometimes, as the aquifer flows under an uneven surface, it breaks out at the surface. This is called a spring. A community blessed with a spring can protect that water from contamination rather than digging a well to reach it.
Sometimes, underground water seeps very deeply to where the earth gets hot, below the cool crust, and warmed by the core of the earth. This water gets heated, and when its steam expands, it is forced upwards to the surface, sometimes emerging as a hot spring. Many hot springs have picked up various minerals from deep below the earth, some poisonous, some medicinally beneficial, seldom drinkable.
What Do You Do?
This is not a technical or scientific document, but intends only to give you enough engineering, meteorological and geological information to help you do your job of empowering communities. Community members, like you, do not need to be hyrdrogeologists, meteorologists or engineers, to have enough knowledge to develop a management plan for drinking water. You may wish to learn more details elsewhere, and this document encourages you to do that, so that you can guide the community to make its own decisions.
Do not lecture to the community members, as this document is doing to you. They all know the three sources and some of the advantages and disadvantages of each. In a planning session, use your board (or a flip chart) and draw out the above from the community members, writing each on the board as you do. Then review the potential sources in terms of whether the community members have seriously considered each in choosing their appropriate package (a combination of sources). Encourage the community members to select a choice of sources, and vary their use as they change with the seasons of the year. Rigid reliance on only one kind of source is not advised.
The key concept is "water management" and, to become empowered, community members must manage their own water supplies.
© Copyright 1967, 1987, 2007 Phil Bartle