Technologies for Rural Development/Using water resources
Water has always been the most necessary resource for life on earth and therefore human development. Once fire was discovered and used to heat food it became possible to use water to boil some food times to make them more edible. It is believed that water was used for cooking as early as ----- by the poeple who lived in-----. Population density was always highest in river basins as they are very fertile lands. Ancient civilizations flourished near the great rivers such as the Nile and Indus. It is known that water was used to irrigate crops to improve yields as early as 5500BC in Mesopotamia now present day Iraq. These basic types of irrigation are still used in many parts of the world. Early civilizations also used channelled water as a levelling device for construction. This principle is still used by most builders today; by using a transparent pipe filled with water to compare levels.
The Water Cycle
Water is the most important resource for the success of any community or project. All water resources are linked together in a huge global cycle. Understanding this cycle is very important for making decisions about what technologies and processes should be used to utilise the available water resources.
The water cycle has four main storage phases. These are:
- In the ocean
- In the atmosphere
- On land
- Under the ground
The majority of the water in the world is stored in the ocean. This water is heated up by the sun and evaporates into the air. The water is then stored in vapour form in the clouds until it falls to the earth as rain, hail or snow. When the water falls to earth there are many different processes that can happen. It can be stored as snow and ice in cold areas of the world for great lengths of time; it can flow across the ground as runoff and enter into streams, rivers and lakes; it can be absorbed directly by plants; or it can filter its way under the ground.
The water that infiltrates into earth becomes part of the groundwater system. This water is a very important resource for development because the process of infiltration, which can take a long time with the water flowing over great distances, causes the water to be purified and have important minerals added.
Drinkable or potable water is a resource that is scarce in many parts of the world; it is also affected very easily by many types of pollution. Before drinking any water from an unknown source it is important to test its quality.
Water quality testing
A good indication of the quality of a water resource can be taken from the odour, the colour, and the quantity of particles. These three concepts give a general indication, before drinking it is best to filter it or get it tested in a laboratory if available.
If water is not potable there are a range of filtering processing that can improve its quality.
In polluted or even unfiltered mountain water there are many parasitic organisms and inorganic chemicals that are dangerous to humans, because of this it is very important to filter water.
If no energy or technology is available the simplest way to filter water is using a cloth. Water taken from any source is put into a container and left to settle, and then the water is passed through a cloth folded over itself about 8 times. The best type of cloth to use is cotton. This basic filter is effective against simple organisms and to some extent against cholera. However it is not very effective against giardia or cryptosporidium.
Carbon Filters are more advanced filters that require manufacturing; they are most effective for filtering chlorine and volatile organic compounds.
Advanced filtrations systems that are used all over the world to clean drinking water typically have the following components:
- A sediment filter to trap particles including rust and calcium carbonate.
- A second sediment filter with smaller pores is sometimes included.
- An activated carbon filter to trap organic chemicals and chlorination.
- A reverse osmosis filter with a thin film composite membrane.
- A second carbon filter to capture those chemicals not removed by the RO membrane is sometimes used.
- An ultra-violet lamp can be used for disinfection of the remaining microbes.
The filters range in size and capacity for large industrial installations to supply water for cities, to small portable devices that use gravity to filter water.
How to make:
- ClayPotFilter : make the lower part of the clay pot with a mix of sawdust and clay... during the baking process, the sawdust will transform into active coal and allow water to pass but retain the bacteria. Only use a limited diameter range of sawdust, not to big-not to dusty. Search for ClayPotFilter for more info
- CocaColaWaterDisinfector : works with clear, transparent water. Lay the bottle on its side, paint half of the bottle black... the sun will kill micro-organisms, viruses and cycsts in various ways:
- raise in temperature... it doesn't need to be boiling... boiling is a great visual feedback to know for sure you have reached far beyond survival temperature of micro-organisms, viruses and cysts. It's actually about getting above a minimun kill-off temperature, and how long you stay at a certain temperature above that minimum temperature. In a warm country, on a sunny day... 2 hours will do just fine.
- a certain wavelenght in the UV in the sunlight, will split oxygen molecules in its radicals, making oxigenated water... that way, you burn little holes in the organisms/organic material... it's a way of chemically burning.
- A certain wavelenght in the UV spectrum has the same lenght as the average bond distance of the molecules in the membrane... it can induce a self-resonance leading to rupture of the membrane, which kills the bacteria
- Idem to the previous but on the DNA level... the bacteria won't be able to survive. Search for SODIS for more info.
Extraction from Groundwater
Ground water is generally the best quality water available for drinking and irrigation, during the years of natural filtration through the earth the water absorbs minerals which are important for life support, during this process contaminants are generally removed.
The water table is found at different depths in different regions of the earth, this depth also varies over time due to water extraction and the regeneration process that depends on rainfall and natural water storage in lakes and rivers.
In areas where the water table is close to the surface small wells can be dug by hand or using machinery if available.
One option that has been used for centuries is the hand power percussion drill. It was first used by the chinese around 3000 years ago.
If drilling machines are available they can be used to extract water from greater depths.
Rope and washer pump
Irrigation for agriculture
In many areas around the world rivers and streams are partially or fully diverted for irrigation purposes. This has the advantage of supplying water using gravity. However it is very important to consider the effects of reducing the flow in the river or stream. The flora and fauna may not be able to survive in a dry season without the normal flow; these changes can affect the lives of the people and animals living downstream.
wadis for soaking in groundwater
Environmental concerns when dealing with Water
Water absorbs almost everything that it comes into contact with. However, only over long times and through specific processes does water returned to a clean state. When dealing with water it is important to consider that the water you are using is just in one of the phases of its continual cycle. Therefore, by keeping it as clean as possible at every stage of the water cycle, you can be sure that when the water comes back around it will be fit for use.