RAIN WATER HARVESTING FOR RURAL WATER SUPPLY BACKGROUND Ms Annah Kamutati Botswana Technology Centre Private bag 0082, Gaborone - Botswana. Tel: 00267 3914161 Fax: 00267 3974677 Email: akamutati@botec.bw Botswana s climate is basically semi-arid. Rainfall is low, unreliable, unevenly distributed and highly variable from year to year. Drought is a recurrent phenomenon, most rivers are ephemeral, and hence water is a scarce resource. Water demand in rural Botswana is increasing rapidly and this is stressing the supply sources which in most cases are ground water. It has been estimated (Department of water Affairs 2000 Monitoring report) that 80% of Botswana inhabitants receive their water from underground sources. The increasing pressure on these has led to ground water mining, salt intrusion and the sources are also faced with pollution from pit latrines. These limited resources together with water demand management strategies, are used to combat the increasing demand. Water authorities are faced with expensive challenges such as borehole drilling, desalination, transfer pipelines developed over long distance like the 400 km North South carrier. In the face of increasing water scarcity and escalating demand, rainwater harvesting appears to be one of the most promising alternatives for supply of freshwater. The pressures on rural water supplies, greater environmental impacts associated with new projects as well as deteriorating water quality, constrain the ability of government to meet the demand for freshwater. These also present an opportunity for augmentation of water supplies using this technology.
Mean annual rainfall in Botswana (Department of Water Affairs)
STATUS QUO Rural Communities in Botswana The country has a population of just below two million distributed over total area of 582 000 km sq. This makes her one of the least populated countries with 48% of her population living in rural areas. The rural population is heavily dependent on agriculture for their livelihood and the availability of water largely determines their well being. By tradition the Batswana (people of Botswana) lived in three types of settlements. The main village of domicile, lands areas and the cattle post system constituted the tripartite settlement pattern which is still largely unchanged. However, neither the lands area nor the cattle posts are intended to be permanent settlements. They are regarded as temporary settlement where some household members go to grow crops or graze livestock for a period ranging from 3 to 8 months after which they return to the village of origin. The rural Government supplies water for drinking and the farmers provide for their agriculture. The following illustrate the tripartite arrangement as well as areas of water demand; People staying in all three points of settlements; villages, lands and cattle posts, there are water reticulation systems in the village, but they have to find water for drinking and livestock in the cattle post and lands. Another group of farmers is those that rear cattle only, especially in the Kalahari Desert where crop growing is almost impossible. Despite having villages for home, these people stay in the cattle post all their time. They need water for livestock and domestic purposes. Another variation is staying at the village and only having land to plough and no cattle. The last group, those that stay in the village without ploughing and with no cattle to rear, either get free water from government standpipes or pay for their own yard connections. In a number of rural villages there are schools, clinics and institutional houses. These use considerably high amounts of water according to rural standards. Although government provides water for drinking, there are limitations due to saline water resulting in adoption of expensive processes such as desalination. Low recharge rates to ground sources; scattered population making interconnections costly. Given these challenges, domestic supply cannot be said to be ultimate. More interventions are needed and among various alternative technologies RWH is a sound solution. RAIN WATER HARVESTING an overview Rain water harvesting is a technology used to collect and store rain water for various uses. This Technology is not new; available documentation suggests that rainwater harvesting has been practiced in Botswana for a long time, however the practice cannot be said to have been popularized and lacks continuity.
Methods of Harvesting Rainwater Techniques used to collect rainwater arise from practices employed by ancient civilizations. These are upgraded and improved through modernization and innovation. A rainwater harvesting system consists of three principal components; the catchments area, the collection device, and the conveyance system. Catchments Area Any impervious and clean surface can be used as a catchment area. Rain falls onto them and flows on to other components of the system. Different types of catchments from Botswana as well as other countries will be briefly discussed Roof top catchments In this basic method, inhabitants use existing roofs of their houses. Rain falls on it and impermeable surface creates run-off. No additional costs are incurred and the amount and quality of rainwater collected depends on the area and type of roofing material. Examples of roofs are corrugated iron, concrete, thatch, tile (clay, corrugated iron). Land surface catchments Rainwater harvesting using ground or land surface catchment areas is a less complex way of collecting rainwater. Compared to rooftop catchment techniques, ground catchment techniques provide an opportunity for collecting water from a larger surface area. In Botswana, this form of harvesting rainwater is done in naturally occurring surfaces like pans. The pan acts as a collecting surface and storage tanks are built to store the water. There is a possibility of high rates of water loss due to infiltration into the ground. Because of the often marginal quality of the water collected, this technique is mainly suitable for storing water for agricultural purposes. These could be enhanced by improving runoff capacity of the pan through techniques such as compaction, increasing land slope and artificial cover. Rock Catchment As in the land surface catchment, this form of catchments makes use of naturally occurring rocks. This surface allows considerable amounts of water to flow over them and collect in the lower points of the surface. An example is shown in the picture below.
Rock catchment project in Oodi Botswana Road Catchment Botswana has well constructed road networks design of which includes proper drainage. However, the drained water is never harvested instead it is disposed into the environment and in most cases becomes the cause of local flooding. Even though road catchment has never been practiced in Botswana, this is an area that could be used to benefit those communities who reside near any form of road. This method carries with it a limitation of quality due to the materials used and oil spills. It would therefore be advisable to use water from these sources for non portable purposes. An example of road catchment in a rural area is shown below.
Road catchment in the Gansu province, China Purposely built catchments As the name implies, these are constructed specifically for creating run-off. Varieties of this method range from enhancement of existing hard surfaces like mountain tops or construction of roofs for water collection. The picture below shows a purposely build roof used to harvest water for drinking in the lands areas. Purposely build roof for catchment (Courtesy-Water Affairs Botswana) Conveyance Systems Conveyance systems are required to transfer the rainwater collected from the catchment area to the storage tanks. These include gutters & down pipes for roof catchments; channels in the case of road catchments e.t.c. Variations of these components depend on extend of use, amount harvested and the type of catchments area. Example of gutter network for roof harvesting is shown in the picture below;
Gutter system with first flush Sanitas Botswana Storage devices Storage tanks are commonly used as collection devices for harvested water. These are either underground or surface tanks made of different materials. Those commonly used in Botswana are, Ferro cement tanks Brick tanks Corrugated iron tanks Plastic tanks SOME OF THE RAINWATER HARVESTING INITIATIVES IN THE COUNTRY Some activities have taken place in line with promotion and utilization of this resource in the rural areas. These were done by the Government of Botswana and other nongovernmental organizations. Some of the initiatives are as follows; Construction of rainwater tanks in schools, clinics and administration buildings. These tanks utilize the large roof surface areas of the roof blocks. The water is then used by the kids in washing their dishes after eating. Ministry of agriculture conducted a program assisting farmers in constructing rainwater tanks country wide. The initial objective of this program was to provide water for draught animals to allow for early ploughing. People however went on and used the harvested water for drinking and other domestic purposes Ministry of agriculture have also embarked on the construction of earth multi purpose dams for livestock watering. Rural Industries Innovation Center (RIIC), a multidisciplinary organization involved in research and development of technology, pioneered a project in Zutshwa Kgalagadi. In this project, brick tanks were constructed to collect run-off from the pan. This water is used for small stock watering.
Some of these projects are shown below. harvesting in Botswana (John Gould) Pan Roof catchment tank in a Primary School - Botswana. Construction of a ferrocememnt tanks (BOTEC) for use in flood control
EXAMPLE OF RURAL LIVES TRANSFORMED BY RWH RWH has transformed rural people s lives before. Success stories have been reported from China, India, and other countries around the world. The Gansu Province, China Gansu is one of the driest provinces in China. Annual precipitation is about 300mm, while potential evaporation ranges from 1500 2000. Surface and ground water resources are limited, thus agriculture in the province relies on rainfall and people generally suffer from inadequate supplies of water. Positive results from the research, demonstration and extension projects carried yielded in the 121 rainwater project. In this initiative the government provided material for the construction of one catchment area, two underground storage tanks, and one small piece of land to be irrigated by the harvested water. The following techniques are used to harvest water under this initiative as well as other extension works. Typical 121 layout
House with a paved yard and an orchard constructed under the 121 project. Water is harvested from the roof tops and yard for domestic use. The 121 project proved to be successful in providing drinking water and developing irrigated land for courtyard economy. Within five years of the project 2, 183, 000 rainwater tanks were built supplying water to 1.97 million people. The government made a lot more initiatives based on the success of the 121 project, to improve the agriculture production and peoples living conditions. More research and larger magnitude projects were carried out and they still continue to date. The Research, demonstration & Extension projects After releasing that RWH is a potential source of water the Chinese government embarked on continuous research, demonstration and extension projects. An organization called Gansu Research Institute for Water Conservancy, has a mandate to carry out this circle of research on methods of harvesting, demonstration and execution of extension projects. This has led to continued development and upgrading for the better RWH exercise. The government also offers packages for new constructions, promotions resulting in RWH in China is getting better and better. THE ROLE OF RWH IN RURAL DEVELOPMENT Given the condition of rural communities in Botswana, surely rainwater harvesting can find a place in rural water supply if the following could be considered; RWH can be an effective way of water supply in the land areas. The government does not supply water to these places and it s up to the farmers to find ways of getting it. Since the same only stay there during the rainy season, the harvested water can be their water supply.
It can serve as a sustainable development mode for areas in Kahalari. Salty aquifers and very deep low yielding boreholes force farmers to abandon good pieces of farming land. If rain water is used to augment the supply, then farming will be affordable and food sufficiency will result. Integration of RWH with traditional moisture conservation methods will bring breakthrough in rain fed agriculture resulting improved yield, better income and better life for the people. The unemployed living in villages, who cannot afford fruits and vegetables, could embark on growing these. Botswana is blessed with large pieces of land as residential plots. These people could harvest water from their house roofs and use it for gardening. Owing to the limited amount of water available, coupled with the walking distance to the water point gardening is impossible. Once rainwater has made this possible, healthy eating will be the result. Water and sanitation are inseparable. More water will definitely result in improved sanitation and a healthier population. Sanitation problems at rural schools can better be solved by this simple technology. Proper and timely maintenance of the tanks to ensure reliable operation and water quality, optimum utilization of the roof to increase the quantity could go a long way in transforming the school grounds, landscaping, gardening and savings on water bills. RWH AND THE SADDC MANDATE Water is forever scarce in the SADC region therefore; exploitation and optimum use of the available sources is of paramount importance. Efficient incorporation of RWH technologies in the water supply will contribute to the implementation of the SADC mandate as reflected in the following quotes; The Millennium Development Goals (MDGs) stipulate that the world should halve the number of people without access to clean water and sanitation by the year 2015. For Africa to meet this target, it means ensuring improved access to safe water for 405 million people and improved sanitation for 247 million. (SADC Today, Vol.7 No.2 June 2004) Water resources management remains a major challenge and priority in 2004 for the SADC region, which is often subjected to drought and floods, and where more than half of the rural population still does not have access to clean water and sanitation. CONCLUSION Rainwater harvesting activities are very much alive in some countries, being revived in others while in some it is a thing of the past with less or no appropriate documentation. For countries with success stories, they could be attributed to certain uniform practices and these could be the spring board to the success of this exercise Continued research and demonstration on materials used and design aspects of RWH Institutional mandate, RWH must be somebody s responsibilities as opposed to independent initiatives as is the case.
Public education, Operation and maintenance Economical analysis REFERENCES: 1. http://www.acdi-cida.gc.ca 2. The national atlas of Botswana 3. http://www.sardc.net 4. http://www.sahims.net/doclibrary/09_03/17/briefcases/water/defining%20and%20m ainstreaminig%20water%20resources.pdf 5. International course on Rainwater harvesting and utilization 6. Gould J. and Niessen- Petersen, E (1999) Rainwater Catchment systems for domestic Supply ISBN 1-85339-456-4 7. Rakaisa D.M. (unpublished) report of rainwater Harvesting workshop Gaborone Botswana 2004. 8. Government of Botswana (1997) policy Guidelines Arable Lands Development Program Down payment/ Grant Scheme for on Farm Investment Packages.