Kadenge Kamadi reports on how one Kenyan village is tackling water scarcity by building dams that use technology first employed by the Romans in 400BC
Access to water has always been a big challenge for people in the developing world, with the situation particularly dire for communities living in arid and semi-arid regions. Not only does a lack of water impact negatively on agriculture – often the main economic activity – but in some instances, competition for this vital natural resource has led to conflict between communities.
Villagers in one dry part of Kenya are increasingly using sand dams as a way out of this problem. This relatively low-cost, low-maintenance technology, developed by the Romans in 400BC, has put Masongaleni in the Kibwezi division of Makueni county on the map as a perfect example of what is possible through rainwater harvesting and dry-land management.
Dryer and dryer
Masongaleni village lies about 300km east of Kenya’s capital Nairobi. The village is accessed by a deeply gullied dirt road 40km from the main highway linking Nairobi to the country’s second largest city, the port of Mombasa. With annual rainfall totalling as little as 300mm, meaningful agriculture is not possible in Kibwezi, which has a population of 170,000.
By comparison, Kitale, where much of Kenya’s maize is grown, has an average annual rainfall of 1,269mm. The fact that the Kibwezi can go for months at a time without a drop of rain confirms the area’s status as an arid region. “Kibwezi has been a food insecure region for many years and aid has remained a major source of food for the majority of people here,” says Mary Muteli, the officer responsible for the area at Kenya’s ministry of agriculture.
Things are beginning to change thanks in large part to the construction of sand dams, which are providing a much needed lifeline to villagers. The residents are now able to meet their domestic water needs along with those of their livestock as a result, and they have become less dependent on rainfall to grow their crops.
They are also able to irrigate their farms, which was something they had previously not been able to do. “Water from the dam irrigates our fruit trees. We were advised to construct terraces and plant pawpaw and mango trees, which are doing very well here,” says Cyrus Muloki, a member of Ngoloosi self-help group.
The group, which has more than 50 members, is one among many in the area formed by villagers to help alleviate the water scarcity problem. In 2011, the group constructed a sand dam on the Kwa Kasolo River. This project has helped the members, who each now own at least 10 fruit trees. One farmer, Jonathan Kituku, has successfully planted Melia vokensii, a fruit tree common to east Africa, intercropped with mung beans on a large scale. He has been able to make good money as a result.
Working together
The sand dams are constructed of locally available materials, and the villagers have been trained to build the dams by technicians from the Africa Sand Dam Foundation (ASDF) in collaboration with SearNet, a network of rainwater harvesting associations.
These non-governmental organisations, working with various partners, have helped build more than 70 dams in the region, benefitting 21,000 households and 85,000 villagers. ASDF is currently working with 42 village groups in Kibwezi and is planning to construct 45 more dams by the end of the year.
“Sand dams have helped to raise the water table in this area, meaning that farmers can now grow crops with relative ease,” says Jacqueline Naomi, a water technician working with ASDF. According to Naomi the high success rate of ASDF projects stems from empowering villagers to seize ownership of the dam initiative from the outset.
The construction of the dam is a community driven process, she explains. The villagers identify the appropriate site for the dam and provide construction materials such as sand, water and stones, as well as free labour during construction and for regular maintenance.
“ASDF chip in with the technical knowhow and skilled manpower, in addition to donating hardware materials such as cement, steel and timber,” says Naomi.
More than a water source
Despite the area’s low rainfall, massive runoff of between 1,150m3 and 2,600m3 is generated per hectare, pointing to the region’s huge potential for rainwater harvesting. The water can be stored either in the soil or in surface and underground reservoirs.
A sand dam is a reinforced concrete wall built across a seasonal river to trap and store water underneath sand that is collected within the wall, thereby preventing excessive evaporation. The dam wall is typically 4m in height and 90m across, and fills with sand after two or three seasons.
“One metre of sand makes evaporation virtually impossible,” says Andrew Musila, development director at ASDF. A 4m x 90m dam can hold between 2,000m3 and 10,000m3 of water, enough to cater for the needs of 2,500 people and their livestock, as well as agricultural irrigation.
“When the dam is full of sand, the community will have a constant water supply for four years without the need for rain,” explains Musila.
By filtering water and cleaning it in the storage process, the sand prevents parasites from contaminating the water with harmful pathogens. Incidences of malaria and diarrhoea, which are partly responsible for high mortality rates in children under five in Africa, are drastically reduced as a result.
There are important factors to consider when deciding on the suitability of a sand dam site. This includes the existence of bedrock running across the river channel and the availability of sand in the river. The bedrock is needed to prevent the loss of trapped water through seepage, while the deposited sand contains the water and prevents evaporation.
Besides sand dams, other water harvesting methods are also proving useful to villagers, such as the construction of semi-circular bunds, or “oduorims”, and trapezoid-shaped ponds – which are designed to collect as much water as possible. Already, more than 200 trapezoidal ponds have been constructed in Kibwezi. The ponds have helped villagers grow vegetables, fruit trees and cereal crops, such as sorghum. They have also been important in growing pasture for livestock.
Given that women and children in rural Africa spend an average of six hours each day trekking 6km looking for water, these water harvesting techniques are saving time and effort that is put better to use elsewhere. In addition, during the drought period, the little water that is available from open water sources is usually unhygienic, heightening the risk of contracting waterborne diseases.
One of the key advantages associated with water harvesting is that small-scale irrigation of vegetables works well. Villagers’ incomes have been boosted because vegetables can now be grown all year round, unlike before when the planting had to coincide with the rains. In addition to improving livelihoods, food security in the region has also been enhanced.
Joyce Kasyoki uses irrigated water from a trapezoidal pond on her farm to grow mango trees, tomato plants, kale and a grass that is converted into hay. She sells bales of hay for 200 Kenyan shillings (KES) each, around $2.50, and a bunch of 10 kale leaves for KES 6 ($0.07).
Supporting ecosystems
The raised water table in the Kibwezi area has made it possible to establish tree nurseries near the sand dams. This is helping to rehabilitate ecosystems in the dry land, and the trees provide up to 90% of the fuel needed by the rural population in Africa, relieving women of the burden of spending two hours a day looking for firewood.
At another level, the trees being planted in the nurseries are chosen because they are fertiliser trees and fodder shrubs. Villagers have been trained in agroforestry techniques by the World Agroforestry Centre (ICRAF) on how to grow the trees and use them in their farms.
These fertiliser trees include a species of acacia popularly known as whitethorn, or mkababu in Swahili, whose deep-penetrating root system makes it highly resistant to drought; and Sesbania sesban, commonly known as the Egyptian rattle pod.
These tree species fix nitrogen in the soil, enriching it, and are important for rural farming populations who have virtually no access to commercial fertilisers. Also, foliage from these trees provides feed for livestock and the high nitrogen content has been shown to increase milk production.
ICRAF has evidence that these fodder shrubs have a high impact on net income from milk production; increasing the Kenyan dairy sector’s turnover by up to $29.6 million over the past 15 years.
For the average, resource-poor dairy farmer milk production has been increased from five litres to 50 litres a day through the addition of fodder shrubs into animal feed. An estimated 225,000 smallholder farmers in East Africa grow Egyptian rattle pod trees, for example, to help feed their dairy livestock.
Raising resources
Research shows that rainwater harvesting remains pitifully low in Kenya. Just 1% to 3% of the rain that falls on the country is harvested, with the rest flowing into the ocean. The main reason is because the resources to construct water harvesting technologies, such as sand dams, although relatively cheap, are still costly for many villages. According to Naomi at ASDF, a standard sand dam would cost about KES 700,000 ($8,400), not including labour.
“In addition, the region’s topography matters a great deal, with only populations near a river benefiting, rather than those living further away,” says Kipruto Cherogony, a soil and water engineer at SearNet. Hilltop communities in particular are at a disadvantage, because pumping water uphill is very expensive.
“To ensure the success of projects and keep costs at a minimum, we have to start with the best sites and they are not readily available,” explains Cherogony. The best sites for sand dams are in rivers which already contain deposited sand, he says, and these are usually large rivers.
The implications of improving access to clean water in Africa cannot be overstated, according to a new report from charity WaterAid. Published in March, Everyone everywhere reveals that the lack of progress made in improving access to water, sanitation and hygiene in the continent is hampering economic and human development, particularly in child health, nutrition and education.
Figures produced by the World Health Organisation (WHO) reveal that Africa could gain $33 billion each year if every citizen had access to water and sanitation. Of this, $4.5 billion would come from reduced healthcare costs; $7.2 billion could be gained from reduced mortality rates; $2 billion from fewer work absences; and $19.5 billion in time saved – on activities such as walking to collect water.
The Institute of Health Metrics estimates that 550,000 people die of diarrhoea diseases every year in sub-Saharan Africa. The vast majority (88%) can be linked to lack of water, sanitation and hygiene, says WHO.
In the words of the Liberian president, Johnson Sirleaf: “It will not be possible to make progress in eradicating poverty, reducing inequality and securing sustainable economic development in the future without improving access to water.”
And, with every dollar invested in water and sanitation producing $4 in increased productivity, according to WHO, the construction of sand dams in Kenya is providing a crucial source of water and economic prosperity.
