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Sand dams are a simple, low-cost and low-maintenance, replicable rainwater harvesting technology. They provide a clean, local water supply for domestic and farming use and are suited to semi-arid areas of the world.
A sand dam is a reinforced concrete wall (or a similarly robust and impermeable weir) built 1–5 metres high across a seasonal sand river.
When it rains the dam captures soil laden water behind it – the sand in the water sinks to the bottom, whilst the silt remains suspended in the water.
Research on Kenyan dams shows that only 1 to 3% of rainwater is retained behind any individual dam, the remainder continues its natural flow towards the ocean. [1] Eventually the dams fill with sand - sometimes after only one rainfall or over 1 – 3 seasons. 25 to 40% of the volume of the sand held is actually water.
A mature sand dam can store millions of litres of water – refilling after each rainfall providing a year round supply of clean water to over 1,000 people.
The highest concentration of sand dams with the strongest track record is found in Kenya although examples are found throughout world’s semi-arid regions from Angola to Zimbabwe. Further examples are recorded in Japan, India, Thailand, SW USA and Brazil.
Sand dams can be built in the upper and middle courses of seasonal sandy river valleys (also known as wadis). Typically, sand dams are built in the transition zone between hills and plains where the gradient of the river bed is between 0.2 - 4%, but in extreme cases sand storage dams have been constructed on slopes of 10-16% (Nilsson 1988). Dams must be built on bed rock or highly compacted sub-soil. For the obvious reason of economy on materials and labour, the stream must be reasonably narrow with well defined and stable river banks and the bedrock or impermeable subsoil within a few metres of the stream bed. Rocky banks and gorges are the most apt features. Further advice on the siting, design and construction of sand dams is available from the organisations and in the manuals listed below
There are two simple ways:
On a global scale climate change and effects there of have exerted tremendous pressure on the biophysical, economic, political and social systems that govern the sustenance of a majority of African populations. (Zierrogel et al, 2009)
“Climate Change is expected to intensify existing problems and create new combinations of risks, particularly in Africa where there is widespread poverty and dependence on the natural environment.” (Zierrogel et al. 2009)
Kitui is a region in Eastern Kenya, East Africa, where the sand dam project has been relatively more successful in comparison to other regions that adopted the same or similar systems. The Kitui region has approximately five hundred functional sand dams that help with water storage for subsistence and commercial purposes for example irrigation, domestic use and for feeding and sustaining livestock. (Maurits, 2008)
Effectiveness of Sand Dams in Kitui
With the setup of over 500 dams in the region there is no question to how these sand dams are a major community requirement. The image below shows an overview of the multiple uses of sand dams in the Kitui region. (Lasagne, 2008)
Image: Table showing Sand Dams use in Kitui (Lasagne, 2008)
Human welfare:- these dams provide water security during the dry season when numerous rivers and wells dry up due to the harsh conditions of the region. (Lasagne, 2008)
Quality of nature:- The dams provide water to the ecosystem by feeding the water table hence trees and flora are able to thrive in the surrounding areas. (Lasagne, 2008)
Food capacity:- Due to access to water reserves numerous individuals engage in subsistence and semi-commercial farming which creates a source of income and livelihood for the Kitui People. (Lasagne, 2008)
Industrial use:- On a larger scale these dams provide water for industrial capacity as individuals are able to engage on economic activities such as charcoal production, basket making and brick laying which creates a semi-stable source of income for the locals. (Lasagne, 2008)
Hindrances to the sand dam project
There are numerous obstacles to the sand dam projects but the major ones that stand out are irregularity of the rainy seasons, slow funding, lack of communal platforms to run the projects and maintain them. (Lasagne, 2008)
Conclusion
“The average income of farmers using sand dams rose with 9000 KSh. (USD 120), while less than 3% of total runoff is used. It is estimated that in 10 years time, more than 100,000 people have better access to water through low cost measure at an investment of about 35 USD per capita.” (Lasagne, 2008) If these projects had more government, Non-governmental participation and an increased community involvement, Kitui could be a world renown model for the ability of rural communities to combat drought , famine and other effects of climate change.
Polish Humanitarian Action building dams in Kenya and Madagascar
The Geography of Kenya is diverse, varying amongst its 47 counties. Kenya has a coastline on the Indian Ocean, which contains swamps of East African mangroves. Inland are broad plains and numerous hills. Kenya borders South Sudan to the northwest, Uganda to the west, Somalia to the east, Tanzania to the south, and Ethiopia to the north. Kenya currently faces border disputes with South Sudan over the Ilemi Triangle and with Somalia over Jubbaland where, if the Somalian Government gives it up, it could be a new part of Kenya, which would bring the total land area of Kenya to approximately 692,939 km2.
Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit, aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water. Rainwater harvesting differs from stormwater harvesting as the runoff is typically collected from roofs and other area surfaces for storage and subsequent reuse. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.
The ca. 1000 km long Tana River is the longest river in Kenya, it is also called Sagana River in the Mt Kenya region and gives its name to the Tana River County. Its catchment covers ca. 100,000 km2 and can be divided into the headwaters and the lower Tana consisting of the section downstream of Kora where the river flows for ca. 700 km through semi-arid plains. Its tributaries include some major rivers in the Central Region like Thika, Ragati River, Nyamindi, Thiba ,Mathioya, Chania, Thuci and Mutonga. The river rises from Mt Kenya in Nyeri. It initially runs southwest before turning south around the massif of Mount Kenya and meanders all the way up to the Indian Ocean. A series of hydroelectric dams has been constructed along the river. These include the Masinga Dam, the Kamburu Dam, the Gitaru Dam, the Kindaruma Dam and the Kiambere Dam. en The Masinga Reservoir and the Kiambere Reservoir, created by the Masinga and Kiambere dams respectively, serve a dual purpose: hydro-electric power (HEP) generation and agricultural irrigation. The other three are used exclusively for HEP generation. A 2003 study reported that two-thirds of Kenya's electrical needs were supplied by the series of dams along the Tana River. Many people believe this river has groundwater underneath it, but it doesn't. The electricity is then supplied to the national grid system and distributed countrywide through a series of substations, transformers and cables.
A reservoir is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation.
Environmental issues in Kenya include deforestation, soil erosion, desertification, water shortage and degraded water quality, flooding, poaching, and domestic and industrial pollution.
Rajendra Singh is an Indian water conservationist and environmentalist from Alwar district, Rajasthan in India. Also known as "waterman of India", he won the Magsaysay Award in 2001 and Stockholm Water Prize in 2015. He runs an NGO called 'Tarun Bharat Sangh' (TBS), which was founded in 1975. The NGO based in village hori-Bhikampura in Thanagazi tehsil, near Sariska Tiger Reserve, has been instrumental in fighting the slow bureaucracy, mining lobby and has helped villagers take charge of water management in their semi-arid area as it lies close to Thar Desert, through the use of johad, rainwater storage tanks, check dams and other time-tested as well as path-breaking techniques. Starting from a single village in 1985, over the years TBS helped build over 8,600 johads and other water conservation structures to collect rainwater for the dry seasons, has brought water back to over 1,000 villages and revived five rivers in Rajasthan, Arvari, Ruparel, Sarsa, Bhagani and Jahajwali. He is one of the members of the National Ganga River Basin Authority (NGRBA) which was set up in 2009, by the Government of India as an empowered planning, financing, monitoring and coordinating authority for the Ganges (Ganga), in exercise of the powers conferred under the Environment (Protection) Act, 1986.
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally and through anthropogenic processes, where rainwater and/or reclaimed water is routed to the subsurface.
An irrigation tank or tank is an artificial reservoir of any size. In countries like Sri Lanka and India they are part of historic methods of harvesting and preserving rainwater, critical in regions without perennial water resources. A tank is often an earthen bund constructed across a long slope to collect and store surface water from the above catchment and by taking advantage of local topography. The water would be used primarily for agriculture and drinking water, but also for bathing and rituals. The word tank is the English language substitute for several vernacular terms.
Water resources management is a significant challenge for Mexico. The country has in place a system of water resources management that includes both central (federal) and decentralized institutions. Furthermore, water management is imposing a heavy cost to the economy.
The aim of water security is to make the most of water's benefits for humans and ecosystems. The second aim is to limit the risks of destructive impacts of water to an acceptable level. These risks include for example too much water (flood), too little water or poor quality (polluted) water. People who live with a high level of water security always have access to "an acceptable quantity and quality of water for health, livelihoods and production". For example, access to water, sanitation and hygiene services is one part of water security. Some organizations use the term water security more narrowly for water supply aspects only.
Desert greening is the process of afforestation or revegetation of deserts for ecological restoration (biodiversity), sustainable farming and forestry, but also for reclamation of natural water systems and other ecological systems that support life. The term "desert greening" is intended to apply to both cold and hot arid and semi-arid deserts. It does not apply to ice capped or permafrost regions. It pertains to roughly 32 million square kilometres of land. Deserts span all seven continents of the Earth and make up nearly a fifth of the Earth's landmass, areas that recently have been increasing in size.
Water supply and sanitation in Kenya is characterised by low levels of access to water and sanitation, in particular in urban slums and in rural areas, as well as poor service quality in the form of intermittent water supply. Seasonal and regional water scarcity in Kenya exacerbates the difficulty to improve water supply.
The main causes of water scarcity in Africa are physical and economic water scarcity, rapid population growth, and the effects of climate change on the water cycle. Water scarcity is the lack of fresh water resources to meet the standard water demand. The rainfall in sub-Saharan Africa is highly seasonal and unevenly distributed, leading to frequent floods and droughts.
Namibia is an arid country that is regularly afflicted by droughts. Large rivers flow only along its northern and southern borders, but they are far from the population centers. They are also far from the country's mines, which are large water users. In order to confront this challenge, the country has built dams to capture the flow from ephemeral rivers, constructed pipelines to transport water over large distances, pioneered potable water reuse in its capital Windhoek located in the central part of Namibia, and built Sub-Saharan Africa's first large seawater desalination plant to supply a uranium mine and the city of Swakopmund with water. A large scheme to bring water from the Okavango River in the North to Windhoek, the Eastern National Water Carrier, was only partially completed during the 1980s.
Water issues in developing countries include scarcity of drinking water, poor infrastructure for water and sanitation access, water pollution, and low levels of water security. Over one billion people in developing countries have inadequate access to clean water. The main barriers to addressing water problems in developing nations include poverty, costs of infrastructure, and poor governance. The effects of climate change on the water cycle can make these problems worse.
Mutomo District was a former district in the Eastern Province of Kenya. Its population is 180,000. The administrative center of the district is Mutomo. In 2010, it was merged into Kitui County.
South Eastern Kenya University "SEKU" is a public university with its main campus located in Kwa Vonza, Kitui County, Kenya.
Climate change is posing an increasing threat to global socioeconomic development and environmental sustainability. Developing countries with low adaptive capacity and high vulnerability to the phenomenon are disproportionately affected. Climate change in Kenya is increasingly impacting the lives of Kenya's citizens and the environment. Climate Change has led to more frequent extreme weather events like droughts which last longer than usual, irregular and unpredictable rainfall, flooding and increasing temperatures.
Between 2008 and early 2010, Kenya, one of the countries of Eastern Africa, was affected by a severe drought, which put ten million people at risk of hunger and caused a large number of deaths to livestock in Kenyan Arid and Semi-Arid Lands (ASALs), constituting around 88% of the country.
Rainwater management is a series of countermeasures to reduce runoff volume and improve water quality by replicating the natural hydrology and water balance of a site, with consideration of rainwater harvesting, urban flood management and rainwater runoff pollution control.