Reservoir in N’Gala (Bougouni) (HELVETAS SwissIntercooperation)
The installation of earth embankment dams in lowland areas comprises the following elements: 1) a compacted earth embankment, 100 to 450 metres in length; 2) a side spillway built with rubble or cyclopean concrete, 40 to 75 metres in length and connected to the embankment with lock walls; 3) a spillway stilling basin of loose stones; 4) dam height of up to five metres and a crest width of up to four metres; 5) a pond upstream of the embankment dug up to three to four metres deep for storing water throughout the dry season and, thereby, ensuring supplies for watering animals, market gardening and fish farming.
Embankment dams retain water in the basin for several months after the end of the rainy season, which can be used for watering livestock and crops off season; and they help raise the water table, which makes well water more easily accessible (at a depth of one to five metres). These dams are used for both controlled and free submersion.
The side of the embankment is about one metre higher than that of the side spillway. When the water level reaches the height of the side spillway, water flows down through the structure and continues along the riverbed on its normal route downstream. In-season rice growing is carried out both upstream and downstream of the dam. Upstream growers farming areas peripheral to the reservoir are advised to use varieties of floating rice or those that can withstand prolonged flooding. The seedlings for this kind of rice must be sown before the reservoir fills with water.
At the end of the growing season, the water is retained in the reservoir for watering animals and for fishing. Market gardening activities are carried out along the entire length of the river, with water being extracted from dug wells (sumps two to six metres deep).
In Mali, there are around 15 schemes in place in the circles of Sikasso, Kadiolo, Bougouni and Yanfolila, covering more than 1,000 hectares and benefiting 1,500 rural families. In these areas, more than 60% of rice growers are women. More than 100,000 head of cattle are watered each year from the reservoirs. The very large quantity of stored water considerably increases the potential to use land for vegetable and tree growing.
Local people formulate the requirement and negotiate with the commune on the investment programme; they identify the rules of access and set up the farming cooperatives and management bodies. The commune plans investments and assumes overall control of the construction work, delegates management to users, and validates the farming rules and oversees their correct application. Consultancies carry out the socio-economic, environmental and technical studies (scheme design, plans, models), draw up the invitation to tender document and support the tender selection process, and monitor and inspect works. Technical services oversee the application of technical and environmental standards and participate in ensuring sound financial practices (collection, financial control, public service concessions). Contractors carry out the construction work. The project team provides training (planning, social engineering, studies involving farmers, etc.), advisory support (organisation of users, formulation and validation of rules, area development plan, plan to develop and exploit value chains, selection of suitable crop varieties, management delegation procedures, procedures for securing land titles, etc.) and co-financing.
The users are divided up into management and maintenance teams and their respective responsibilities are clearly defined prior to the interim and final acceptance of works.
This type of scheme is effective in areas with good rainfall levels and in lowland areas where the water table is not very low. It is important to select lowland areas with the potential to store a substantial volume of water (topographic basins). This type of scheme works best in southern areas of Mali with 1,100 to 1,200 millimetres of precipitation per year.
Localização: Kadiolo, Sikasso, Bougouni, Yanfolila, Mali, Mali
Nº de sites de tecnologia analisados:
Difusão da tecnologia: Uniformemente difundida numa área (10.0 km²)
Em uma área permanentemente protegida?:
Data da implementação: 10-50 anos atrás
Tipo de introdução
In Mali, there are around 15 schemes in place in the circles of Sikasso, Kadiolo, Bougouni and Yanfolila, covering more than 1,000 hectares and benefiting 1,500 rural families. In these areas, more than 60% of rice growers are women. More than 100,000 head of cattle are watered each year from the reservoirs. The very large quantity of stored water considerably increases the potential to use land for vegetable and tree growing.
