Access to water for the greatest number of people has been one of the components of the social project of Burkina Faso for decades. In spite of the many actions carried out, water supply difficulties persist in the country. They are the result of two aggravating contextual factors: natural water scarcity and urban growth, which puts increasing pressure on the available resource and on existing infrastructures. Ouagadougou has climatic and geographical conditions that lead to an almost endemic water shortage with a permanent risk of drought. The natural hydrographic network is very limited. It consists of a single talweg, the Boulmigou, which crosses the city from east to west, to which a series of very temporary streams are connected due to climatic conditions. The city belongs to the northern Sudanese climatic domain characterized by relatively high annual temperature amplitudes and very irregular rainfall. Rainfall is heavy in July-August in terms of volume and in May and September in terms of strength. A large part of the rainfall is returned to the atmosphere by evapotranspiration, thus reducing the amount of rain that actually infiltrates the subsoil. This infiltration is further compromised by the waterproofing of urbanized surfaces, which promotes runoff.

Providing water to the population

To meet the ever-increasing need for water, the Loumbila Dam, located 20 kilometers from the capital, was built in 1970. Subsequently, as the rainfall deficit in 1983 led to the very partial filling of the dams, a program to develop catchment assets exploiting underground resources was set up, particularly in the outlying districts of the city, through the construction of mechanical boreholes or manual pumps. However, drilling is only a short-term complementary solution due to the absence of continuous and large-capacity aquifers. In 2006, the State began the construction of the Ziga Dam on the Nankamba River, located about 50 kilometers from the city, to serve as a third source of supply. This dam should ensure the sustainability of the water supply to the capital.

100% of the capital’s population has access to water

With a capacity of 207.8 million m3 of water and a catchment area of approximately 20,800 km2, the Ziga Dam was impounded in 2000. It feeds an eponymous plant of 12,000m3 per hour and includes two raw water stations (SP1 and SP1 bis), a treatment plant and two drinking water discharge stations (SP2 and SP2 bis). The dam produces 12,000m3 per hour for the needs of approximately 2,400,000 and 1210 fountain terminals in the Burkinabé capital and surroundings. Thus, the Ziga Dam alone is sufficient to cover the needs of the population of the Burkinabé capital estimated at about 2,800,000 inhabitants. The intermittent water supply in the capital is now a distant memory for the inhabitants.

Threats to water quality

The people living along the dam practice market gardening on the banks and move into the dam bed as the water recedes. To control insects and pests (worms, rats, rat thieves, hares, partridges, wild guinea fowl, ...) that destroy their vegetables, they use synthetic pesticides, many of which are prohibited. Fertilizers are also used. This poses a serious threat to water quality and, by ricochet, to the lives of the population. Another element that threatens the quality of the water produced by the Ziga Dam comes from nature: algae, whose development is caused by animal excrement and chemical fertilizers. In addition to threatening the quality and sustainability of the water, these algae increase the cost of water production. In fact, these plants produce substances that give the water rotten and septic tank odors as well as moldy flavors that endanger the water’s drinking quality.

Natural and innovative solution

In view of the negative impact of algae on water quality, the environmental and social laboratory of Burkina Faso’s National Office for Water and Sanitation (ONEA) has been developing since 2010 alternative solutions to the misuse of chemicals. The innovative solution found by ONEA to overcome these toxic algae is the introduction of planktophagous fish, tilapias (for which these toxic algae are a main food), into the dam water. Thus 4.5 million tilapias of 50 grams have been introduced for the purification of the 208 million m3 of water of Ziga. In terms of benefits, this allows ONEA to lower the quantity of chemicals used to always serve quality water. After 3 years, the populations are allowed to catch these fish, (non-toxic for humans), which allows the injection of 315 million FCFA into the economy.

Protection measures

In addition, ONEA has taken strict measures to protect the dam water from other sources of pollution. An easement zone or protection perimeter has been defined around the dam to prevent certain acts of pollution by man and damage to the catchment facilities. To this end, it is strictly forbidden to fish (outside the periods set aside for tilapia fishing), to water the animals and to market gardening on the banks upstream from the dam. Ordinary fishing is only permitted downstream. Finally, in order to fightn against silting and evaporation of water from the Ziga Dam, the National Water and Sanitation Corporation (ONEA) is gradually reforesting the Ziga Dam’s easement zone.

Regular quality control

Like all water produced in Burkina Faso by ONEA, the Ziga Dam waters are subject to universal conformity control, in particular the standards (WHO Recommendations) in force, for physico-chemical, organoleptic and microbiological parameters. This control is carried out in several phases. Firstly, on-the-spot monitoring by the water production agents every two hours. Secondly, internal monitoring by ONEA’s Central Laboratory at least once a month, with the capacity to search for micropollutants (heavy metals and pesticides). Finally, the external control of the National Laboratory of Public Health.

From dam to faucet

The Ziga Dam was built with the financing of 12 donors and cost about 150 billion FCFA for Phase I, and 107 billion FCFA for Phase II. Its implementation will ensure universal access to drinking water for the population of Ouagadougou, but also improve the quality of service by ensuring continuity of service 24 hours a day, including in the hot season and in all districts of the capital city. With this «Ziga Dam» project, we can say that the objective of the President of Faso, His Excellency Roch Marc Christian KABORÉ, who has committed to eradicate the chore of fetching water by 2020, has been achieved for the city of Ouagadougou. Finally, it should be noted that in terms of access to water in Burkina Faso, with respect to Goal 6 of Sustainable Development, progress was recorded in 2017 with an access rate to drinking water of 66.2% in rural areas and 91.7% in urban areas.