Saint Louis is a West African municipality that experiences water delivery and wastewater management challenges. These challenges largely stem from the national water utility’s inability to keep up with the pace of urban growth and provide adequate service for all residents. Due to its geographic location, the city also experiences dramatic flooding from multiple sources – which the national government struggles to address. The following proposal recommends (1) installing a system of small-scale treatment wetlands across Saint Louis to clean rain and wastewater for non-potable uses and (2) devolving the water utility control from the national level to local government to improve management and harness local capacity. By transforming wastewater and rainwater from a waste product and a nuisance to a resource, Saint Louis could also reduce pressure on its drinking water supply.
THE CONTEXT
Saint Louis sits in the Northwest of Senegal, at the country’s border with Mauritania and the mouth of the Senegal River. The municipality is the former French colonial capital and played a pivotal role during the Atlantic Slave Trade. Today, it is small relative to the capital, with a population of 200,000 people compared to Dakar’s 3.4 million. Despite its small population, Saint Louis remains culturally significant as a tourism hub and economically relevant due to its fishery industry. Today, the municipality is growing at roughly 3%. (Agence Nationale de la Statistique et de la Demographie, 2016) This rapid growth led the city to expand beyond the island and much of the recent development is characterized by spontaneous settlements. In addition, many of Saint Louis’ residents are poor. Based on anecdotal evidence roughly one-third of the population lives below the global poverty rate of 3.10 USD per day.
Saint Louis climate is influenced by two powerful climatic forces: the Sahara Desert and the Atlantic Ocean. As such, the climate oscillates between an extended dry season and a monsoon season, and the municipality is exposed to booth drought and flooding hazards. Looking to the future, climate models predict that the dry season will extend longer, and the rain season will become more intense and erratic. (Oxford Research Encyclopedia of Climate Science) The municipality’s water portfolio is divided between two sources. The first source is a tributary of the Senegal River and the second is an unconfined aquifer within the Senegal-Mauritania aquifer basin.
MANAGEMENT CHALLENGES
Today, Saint Louis does not experience physical scarcity. Instead, its challenges are managerial and economic mainly due to low government capacity and rapid urbanization. Senegal operates through a unitary system and most water utility functions are overseen at the national level. The national government does not have the manpower or finances to keep up with the pace of growth. It is unable to plan for where people should build, cannot install physical infrastructure quickly enough and struggles to maintain the system. These factors contribute to an unreliable and often expensive water supply and the pollution of water ways. In addition, many residents cannot afford the municipal system or private providers. Often, wastewater is dumped directly in waterways or the surroundings.
Saint Louis could experience physical scarcity in the future. The world bank predicts that water withdrawals in Senegal will increase by 50-60% by 2035 from 2020 levels due to population growth and lifestyle changes. Such withdrawal increases could lead to an overdrawing of the sources available to Saint Louis.
INTERVENTION 1: NEIGHBOURHOOD-SCALE TREATMENT WETLAND SYSTEM
A system of neighborhood-scale treatment wetlands is a low-tech strategy that is appropriate for Saint Louis’ context. The system and equipment are more rudimentary. In terms of construction and maintenance costs, treatment wetlands are cheaper than centralized treatment plants. For example, the Barangay Villareal treatment wetlands in the Philippines cost 500,000 euros to construct – this is about 175$ per person that it serves. While a traditional plant cost around $1,000 dollars per person for the same amount of waste generated. This system also doesn’t require a skilled workforce for operation and if there is some sort of damage it is easy to repair. Finally, a decentralized system does not stop operating if one part of the system fails.
A neighborhood-scale system does require more manpower. However, in Senegal’s context this would be welcome. The country is experiencing a labour crisis, where roughly 70% of the workforce does not have a job that sufficiently supports their lives. A low-tech system that requires more labour would provide more jobs that are accessible from a low-skill entry point.
The proposed wetland treatment system would be a three-stage system based on the French Reed Bed concept but adapted to Senegal’s climate using recommendations from the Gaston Berger University pilot study. The wetland system would be largely gravity fed and require minimal mechanical equipment. The wetlands would be located at low points and wastewater conveyed to them through a pipe system. While stormwater would travel to the wetlands through open culverts installed parallel to roadways. Residents would also be able to individually drop off waste. Since Saint Louis will save money on the treatment part of the system, the municipality can invest more into installing pipes and culverts. To address the risk of effluent escaping into the environment due to flooding or a rising water table due to sea level rise, the first treatment stage in the wetlands would occur in confined tanks and the open wetlands would have a concrete liner. A pump to move water from the tanks to the second stage is the only mechanical equipment required. The diagram above explain the wetland treatment concept. Ultimately, the wetland system is limited in its capacity to ensure the removal microscopic pollutants that would make the water safe to drink.
TRANSFER POWER TO LOCAL GOVERNMENT & COMMUNITY STEWARDS
There are three national agencies responsible for municipal water systems. Senegal’s drinking water is supplied through a public-private partnership. Société Nationale des Eaux du Senegal (SONES) is the publicly owned holding company that owns Senegal’s potable water infrastructure. SONES is also responsible for capital planning and financing, monitoring water quality, infrastructure construction, and public outreach (SONES, 2024). Sen’Eau, 55% of which is state-owned, is responsible for operation and distribution. Suez Group, a French multi-national water and waste management firm, is working with Sen’Eau as a technical partner to improve access and efficiency. Office National de l’Assainissement du Senegal (ONAS) manages the city’s waste and rainwater. It is public and operates under the national Ministry of Water and Sanitation.
To ensure effective operation & maintenance of neighborhood-scale infrastructure, the wetland strategy should be complemented with water sector reform. Power should be devolved from the national government down to the local level. The table below describes how the neighbourhood-scale wetland system would be managed. This move will also address the national government’s limited capacity. Decentralizing management to the local level will allow for better monitoring, context-specific interventions and the nimble adjustment of the management system as issues come up. In addition, it allows people to have more control over their water supply. There will be more jobs created at the local level and the municipality can tap into the existing network of community stewardship.
Due to low government capacity, Saint Louis communities are already engaged in effort to bring other services to their residents and managing the treatment wetland could be an activity around which communities organize. Residents would be paid for their work. Since it is low-skilled labour, the position would be accessible to more people and would cost the government less. The work would be part time and could supplement other income. In addition, Gaston Berger University could continue their work on treatment wetland research by acting as the technical steward for the wetland system. Their responsibilities would include knowledge and technical skills sharing to the community and the local government and leading community science efforts to monitor the wetland efficacy.
ENABLING POLICY
Wastewater use for irrigation is already explicitly written into Senegal’s national sanitation code and people are comfortable with this wastewater reuse. It seems feasible to expand the scope of wastewater re-use for other non-potables uses. In addition, the city is in the process of decentralization reform. The process began in 1996 and in 2013 ACT III further devolved national authority to municipalities. The national government devolved more responsibility to municipal governments, including land use planning, waste collection and overseeing public transportation. As such, the next logical step would be to give municipalities authority over their water utility systems – especially considering the reciprocal relationship between land use, transportation networks and infrastructure.
These two policy reforms will need to be supplemented by an education campaign. There is precedent for successful education campaigns – in 2000, Dakar launched a wastewater reuse pilot project for agricultural irrigation from a municipal plant. Initially the project wasn’t incredible popular, but through public forums and understanding of imminent drought the project ended up being successful and was scaled up. Now that people are used to reuse for agriculture, the uses can be scaled up to other non-potable uses.
CONCLUSION
Saint Louis is a rapidly growing city that faces managerial and economic challenges that impact the commune’s ability to provide water for its residents and to treat wastewater safely and effectively. By building a system of treatment wetlands, Saint Louis would “hit two birds with one stone” — it would be able to treat more wastewater at a lower cost, while also alleviating pressure from the drinking water system. In addition, by choosing a lower-cost strategy for treatment, the commune could invest more into expanding its water infrastructure. Devolving power to municipalities and community groups would provide more control for residents over their water supply.