The paper explores how a project implemented in the framework of the LIRA2030 Africa programme is contributing to the achievement of the Sustainable Development Goals (SDG) on water, sanitation and health in the West African coastal cities of Cotonou (Benin) and Lomé (Togo). Based on co-produced knowledge on water, sanitation and health risks, collected through a transdisciplinary approach, we investigated socio-ecological sanitation and the applicability of an Ecohealth model to support SDGs 3, 6 and 11. According to our findings, the basis for the achievement of SDGs in these cities lies in addressing bad sanitation and hygiene related to a linear urban metabolism, poor groundwater quality and the occurrence of health risks (malaria, gastroenteritis, diarrheal). In this regard, the projects contributed by developing socioecological sanitation facilities for groundwater quality improvement and protection and for health risk reduction. An Ecohealth model was also developed to help improve and maintain the quality of groundwater in the study cities to promote healthy living and for sustainability. Social impacts of the SDG achievement could really help in sustainable development and the well-being in the coastal West African cities.

In the coastal cities of West Africa, land use change, rapid population growth, bad sanitation systems and poor environmental governance degrade the quality of groundwater. This study aimed to assess alternative, acceptable, affordable sanitation disposal and practices for groundwater quality rehabilitation in the cities of Cotonou and Lomé. The study was based on the participatory transdisciplinary approach, field surveys, feedback from interactions with stakeholders, experiences of the practitioners and institutional consultations. This multi-stakeholder approach helped to appreciate ecological aspects of sanitation disposal and its implications on water quality improvement. SWOT model was used to analyze the relevance of assessed ecological system. Well water quality is deteriorated by traditional waste management disposal. Ecological sanitation systems are septic tanks on polyethylene, above-ground latrines and phytoremediation technique in the swamp areas. Collected wastes are used for composting and biogas production. Based on the optimist scenario at 2030 horizon, kind success factors of groundwater security are participation of citizens, existence of sanitation market, valorization of the waste by category, low-cost disposal adaptable to the individual, household and neighborhood's scales. The strategic directions rely on funding and public policies for WASH, ecological sanitation disposal, cultural environment and good sanitation practices for emergence of new sanitation system to secure and sustain well water quality. But the social acceptability of ecological disposal is limited by the society's multicultural heritage.

Urban metabolism, a process of material, energy and water flows, consumption or transformation in the cities and outflows of wastes, has impacts on the shallow groundwater. This study addressed the relationship between the urban metabolic system and well water physicochemical and bacteriological quality in the coastal cities of Cotonou and Lomé. A participatory transdisciplinary approach, involving non-academics and academics stakeholders was used to analyse urban inflows and outflows related to groundwater quality. Standard methods were used to measure well water quality from 100 seasonal samples. Waste management revealed poor sanitation and hence a linear urban metabolism with no solid and liquid wastes and excreta recycling. This form of city metabolism reinforced by the seawater inflow is the main source of groundwater quality deterioration in Cotonou and Lomé. The principal water types Ca 2+ -Mg 2+ -Cl − -2 4 SO − (48.21%), Na + -K + -Cl − -2 4 SO − (65.9%) and the Gibbs diagram suggested water-rock interactions and dominance of cations exchange on the hydrogeological compositions, also seasonally controlled by saltwater intrusion or anthropogenic salinization. The water quality index on the range of 35.90 to 169.60 in Cotonou and 82.94 to 364.68 in Lomé indicated well water very poor quality to unsuitable for drinking. Moreover, the bacteriological quality was bad due to total coliforms (112 -1812; 1 -1000 UFC/100 mL respectively in Cotonou and Lomé), Escherichia coli (40 -780; 1 -112 UFC/100 mL), faecal enterococci/streptococcus (18 -736; 1 -118 UFC/100 mL). The findings could help to sustain groundwater quality by controlling the pollution sources linked to urban metabolism.

<p>The city of Cotonou (Benin) in the delta of the River Ouémé and the city of Lomé (Togo) closed to the River Zio and depending lagoons have hydrosystems include aquifers and urban ecology under pressure of annual floods and discharge. So, bad sanitation and hygiene, poor physicochemical and bacteriological groundwater quality and occurrence of health risks (malaria, gastroenteritis, diarrheal) are observed ecohydrological characteristics. Well water quality data, sanitation and hygiene related public health data linking to the flow data of referred rivers are used to highlight a complexity of the ecohydrological state of the cities. With regard to the global agenda 2030 specifically the SDG 3, 6 and 11, an ecohealth model was developed to contribute in improvement of well water quality and to promote sustainable healthy living in the study area. Elaborated ecohealth model supports pathways on how improved human health could be attained from better groundwater and waste management in the whole west African coastal cities. In Cotonou and Lomé, recurrent floods, controlled by hydrological variation on the depending river basin affects urban ecology and human settlements. The footprint of the interactions is deterioration of environment patterns, of groundwater quality and higher prevalence of waterborne diseases. Referring to knowledge on public health (current and expected status), the model ecohealth is generated by establishing a relationship between floods, aquifers (hydrosystem) and sanitation and hygiene systems (disposal). Given that the urban population faces problems of unsafe sanitation and hygiene, and well water quality degradation, adequate information-education-communication (IEC) for social change approach was used to help in adoption of socio-ecological sanitation systems for water security and its accessibility. Dry toilets, above ground and watertight pit latrines and polyethylene septic tanks are the proposed sanitation disposals. Effective implementation of developed ecohealth model could have great social impacts and help in sustainable well-being in the coastal West African cities.</p><p>Keywords: River delta, coastal city, groundwater quality, floods, ecohealth model </p>

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