Experimenting with Multidisciplinary, Participatory Diagnosis and Community Engagement to Rehabilitate Endangered Watersheds in African Urban Settings: The Case of Lake Chivero in Zimbabwe

Urban watersheds in sub-Saharan Africa face unprecedented environmental degradation due to rapid urbanization, inadequate infrastructure, and governance failures. Lake Chivero, a shallow hypereutrophic reservoir constructed in 1952 on Zimbabwe's Manyame River, exemplifies this crisis. Serving as the primary water source for Harare and its dormitory towns of Chitungwiza and Ruwa a combined population exceeding 2.4 million. The lake has experienced catastrophic deterioration over seven decades. This study presents an innovative multidisciplinary framework combining Critical Zone Sciences with participatory diagnosis and community engagement to address complex socio-environmental challenges threatening water security in rapidly urbanizing African contexts. This framework offers scalable insights for addressing watershed degradation across African urban centers where rapid demographic transitions outpace infrastructure development and governance capacity, demonstrating how transdisciplinary approaches can bridge science-policy-community divides to achieve sustainable water resource management.

Lake Chivero's degradation manifests across multiple dimensions. Sedimentation has consumed 18% of the reservoir's storage capacity (49,126,170.34 m³), with annual capacity losses averaging 792,357 m³ year⁻¹ since 1953. Current sedimentation rates of 352.31 m³ year⁻¹ km⁻² project a remaining useful life of merely 106.63 years, pointing to a "2050 Doomsday Scenario." Sediment composition analysis reveals concerning proportions of mud (54%), sand (24%), and silt (22%). Nutrient pollution has escalated dramatically, with combined nitrogen and phosphorus loads surging from 3,524 tons in 2000 to 38,940 tons in 2012, an increase primarily attributable to untreated and partially treated sewage effluent. This pollution has triggered extensive water hyacinth (Pontederia crassipes) proliferation, linked to sewage effluent and abattoir waste discharge. Public health consequences include cholera outbreaks, waterborne diseases, and elevated cancer incidence rates, while ecological and economic impacts manifest in green-colored water and ecosystem collapse, as well as ballooned water treatment and public costs.

The research identifies governance fragmentation and knowledge silos as critical barriers to effective watershed management. Population growth from 200,000 during the colonial era to over 2.4 million by 2022, compounded by civil conflict in the 1970s, rural-urban migration, economic structural adjustment programs (ESAP), and informal settlement expansion, has overwhelmed water and sanitation infrastructure. Policy dissonance, corruption, informal waste management through opaque private contracts, chemically intensive agriculture, and politically connected land speculation further exacerbate environmental stress.

Our methodological innovation addresses these challenges through deliberate transdisciplinary integration. The research team comprises experts in social sciences, governance, environmental science, GIS, soil science, hydrology, waste management, and renewable energy. We hypothesize that fragmented relationships among stakeholder’s stem fundamentally from asymmetric data access and exclusion of local communities from knowledge production and decision-making processes. Our approach systematically reviews published literature while collecting primary field data, then transforms scientific findings into accessible formats for policymakers, government officials, planners, and local communities.

Participatory diagnosis employs ethnographic methods including "photovoice" to capture thick descriptions of lived experiences, validating local knowledge systems alongside scientific data. GIS-based time series analysis integrates scientific measurements with ethno-environmental perspectives, creating space for authentic dialogue. This methodology enables collaborative problem identification and solution co-creation grounded in shared visions and mutual trust. Thematic analysis using NVivo software ensures rigorous qualitative data interpretation.