New report highlights how cooperation between Mozambique and Zimbabwe is key to a resilient shared basin

A basin that sustains millions 

The numbers alone tell a story of interdependence. The BUPUSA Tri-Basin drains 161,447 km², with 55 percent of its area in Zimbabwe and 45 percent in Mozambique. Nearly seven million people rely on the three rivers for drinking water, and the basin supports agriculture, fisheries, aquaculture, and industry on both sides of the border. Rainfall varies enormously across the basin – from around 2,000 mm a year in the mountainous headwaters of the Pungwe to as little as 550 mm in parts of the Save. This variability, combined with high evaporation rates, makes water a precious and sometimes contested resource. 

A changing environment 

The Atlas is built around a Causal Chain Analysis, a framework that traces environmental change back through its immediate and underlying causes to identify where action can make the most difference. Applying this lens to the BUPUSA basin reveals a set of interlinked pressures. 

Land cover is changing quickly. Forests and woodlands still cover just under half of the Buzi and Pungwe basins, but uncontrolled fires, cropland expansion, fuelwood collection and charcoal production are steadily eating into them. Artisanal and small-scale mining, particularly gold mining along riverbanks, is a recurring theme: it silts up rivers and dams, degrades water quality, and in places has introduced mercury and cyanide into the environment. 

Water quality overall remains within acceptable limits across much of the basin, but the Atlas flags specific hotspots: elevated zinc and titanium in parts of the Buzi basin, high iron and suspended solids in the Save, and localised traces of cyanide and mercury near mining sites. Meanwhile, water demand is rising. In the Pungwe basin, total water use is projected to grow from 810 million cubic metres a year in 2020 to over 1,300 million cubic metres by 2035. A trend replicated, in different degrees, across all three basins as populations grow and irrigation expands. 

Biodiversity in the basin is significant and, in places, still recovering. Gorongosa National Park in the Pungwe basin alone hosts more than 6,300 recorded species, 25 of them endemic, and 750 species on the IUCN Red List of Threatened Species. Restoration efforts have helped populations of buffalo, elephant, hippopotamus and lion to rebound. But invasive plant species are spreading in the Chimanimani, Vumba and Nyanga mountains, and deforestation, wildfire and poaching continue to threaten habitats across the basin. 

Living with climate extremes 

The BUPUSA basin experiences a tropical storm most years and a cyclone roughly once every three years, almost all originating in the south-west Indian Ocean. The human cost of these events can be severe: Cyclone Idai in 2019 brought up to 400 mm of rain in a day or two, triggered landslides, killed more than 1,500 people and displaced 400,000 people, while water and sanitation infrastructure. 

Looking ahead, the Atlas draws on regional climate projections to sketch a drier, hotter future. Temperatures across the three basins are projected to rise by close to 2°C under a moderate emissions scenario, and by 3.5–4°C under a high emissions scenario, by the end of the century. The Atlas also highlights the value of combining scientific climate services with the indigenous knowledge systems that many communities already use – reading indicator plants, animal behaviour and atmospheric signs – to anticipate the coming season, while noting that increasing climate variability is itself eroding the reliability of these traditional forecasting methods. 

Cooperation as the backbone of resilience 

None of these challenges can be managed by one country alone, and the Atlas devotes a full chapter to the transboundary governance that has developed between Mozambique and Zimbabwe over the past three decades. A Joint Water Commission was established in 2002, followed by Water-Sharing Agreements for the Pungwe (2016), Buzi (2019) and Save basins. In May 2023, the two governments went a step further, establishing the Buzi, Pungwe, and Save Watercourses Commission (BUPUSACOM), launched formally in Beira that July. This landmark moment is described in the Atlas as “significant and remarkable” in the history of cooperation between the two countries. 

The lessons the Atlas draws from this process are practical ones: political commitment and mutual respect between riparian states are essential; continuity of representatives in negotiations avoids deadlock; and language differences and differing institutional expectations need to be understood to ensure effective cooperation. 

A roadmap, not just a record 

The Atlas closes by translating its evidence into a Strategic Action Programme, setting out concrete actions against each major challenge: enforcing existing regulations on mining, agriculture and waste disposal rather than drafting new ones; investing in gauging stations and shared hydrological data to underpin fair water allocation; building climate-resilient infrastructure and multi-hazard early warning systems; and formally involving communities and indigenous knowledge in basin management decisions. 

The Atlas calls for “significant transformation” in how natural resources in the basin are extracted, managed and protected, warning that without it, land and water degradation, combined with intensifying climate extremes, will increasingly threaten the livelihoods of the millions who depend on this shared basin. Encouragingly, it also points to what already exists to build on: a functioning transboundary commission, ratified sharing agreements, an emerging flood forecasting and early warning system, and – with this Atlas itself – a shared evidence base that both countries can now draw on together. 

As the authors put it, the case for action is clear and compelling. What remains is the harder work of implementation, on both sides of the Buzi, Pungwe and Save.