Over one million people in sub-Saharan Africa will contract malaria this year because they live near a large dam, according to a new study, published in Malaria Journal in September 2015. The study was undertaken as part of the CGIAR Research Program on Water, Land and Ecosystems.
Researchers correlated the location of large dams with the incidence of malaria and quantified impacts across the region. They found that construction of 78 major new dams anticipated in sub-Saharan Africa over the next few years will lead to an additional 56,000 malaria cases annually.
The researchers found that a total of 15 million people live within five kilometres of dam reservoirs and are at risk, and at least 1.1 million malaria cases annually are linked to the presence of the dams. The risk is particularly high in areas of sub-Saharan Africa with “unstable” malaria transmission, where malaria is seasonal. The study indicated that the impact of dams on malaria in unstable areas could either lead to intensified malaria transmission or change the nature of transmission from seasonal to perennial.
Previous research has identified increased malarial incidence near major sub-Saharan dams such as the Akosombo Dam in Ghana, the Koka Dam in Ethiopia and the Kamburu Dam in Kenya, but until now, no attempt has been made to assess the cumulative effect of large dam building on malaria.
Major implications for new dam projects
There are major implications for new dam projects and how health impacts should be assessed prior to construction. Encouraged by the increased volume of international aid for water resource development, sub-Saharan Africa has, in recent years, experienced a new era of large dam construction.
Many African countries are planning new dams to help drive economic growth and increase water security. Improved water storage for growing populations, irrigation and hydropower generation is indeed badly needed for a fast developing continent. But the researchers warn that building new dams has potential costs as well as benefits.
The study notes that despite growing evidence of the impact of dams on malaria, there is scant evidence of their negative impacts being fully offset.
How the increased malaria risk can be managed
The authors make recommendations about how the increased malaria risk can be managed.
Dam reservoirs could be more effectively designed and managed to reduce mosquito breeding. For instance, one option is to adopt operating schedules that, at critical times, dry out shoreline areas where mosquitoes tend to breed. Dam developers should also consider increasing investment in integrated malaria intervention programmes that include measures such as bed net distribution. Other environmental controls, such as introducing fish that eat mosquito larva in dam reservoirs, could also help reduce malaria cases in some instances.
Read the study:Malaria Journal