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IWMI
Research on Malaria
& Water Management
Malaria in tank cascade systems
South Asia has thousands of tank cascade irrigation systems. Most are in need of rehabilitation. The stagnant pools formed by water leaking from the system create an ideal mosquito breeding ground along the entire irrigation network, near thousands of rural villages.
IWMI hydrologist Yatuka Matsuno recalls the early discussions with Sri Lankan partners. "When presented with the flushing approach, irrigation engineers' reaction was that that it could not be done, because there was no additional water in the system for this operation. We showed that the canals could be flushed effectively using the same amount of water. Because we have precise data about the development cycle of the mosquito and its breeding places, we now know exactly at what periods in the insect's development to flush the system."
The data generated by the IWMI team since 1994 set out the priorities and imperatives needed to reduce malaria in the study area in Sri Lanka. The rehabilitation of tanks to reduce water seepage is in progress. Several options to regulate water flows through canals are being evaluated in association with the Mahaweli Irrigation Authority.
Discussions with local farmer organizations and small-scale tour operators showed that not stakeholders have the same interest in water management in this tank cascade system. The rehabilitation works appear to reduce mosquito breeding downstream but upstream water users perceive disadvantages. Evaluation of the interventions on malaria incidence and socio-economic parameters is ongoing. Conclusive results are expected by 2003.
Semiarid areas: Will reduced salinity trigger new epidemics?
Some have questioned the usefulness of doing malaria research in an area such as the Punjab -the vast semiarid area that spans southeastern Pakistan and northwestern India- whose malaria figures have declined steadily for the past 20 years. The last major epidemic was in the 1970s.
IWMI's Water, Health and Environment Theme Leader Felix Amerasinghe explains why doing malaria research here today is vital for the region. "The Punjab has a clay layer just below the surface that prevents adequate drainage and creates water logging. This leaves behind a large quantities of saline water, making the soil infertile for most crops. Both the Indian and Pakistani governments are planning to restore this agricultural land by building large-scale drainage schemes. Better drainage will reduce salinity. It will also will leave behind fresh water that attracts malaria breeding mosquitoes.
Here, IWMI's primary research hypothesis is: 'Is the steady reduction in malaria over the past 20 years related to progressive water and soil salinization? Has salinity made standing water in this region unfit for breeding habits of malaria vector mosquitoes?'
If this is the case, a program that reduces surface water salinity in the Punjab could trigger a serious malaria epidemic. Having a clear understanding of the situation today will help these governments have an anti-malaria strategy in place when these new agricultural lands are restored.
Rice ecosystems:
Do new water saving practices discourage or encourage the disease?
Some Asian and African countries are beginning to use an alternate wet and dry irrigation technique for rice cultivation. It involves draining fields, then releasing new water at critical moments in the rice growth cycle. It is said that this practice requires less water and can strengthen roots.
The health risk of the alternate wet and dry technique is caused by pools of standing water left in fields that are not properly leveled and drained, creating a breeding ground for mosquitoes that carry malaria and Japanese encephalitis. Looking at China alone, with its millions of square kilometers of rice cultivation, the potential for increased disease transmission could become a serious health concern if the alternate wet and dry practice is expanded.
IWMI's research in malaria in rice ecosystems is being done in several field trials in India and Kenya. There are plans for a similar project in China, where IWMI has been working with the International Rice Research Institute (IRRI), Wuhan University and the Zhang He Irrigation System on the question of water saving in wet/dry irrigation.
"For water management to be effective in preventing these diseases in a rice ecosystem, every farmer must appreciate the importance of leveling the field and emptying water from fields at the prescribed time," says Felix Amerasinghe, on the importance of the involvement of farmers. IWMI researchers are looking into the best ways to implement farmer participation on a large scale.
last updated 1 January 2004
On this page:
Malaria in tank cascade systems: How can better water
management help?
Malaria in semiarid areas: Will reduced salinity trigger
new epidemics?
Rice ecosystems: Do new water saving practices discourage
or encourage the disease?