Y. Matsuno

Anopheles culicifacies breeding in Sri Lanka and options for control through water management

This paper assesses the options for control of malaria vectors through different water management practices in a natural stream in Sri Lanka. The association between water level in the stream and breeding of the immature stages of the primary vector Anopheles culicifacies was investigated and the feasibility of using existing irrigation infrastructure to reduce the breeding potential discussed. The most feasible option would be to implement a management routine where water is released periodically from an upstream reservoir to reduce the number of breeding sites downstream. This study indicates that by regulating the water level above 20 cm in the stream throughout the dry season the breeding of A. culicifacies could be significantly reduced. The intervention would have only limited impact on the water lost for agriculture and the management input would be minimal. However, for the intervention to work a high degree of support from the local community is essential and consultation between government departments needed.

Limitations of Irrigation Water Quality Guidelines from a Multiple Use Perspective

The standards for irrigation water qualityare currently provided by global andnational guidelines that are mostly basedon the assumption that threshold valuescould be applied to protect crops. Thisapproach can create problems for a largelyunrecognized group of people who make useof irrigation water for non-agriculturalpurposes. At the same time, increasingwater scarcity will lead to the need forrecycling of water in irrigated riverbasins, and the use of low qualityirrigation water. Apart from hazards ofhigh pollutant levels, a sustainabilitycriterion has to be included in the waterquality guidelines to account for long-termlow-level application of certain pollutantsthat can accumulate in the environment.Using the example of cadmium, it is arguedthat the current guidelines need to berevised and should take local factors andfuture developments into account.

A Framework for Valuing Ecological Services of Irrigation Water – A Case of an Irrigation-Wetland System in Sri Lanka

In many countries, irrigation water is usedfor several purposes other than irrigatingfield crops. In Sri Lanka, irrigationwater from canals, wells, and reservoirs isused for domestic purposes, industry,livestock, and fisheries, and it alsocontributes to sustain the environment. However, policy makers and water managersin irrigation systems only take intoaccount water used for irrigating the fieldcrops and sometimes water used for domesticpurposes. Owing to the failure torecognize the different uses and users ofwater, the water in irrigation systems hasbeen undervalued. This paper presents theenvironmental impact of irrigation and aframework for valuing water for itsmultiple and often competing uses,especially focusing on water uses forecological services, in this case wetlands.The south coastal area of Sri Lanka wasselected as a site for a case study, including2,610 ha of irrigated area and adownstream wetland area of 2,250 ha whichhas five lagoons. This wetland areacombines coastal, marine and freshwaterecosystems in a tropical environment inwhich distinct plant and animal speciescoexist in a delicate balance. All users ofwater and other resources, and theirenvironmental problems were identified. Thispaper discusses the policy and managementimplications of valuing water for competinguses.