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WATER MANAGEMENT IMPACTS ON HUMAN HEALTH Health related research at IWMI: Irrigation - domestic water supply linkages Vector borne diseases Example of water management for malaria control Fifth IHP/IAHS George Kovacs Colloquium, Paris, 2-3 June 2000 Slide 2 Research Hypotheses 4 The operation of irrigation systems can be changed so as to achieve positive health impacts, without negative impacts on agricultural performance 4 Non-agricultural benefits of water use in irrigation systems are substantial and generally underestimated Slide 3 Multiple uses of water Impact of irrigation water management on shallow drinking wells Slide 4 WATER MANAGEMENT FOR MALARIA CONTROL: CASE STUDY FROM SRI LANKA Slide 5 Malaria in Sri Lanka 500,000 cases per year economic losses 4Parasite 4Mosquito 4Water 4Human behavior Slide 6 Colombo YAN-OYA STREAM HURULUWEWA HABARANA SRI LANKA HURULUWEWA WATERSHED Slide 7 Slide 8 Flowing Depth Pooling STREAM WATER DEPTH AND VECTOR BREEDING DEPTH (cm)WEEKS LARVAE / WEEK 0 - 19 20 17.9 20 - 29 4 1.8 30 - 39 6 3.5 40 - 49 7 2.4 50 or more 26 0.7 Konradsen et al. 1998 There was a relationship between stream water depth and vector breeding Slide 9 Avg. annual total rainfall (mm) Slide 10 HURULUWEWA WATERSHED ANOPHELES CULICIFACIES IN RELATION TO THE YAN-OYA STREAM AN. CULICIFACIES (No. per house) DISTANCE FROM YAN-OYA STREAM (KM) MALARIA (Cases per 1000) Villages situated close to the stream had more vectors and a greater incidence of malaria than those located further away Slide 11 Temporal fluctuation in Anopheles culicifacies and human malaria cases 19941995 1996 Number of larvae Number of adult mosquitoes Human malaria cases Slide 12 WATER BALANCE ESTIMATION Matsuno et al. 1999 HABARANA RESERVOIR COMMAND AREA 55 Ha HURULUWEWA RESERVOIR ET Deep Percolation YAN- OYA Conveyance Loss (CL) Runoff (RF) Mahaweli System QS QR QV Rain Gauge Met. Station QV = QS + QR + RF - CL Slide 13 HYDROLOGY & MOSQUITOES: SIMULATIONS 1. Water issued for 2 rice seasons (current practice) 2. Water issued for 1 rice season; diversified crops in 2nd season 3. Reservoir rehabilitation: seepage losses reduced 4. Mahaweli water redistributed over longer period 5. Extra 200,000m 3 of water from Mahaweli system Slide 14 MATSUNO ET AL. 1999 YAN OYA STREAM - SIMULATIONS CURRENT FLOW MODIFIED FLOW Slide 15 Cost of malaria control US$ * Insecticide spraying2.75 Impregnated bed nets1.02 Larviciding0.53 Water management0.26 * Total annual cost per individual protected Slide 16 Alternate wet dry irrigation in rice cultivation Water saving Increased yields Control of vector mosquitoes Slide 17 ON-FARM WATER MANAGEMENT - INDIAN COUNCIL OF AGRIC. RESEARCH (ICAR) Orissa Loam 7 cm water 16% 44% 3 dry days Gujerat Clay 7 cm water 10-23% 20-29% 1 dry day TNadu Porous 5 cm water 25% 23% 1 dry day Kerala Sandy 7 cm water 77% 79% 1-2 dry days (Source: Batta, Singh & Sharma, 1998) Center Soil Water Regime Yield Increase Water Saving Slide 18 AWDI STUDIES: WATER, YIELD & MOSQUITOES Bali 1936 An. aconitus -75 -8 Portugal 1936-39 An. atroparvus -18 -80 +6/+8 China 1978-79 An. sinensis -53 -81 +13 Cx. Tritaeniorhynchus India 1990-91 Cx. Tritaeniorhynchus -75 0/+4 Kenya 1998-99 An. arabiensis (in press) India 1999-2000 Culex, Anopheles (in progress) Sri Lanka 2000 Culex, Anopheles (proposed) AREA YEAR VECTOR PERCENTAGE CHANGE WATER MOSQ YIELD Slide 19 IMPLEMENTING WATER MANAGEMENT - CONSTRAINTS Engineers and irrigation managers: Lack of knowledge and understanding of the problem Lack of interest or commitment (this is a health sector problem) Health sector: Unrealistic expectations, without an understanding of water dynamics and associated factors Slide 20 Criteria for effective use of water management for vector control Measures must be: effective against target vector socially acceptable cost-effective economically sustainable compatible with local agricultural practices Slide 21