Integrated assessment of irrigation and agriculture management challenges in Nepal: An interdisciplinary perspective.

Agriculture plays a critical role in ensuring food and nutrition security, livelihood, and rural employment in Nepal. Despite substantial investments and institutional reforms, irrigation projects have faced consistently low performance. While existing studies have shed light on technical aspects of irrigation performance, they often focus on specific themes rather than holistic evaluations of sustainability. This research systematically assesses barriers and challenges to effective irrigation water management in Nepal by assessing and ranking the challenges faced by three irrigation systems in western Nepal: Mahakali, Rani Jamara Kulariya, and Babai. To investigate these challenges, we collected data from 449 households, which provided insights into 33 indicators representing key barriers to effective irrigation and agricultural management. The identified challenges were categorized into four broad thematic areas: physical and structural, agricultural and water, socioeconomic and market, and gender and governance. A comprehensive evaluation was conducted to compare these challenges among the three irrigation schemes, different thematic areas, and various locations within each scheme (namely, the head, mid, and tail sections of the system). The findings revealed that timely access and availability of fertilizers, spring water availability and fair market prices of agricultural products are the most significant challenges. The Babai irrigation system faced the most substantial challenges among the three systems, particularly in the mid section. These findings emphasize the interconnectedness of these challenges, highlighting the need for a holistic approach to planning, implementation, and management. Integrated strategies are essential to address socioeconomic, market, and endogenous farming issues, ensuring reliable irrigation water availability for sustainable agricultural production.

The impact of large and small dams on malaria transmission in four basins in Africa.

Expansion of various types of water infrastructure is critical to water security in Africa. To date, analysis of adverse disease impacts has focused mainly on large dams. The aim of this study was to examine the effect of both small and large dams on malaria in four river basins in sub-Saharan Africa (i.e., the Limpopo, Omo-Turkana, Volta and Zambezi river basins). The European Commission's Joint Research Center (JRC) Yearly Water Classification History v1.0 data set was used to identify water bodies in each of the basins. Annual malaria incidence data were obtained from the Malaria Atlas Project (MAP) database for the years 2000, 2005, 2010 and 2015. A total of 4907 small dams and 258 large dams in the four basins, with 14.7million people living close (< 5 km) to their reservoirs in 2015, were analysed. The annual number of malaria cases attributable to dams of either size across the four basins was 0.9-1.7 million depending on the year, of which between 77 and 85% was due to small dams. The majority of these cases occur in areas of stable transmission. Malaria incidence per kilometre of reservoir shoreline varied between years but for small dams was typically 2-7 times greater than that for large dams in the same basin. Between 2000 and 2015, the annual malaria incidence showed a broadly declining trend for both large and small dam reservoirs in areas of stable transmission in all four basins. In conclusion, the malaria impact of dams is far greater than previously recognized. Small and large dams represent hotspots of malaria transmission and, as such, should be a critical focus of future disease control efforts.

Malaria around large dams in Africa: effect of environmental and transmission endemicity factors.

BACKGROUND: The impact of large dams on malaria has received widespread attention. However, understanding how dam topography and transmission endemicity influence malaria incidences is limited. METHODS: Data from the European Commission's Joint Research Center and Shuttle Radar Topography Mission were used to determine reservoir perimeters and shoreline slope of African dams. Georeferenced data from the Malaria Atlas Project (MAP) were used to estimate malaria incidence rates in communities near reservoir shorelines. Population data from the WorldPop database were used to estimate the population at risk of malaria around dams in stable and unstable areas. RESULTS: The data showed that people living near (< 5 km) large dams in sub-Saharan Africa grew from 14.4 million in 2000 to 18.7 million in 2015. Overall, across sub-Saharan Africa between 0.7 and 1.6 million malaria cases per year are attributable to large dams. Whilst annual malaria incidence declined markedly in both stable and unstable areas between 2000 and 2015, the malaria impact of dams appeared to increase in unstable areas, but decreased in stable areas. Shoreline slope was found to be the most important malaria risk factor in dam-affected geographies, explaining 41-82% (P < 0.001) of the variation in malaria incidence around reservoirs. CONCLUSION: Gentler, more gradual shoreline slopes were associated with much greater malaria risk. Dam-related environmental variables such as dam topography and shoreline slopes are an important factor that should be considered in efforts to predict and control malaria around dams.

Malaria and large dams in sub-Saharan Africa: future impacts in a changing climate.

BACKGROUND: Sub-Saharan Africa (SSA) has embarked on a new era of dam building to improve food security and promote economic development. Nonetheless, the future impacts of dams on malaria transmission are poorly understood and seldom investigated in the context of climate and demographic change. METHODS: The distribution of malaria in the vicinity of 1268 existing dams in SSA was mapped under the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathways (RCP) 2.6 and 8.5. Population projections and malaria incidence estimates were used to compute population at risk of malaria in both RCPs. Assuming no change in socio-economic interventions that may mitigate impacts, the change in malaria stability and malaria burden in the vicinity of the dams was calculated for the two RCPs through to the 2080s. Results were compared against the 2010 baseline. The annual number of malaria cases associated with dams and climate change was determined for each of the RCPs. RESULTS: The number of dams located in malarious areas is projected to increase in both RCPs. Population growth will add to the risk of transmission. The population at risk of malaria around existing dams and associated reservoirs, is estimated to increase from 15 million in 2010 to 21-23 million in the 2020s, 25-26 million in the 2050s and 28-29 million in the 2080s, depending on RCP. The number of malaria cases associated with dams in malarious areas is expected to increase from 1.1 million in 2010 to 1.2-1.6 million in the 2020s, 2.1-3.0 million in the 2050s and 2.4-3.0 million in the 2080s depending on RCP. The number of cases will always be higher in RCP 8.5 than RCP 2.6. CONCLUSION: In the absence of changes in other factors that affect transmission (e.g., socio-economic), the impact of dams on malaria in SSA will be significantly exacerbated by climate change and increases in population. Areas without malaria transmission at present, which will transition to regions of unstable transmission, may be worst affected. Modifying conventional water management frameworks to improve malaria control, holds the potential to mitigate some of this increase and should be more actively implemented.

Malaria impact of large dams in sub-Saharan Africa: maps, estimates and predictions.

BACKGROUND: While there is growing recognition of the malaria impacts of large dams in sub-Saharan Africa, the cumulative malaria impact of reservoirs associated with current and future dam developments has not been quantified. The objective of this study was to estimate the current and predict the future impact of large dams on malaria in different eco-epidemiological settings across sub-Saharan Africa. METHODS: The locations of 1268 existing and 78 planned large dams in sub-Saharan Africa were mapped against the malaria stability index (stable, unstable and no malaria). The Plasmodium falciparum infection rate (PfIR) was determined for populations at different distances (<1, 1-2, 2-5, 5-9 km) from the associated reservoirs using the Malaria Atlas Project (MAP) and WorldPop databases. Results derived from MAP were verified by comparison with the results of detailed epidemiological studies conducted at 11 dams. RESULTS: Of the 1268 existing dams, 723 are located in malarious areas. Currently, about 15 million people live in close proximity (<5 km) to the reservoirs associated with these dams. A total of 1.1 million malaria cases annually are associated with them: 919,000 cases due to the presence of 416 dams in areas of unstable transmission and 204,000 cases due to the presence of 307 dams in areas of stable transmission. Of the 78 planned dams, 60 will be located in malarious areas and these will create an additional 56,000 cases annually. The variation in annual PfIR in communities as a function of distance from reservoirs was statistically significant in areas of unstable transmission but not in areas of stable transmission. CONCLUSION: In sub-Saharan Africa, dams contribute significantly to malaria risk particularly in areas of unstable transmission. Additional malaria control measures are thus required to reduce the impact of dams on malaria.

How does an Ethiopian dam increase malaria? Entomological determinants around the Koka reservoir.

OBJECTIVES: To identify entomological determinants of increased malaria transmission in the vicinity of the Koka reservoir in Central Ethiopia. METHODS: Larval and adult mosquitoes were collected between August 2006 and December 2007 in villages close to (<1km) and farther away from (>6 km) the Koka reservoir. Adult mosquitoes were tested for the source of blood meal and sporozoites. RESULTS: In reservoir villages, shoreline puddles and seepage at the base of the dam were the most productive Anopheles-breeding habitats. In villages farther from the dam (control villages), rain pools were important breeding habitats. About five times more mature anopheline larvae and six times more adult anophelines were found in the villages near the reservoir. Anopheles arabiensis and Anopheles pharoensis were the most abundant species in the reservoir villages throughout the study period. The majority of adult and larval anophelines were collected during the peak malaria transmission season (September-October). Blood meal tests suggested that A. arabiensis fed on humans more commonly (74.6%) than A. pharoensis (62.3%). Plasmodium falciparum-infected A. arabiensis (0.97-1.32%) and A. pharoensis (0.47-0.70%) were present in the reservoir villages. No P. falciparum-infected anophelines were present in the control villages. CONCLUSIONS: The Koka reservoir contributes to increased numbers of productive Anopheles-breeding sites. This is the likely the cause for the greater abundance of malaria vectors and higher number of malaria cases evidenced in the reservoir villages. Complementing current malaria control strategies with source reduction interventions should be considered to reduce malaria in the vicinity of the reservoir.

Effect of a large dam on malaria risk: the Koka reservoir in Ethiopia.

OBJECTIVE: To determine whether the Koka water reservoir in the Rift Valley of Ethiopia contributes to the malaria burden in its vicinity. METHODS: Frequency of malaria diagnosis in fever clinics was correlated with distance of residence from the margin of the Koka reservoir. Annual as well as seasonal malaria case rates were determined in cohorts residing < 3, 3-6 and 6-9 km from the reservoir. Plasmodium falciparum risk was compared with that of Plasmodium vivax. A multiple variable regression model was used to explore associations between malaria case rates and proximity to the reservoir, controlling for other suspected influences on malaria transmission. RESULTS: Malaria case rates among people living within 3 km of the reservoir are about 1.5 times as great as for those living between 3 and 6 km from the reservoir and 2.3 times as great for those living 6-9 km from the reservoir. Proximity to the reservoir is associated with greater malaria case rates in periods of more intense transmission. Plasmodium falciparum is most prevalent in communities located close to the reservoir and P. vivax in more distant villages. The presence of the reservoir, coupled with inter-annual climatic variations, explains more than half of the region's variability in malaria case rates. CONCLUSION: Large water impoundments are likely to exacerbate malaria transmission in malaria-endemic parts of sub-Saharan Africa.