Lydia Olaka

Climatic, Socio-economic, and Health Factors Affecting Human Vulnerability to Cholera in the Lake Victoria Basin, East Africa

Abstract Cholera epidemics have a recorded history in the eastern Africa region dating to 1836. Cholera is now endemic in the Lake Victoria basin, a region with one of the poorest and fastest growing populations in the world. Analyses of precipitation, temperatures, and hydrological characteristics of selected stations in the Lake Victoria basin show that cholera epidemics are closely associated with El Niño years. Similarly, sustained temperatures high above normal (Tmax) in two consecutive seasons, followed by a slight cooling in the second season, trigger an outbreak of a cholera epidemic. The health and socioeconomic systems that the lake basin communities rely upon are not robust enough to cope with cholera outbreaks, thus rendering them vulnerable to the impact of climate variability and change. Collectively, this report argues that communities living around the Lake Victoria basin are vulnerable to climate-induced cholera that is aggravated by the low socioeconomic status and lack of an adequate health care system. In assessing the communities adaptive capacity, the report concludes that persistent levels of poverty have made these communities vulnerable to cholera epidemics.

Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study.

Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02-75 mg/L. 73% exceed the health limit (1.5mg/L) in both dry and wet seasons. F(-) concentrations in rivers are lower (0.2-9.2mg/L) than groundwater (0.09 to 43.6 mg/L) while saline lake waters have the highest concentrations (0.27-75 mg/L). The higher values are confined to elevations below 2000 masl. Oxygen (δ(18)O) and hydrogen (δD) isotopic values range from -6.2 to +5.8‰ and -31.3 to +33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750-6000 ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (<1000 ppm). Thus, geochemical F(-) enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management in Naivasha as well as similar active rift setting environments.

Remote Sensing of African Lakes: A Review

The optical complexity and small size of inland waters make the application of remote sensing more challenging than for the open ocean. However, in Africa, where in situ monitoring of important water bodies is financially, institutionally and spatially constrained, there is strong demand for remote sensing to fill the critical information gap. Here we review a wide range of applications of both passive and active remote sensing to African lakes. The applications fall into five main categories: (1) visible, NIR, thermal and microwave sensing of lake area; (2) altimetric and gravimetric sensing of lake level; (3) thermal sensing of lake surface temperature; (4) visible, NIR and microwave sensing of macrophytes; and (5) optical sensing of trophic conditions including chlorophyll-a and euphotic depth. Sensors used include Landsat MSS, TM and ETM+, MERIS, MODIS, SeaWiFS, AVHRR, Meteosat, TOPEX/Poseidon, Jason-1, OSTM/Jason-2, ERS-1, ERS-2, Envisat, GFO, ICESat, ALOS-PALSAR and GRACE. The majority of studies have been applied to the “great” lakes such as Chad, Malawi, Tanganyika and Victoria; however, there is a growing body of literature on smaller lakes. We examine the possibilities that remote sensing offers to monitoring and management of African lakes as well as the potential limitations of the technology using Lake Victoria as an illustrative case.

Climate change and pastoralists: perceptions and adaptation in montane Kenya

Tropical montane forests are amongst the most threatened ecosystems by climate change. However, little is known about climatic changes already observed in these montane areas in Africa, or the adaptation strategies used by pastoralist communities. This article, focused on three mountains in northern Kenya, aims to fill these knowledge gaps. Focus-group discussions with village elders were organized in 10 villages on each mountain (nu2009=u200930). Villages covered different pastoralist ethnic groups. Historical data on rainfall, temperature and fog were gathered from Marsabit Meteorological station. All participants reported changes in the amount and distribution of rainfall, fog, temperature and wind for the past 20–30 years; regardless of the mountain or ethnicity. They particularly highlighted the reduction in fog. Meteorological evidence on rainfall, temperature and fog agreed with local perceptions; particularly important was a 60% reduction in hours of fog per year since 1981. Starting farming and shifting to camel herding were the adaptive strategies most commonly mentioned. Some adaptive strategies were only mentioned in one mountain or by one ethnic group (e.g. starting the cultivation of khat). We highlight the potential use of local communities’ perceptions to complement climatic records in data-deficient areas, such as many tropical mountains, and emphasize the need for more research focused on the adaptation strategies used by pastoralists.