Browsing by Author "Shemsanga, Ceven"
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Item Climate change impacts, vulnerability, and adaptation in East Africa (EA) and South America (SA)(Springer Nature, 2012) Omambia, Anne Nyatichi; Shemsanga, Ceven; Hernandez, Ivonne Andrea SanchezIn recent decades, global climate change has continued to cause devastating impacts to various places on Earth. Geographic and socioeconomic characteristics in East Africa (EA) and South America (SA) make the regions among the most vulnerable to the current temperature variations attracting several studies with wider implications. Presently, in these two regions, remarkable evidence of climate change includes repeated droughts and increase in dry lands affecting water and food availability for humans, livestock, and wildlife (EA), intensification of climate-sensitive diseases, sea level rise, fast retreat of glaciers on Mount Kilimanjaro in Tanzania, Mount Kenya in Kenya, and Andeans Mountains of South America, change in the rainfall patterns in the Amazon forests and in the whole of EA, and increasing of the frequency and intensity of the El Niño and La Niña phenomenon in the South Pacific that affect both EA and SA, among others. Although these two regions are not major contributors of greenhouse gases (GHGs), the poor conservation of strategic ecosystems through deforestation of the Amazon forests in SA and various forests in EA coupled with intensification of agriculture, land degradation, rapid rates of urbanization and industrialization all driven by rapid population increase are putting a strain on valuable natural resources whose conservation would be critical in mitigating climate change. Adaptation measures have been constrained by climate change impacts. In both regions, poverty is widespread and climate change impacts have jeopardized most poverty alleviation initiatives including realization of some of the Millennium Development Goals (MDGs). Moreover, both regions have a strong dependency on rain-fed agriculture for economic development with hydroelectricity and biomass as main sources of energy. Consequently, adaptation measures are required for all the sectors, but especially in agriculture, health, and energy where the loss of soil productivity, increasing spread of climate-sensitive diseases, reduction of water and energy source supply are already threatening the social and economic security of both regions. Both regions have a wealth of indigenous knowledge and coping mechanisms of various local communities that should be incorporated into conventional adaptation measures of climate change. This chapter describes the main climate change impacts in EA and SA, vulnerabilities thereon, and adaptation measures that offer an opportunity to the two regions to develop in a sustainable way.Item Combating climate change in Kenya: efforts, challenges and opportunities(Marsland Press, 2009) Omambia, Anne Nyatichi; Shemsanga, Ceven; Li, YilianIncrease in emissions of CO2 gas and other greenhouse gases (GHG) such as methane, nitrous oxide, CFC, HCFC and halogens into the atmosphere has led to the overall rise in mean global temperature over the years and the resultant climate change. Key anthropogenic activities responsible include fossil fuel combustion and land -use changes especially tropical deforestation. For developing countries such as Kenya, climate change is a threat to livelihood support systems. Kenya is currently experiencing the effect of climate change especially variation in weather patterns. Prolonged drought and famine has currently left over 10 million people faced with starvation, while floods and resurgence of pests and diseases have been noted in other parts of the country. Widespread poverty, inadequate socio-economic resources and a large climate -dependent agricultural sector makes the country vulnerable to the vagaries of climate change and ill-equipped to adapt to the long-term changes in climate. In spite of these, Kenya has embarked on various measures to mitigate climate change such as adoption of clean development mechanism, reaforestation and spread of green technology. This research focused on Kenya’s effort hitherto in combating climate change, the challenges thereon and opportunities for improvement.Item The cost of climate change in Tanzania: impacts and adaptation(Marsland Press, 2010) Shemsanga, Ceven; Omambia, Anne Nyatichi; Gu, YanshengIn recent years, Tanzania has witnessed a number of climate related disasters namely, flooding, droughts, widespread crop failures, livestock deaths and intensification of climate sensitive diseases among others. Regular climate discussions in the country have often underestimate crucial problems related to climate change like chronic energy crisis and influx of people to urban areas arguably because of failing agriculture in farming areas. This paper has highlighted the fact that the poor, usually with limited resources and who contribute the least to the causes of climate change are the most affected in many ways. In addition, it gives a detailed account of the issues of climate change in Tanzania and explains the effects of climate variability using examples. The effects of climate change in the country are widespread and significantly interfere with agriculture, while at the same time, reducing the ability of the society to deliver services. Indigenous knowledge such as survival skills and coping mechanisms adopted by different societies in Tanzania, have been discussed in the paper. Such coping mechanisms however are overwhelmed by the impacts of climate change on the people. Different institutions including the government have taken some positive steps towards combating climate change; however the efforts done so far are insufficient. In addition, addressing climate change in Tanzania is hindered with inadequate resources, corruption and poor coordination and implementation of combating measures. Generally current climate variability in the nation is an issue of concern for all future plans and must be addressed.Item Delineation of the aquifer structure and estimation of hydraulic properties on the flanks of Mount Meru, Northern Tanzania(Elsevier, 2022) Bennett, George; Camp, Marc Van; Shemsanga, Ceven; Kervyn, Matthieu; Walraevens, KristineUnderstanding of the aquifer structure and its hydraulic properties provides comprehensive knowledge for proper groundwater utilisation and management. This study delineated the aquifer structure using litho-hydrostratigraphical cross-sections, and estimated the hydraulic parameters using single well pumping tests for various locations on and around Mount Meru. Results show that, the aquifer system on the flanks of Mount Meru is a sloping aquifer with sloping beds. On the far east of the eastern flank, the aquifer is composed of debris avalanche deposits, while on the north-eastern and west flanks the aquifer is composed of weathered fractured lava, whereas on the south-western flank, the aquifer is composed of different layers: pyroclastics on the top, weathered fractured lava, weathered pyroclastics, and weathered fractured lava at the bottom. The aquifer is semi-confined on the north-eastern and western flanks; on the north-eastern flank, the overlying debris avalanche deposits acting as an aquitard, while on the western flank, the overlying layers: pyroclastics and unweathered lava acting as an aquitard and aquiclude, respectively. The aquifer is unconfined on the far east of the eastern flank and south-western flank. The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth, while variable, both at the shallow depth of hand-dug wells and the larger depth of boreholes, on the south-western flank; indicating aquifer heterogeneity. On the north-eastern flank, the topmost part of the aquifer, exploited by hand-dug wells, has a low transmissivity (T = 1.3 m2/d) and potential for smaller withdrawals for local water supply with limited consumption, while the upper part of the aquifer, captured by boreholes, has an intermediate transmissivity (T = 35 m2/d) and potential for local water supply, whereas the deeper part of the aquifer has a high transmissivity (T = 788 m2/d) with potential of somewhat regional importance. On the western flank, the aquifer has a very low transmissivity (T = 0.4 m2/d) and potential for local water supply with limited consumption. On the south-western flank, on average, the topmost part of the aquifer, exploited by hand-dug wells, has very low to intermediate transmissivity (range of T: 0.3–21 m2/d), leading to variable potential for smaller withdrawals for local water supply (private consumption), whereas the deeper part of the aquifer, captured by boreholes, has low to intermediate transmissivity (range of T: 9–43 m2/d) and potential for local water supplyItem Estimation of groundwater recharge from groundwater level fluctuations and baseflow rates around Mount Meru, Tanzania(Elsevier BV, 2024) Bennett, George; Shemsanga, Ceven; Kervyn, Matthieu; Walraevens, KristineEstimating groundwater recharge, direct runoff and baseflow is essential for understanding groundwater resource availability and managing groundwater systems. This study estimates groundwater recharge, direct runoff and baseflow on two slopes of Mount Meru: the northern and southern slopes using the water-table fluctuation (WTF) method and baseflow separation technique. High-frequency groundwater level measurements in five shallow wells over three hydrological years from 2018 to 2021 were analysed, while streamflow data in four gauging stations over nine hydrological years from 2010 to 2019 were used. The results of the WTF method show that the aquifer undergoes an average recharge of 544 mm/year and 90 mm/year on the south-western and north-eastern slopes, respectively. On average, this recharge is about 53% and 13% of the annual rainfall on each slope. The baseflow results show that the aquifer on the south-eastern and north-western slopes recharges an average of 88 mm/year and 54 mm/year, respectively, which is on average about 12% and 7% of annual rainfall, respectively. In general, the high recharge on the south-western slope is attributed to the high rainfall, and the high hydraulic conductivity and high hydraulic diffusivity of the pyroclastic deposits compared to the debris avalanche deposits on the north-eastern slope. In addition, debris avalanche deposits show homogeneous recharge conditions, while pyroclastic deposits show heterogeneous recharge conditions. The WTF method can be useful to identify areas of preferential recharge so that preferential groundwater flow paths can be mapped for focused recharge of surface runoff during the rainy season.Item Geogenic groundwater pollution in volcanic rock aquifer systems on the eastern, western and northern flanks of Mount Meru, Tanzania–special reference to fluoride(Vrije Universiteit Brussel, 2019) Bennett, George; Rombaut, Stefanie; Van Reybrouck, Jill; Shemsanga, Ceven; Kisaka, Mary; Tomašek, Ines; Fontijn, Karen; Kervyn, Matthieu; Walraevens, KristineNo abstractItem Hydrochemical characterisation of high-fluoride groundwater and development of a conceptual groundwater flow model using a combined hydrogeological and hydrochemical approach on an active volcano: Mount Meru, Northern Tanzania(MPDI, 2021) Bennett, George; Reybrouck, Jill Van; Shemsanga, Ceven; Kisaka, Mary; Tomašek, Ines; Fontijn, Karen; Kervyn, Matthieu; Walraevens, KristineThis study characterises high-fluoride groundwater in the aquifer system on the flanks of Mount Meru, focusing on parts of the flanks that were only partially or not at all covered by previous research. Additionally, we analyse the impact of rainwater recharge on groundwater chemistry by monitoring spring discharges during water sampling. The results show that the main groundwater type in the study area is NaHCO3 alkaline groundwater (average pH = 7.8). High F− values were recorded: in 175 groundwater samples, the concentrations range from 0.15 to 301 mg/L (mean: 21.89 mg/L, median: 9.67 mg/L), with 91% of the samples containing F− values above the WHO health-based guideline for drinking water (1.5 mg/L), whereas 39% of the samples have Na+ concentrations above the WHO taste-based guideline of 200 mg/L. The temporal variability in F− concentrations between different seasons is due to the impact of the local groundwater recharge. We recommend that a detailed ecohydrological study should be carried out for the low-fluoride springs from the high-altitude recharge areas on the eastern and northwestern flanks of Mount Meru inside Arusha National Park. These springs are extracted for drinking purposes. An ecohydrological study is required for the management of these springs and their potential enhanced exploitation to ensure the sustainability of this water extraction practice. Another strategy for obtaining safe drinking water could be to use a large-scale filtering system to remove F− from the groundwater.Item Hydrogeochemical characteristics of shallow groundwater in volcanic rock aquifer systems in the western and northern flanks of Mount Meru, Tanzania(Ghent University, 2018) Bennett, George; Walraevens, Kristine; Van Reybrouck, Jill; Segers, Laura; Shemsanga, Ceven; Kisaka, Mary; Kervyn, Matthieu; Fontijn, Karen.No abstractItem Hydrogeochemical characterization of the groundwater in northern and eastern areas of Kilwa district and Songosongo Island in, Tanzania(Wiley, 2024) Mlay, Asantael Herman; Shemsanga, Ceven; Bennett, George; Ntalikwa, JustinThis study aimed to investigate the hydrochemical and hydrogeochemical facies and mechanisms controlling groundwater quality from the northern and eastern parts of Kilwa district and Songosongo Island in Tanzania. Multifaceted methods were used to analyze the hydrochemical properties of water in relation to local geology and proximity to the Indian Ocean. The pH of the groundwater ranged from 5.18 to 7.56 with an average value of 6.64 which is slightly acidic. Electrical Conductivity (EC) ranged from 354 to 1429.50 μS/cm with an average value of 1652.6 μS/cm while Total Dissolved Solids (TDS) values varied from 170 to 1825 mg/L with an average value of 918.8 mg/L. The average values for Ca2+, Mg2+, Na+, and K+ were 36.9, 21.4, 152.5, and 13.31 mg/L, while for NO3−, Cl−, HCO3−, and SO42- were 2.1, 256.3, 156.6, and 45.8, respectively. The study found that groundwater closest to the ocean had elevated values of TDS, Na+, and Cl− and were more affected by seawater intrusion compared to those further inland. The dominant groundwater type was established to be Na-Cl mostly nearest to the ocean while Ca-Mg-Cl was more encountered towards the inland. The groundwater in the northern and eastern parts of Kilwa is mainly controlled by seawater intrusion and recharge water. The Neogene formations consisting of clay, silts, coastal sands, and alluvium had lower Na+, Cl−, EC, and TDS values than the Paleogene which is more influenced by marine sediments. Thus, these findings call for improved groundwater monitoring to track changes in water quality since several parameters including sodium, magnesium, chlorides, TDS, EC, and pH were higher than recommended values for drinking purposes. However, the majority of the water samples were suitable for human consumption.Item Identification of low fluoride areas using conceptual groundwater flow model and hydrogeochemical system analysis in the aquifer system on the flanks of an active volcano: Mount Meru, Northern Tanzania(Elsevier, 2022) Bennett, George; Reybrouck, Jill Van; Shemsanga, Ceven; Kisaka, Mary; Tomašek, Ines; Fontijn, Karen; Kervyn, Matthieu; Walraevens, KristineThis study investigates the localities of low and high F− groundwaters in the aquifer system on the flanks of Mount Meru to come up with guidelines to provide groundwater that can be used for drinking water supply without health impacts on the population. Our study focuses on parts of the flanks which were only partially or not at all covered by previous research. Results show that the groundwater chemistry of F−-rich NaHCO3 alkaline groundwater in the area is controlled by dissolution of weathering aluminosilicate minerals, dissolution of F−-bearing minerals, the precipitation of carbonate minerals as secondary products and the dissolution of magmatic gases. The low F− groundwaters which can be used for drinking water supply without health impacts under the WHO limit (1.5 mg/L) are the low-fluoride springs from the high altitude recharge areas on the eastern and north-western flanks of Mount Meru inside Arusha National Park, whereas on the western flank the groundwater meets the Tanzanian limit (4.0 mg/L). On the south-western flank, the shallow aquifer composed of alluvium deposits at lower elevations, shows F− values that meet the Tanzanian limit. One of the three investigated deep boreholes on this flank also meets the Tanzanian limit, suggesting a possibility of finding relatively low F− groundwaters in the deep aquifer. Yet, in general, the deposits at lower elevations are found to contain high to very high F− values, whereas the deposits at high elevations contain groundwater of low F− values. Thus, the internal texture and grain size of geological formations, the burial depth of these formations and the water residence times are the factors determining the groundwater mineralisation and F− concentrations in the area. The study identified that the deep hydrothermal system has influence on the high F− groundwaters on the eastern and north-eastern flanks of Mount Meru.Item The late quaternary eruptive history of Meru volcano, northern Tanzania(Elsevier, 2021) Kisaka, Mary; Fontijn, Karen; Shemsanga, Ceven; Tomašek, Ines; Gaduputi, Sankaranna; Debaille, Vinciane; Delcamp, Audray; Kervyn, MatthieuMt. Meru, in the northern Tanzania divergence zone within the East African Rift System, is a historically active volcano, with its last eruption in 1910 CE. The flank deposits of Meru are dominated by lava flows, debris avalanche deposits as well as major pyroclastic formations indicative of Plinian-style eruptions. The stratigraphy, spatial extent, and chronology of these pyroclastic deposits have, however, not been systematically studied. Here we report on the detailed reconstruction of the stratigraphy and eruptive dynamics of Late Quaternary Meru explosive eruptions, based on field investigations, geochronological and geochemical analyses. The findings indicate that Meru had at least three moderate-to-large-scale explosive eruptions over the past 40,000 years. The oldest Meru explosive event we recognize (MXP1) generated pyroclastic density currents (PDCs), while the second (MXP2) and the third, most intense explosive event (MXP3) generated both pyroclastic fallout and PDCs. Conventional radiocarbon dating of 6 palaeosols underlying MXP2 and MXP3, dated at ~34.1–38.5 ka cal BP and ~31.5–36.9 ka cal BP respectively, suggest these two eruptions may have followed each other relatively close in time. The compositional range of pumice lapilli of both MXP2 and MXP3 is limited to tephriphonolite-phonolite. Dispersal and thickness data of the better preserved and larger MXP3 deposits suggest a minimum bulk volume of 2.5 km3 of pumice fallout and 1.2 km3 of PDCs, respectively, which corresponds to a total erupted mass of at least 2.7 × 1012 kg and a magnitude of 5.4. Similar large-scale eruptions in the future would have a considerable impact on the nearby large urban population in Arusha city and its suburbs. This new information is, therefore, vital for the long-term volcanic hazard assessment in Northern Tanzania.Item Naturally occurring potentially toxic elements in groundwater from the volcanic landscape around Mount Meru, Arusha, Tanzania and their potential health hazard(Elsevier, 2021) Tomašek, Ines; Mouri, Hassina; Dille, Antoine; Bennett, George; Bhattacharya, Prosun; Brion, Natacha; Elskens, Marc; Fontijn, Karen; Gao, Yue; Gevera, Patrick Kirita; Ijumulana, Julian; Kisaka, Mary; Leermakers, Martine; Shemsanga, Ceven; Walraevens, Kristine; Wragg, Joanna; Kervyn, MatthieuThe population of the semi-arid areas of the countries in the East African Rift Valley (EARV) is faced with serious problems associated with the availability and the quality of the drinking water. In these areas, the drinking water supply largely relies on groundwater characterised by elevated fluoride concentration (> 1.5 mg/L), resulting from interactions with the surrounding alkaline volcanic rocks. This geochemical anomaly is often associated with the presence of other naturally occurring potentially toxic elements (PTEs), such as As, Mo, U, V, which are known to cause adverse effects on human health. This study reports on the occurrence of such PTEs in the groundwater on the populated flanks of Mt. Meru, an active volcano situated in the EARV. Our results show that the majority of analysed PTEs (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Se, Sr, Pb, and Zn) are within the acceptable limits for drinking purpose in samples collected from wells, springs and tap systems, suggesting that there is no immediate health risk associated with these PTEs. However, some of the samples were found to exceed the WHO tolerance limit for U (> 30 μg/L) and Mo (> 70 μg/L). The sample analysis also revealed that in some of the collected samples, the concentrations of total dissolved solids, Na+ and K+ exceed the permissible limits. The concerning levels of major parameters and PTEs were found to be associated with areas covered with debris avalanche deposits on the northeast flank, and volcanic ash and alluvial deposits on the southwest flanks of the volcano. The study highlights the need to extend the range of elements monitored in the regional groundwater and make a more routine measurement of PTEs to ensure drinking water safety and effective water management measuresItem Statistics in climate variability, dry spells, and implications for local livelihoods in semiarid regions of Tanzania: the way forward(Springer, 2016) Shemsanga, Ceven; Muzuka, A. N. N.; Martz, L.; Komakech, H.; Omambia, A. N.The Dodoma municipality, a semiarid region of Tanzania, is characterized by limited rains, lack of surface water sources, and a high frequency of extreme climate events, particularly droughts and floods. These disadvantaged settings make it vital to study long-term climate trends for signals and patterns of shifting climate regimes for integrity of local livelihood support systems, especially agriculture, recharge, and pasture developments. The area has fairly long climate records, some of which extend to about 100 years. This chapter presents detailed analysis of six climate parameters, namely, rainfall (R), atmospheric relative humidity (ARH), temperature (T), sunshine (S), radiation (RD), wind speed (WS), and evaporation (ET) records from three meteorological stations, namely, Hombolo Agrovet (HMS), Dodoma (DMS), and Makutupora (MMS). The parameters above were statistically and graphically analyzed in four time scales, namely, monthly, seasonal, annual, and time series. The results showed the area is characterized by slight spatial variability in R intensity and T magnitudes with HMS having higher T and rains than DMS and MMS. Further there are clear decreasing trends in ARH and R, while T, S, WS, ET, and RD parameters showed characteristic increasing trends. Thus, except for extreme rain events, particularly El Niño-Southern Oscillations (ENSO), which are characterized by abnormally increased R magnitudes, R intensity has generally decreased in which over the past 91 years, there has been a net R decrease of 54 mm out of annual rains of only about 550 mm/year. Compared to annual time step, however, monthly step reveals more silent features like shortening of the growing seasons. Similarly, the frequency and severity of drought episodes are increasing, all of which adversely impact agriculture, pasture development, and recharge. Similarly, disappearance of R in some months, shifting seasonality, and general declining R intensities and magnitudes are clearly observed. May rains have largely disappeared, while in January, February, March, and April rains have decreased and hence shortening the length of growing season. On the other hand, clear warming trends and declining ARH were also observed. Yet the area is marked by cyclic wetting and drying events where in recent years, drying cycles have been prolonged. However, there is more variability in the mean minimum temperature (MMT) than in mean maximum temperatures (MMMT) in all stations. Between 1961 and 2012, there has been a net 1.13 and 0.778 °C increases in annual MMT and MMMT in DMS, respectively. Like for R trends, silent features are more evident under monthly T data than annual time steps where it is clear that June had the highest increase in MMT (1.54 °C), while April had the least (only 0.662 °C). However, both trends have the potential of affecting major livelihood support systems particularly agriculture and pasture development, but also local groundwater recharge that is vital for the local economy. The study area therefore offers a rare opportunity to understand and manage changing climate regimes including on extent of dry spells and longevity of growing seasons. The changing climate trends consequently call for significant adaptation and mitigation strategies so that local activities adjust to the current climate regimes particularly on onset and end of rainfall seasons and recharge fluxes