Browsing by Author "Muzuka, A. N. N."

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    Fault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa
    (AGU Advancing Earth and Space Science, 2017) Weinstein, A.; Oliva, S. J.; Ebinger, C. J.; Roecker, S.; Tiberi, C.; Aman, M.; Lambert, C.; Witkin, E.; Albaric, J.; Gautier, S.; Peyrat, S.; Muirhead, J. D.; Muzuka, A. N. N.; Mulibo, G.; Kianji, G.; Ferdinand-Wambura, R.; Msabi, M.; Rodzianko, A.; Hadfield, R.; Illsley-Kemp, F.; Fischer, T. P.
    Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3-D velocity model reveal lower crustal earthquakes beneath the central basins and along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6–10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.8760.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along-axis stress rotation of _608 in the magmatically active zone. New and prior mechanisms show predominantly normal slip along steep nodal planes, with extension directions _N908E north and south of an active volcanic chain consistent with geodetic data, and _N1508E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early-stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.
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    Indigenous knowledge on development and management of shallow dug wells of Dodoma Municipality in Tanzania
    (Springer, 2018) Shemsanga, C.; Muzuka, A. N. N.; Martz, L.; Komakech, H.; Mcharo, E.
    Dodoma city, central Tanzania, seats in a semi-arid region of East Africa with limited rains and surface water resources. Consequently, the area largely depends on shallow and deep aquifers for its freshwater needs. Owing to harsh climatic conditions, chronic lack of year-round surface water bodies and, limited development of water distribution infrastructures, over year’s local people have nurtured, developed and, passed on important indigenous knowledge (IK) on exploiting and managing shallow aquifers (SAs). However, there is no clear documented administrative plans for the SAs and the roles of IK, which is widely practised in developing SDWs and managing SAs, are not properly documented. This study intended to assess the extent of shallow dug wells (SDWs) utilization and contribution of IK on management of SAs of indigenous people of Dodoma Municipality. The methods followed include critical field observations, measurements and, focus group discussions done during both the dry season (Sep.–Oct. 2013) and wet season (Dec. 2013–Feb. 2014). The results show that SDWs occur widely in the city, particularly in the suburbs, where they often serve as the only sources of freshwater and heavily dependent by the populace. It is clear that there is rich IK on management of SAs including on groundwater exploration, digging, water allocation, pricing, and even on water quality and, water treatment skills. The aforementioned IK clearly contribute to water sufficiency to the populace and general management of groundwater such as enhancing recharge mechanisms where about 1% of local rainfall is recharged through a network of SDWs compared to ~ 5–10% that is natu-rally being recharged by rainfall through the vadose zone. Thus, as much as the current policy framework and groundwater managers do not recognize the roles of IK and contributions of SDWs as key water sources, it is clear that IK contributes to the groundwater management and SDWs already support large part of the society. While it is globally appreciated that vital skills on SDWs management are vanishing, local people in Dodoma still retain them and should, therefore, be preserved. It is further recommended that IK are strengthened, improved and most importantly, incorporated in the local water resources management plans that already advocate on integrated approaches but which clearly ignores the IK and the local people’s efforts to explore and manage water resource, particularly SAs.
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    Origin and mechanisms of high salinity in Hombolo Dam and groundwater in Dodoma municipality Tanzania, revealed
    (Springer, 2017) Shemsanga, C.; Muzuka, A. N. N.; Martz, L.; Komakech, H. C.; Elisante, E.; Kisaka, M.; Ntuza, C.
    The Hombolo dam (HD), in central Tanzania, is a shallow reservoir characterized by high salinity that limits itsuse for human activities. The origin of the salinity, mechanisms of reaching and concentrating in the dam remain unclear. These were assessed using hydrogeo chemical facies, water type evolutions and mapping. The source of HD salinity was identified to be shallow groundwater (SG) and runoff from a seasonal floodplain with NaCl-rich lithological mat-erails,alongLittleKinyasungweRiverthatfeedsthedam.TheNaCl-rich lithological units, about 5–7 km upstream of the dam, were highly concentrated with NaCl to the extent that the local community was commercially separating table salt from them. The physicochemical parameters from these NaCl-richlithological materials were well represented in HD and nearby groundwater sources, which suggests active water interactions. Water type evolution and surface hydrology assessments clearly showed that SG in the salty-floodplain was influenced by evaporation (ET) and was periodically carried to the HD. Clearly; HD water had high chemical similarity with the nearby SG. This agrees with previous studies that HD is partly fed by the local aquifer. However, this is the first attempt at mapping its physical origin. The origin of HD salinity was further supported by the spatial distribution of electrical conductivity (EC), where very high EC (up to21,230lScm-1) was recorded in SG within the NaCl-richlithological unit while water sources far away from the NaCl-rich materials had much lower EC values. Thus, the study disagrees with previous conclusions that HD salinity was sorely due to high dam surface ET but is primarily due to geological reasons. Comparisons of HD with a nearby Matumbulu dam (MD), another earthen dam in climatologically similar settings, reveals that MD water was less saline/mineralised. This further shows that HD high salinity is most likely a geologic phenomenon, but local climatic factors, namely high ET, decreasing rainfall and warming trends are likely to have concentrated the salts further. Although HD is widely/ideally used for grape vine irrigation, it was clearly revealed that its prolonged usage would potentially affect the soil and grape productivity due to high salinity.
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    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