Browsing by Author "Mahwa, Joshua"

Now showing 1 - 4 of 4
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    Impact of Xiaolangdi Reservoir on the Evolution of Water Infiltration Influence Zones of the Secondary Perched Reach of the Lower Yellow River
    (MDPI AG, 2023) Zhang, Min; Ping, Jianhua; Zou, Yafei; Li, He; Mahwa, Joshua; Zhao, Jichang; Liu, Jiaqi
    Understanding the complex interplay between water management infrastructure and groundwater dynamics is crucial for sustainable resource utilization. This study investigates water infiltration dynamics in the secondary perched reach of the Yellow River after the operation of the Xiaolangdi Reservoir. The methodology included the application of the single-factor analysis of variance and water balance method, alongside a dual-structure, one-dimensional seepage model to simulate interactions within the system, while exploring characteristics of the groundwater flow system and the exploitation depth of below 100 m. Furthermore, we studied the influence zone range and alterations in river water infiltration in the secondary perched reach of the river following the operation of Xiaolangdi Reservoir. The results show that before the operation of the reservoir, the influence ranges of the north and south banks of the aboveground reach extended from 20.13 km to 20.48 km and 15.85 km to 16.13 km, respectively. Following the initiation of the reservoir, the river channel underwent scouring, leading to enhanced riverbed permeability. Additionally, the influence of long-term groundwater exploitation on both riverbanks extended the influence range of groundwater recharge within the secondary perched reach of the river. The influence zone of the north bank is now 23.41 km–26.74 km and the south bank 18.43 km–21.05 km. After years of shallow groundwater extraction, multiple groundwater depression cones emerged within the five major groundwater source areas on both sides of the river. Notably, deeper water levels (Zhengzhou to Kaifeng) have significantly decreased, with a drop of 42 m to 20 m to 15 m. This change in groundwater dynamics extended beyond the main channel of the river, creating a localized shallow groundwater field.
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    Mapping the spatial distribution of fossil geothermal manifestations and assessment of geothermal potential of the Tangyin rift, Southeast of Taihang Mountain in China
    (Springer Nature, 2022) Mahwa, Joshua; Li, Da-jiang; Ping, Jian-hua; Leng, Wei; Tang, Jia-bo; Shao, Dong-yun
    The spatial prediction of geothermal sites along the southeast side of Taihang Mountain in the Tangyin rift is a critical goal in the development of renewable energy resources in cities such as Hebi in Henan province, which has significant potential for geothermal energy production due to the existence of deep faults and Cenozoic volcano. The study aimed to delineate areas with high geothermal manifestations for detailed geothermal exploration and well-test drilling. To define favorable zones for geothermal potentiality, multi-source datasets were chosen to generate evidence thematic layers that demonstrate the distribution of geothermal anomalies such as geologic maps, structural maps, Land Surface Temperature maps (LST), and hydrothermal mineral alterations maps. The remote sensing and Geographical Information System (GIS) approaches were integrated to map fossil geothermal manifestations and appraise the promising geothermal zones from Landsat 8 OLI/TIRS and Advanced Spaceborne Thermal Emission and Reflection Radiometer-Digital Elevation Model (ASTER-DEM) dataset using the Analytic Hierarchy Process (AHP), which is one of the Mult-criteria Decision Making methods. Results show LST values ranging from 22.6°C to 45.4°C, with the highest values found along the faults and volcanic areas. The hydrothermal alteration minerals discriminated from band ratios of 4/2, 6/5, and 6/7 for iron oxide, ferrous minerals, and clays reveal the presence of high amount of montmorillonite and illite minerals along the faults and volcanoes which are related to hot fluid circulation from subsurface. Structural analysis shows that the major structural trend follows the NNE Tangdong and Tangxi faults, with high density on the west side of the Tangxi fault where there is good exposure of outcrop but less fault density on the east side due to sedimentation in a low land which may conceal geological structures. Lastly, all the thematic layers of geothermal factors were reclassified, ranked, and integrated by the weight overlay logic model based on the influence of geothermal suitability to map potential areas for geothermal resources whereby 5 zones were obtained ranging from very poor to very good. The promising potential sites are mostly found along the highly deep structures of the major Tangxi fault crosscutting the permeable lithology of carbonate rocks and around the Hebi volcanoes. The distribution of hot springs and geothermal wells of the Hebi field were correlated and verified against the potential geothermal anomalies map. The overall integrated method proposes an advanced technique for designing the Tangyin rift’s exploration plan and development actions for geothermal resources utilization, which can be used for exploration of any unveiling geothermal potential sites.
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    Structural framework and its effects on traps formation in the south-eastern part of Rukwa basin
    (The University of Dodoma, 2017) Mahwa, Joshua
    This work presents the first detailed, structural framework, characteristics and types of traps which are found in the South-Eastern part Rukwa basin, located in the Western Branch of the East African Rift System, South-Western Tanzania. The goal of this work is to examine the structural framework which controls trapping characteristic of the Rukwa basin within the Karoo and Lower Lake Beds reservoir. 2D seismic datasets that were collected in 1983 by Amocco obtained from TPDC were analyzed by using Petrel software and the major structures and stratigraphic sequence were traced and interpreted to characterize the shape and the extent of the structures such as faults and folds which forms traps. These structures which form traps found within the Karoo formation and in Lower Lake bed formation. Three traps fields have been identified as potential traps in the Rukwa basin which are controlled by faults whereby, fold traps have been identified as minor traps. Rukwa basin has been found to have source rock, reservoir rock, seal rock, maturation of hydrocarbon, high geothermal gradient and identified trap field from this study favour the accumulation of Hydrocarbons within the Basin. The study of migration path of Hydrocarbons in Rukwa basin will guarantee the accumulation of Hydrocarbon in the identified Trap field.
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    Tectonics and hydrogeochemical features of geothermal waters in Tangyin Rift SE Taihang Mountain
    (Elsevier, 2023) Mahwa, Joshua; Ping, Jianhua; Leng, Wei; Zhao, Jichang; Liu, Jiaqi
    Geothermal exploration in the Tangyin rift is gaining very important attention due to the increased demand for electricity and space heating in the Hebi City area. Due to geological and tectonic settings of rifting extension, volcanism and a thin lithosphere, it possesses a considerable amount of geothermal potential. Efforts to replace sporadic coal use with clean energy sources like gas, geothermal and electricity have helped reduce air pollutants brought about by many household activities. The present work conducts in-depth structural analysis, geochemistry (major and trace elements), and stable isotope analyses of geothermal waters in an attempt to decipher their hydrogeochemical evolution and their influence on the geothermal potential of Tangyin rift. Correlation analyses are used to determine the geochemical mechanisms that control the geochemistry of geothermal waters. The results indicate that large faults' deformational model, permeability, fluid transportation, and fluid flow direction are influenced by major faults trending NNE-SSW. Furthermore, the waters are classified into five types of hydrogeochemical: Ca-HCO3, Na-Cl–SO4, Ca-Mg-HCO3, Na-HCO3 and Ca-Cl. The Na-Cl-SO4 waters are connected with the Hebi volcano and ascend directly. Subsurface activities including cold water mixing and water-rock interaction have a higher impact on the region's Ca-HCO3 shallow ground waters. The geothermal system is characterized by convection-dominated geothermal play coupled with volcanism, replenished by meteoric fluids flowing through fractures and faults from Taihang Mountain and affected by CO2-rich waters from deeper levels. The reservoir is defined as immature water by the Giggenbach Na-K-Mg triangular diagram and mineral saturation indices (SI) that estimate an average reservoir temperature of 220 °C. Finally, the conceptual hydrogeological model for the Tangyin rift geothermal system was developed which can be used for studying the target for geothermal energy development.