Application of the modified pitman and swat models for groundwater recharge estimation in the upstream area of the Uitenhage artesian basin, South Africa
- Authors: Wasswa, Peter
- Date: 2024-04-04
- Subjects: Hydrologic models , Groundwater recharge , Runoff Mathematical models , Rain and rainfall Mathematical models , Water-supply Management , Artesian basins South Africa Eastern Cape
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435400 , vital:73154
- Description: The world's most plentiful source of freshwater is thought to be groundwater. During extended dry times, it serves as an essential storage component and guards against environmental catastrophes. Despite its critical functions in the aforementioned scenarios, it is often insufficiently understood and inadequately managed. As a result, it calls for the adoption of integrated methods to comprehend the dynamics of groundwater recharge. Thus, the current study evaluated the applicability and suitability of the Modified Pitman and SWAT models for groundwater recharge estimation in the upstream area of UAB for the period that spanned from 1993 to 2021. It was achieved by using a qualitative conceptual-perceptual model to inform the two hydrological models, Modified Pitman, and SWAT. The developed qualitative conceptual-perceptual model depicted the dominancy of irregularly folded and fractured TMG rock outcrops coupled with fault systems in the upstream area. In the downward section, TMG is overlaid by the aquiclude from the Uitenhage Group which is responsible for the artesian conditions. Groundwater potential zones were classified as Poor, Fair, Good, and Excellent, with 65.4% and 8.7% of the upstream area attributed to Good and Excellent zones respectively. Both Modified Pitman and SWAT predicted decreasing rates of groundwater recharge in the upstream area over time, though Mann-Kendal trend tests done at 5% signifance level depicted significant decreasing rates in SWAT predicted recharge compared to Modified Pitman predicted recharge. The two models did also predict recharge and other water balance components with differing peaks, lows and timings. Modified Pitman predicted mean annual recharge of 63.3-92.8 mm where as SWAT predicted mean annual recharge of 14.4-182.8 mm. In reference to earlier findings within TMG areas, estimated percentages of groundwater recharge were close to those simulated by both Pitman and SWAT models. Modified Pitman and SWAT models appear to both be reasonable tools to estimate recharge in TMG setting, producing relatively similar results to one another and to other regional estimates. Since the current study estimated low recharge rates (Modified Pitman; ~9.3-13.6% MAP), (SWAT; ~2.1-26.7% MAP) which are close to those predicted in other TMG areas, the study recommends exercising caution when developing a water supply strategy in the current study area. The recharge rates within the pertinent recharging areas should be considered when designing and sitting abstraction points such as boreholes and a sustainable abstraction rate in any one borehole for improved sustainable management of groundwater resources. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-04-04
- Authors: Wasswa, Peter
- Date: 2024-04-04
- Subjects: Hydrologic models , Groundwater recharge , Runoff Mathematical models , Rain and rainfall Mathematical models , Water-supply Management , Artesian basins South Africa Eastern Cape
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435400 , vital:73154
- Description: The world's most plentiful source of freshwater is thought to be groundwater. During extended dry times, it serves as an essential storage component and guards against environmental catastrophes. Despite its critical functions in the aforementioned scenarios, it is often insufficiently understood and inadequately managed. As a result, it calls for the adoption of integrated methods to comprehend the dynamics of groundwater recharge. Thus, the current study evaluated the applicability and suitability of the Modified Pitman and SWAT models for groundwater recharge estimation in the upstream area of UAB for the period that spanned from 1993 to 2021. It was achieved by using a qualitative conceptual-perceptual model to inform the two hydrological models, Modified Pitman, and SWAT. The developed qualitative conceptual-perceptual model depicted the dominancy of irregularly folded and fractured TMG rock outcrops coupled with fault systems in the upstream area. In the downward section, TMG is overlaid by the aquiclude from the Uitenhage Group which is responsible for the artesian conditions. Groundwater potential zones were classified as Poor, Fair, Good, and Excellent, with 65.4% and 8.7% of the upstream area attributed to Good and Excellent zones respectively. Both Modified Pitman and SWAT predicted decreasing rates of groundwater recharge in the upstream area over time, though Mann-Kendal trend tests done at 5% signifance level depicted significant decreasing rates in SWAT predicted recharge compared to Modified Pitman predicted recharge. The two models did also predict recharge and other water balance components with differing peaks, lows and timings. Modified Pitman predicted mean annual recharge of 63.3-92.8 mm where as SWAT predicted mean annual recharge of 14.4-182.8 mm. In reference to earlier findings within TMG areas, estimated percentages of groundwater recharge were close to those simulated by both Pitman and SWAT models. Modified Pitman and SWAT models appear to both be reasonable tools to estimate recharge in TMG setting, producing relatively similar results to one another and to other regional estimates. Since the current study estimated low recharge rates (Modified Pitman; ~9.3-13.6% MAP), (SWAT; ~2.1-26.7% MAP) which are close to those predicted in other TMG areas, the study recommends exercising caution when developing a water supply strategy in the current study area. The recharge rates within the pertinent recharging areas should be considered when designing and sitting abstraction points such as boreholes and a sustainable abstraction rate in any one borehole for improved sustainable management of groundwater resources. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-04-04
Spatiotemporal recharge determination in response to episodic rainfall events within the Central Karoo, South Africa
- Authors: Williams, Aarifah
- Date: 2024-04
- Subjects: Groundwater -- South Africa -- Beaufort West , Groundwater recharge , Hydrogeology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64459 , vital:73735
- Description: With inadequate and unpredictable rainfall patterns resulting in a mean annual precipitation of 464 mm, South Africa is classified as a water-stressed semi-arid country. Consequently, between 2015 and 2021, the majority of South Africa was confronted with severe drought conditions, with numerous dams running dry across the country. The Beaufort West Municipality is a prime example of the adverse effects of South Africa's inadequate and erratic rainfall patterns. In Beaufort West, a town located within the Central Karoo region of the Western Cape, groundwater is the primary source of water. Since recharge within the region is episodic, occurring irregularly, understanding the dynamics surrounding recharge in the area is essential for achieving sustainable long-term water resource management. This study aimed to gain a better understanding of how the aquifers within the Beaufort West Municipality Well Fields respond to extended periods of drought, extreme episodic precipitation events and excessive abstraction. This study aimed to quantify extreme recharge in the Beaufort West municipal wellfields using the water-table fluctuation (WTF) method. Additionally, it sought to deepen comprehension of the local climate's interaction with groundwater levels, surface water dynamics, and recharge through a 32-year historical data analysis (1990 to 2022) encompassing precipitation, evaporation, and surface water parameters. Findings revealed the complex relationship between precipitation, evaporation, regional geology, and water abstraction, influencing recharge periods, duration, and mechanisms across different regions within the aquifer system. Groundwater levels exhibited rapid declines during droughts due to extensive well field abstraction, but recovery was evident following episodic high precipitation events in 1993, 1996, 2010/2011, and 2019/2020. This comprehensive analysis serves as a valuable foundation for informed water resource management strategies, emphasizing the need for diversified approaches ensure the long-term water security and resilience of the Beaufort West Municipality. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Williams, Aarifah
- Date: 2024-04
- Subjects: Groundwater -- South Africa -- Beaufort West , Groundwater recharge , Hydrogeology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64459 , vital:73735
- Description: With inadequate and unpredictable rainfall patterns resulting in a mean annual precipitation of 464 mm, South Africa is classified as a water-stressed semi-arid country. Consequently, between 2015 and 2021, the majority of South Africa was confronted with severe drought conditions, with numerous dams running dry across the country. The Beaufort West Municipality is a prime example of the adverse effects of South Africa's inadequate and erratic rainfall patterns. In Beaufort West, a town located within the Central Karoo region of the Western Cape, groundwater is the primary source of water. Since recharge within the region is episodic, occurring irregularly, understanding the dynamics surrounding recharge in the area is essential for achieving sustainable long-term water resource management. This study aimed to gain a better understanding of how the aquifers within the Beaufort West Municipality Well Fields respond to extended periods of drought, extreme episodic precipitation events and excessive abstraction. This study aimed to quantify extreme recharge in the Beaufort West municipal wellfields using the water-table fluctuation (WTF) method. Additionally, it sought to deepen comprehension of the local climate's interaction with groundwater levels, surface water dynamics, and recharge through a 32-year historical data analysis (1990 to 2022) encompassing precipitation, evaporation, and surface water parameters. Findings revealed the complex relationship between precipitation, evaporation, regional geology, and water abstraction, influencing recharge periods, duration, and mechanisms across different regions within the aquifer system. Groundwater levels exhibited rapid declines during droughts due to extensive well field abstraction, but recovery was evident following episodic high precipitation events in 1993, 1996, 2010/2011, and 2019/2020. This comprehensive analysis serves as a valuable foundation for informed water resource management strategies, emphasizing the need for diversified approaches ensure the long-term water security and resilience of the Beaufort West Municipality. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
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