Hydrogeological controls on groundwater recharge in a weathered crystalline aquifer: A case study from the Makutapora groundwater basin, Tanzania

2020 ◽  
Author(s):  
Emanuel Zarate ◽  
Alan MacDonald ◽  
Russell Swift ◽  
Jonathan Chambers ◽  
Japhet Kashaigili ◽  
...  
Keyword(s):  
Groundwater Recharge ◽  
Crucial Role ◽  
Numerical Models ◽  
Groundwater Resources ◽  
Crystalline Rock ◽  
Aquifer Recharge ◽  
Crystalline Aquifer ◽  
Geophysical Surveys ◽  
Groundwater Basin ◽  
Semi Arid

<p>Drylands (semi-arid/arid regions) represent >35% of the Earth’s surface, support a population of around 2 billion people, and are forecast to be increasingly water stressed in coming decades. Groundwater is the most reliable source of water in drylands, and it is likely that the structure and hydraulic properties of superficial geology play a crucial role in controlling groundwater recharge in these regions.  However, the spatio-temporal hydrogeological controls on the rates of groundwater recharge, and their sensitivity to environmental change are poorly resolved.</p><p>In the Makutapora groundwater basin (Tanzania), an analogue for semi-arid tropical areas underlain by weathered and fractured crystalline rock aquifers, we conducted a series of geophysical surveys using Electrical Resistivity Tomography (ERT) and frequency domain electromagnetic methods (FDEM). Using these data, in conjunction with borehole logs, we identify and delineate five major lithological units in the basin: 1) Superficial deposits of coarse sand (>200 Ω m) 2) Highly conductive smectitic clays (1-10 Ω m) 3) Decomposed pedolitic soils (30-100 Ω m) 4) Weathered saprolite (100-700 Ω m) and 5) Fractured granitic basement (>700 Ω m). We also identify 10-50m wide zones of normal faulting extending across the basin and cutting through these units, interpreted with the aid of analysis of a digital elevation model alongside the geophysics data.</p><p>These results are combined with existing long-term hydrological and hydrogeological records to build conceptual models of the processes governing recharge. We hypothesise that: 1) Zones of active faulting provide permeable pathways enabling greater recharge to occur; 2) Superficial sand deposits may act as collectors and stores that slowly feed recharge into these fault zones; 3) Windows within layers of smectitic clay underlying ephemeral streams may provide pathways for focused recharge via transmission losses; and 4) Overbank flooding during high-intensity precipitation events that inundate a greater area of the basin increases the probability of activating such permeable pathways.</p><p>Our results suggest that configurations of superficial geology may play a crucial role in controlling patterns, rates and timing of groundwater recharge in dryland settings. They also provide a physical basis to improve numerical models of groundwater recharge in drylands, and a conceptual framework to evaluate strategies (e.g. Managed Aquifer Recharge) to artificially enhance the availability of groundwater resources in these regions.</p>

Focused groundwater recharge in a dryland environment: hydrometric and isotopic evidence from central Tanzania

2020 ◽  
Author(s):  
David Seddon ◽  
Japhet J. Kashaigili ◽  
Richard G. Taylor ◽  
Mark O. Cuthbert ◽  
Lucas Mihale ◽  
...  
Keyword(s):  
Groundwater Recharge ◽  
Surface Waters ◽  
Poverty Alleviation ◽  
Managed Aquifer Recharge ◽  
Sub Saharan Africa ◽  
Aquifer Recharge ◽  
Ephemeral Stream ◽  
Groundwater Levels ◽  
Sub Saharan ◽  
Semi Arid

<p>Groundwater, and its replenishment via recharge, is critical to livelihoods and poverty alleviation in drylands of sub-Saharan Africa and beyond, yet the processes by which groundwater is replenished remain inadequately observed and resolved. Here, we present three lines of evidence, from an extensively-monitored wellfield in central semi-arid Tanzania, indicating focused groundwater recharge occurring via leakage from episodic, ephemeral stream discharges. First, the duration of ephemeral streamflow observed from daily records from 2007 to 2016 correlates strongly (R<sup>2</sup> = 0.85) with the magnitude of groundwater recharge events observed and estimated from piezometric observations. Second, high-resolution (hourly) monitoring of groundwater levels and stream stage, established in advance of the 2015-16 El Niño, shows the formation and decay of groundwater mounds beneath episodically inundated adjacent streambeds. Third, stable-isotope ratios of O and H of groundwater and precipitation as well as perennial and ephemeral surface waters trace the origin of groundwater to ephemeral stream discharges. The identification and characterisation of focused groundwater recharge have important implications not only, locally, for protecting and potentially augmenting replenishment of a wellfield supplying the capital of Tanzania through Managed Aquifer Recharge but also, more widely, in understanding and modelling groundwater recharge in dryland environments.</p>

scholarly journals Using multiple methods to understand groundwater recharge in a semi-arid area

2020 ◽  
Author(s):  
Shovon Barua ◽  
Ian Cartwright ◽  
P. Evan Dresel ◽  
Edoardo Daly
Keyword(s):  
Groundwater Recharge ◽  
Water Table ◽  
Groundwater Resources ◽  
Land Use Changes ◽  
Arid Area ◽  
Plantation Forest ◽  
Land Clearing ◽  
Water Table Fluctuations ◽  
Recharge Rates ◽  
Semi Arid

Abstract. Understanding recharge in semi-arid areas is important for the sustainable management of groundwater resources. This study focuses on estimating groundwater recharge rates and understanding the impacts of land-use changes on recharge in a semi-arid area. Two adjacent catchments in southeast Australia were cleared ~180 years ago following European settlement; in one of these catchments eucalypt plantation forest was subsequently established ~ 20 years ago. Chloride mass balance yields recharge rates of 0.2 to 61.6 mm yr−1 (typically up to 11.2 mm yr−1). The lower of these values probably represent recharge rates prior to land clearing, whereas the higher likely reflects recharge rates following initial land clearing. The low pre-land clearing recharge rates are consistent with the presence of groundwater that has residence times that are up to 24,700 years (calculated using radiocarbon) and the moderate to low hydraulic conductivities (0.31 to 0.002 m day−1) of the clay-rich aquifers. Recharge rates estimated from tritium activities and water table fluctuations reflect those following the initial land clearing. However, recharge rates estimated using water table fluctuations (15 to 500 mm yr−1) are significantly higher than those estimated using tritium renewal rates (0.01 to 89 mm yr−1; typically

scholarly journals Identifying potential sites for artificial groundwater recharge using GIS and AHP techniques: A case study of Erbil basin, Iraq

2022 ◽  
Author(s):  
Omeed H. Al-Kakey ◽  
◽  
Arsalan A. Othman ◽  
Broder J. Merkel ◽  
◽  
...  
Keyword(s):  
Groundwater Recharge ◽  
Sustainable Management ◽  
Groundwater Resources ◽  
Data Availability ◽  
Coefficient Of Determination ◽  
Negative Consequences ◽  
Aquifer Recharge ◽  
Artificial Groundwater Recharge ◽  
Runoff Water ◽  
Thematic Layers

Excessive extraction, uncontrolled withdrawal of groundwater, and unregulated practices have caused severe depletion of groundwater resources in the Erbil basin, Iraq. This situation has had a number of negative consequences on human settlement, agricultural activities, clean water supply, and the environment. Runoff harvesting and artificial groundwater recharge play a significant role in the sustainable management of water resources, particularly in arid and semi-arid regions. This study aims to: (1) delineate groundwater recharge zones using multiple thematic layers that control the groundwater recharge process, and (2) identify prospective sites and structures to perform artificial groundwater recharge. In order to generate a potential map for groundwater recharge zones, seven thematic layers are considered in this study, namely, topographic position index, geomorphology, lithology, land cover, slope, drainage-length density, and lineament-length density. After that, the analytic hierarchy process was applied to weight, rank, and reclassify these seven thematic layers. All maps are then integrated within the ArcGIS environment for delineating groundwater recharge zones. Accordingly, the resulting map categorizes the study area into five zones: extremely high, high, moderate, low, and extremely low potential for groundwater recharge. As expected, areas along the Greater Zab river show the highest possibility for groundwater recharge. Likewise, rugged eastern hills demonstrate an encouraging capacity for artificial aquifer recharge, whereas the least effective area is represented by built-up land. Based on the generated map, two dams are proposed as promising artificial recharge structures for harvesting runoff water east of Erbil city. Lastly, the resulting map of the potential groundwater recharge zones is verified using static water level data, where the coefficient of determination (R2) achieved a satisfactory result (0.73). These findings provide crucial evidence for implementing a sustainable management plan of surface and groundwater resources. The applied method is eventually valid for regions where appropriate and adequate field data availability is a serious issue.

Estimation of Spatial and Temporal Groundwater Balance Components in Khadir Canal Sub-Division, Chaj Doab, Pakistan

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 178
Author(s):  
Muhammad Aslam ◽  
Ali Salem ◽  
Vijay P. Singh ◽  
Muhammad Arshad
Keyword(s):  
Land Use ◽  
Water Balance ◽  
Groundwater Recharge ◽  
Groundwater Resources ◽  
Balance Model ◽  
Annual Rainfall ◽  
Water Balance Components ◽  
Aquifer Management ◽  
Groundwater Balance ◽  
Semi Arid

Evaluation of the spatial and temporal distribution of water balance components is required for efficient and sustainable management of groundwater resources, especially in semi-arid and data-poor areas. The Khadir canal sub-division, Chaj Doab, Pakistan, is a semi-arid area which has shallow aquifers which are being pumped by a plethora of wells with no effective monitoring. This study employed a monthly water balance model (water and energy transfer among soil, plants, and atmosphere)—WetSpass-M—to determine the groundwater balance components on annual, seasonal, and monthly time scales for a period of the last 20 years (2000–2019) in the Khadir canal sub-division. The spatial distribution of water balance components depends on soil texture, land use, groundwater level, slope, and meteorological conditions. Inputs for the model included data on topography, slope, soil, groundwater depth, slope, land use, and meteorological data (e.g., precipitation, air temperature, potential evapotranspiration, and wind speed) which were prepared using ArcGIS. The long-term average annual rainfall (455.7 mm) is distributed as 231 mm (51%) evapotranspiration, 109.1 mm (24%) surface runoff, and 115.6 mm (25%) groundwater recharge. About 51% of groundwater recharge occurs in summer, 18% in autumn, 14% in winter, and 17% in spring. Results showed that the WetSpass-M model properly simulated the water balance components of the Khadir canal sub-division. The WetSpass-M model’s findings can be used to develop a regional groundwater model for simulation of different aquifer management scenarios in the Khadir area, Pakistan.

scholarly journals Evaluation of drought impact on groundwater recharge rate using SWAT and Hydrus models on an agricultural island in western Japan

2015 ◽  
Vol 371 ◽  
pp. 143-148 ◽  
Author(s):  
G. Jin ◽  
Y. Shimizu ◽  
S. Onodera ◽  
M. Saito ◽  
K. Matsumori
Keyword(s):  
Groundwater Recharge ◽  
Groundwater Level ◽  
Groundwater Resources ◽  
Water Discharge ◽  
Swat Model ◽  
Spatial And Temporal Variation ◽  
Hydrological Process ◽  
Aquifer Recharge ◽  
Recharge Rate ◽  
Groundwater Recharge Rate

Abstract. Clarifying the variations of groundwater recharge response to a changing non-stationary hydrological process is important for efficiently managing groundwater resources, particularly in regions with limited precipitation that face the risk of water shortage. However, the rate of aquifer recharge is difficult to evaluate in terms of large annual-variations and frequency of flood events. In our research, we attempt to simulate related groundwater recharge processes under variable climate conditions using the SWAT Model, and validate the groundwater recharge using the Hydrus Model. The results show that annual average groundwater recharge comprised approximately 33% of total precipitation, however, larger variation was found for groundwater recharge and surface runoff compared to evapotranspiration, which fluctuated with annual precipitation variations. The annual variation of groundwater resources is shown to be related to precipitation. In spatial variations, the upstream is the main surface water discharge area; the middle and downstream areas are the main groundwater recharge areas. Validation by the Hydrus Model shows that the estimated and simulated groundwater levels are consistent in our research area. The groundwater level shows a quick response to the groundwater recharge rate. The rainfall intensity had a great impact on the changes of the groundwater level. Consequently, it was estimated that large spatial and temporal variation of the groundwater recharge rate would be affected by precipitation uncertainty in future.

scholarly journals Global-scale modeling of groundwater recharge

2008 ◽  
Vol 12 (3) ◽  
pp. 863-885 ◽  
Author(s):  
P. Döll ◽  
K. Fiedler
Keyword(s):  
Water Resources ◽  
Groundwater Recharge ◽  
Arid Regions ◽  
Groundwater Resources ◽  
Global Scale ◽  
Unbiased Estimation ◽  
Data Sets ◽  
Total Runoff ◽  
Semi Arid

Abstract. Long-term average groundwater recharge, which is equivalent to renewable groundwater resources, is the major limiting factor for the sustainable use of groundwater. Compared to surface water resources, groundwater resources are more protected from pollution, and their use is less restricted by seasonal and inter-annual flow variations. To support water management in a globalized world, it is necessary to estimate groundwater recharge at the global scale. Here, we present a best estimate of global-scale long-term average diffuse groundwater recharge (i.e. renewable groundwater resources) that has been calculated by the most recent version of the WaterGAP Global Hydrology Model WGHM (spatial resolution of 0.5° by 0.5°, daily time steps). The estimate was obtained using two state-of-the-art global data sets of gridded observed precipitation that we corrected for measurement errors, which also allowed to quantify the uncertainty due to these equally uncertain data sets. The standard WGHM groundwater recharge algorithm was modified for semi-arid and arid regions, based on independent estimates of diffuse groundwater recharge, which lead to an unbiased estimation of groundwater recharge in these regions. WGHM was tuned against observed long-term average river discharge at 1235 gauging stations by adjusting, individually for each basin, the partitioning of precipitation into evapotranspiration and total runoff. We estimate that global groundwater recharge was 12 666 km3/yr for the climate normal 1961–1990, i.e. 32% of total renewable water resources. In semi-arid and arid regions, mountainous regions, permafrost regions and in the Asian Monsoon region, groundwater recharge accounts for a lower fraction of total runoff, which makes these regions particularly vulnerable to seasonal and inter-annual precipitation variability and water pollution. Average per-capita renewable groundwater resources of countries vary between 8 m3/(capita yr) for Egypt to more than 1 million m3/(capita yr) for the Falkland Islands, the global average in the year 2000 being 2091 m3/(capita yr). Regarding the uncertainty of estimated groundwater resources due to the two precipitation data sets, deviation from the mean is 1.1% for the global value, and less than 1% for 50 out of the 165 countries considered, between 1 and 5% for 62, between 5 and 20% for 43 and between 20 and 80% for 10 countries. Deviations at the grid scale can be much larger, ranging between 0 and 186 mm/yr.

scholarly journals Assessment of Groundwater Recharge in Agro-Urban Watersheds Using Integrated SWAT-MODFLOW Model

2020 ◽  
Vol 12 (16) ◽  
pp. 6593
Author(s):  
Bisrat Ayalew Yifru ◽  
Il-Moon Chung ◽  
Min-Gyu Kim ◽  
Sun Woo Chang
Keyword(s):  
Surface Water ◽  
Groundwater Recharge ◽  
Assessment Tool ◽  
Numerical Models ◽  
Model Performance ◽  
Urban Watersheds ◽  
Aquifer Recharge ◽  
Surface Water Flow ◽  
Calibration Techniques ◽  
Watershed Processes

Numerical models are employed widely to evaluate the hydrological components of a watershed but, traditionally, watershed models simplify either surface or subsurface flow module. In this setup, as a bridge between groundwater and surface water regimes, aquifer recharge is the most affected segment of the water balance. Since the watershed processes are increasingly changed, the need for a comprehensive model with detailed conceptualizing capacity of both groundwater and surface water flow systems is growing. This work focuses on the spatiotemporal groundwater recharge assessment in gauged and ungauged agro-urban watersheds in South Korea using the updated SWAT-MODFLOW model, which integrates the Soil and Water Assessment Tool (SWAT2012) and Newton–Raphson formulation for Modular Finite Difference Groundwater Flow (MODFLOW-NWT) in a single executable code. Before coupling, the setup, calibration, and verification of each model were performed separately. After integration, irrigation pumps and drain cells mapping to SWAT auto-irrigation and subbasins were initiated. Automatic calibration techniques were used for SWAT and MODFLOW-NWT models, but a manual calibration was used for the integrated model. A physical similarity approach was applied to transfer parameters to the ungauged watershed. Statistical model performance indicators revealed that the low streamflow estimation was improved in SWAT-MODFLOW. The spatiotemporal aquifer recharge distribution from both the stream seepage and precipitation showed a substantial change, and most of the aquifer recharge occurs in July–September. The areal annual average recharge reaches about 18% of the precipitation. Low-lying areas receive higher recharge consistently throughout a year. Overall, SWAT-MODFLOW exhibited reasonable versatility in evaluating watershed processes and produced valuable results with reasonable accuracy. The results can be an important input for policymakers in the development of sustainable groundwater protection and abstraction strategies for the region.

scholarly journals Quantifying Groundwater Resources for Municipal Water Use in a Data-Scarce Region

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 184
Author(s):  
Iolanda Borzì ◽  
Brunella Bonaccorso
Keyword(s):  
Groundwater Recharge ◽  
Groundwater Resources ◽  
Aridity Index ◽  
Water Sampling ◽  
Aquifer Recharge ◽  
Water Abstraction ◽  
Monthly Scale ◽  
Annual Scale ◽  
The City ◽  
Resources Planning

Groundwater is a major source of drinking water worldwide, often considered more reliable than surface water and more accessible. Nowadays, there is wide recognition by the scientific community that groundwater resources are under threat from overexploitation and pollution. Furthermore, frequent and prolonged drought periods due to climate change can seriously affect groundwater recharge. For an appropriate and sustainable management of water systems supplied by springs and/or groundwater withdrawn from aquifers through drilling wells or drainage galleries, the need arises to properly quantify groundwater resources availability, mainly at the monthly scale, as groundwater recharge is influenced by seasonality, especially in the Mediterranean areas. Such evaluation is particularly important for ungauged groundwater bodies. This is the case of the aquifer supplying the Santissima Aqueduct, the oldest water supply infrastructure of the city of Messina in Sicily (Southern Italy), whose groundwater flows are measured only occasionally through spring water sampling at the water abstraction plants. Moreover, these plants are barely maintained because they are difficult to reach. In this study, groundwater recharge assessment for the Santissima Aqueduct is carried out through a GIS-based inverse hydrogeological balance methodology. Although this approach was originally designed to assess aquifer recharge at the annual scale, wherever a model conceptualization of the groundwater system was hindered by the lack of data, in the present study some changes are proposed to adjust the model to the monthly scale. In particular, the procedure for evapotranspiration assessment is based on the Global Aridity Index within the Budyko framework. The application of the proposed methodology shows satisfactory results, suggesting that it can be successfully applied for groundwater resources estimation in a context where monthly information is relevant for water resources planning and management.

scholarly journals Global-scale modeling of groundwater recharge

2007 ◽  
Vol 4 (6) ◽  
pp. 4069-4124 ◽  
Author(s):  
P. Döll ◽  
K. Fiedler
Keyword(s):  
Water Resources ◽  
Groundwater Recharge ◽  
Arid Regions ◽  
Groundwater Resources ◽  
Global Scale ◽  
Unbiased Estimation ◽  
Data Sets ◽  
Total Runoff ◽  
Semi Arid

Abstract. Long-term average groundwater recharge, which is equivalent to renewable groundwater resources, is the major limiting factor for the sustainable use of groundwater. Compared to surface water resources, groundwater resources are more protected from pollution, and their use is less restricted by seasonal and inter-annual flow variations. To support water management in a globalized world, it is necessary to estimate groundwater recharge at the global scale. Here, we present a best estimate of global-scale long-term average diffuse groundwater recharge (i.e. renewable groundwater resources) that has been calculated by the most recent version of the WaterGAP Global Hydrology Model WGHM (spatial resolution of 0.5° by 0.5°, daily time steps). The estimate was obtained using two state-of-the art global data sets of gridded observed precipitation that we corrected for measurement errors, which also allowed to quantify the uncertainty due to these equally uncertain data sets. The standard WGHM groundwater recharge algorithm was modified for semi-arid and arid regions, based on independent estimates of diffuse groundwater recharge, which lead to an unbiased estimation of groundwater recharge in these regions. WGHM was tuned against observed long-term average river discharge at 1235 gauging stations by adjusting, individually for each basin, the partitioning of precipitation into evapotranspiration and total runoff. We estimate that global groundwater recharge was 12 666 km3/yr for the climate normal 1961–1990, i.e. 32% of total renewable water resources. In semi-arid and arid regions, mountainous regions, permafrost regions and in the Asian Monsoon region, groundwater recharge accounts for a lower fraction of total runoff, which makes these regions particularly vulnerable to seasonal and inter-annual precipitation variability and water pollution. Average per-capita renewable groundwater resources of countries vary between 8 m3/(capita yr) for Egypt to more than 1 million m3/(capita yr) for the Falkland Islands, the global average in the year 2000 being 2091 m3/(capita yr). Regarding the uncertainty of estimated groundwater resources due to the two precipitation data sets, deviation from the mean is less than 1% for 50 out of the 165 countries considered, between 1 and 5% for 62, between 5 and 20% for 43 and between 20 and 80% for 10 countries. Deviations at the grid scale can be much larger, ranging between 0 and 186 mm/yr.

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