Assessment Of Recharge Research Articles

Revisiting the historical tritium levels in precipitation in Greece - Preliminary assessment of groundwater transit times.

The radioactive isotope of hydrogen, known as tritium (3H), is very often used as a dating tool in hydrogeological studies, since it enters the water cycle as part of the water molecule through precipitation. However, the assessment of groundwater transit times and recharge often requires knowing the local historical records of tritium levels in precipitation during the previous seven decades, or the tritium in precipitation (TIP) time series. Here, we compiled all tritium records in precipitation in Greece, with the majority of stations showing sporadic measurements, with the aim of reconstructing a TIP for groundwater dating purposes. The monitoring station of Vienna proved to be more reliable for filling the gaps in the time series than the Ottawa station. Conventional methods to fill the TIP gaps, such as the correlation method (CM), were compared with more advanced machine learning tools, such as the Convolutional Neural Networks (CNN). The comparison showed that the artificial Intelligence Method (AIM) performed best, due to its ability to capture complex nonlinear trends that are usually inherent in real-world data. The preliminary qualitative assessment of groundwater tritium data from Greece, in comparison to the TIP, showed the occurrence of groundwaters of mean transit times ranging from a few years to decades. Better incorporation of groundwater transit times and recharge rates into the study of aquifer systems is essential for developing strategies for sustainable water management in Greece and worldwide.

Assessment of diffusive recharge at regional scale in karst systems, Amazon basin, Ecuador

Karst systems play a crucial role in drinking water supply and biodiversity. Therefore, their comprehensive characterization of their recharge mechanisms is essential for safeguard water resource quality and sustainable management. This study utilizes the open-access thematic cartography of Ecuador to analyze the lithological, geomorphological, and hydrographic boundaries of groundwater karst systems. Then, employing the APLIS method, the diffusive recharge for each system is calculated. As a result, five hydrogeological karst systems and twelve small isolated karst bodies were delineated within the Amazon Region of Ecuador, collectively occupying a total area of 11112 km2. The effective infiltration of precipitation within these systems was found to vary between 11.11% and 77.11%, with a predominant low infiltration range (20%-40%) covering 48% of the karst area. One of the multiple parameters used in water balance calculations is defined by this research, serving as the initial step in creating conceptual models for evaluating karst aquifer systems in Ecuador from a hydrological perspective. The findings not only offer insights into the vulnerability and characteristics of these systems but also establish the foundation for informed decision-making in sustainable groundwater resource management and protection efforts.

Assessment of groundwater potential recharge areas using advanced decision models and spatial data: Applied to Sbeitla aquifer system, central Tunisia

Sbeitla is located in a semi-arid region, central western Tunisia, where groundwater is considered an essential resource for economic development and social well-being. The main objective of this study is the assessment of potential groundwater recharge and delineation of aquifer recharge. Structural and hydrostructural database coupled with remote sensing techniques (RST), was employed. The lateral variation of recharging zones was determined through ArcGIS software, utilizing TOPSIS approaches. Results reveal that the study area is classified in five classes, very low recharge (45%), low recharge (15%), moderate recharge (20%) and 15% of the plain have good to very good potential recharge. Predominantly located in the southern part of the Sbeitla region, these areas distribution is controlled by some natural features such as geology and geomorphology. The findings show that there are five places in the Sbeitla plain where water can soak into the ground. About 40% of the area doesn't have much water soaking in, while 15% has a little bit. Also, around 25% of the plain has medium amounts soaking in, and 20% has a lot. This tells us where water is going into the ground in Sbeitla, which helps us use it better. The potential recharge for the Sbeitla aquifer system, using TOPSIS and RST, is estimated to 13.5 Mm³/year. Although this recharging rate constitutes only 7% of the total rainfall, there is potential for improvement. TOPSIS and RST approach proves valuable for potential recharge areas mapping. This integrated approach underscores the significance of informed resource management in addressing water challenges in front to climate change. Thus, the combination of parametric methods and MCDM approaches such as TOPSIS, has shown its efficiency in decision for classifying aquifer recharge zones and will be an effective tool to assist researchers in this field.

Assessment of Fluoride Release and Recharge of Giomer After Recharge With Two Different Topical Fluoride Materials and Two Durations: An In Vitro Study

Abstract Aims: The objectives of this study were to determine the fluoride release from a giomer after 24 h, 1 week, and 1 month) and to examine the recharge ability of the giomer after recharge with two different topical fluoride materials and two different durations. Materials and Methods: This is an in vitro study that involved the use of 72 specimens of the tested material; the specimens were divided randomly into three main groups (24 h., 1 week, and 1 month group). Each group consisted of 24 specimens, out of which 12 specimens were recharged with fluoride varnish (six specimens for 12 h and six specimens for 24 h.) and 12 specimens were recharged with APF gel (six specimens for 1 min and six specimens for 4 min). First fluoride release was measured from the tested specimens, and then all of the tested specimens were recharged with different topical fluoride materials with different durations. One-way analysis of variance (ANOVA) and Duncan’s multiple range test were used to determine the significant differences among the groups. The statistical results were considered significant at P ≤ 0.05. Results: The statistical ANOVAs showed there were no statistical significant variations in the mean values of release of all specimens in the 24-h and 1-week group, but there was a highly statistically significance difference in the mean values of release of all specimens in the 1-month group, and after recharge with FV (12 h; 24 h) and APF gel (1 min; 4 min), there was a highly statistically significance difference in the mean values of fluoride release after recharge in the groups (24 h, 1 week, and 1 month). Conclusions: The amount of fluoride released from the giomer was more in the 24-h. group than in other groups. Recharge with APF gel released more fluoride than fluoride varnish. Increasing the time of giomer contact with the recharging material resulted in a greater uptake of fluoride.

Assessment of groundwater recharge and connectivity with surface water in a mountainous watershed using natural tracers in Daejeon, Korea

The water supply from headwater streams in mountainous regions is considered an important source for sustaining both water quality and quantity in lowland areas. The Korean terrain is characterized by mountainous regions, the hydrological environment is significantly impacted by seasonal weather conditions. This study focused on investigating the hydrochemistry and isotopic composition of groundwater and surface water to identify hydrological connectivity within a mountainous watershed area in Daejeon, Korea. The estimated recharge rate using water budget methods suggests that approximately 20% of the total precipitation contributes to groundwater recharge in this site. The δ18O–δ2H values of the water samples indicate a meteoric water source for groundwater recharge, while the isotope composition of surface water reveals altitude effects, implying that groundwater recharges at a higher altitude region. Additionally, water revealed altitude effects suggesting that the groundwater was inferred to recharge at a higher altitude region. The hydrochemical conservative components (87Sr/86Sr ratio and Cl−) indicate that this watershed undergoes temporary similar water–rock interactions along its flow path, but it is also impacted by anthropogenic contaminants from the surrounding public area. The results of the three-component endmember mixing analysis demonstrate that groundwater is predominantly influenced by surface water, indicating a close interrelationship among various water bodies in mountain hydrology. These findings provide a comprehensive approach to water resource management by combining recharge rate estimation and the assessment of water body connectivity using natural tracers.

Modelling groundwater recharge, actual evaporation, and transpiration in semi-arid sites of the Lake Chad basin: the role of soil and vegetation in groundwater recharge

Abstract. The Lake Chad basin, located in the centre of northern Africa, is characterized by strong climate seasonality with a pronounced short annual precipitation period and high potential evapotranspiration. Groundwater is an essential source for drinking-water supply, as well as for agriculture and groundwater-related ecosystems. Thus, assessment of groundwater recharge is very important although also difficult because of the strong effects of evaporation and transpiration, as well as the limited available data. A simple, generalized approach, which requires only limited field data, freely available remote sensing data, and well-established concepts and models, is tested for assessing groundwater recharge in the southern part of the basin. This work uses the FAO dual-Kc concept to estimate E and T coefficients at six locations that differ in soil texture, climate, and vegetation conditions. Measured values of soil water content and chloride concentrations along vertical soil profiles together with different scenarios for E and T partitioning and a Bayesian calibration approach are used to numerically simulate water flow and chloride transport using Hydrus-1D. Average groundwater recharge rates and the associated model uncertainty at the six locations are assessed for the 2003–2016 time period. Annual groundwater recharge varies between 6 and 93 mm and depends strongly on soil texture and related water retention and on vegetation. Interannual variability of groundwater recharge is generally greater than the uncertainty of the simulated groundwater recharge.

Groundwater recharge processes in the Lake Chad Basin based on isotopic and chemical data

The Lake Chad Basin is Africa’s largest endorheic basin. Because water supply for the rural population and most of the urban population depends on groundwater, assessment of groundwater recharge is crucial. Recharge sources for the upper Quaternary aquifer are precipitation, rivers, and swamps. Using water chemistry, and environmental (18O, 2H, 3H) and carbon (14C) isotopes, recharge processes can be assessed and groundwater ages roughly estimated. For this purpose, more than 1,000 samples from groundwater, surface water and precipitation were analysed for hydrochemistry and environmental stable isotopes. Furthermore, 3H measurements and 14C values of dissolved inorganic carbon for groundwater from the northeastern part of the Basin are included in the evaluation. The environmental isotope distribution shows recent recharge from precipitation north of Lake Chad (Kanem Region), where very low 3H values indicate occurrence before the 1960s bomb peak. Focused recharge from fresh river water is typical for Salamat Region in south Chad and the Komadugu Yobe wetlands between Nigeria and Niger. Slightly high δ-values in water occur in the Waza Logone area between Chad and Cameroon. Groundwater along the Lake Chad shore and the Bahr el Ghazal corridor show high δ-values (δ18O –0.78 to 7.45‰, δ2H –13.6 to 30.8‰). Recharge is caused by surface water that undergoes evaporative processes before percolation. Groundwater ages of 600–4,150 years, estimated from 14C analyses combined with high SO4 concentrations, along the Bahr el Ghazal indicate that recharge was caused by residuals of the Mega Lake before it dried out completely.

Assessment of aquifer recharge and groundwater availability in a semiarid region of Brazil in the context of an interbasin water transfer scheme

Particularly in arid and semiarid areas, more and more populations rely almost entirely on imported water. However, the extent to which intentional discharge into transiting riversystems and unintentional leakage may be augmenting water resources for communities along and down gradient of the water transfer scheme has not previously been subject to research. The objective of this study was to assess both the potential of a large-scale watertransfer (WT) scheme to increase groundwater availability by channel transmission losses in a large dryland aquifer system (2,166 km²) in Brazil, and the capability of the receiving streams to transport water downstream under a prolonged drought. An integrated surface-water/groundwater model was developed to improve the estimation of the groundwater resources, considering the spatio-temporal variability of infiltrated rainfall for aquiferrecharge. Aquifer recharge from the WT scheme was simulated under prolonged drought conditions, applying an uncertainty analysis of the most influential fluxes and parameters. The annual recharge (66 mm/year) was approximately twice the amount of water abstracted(1990–2016); however, the annual recharge dropped to 13.9 mm/year from 2012 to 2016, a drought period. Under similar drought conditions, the additional recharge (6.89 × 106 m³/year) from the WT scheme did not compensate for the decrease in groundwater head in areas thatdo not surround the receiving streams. Actually, the additional recharge is counteracted by a decrease of 25% of natural groundwater recharge or an increase of 50% in pumping rate; therefore, WT transmission losses alone would not solve the issue of the unsustainable management of groundwater resources.

Assessment of the potential recharge by infiltration in the northern zone of Loreto, Baja California Sur, Mexico

En este estudio se realiza una estimación de la recarga potencial por infiltración de lluvia en la zona norte de Loreto en el estado de Baja California Sur, México, donde se incluyen las cuenca de Gombedor, Loreto y San Bruno; ello, en respuesta a la escasa información en el área y la urgencia que representa la presión sobre los recursos hídricos. A partir de datos de precipitación y temperatura de las estaciones climáticas cercanas al municipio de Loreto se realizaron modelos de precipitación y temperatura mediante el método de interpolación Kriging; con estos modelos se calcularon la evapotranspiración, el escurrimiento y finalmente la infiltración potencial. Los resultados obtenidos fueron de 5.37 Mm3 año-1 para la cuenca de Gombedor, 13.37 Mm3 año-1 en la cuenca de San Bruno y 7.62 Mm3 año-1 en el norte de Loreto. En la cuenca San Bruno se encuentran los pozos de extracción que surten a la ciudad de Loreto, aquí se estimó una recarga potencial de 1.97 Mm3 año-1 con una precipitación media anual de 207 mm. La infiltración por la lluvia es una de las fuentes más importantes de recarga de los acuíferos, junto con los flujos subterráneos, y la recarga artificial o inducida. El modelo hidrogeológico conceptual permite abordar más fácilmente la situación de la cuenca para elaborar estrategias de manejo. Este tipo de modelos puede resultar eficiente donde no hay aguas superficiales, ya que brinda un buen pronóstico para zonas con pocos datos o que son difícil acceso mediante el uso de técnicas de sistemas de información geográfica y geoestadísticas.

Identifying groundwater recharge and discharge zones using geostatistical simulation of hydraulic head and its derivatives

Identifying groundwater flow directions and the locations of recharge and discharge areas is critical for effective groundwater management. Groundwater flow directions, the concavity and the locations of extrema (i.e., minima and maxima) can be assessed using the first and second derivatives of the hydraulic head surface. We developed a geostatistical method to jointly simulate hydraulic head and its first and second derivatives using sequential Gaussian simulation. The derivative values were used to identify regional groundwater flow directions, and the second derivative test was used to probabilistically map the concavity and the locations of extrema in the hydraulic head surface. By comparing the mapped concavity and extrema to known features, it was possible to attribute areas of recharge and discharge to physical features of the system, such as rivers, lakes and geological outcrops. This was applied to Triassic aquifers in the Galilee Basin (Queensland, Australia) to delineate the likely recharge and discharge areas. This provided an objective assessment of likely recharge and discharge zones and their uncertainty, which is an important addition to a region where the hydrogeology has been the subject of much conjecture.

Frequency domain water table fluctuations reveal impacts of intense rainfall and vadose zone thickness on groundwater recharge

Abstract. Groundwater recharge is difficult to estimate, especially in fractured aquifers, because of the spatial variability of the soil properties and because of the lack of data at basin scale. A relevant method, known as the water table fluctuation (WTF) method, consists in inferring recharge directly from the WTFs observed in boreholes. However, the WTF method neglects the impact of lateral groundwater redistribution in the aquifer; i.e., it assumes that all the WTFs are attributable to recharge. In this study, we developed the WTF approach in the frequency domain to better consider groundwater lateral flow, which quickly redistributes the impulse of recharge and mitigates the link between WTFs and recharge. First, we calibrated a 1D analytical groundwater model to estimate hydrodynamic parameters at each borehole. These parameters were defined from the WTFs recorded for several years, independently of prescribed potential recharge. Second, calibrated models are reversed analytically in the frequency domain to estimate recharge fluctuations (RFs) at weekly to monthly scales from the observed WTFs. Models were tested on two twin sites with a similar climate, fractured aquifer and land use but different hydrogeologic settings: one has been operated as a pumping site for the last 25 years (Ploemeur, France), while the second has not been perturbed by pumping (Guidel). Results confirm the important role of rainfall temporal distribution in generating recharge. While all rainfall contributes to recharge, the ratio of recharge to rainfall minus potential evapotranspiration is frequency-dependent, varying between 20 %–30 % at periods <10 d and 30 %–50 % at monthly scale and reaching 75 % at seasonal timescales. We further show that the unsaturated zone thickness controls the intensity and timing of RFs. Overall, this approach contributes to a better assessment of recharge and helps to improve the representation of groundwater systems within hydrological models. In spite of the heterogeneous nature of aquifers, parameters controlling WTFs can be inferred from WTF time series, providing confidence that the method can be deployed in different geological contexts where long-term water table records are available.

Environmental isotopes and hydrochemical investigation to evalute the seepage from Dwarege dam reservoir South Iraq (Missan Governorate)

In the last few decades, a series of new Hydrological techniques have been developed to help in the assessment of leakage, Seepage and Recharge. The aim of this search is using the environmental isotopes (18O, 2H) combined with Physico-Chemical parameters (EC, Ca2+, Cl- , TDS etc.) have been employed to identify source of Seepage and Leakage pathways within Dwarege Reservoir-South Iraq. It’s the one of important reservoirs in the south of Iraq. In the present study, describes the relationship between the intake water and water dams. Using three types of water, (groundwater, Dwarege Reservoir and after reservoir). The results show that the stable isotopes composition of Groundwater from (-2.50) to ( -2.58%) for ä 18 O and from (–6.13) to ( -6.23%) for äD, respectively. The stable isotopes content of Dwarege reservoir in the studied area ranged from (-2.47%) and (-2.57%) for ä 18 O and from (-7.6%) to (-7.2%) for äD, while the water after Dam recorded (-1.38) for ä 18 O and (-2.27%) for äD, respectively. The hydrochemical facies of groundwater and Dwarege Dam is Ca-SO4 , while the hydrochemical facies of surface water after Dam is Na-Cl, due to the lithology of study area. Based on the result of isotopic values and hydrochemical facies there is interconnection between groundwater and surface water in the study area.

Assessment and feasibility of the potential artificial groundwater recharge in semi-arid crystalline rocks context, Biteira district, Sudan

In Sudan, up to date, artificial recharge with surface water has been rarely investigated in papers. This paper proposed a method to identify and evaluate a potential site for artificial recharge of groundwater in the Biteira district. The targeted area lies in the southern part of Sudan and is underlain by basement rocks. The population's growth, alongside climate change which caused desertification, has augmented water resources' stress over recent years. Moreover, an alternative water resource of groundwater is essential due to limited aquifers. The research integrates the geology, geomorphology, hydrometeorology, and soil texture of the area coupled with infiltration tests data to overcome this problem. In addition, an analysis of the Landsat image to obtain lineaments and geological structures has been done. The results show the average infiltration rate is 2.35 m3/m2, and groundwater flow is estimated to be WWN direction. The study area is suitable for groundwater recharge in case of the construction of a check dam as infrastructure that can pave, favour promoting the artificial recharge. The surface storage capacity achieved at the site for recharge purposes is 20.73 × 106 m3.

Assessment of the potential recharge by infiltration in the northern zone of Loreto, Baja California Sur, Mexico

Assessment of the potential recharge by infiltration in the northern zone of Loreto, Baja California Sur, Mexico

Assessment of Recharge in Shallow Groundwater Aquifers Using Soil and Water Assessment Tool: A Case Study of the Thuthapuzha Subbasin

Aim: To study the spatial and temporal variability of shallow groundwater recharge using the Soil-Water Assessment Tool (SWAT) model on a watershed scale.
 Place of Study: Thuthapuzha subbasin.
 Methodology: Groundwater recharge is a significant factor in groundwater simulations, which may aid in realistic groundwater resource management and decision-making. The study assessed the spatial and temporal variability of shallow groundwater recharge in the Thuthapuzha subbasin using a semi-distributed hydrological model called SWAT. Land use map, soil map, topographic data (Digital Elevation Model [DEM]), and basic meteorological data are the general input data necessary to run the SWAT model. 
 Results: Results from the study show that the average annual groundwater recharge in the Thuthapuzha subbasin estimated using the SWAT model is 201.26 mm/year (from 1992 to 2019). According to the long-term water balance of the whole watershed, runoff accounts for 60% of the average annual precipitation. Evapotranspiration accounts for 27% of the average yearly precipitation in the research region. Meanwhile, groundwater recharge is barely 8% of the average annual rainfall. The topography and land use in the study region were found to influence the spatial variability of groundwater recharge. The groundwater recharge also showed monthly and annual fluctuations. While the major rainy season (South-West monsoon) lasts from June to September, July to September period shows the highest recharge. The comparison of recharge obtained from the SWAT model with the recharge estimated using the rainfall infiltration factor (RIF) method shows a good correlation (R2 = 0.68).
 Conclusion: SWAT modeling is a feasible option over field-scale approaches for assessing groundwater recharge and its response to various influences on a catchment scale.

Assessing and delineation of groundwater recharge areas in coastal arid area southern Tunisia

In Gabès region (southeastern Tunisia), given the semi-arid to arid climate conditions, groundwater is an essential resource to supply the growth needs of the socio-economic development. To ensure sustainable development and preserve water resources, a careful estimation of the present day recharge amount and the delineation of the potential zones of rainfall precipitation are of required for an accurate evaluation of regional water balance. In this context, this study aims to a preliminary assessment of groundwater recharge in Gabes basin in regard to the delineation of the potential recharge areas of phreatic aquifers. Thus, a geological and hydrogeological collected database coupled with remote sensing techniques (RST) were used for the determination of the lateral variation of recharging zone, Treatment by ArcGIS and Matlab softwares and Kohonen self-organizing maps (K-SOM) approaches. The obtained results indicate that five recharge potential areas have been identified and classified as 27% very low, 23% low, 40% moderate recharge, 7% good and 3% very good potential recharge located principally on southern part of the study region. This distribution is controlled principally by the geomorphological, geologic, and hydrogeologic features of the region. Reasonable management strategies based on a perennial exploitation of these low renewable resources are required to optimize the water dependent socio-economic development. The estimated groundwater potential recharge of Gabès aquifer system using K-SOM and RST is of 11.4 Mm3 y−1. This recharging rate is very low it present 7% of the total rain, thus it must be ameliorated. K-SOM and RST approach is a useful method for groundwater potential recharge mapping and is a helpful of wells establishment and groundwater sustainable management. an isotopic analyses is recommended to ameliorate the decision maker to establish the adequate strategy.

A Feasibility Assessment of Potential Artificial Recharge for Increasing Agricultural Areas in the Kerbala Desert in Iraq Using Numerical Groundwater Modeling

Groundwater in Iraq is considered to be an alternative water resource, especially for areas far away from surface water. Groundwater is affected by many factors including climate change, industrial activities, urbanization, and industrialization. In this study, the effect of artificial recharge on the quantity of groundwater in the Dibdibba unconfined aquifer in Iraq was simulated using a groundwater modeling system (GMS). The main raw water source used in the artificial recharge process was the reclaimed water output (tertiary treatment) from the main wastewater treatment plant (WWTP) in Kerbala, with 20 injection wells. After calibration and validation of the three-dimensional numerical model used in this study and taking wastewater recharge rates into account, two different scenarios were applied to obtain the expected behavior of the aquifer when the groundwater levels were augmented with 5% and 10% of the daily outflow production of the WWTP in Kerbala. The model matched the observed head elevations with R2 = 0.951 for steady state and R2= 0.894 for transient simulations. The results indicate that the injection of treated water through 20 wells raised the water table in more than 91 and 136 km2 for 5000 and 10,000 m3/day pumping rates, respectively. Moreover, increasing the volume of water added to the aquifer could lead to establishing new agricultural areas, spanning more than 62 km2, extending about 20 km along the river.

A study of the suitability assessment of groundwater recharge by water supply in the Yongding River

Due to the effect of climate changes and human activities, groundwater over-exploitation and aquifer depletion have become global issues of concern. Artificial recharge of groundwater through a river has been paid more attention among a variety of artificial intervention measures. It is found that not all rivers or river reaches are suitable for artificial recharge of groundwater owing to the limitations of recharge potential by infiltration and storage capacity of the vadose zone. At present, there is still a lack of widely accepted suitability assessment methods. In this study, the Yongding River in the Beijing Plain section and the underlying aquifer are taken as the study area and the case study is carried out. Moreover, the measured data are used to verify the results. The suitability assessment model (LMBGITSC model) constructed by the index system method includes eight indexes: land use types of riverbed, sediment types of riverbed, channel width, channel topographic slope, medium types of the vadose zone, thickness of the vadose zone, specific yield of the vadose zone and horizontal permeability of the vadose zone. The results show that the suitability of groundwater recharge in the Yongding River changes from good degree to medium degree along the river flow direction (except the reaches carried out anti-seepage engineering), presenting a step-type evolution law. The proposed method is of good applicability and can also provide reference for similar regions.

Computation of groundwater recharge prospect in urban environment for sustainable water security

The present work discusses the assessment of groundwater recharge in urban environment of Noida City, National Capital Region (NCR), India, by considering earth observation technology, analytical hierarchical process, and field observation for sustainable aquifer management. The important hydrogeological factors of the city such as land use, water level, geology, soil type, rainfall, normalized difference vegetation index (NDVI), impervious surface area (ISA), and slope were evaluated from satellite data along with published maps and field survey to understand the hydrogeological characteristics under GIS environment. The final observation shows that about 4.9% area demarked as very good groundwater recharge potential, high (9.8), medium (44.4), and (40.9%) low groundwater recharge potential respectively based on integrated contribution of all groundwater recharge contributing factors. The very good potential zones are mainly associated with low lying and near river side and poor are found in highly urbanized area where recharge is very low and open lands were converted into impervious layer. The observed results also verify with actual bore well yield data; its shows good correlation and satisfaction. Findings of the present work clearly indicate that large population and high demand of water in the last two decades cause stress in potential aquifer and urbanization to continue taking place, which will put the city in a very alarming situation in the very near future, if proper recharging and management plan were not to take place. The findings of present work will be very essential data base for water resource management and planning for water security.

Assessment of groundwater recharge along the Guarani aquifer system outcrop zone in São Paulo State (Brazil): an important tool towards integrated management

The quantification of the groundwater recharges represents useful and important information for water resource management. The volumes of infiltrated water are essential to maintain water storage in aquifers, as well as to the discharge of groundwater towards the rivers, especially in tropical areas. The outcrop zones of the Guarani Aquifer System (GAS) in Sao Paulo state (Brazil) are considered as their most important recharge areas; therefore, knowledge about recharge rates and processes is essential. They are also highly vulnerable to groundwater contamination, another important reason to protect them. This study aimed to estimate spatial and temporal variations of groundwater recharge in the mentioned GAS outcrop zones. Recharge rates were estimated using the Spatial Recharge (SR) method and then compared to other two traditional methods (base flow separation and water table fluctuation method). The SR method uses the spatial distribution of the evapotranspiration and rainfall from GLDAS and TRMM databases and the runoff after the Soil Conservation Service (SCS) empirical method. All three methods revealed similar estimates for groundwater recharge, ranging from 150 to 370 mm year−1 (about 17% of the total rainfall). Despite its intrinsic limitations, the SR method allowed robust recharge estimation with ability to cope with spatial and temporal variations, as well, especially in areas lacking hydrological monitoring programs. The SR method provides valuable information for water management policymakers and stakeholders to minimize impacts related to climatic variations and inappropriate land use on recharge processes.