Climate change, driven by increased rainfall variability and rising temperatures, exacerbates water scarcity and significantly affects household water, sanitation, and hygiene practices. In response, households often adopt coping mechanisms that, while intended to conserve water, may result in reduced hygiene and sanitation practices, thereby increasing exposure to health risks. In the Bahi Swamp sub-basin of Tanzania, acute water scarcity prevails due to semi-arid climate conditions, climate change, and inadequate water management, posing significant threats to local livelihoods. To assess household water scarcity, coping strategies, challenges, and measures for sustainable water management, a semi-structured questionnaire was administered to 260 households. The results indicate that most households experience persistent water shortages, causing conflicts over water use. Most households (92%) adopted coping strategies such as purchasing water, storing water, reducing daily consumption, rainwater harvesting, and switching water sources; however, some of these strategies may increase the risk of water-borne diseases and negatively affect overall wellbeing. Rainwater harvesting could serve as an effective strategy for addressing domestic water scarcity. Lack of knowledge and training, and financial constraints are key challenges to sustainable water resource management. Crucial measures include improved access to training and resources, along with financial support or subsidies.

The Bahi Swamp sub-basin, situated in the semi-arid region of central Tanzania, is facing increasing water scarcity due to factors such as climate change and population growth, posing significant threats to food security and community livelihoods. To address the challenge of water availability in the area, this study aims to assess community awareness and practices in sustainable water resource management, with a focus on water harvesting. Data were collected using a semi-structured questionnaire administered to 260 participants. The results show that 47

Inequitable access to marketplaces in rapidly urbanizing cities often results from poorly coordinated spatial planning, leading to service congestion in core areas and critical undersupply in expanding peri-urban neighborhoods. In Dodoma City, Tanzania, the absence of integrated spatial decision-support tools constrains the evidence-based allocation of new marketplace facilities. This study develops and applies a geospatial decision-making framework to identify optimal locations for prospective marketplaces using Geographic Information Systems (GIS) integrated with the Fuzzy Analytic Hierarchy Process (F-AHP). Seven spatial criteria, namely population density, road network connectivity, land use/land cover (LULC), proximity to built-up areas, slope, elevation, and geomorphology, were standardized, weighted via F-AHP, and combined through weighted overlay analysis to generate a Potential Market Areas Map (PMAM). The F-AHP weighting revealed a clear hierarchy, with population density (0.388) and road connectivity (0.261) emerging as the most influential determinants. Validation against 36 existing market locations yielded an excellent Area Under the Curve (AUC) value of 0.968, confirming strong spatial discrimination. Crucially, the framework advances beyond theoretical suitability mapping by integrating the PMAM with administrative ward boundaries and land-use/land cover maps, identifying specific high-priority location clusters in underserved wards such as Mbalawala, Mpunguzi and Ipala. The study provides urban planners and policymakers with a transparent, reproducible decision-support tool for evidence-based site selection that promotes spatial equity, reduces travel burdens, and supports sustainable urban development in Dodoma and comparable rapidly growing African cities.

ABSTRACT Freshwater is the most important resource because it is vital for human health, agriculture, the environment, urbanisation, and sustainable economic growth. This study uses time-series analysis of World Bank data for the period 1980–2020 to analyse status of drinking water supply in the African Great Lakes region. The results show that Kenya has been a water-stressed country since 2010, as it is withdrawing more than 25% of its renewable freshwater resources, while Rwanda is likely to soon become a water-stressed country, while Tanzania, Burundi, and Uganda are far from being water-stressed countries. In the Democratic Republic of the Congo, freshwater resources are used the least, which is attributed to the political instability and conflict cycles in the country. To achieve Sustainable Development Goal 6, clean water and sanitation for all, in the study area by 2030, Tanzania and Uganda will have to quadruple their current efforts, while Rwanda and Kenya will have to increase their current efforts sixfold, and Burundi will have to increase its current efforts eightfold, while the Democratic Republic of the Congo will have to increase its current efforts 30 times, which is almost impossible; these efforts should be reflected in the budgets of the water sector.

This study provides a comprehensive analysis of the groundwater potential of hard rock aquifers in five diverse African case study areas: Lake Tana Basin and Beles Basin in northwestern Ethiopia and Mount Meru in northern Tanzania (comprising volcanic aquifers); the Mekelle area in northern Ethiopia and Jifarah Plain in Libya (consisting of sedimentary aquifers). The evaluation of recharge, transmissivity, and water quality formed the basis of qualitative and quantitative assessment. Multiple methods, including water table fluctuation (WTF), chloride mass balance (CMB), physical hydrological modeling (WetSpass), baseflow separation (BFS), and remote sensing techniques like GRACE satellite data, were employed to estimate groundwater recharge across diverse hydrogeological settings. Topographic contrast, fractured orientation, lineament density, hydro-stratigraphic connections, hydraulic gradient, and distribution of high-flux springs were used to assess IGF from Lake Tana to Beles Basin. The monitoring, sampling, and pumping test sites took into account the high hydromorphological and geological variabilities. Recharge rates varied significantly, with mean values of 315 mm/year in Lake Tana Basin, 193 mm/year in Mount Meru, and as low as 4.3 mm/year in Jifarah Plain. Transmissivity ranged from 0.4 to 6904 m2/day in Lake Tana Basin, up to 790 m2/day in Mount Meru’s fractured lava aquifers, and reached 859 m2/day in the sedimentary aquifers of the Mekelle area. Water quality issues included high TDS levels (up to 3287 mg/L in Mekelle and 11,141 mg/L in Jifarah), elevated fluoride concentrations (>1.5 mg/L) in 90% of Mount Meru samples, and nitrate pollution in shallow aquifers linked to agricultural practice. This study also highlights the phenomenon of inter-basin deep groundwater flow, emphasizing its role in groundwater potential assessment and challenging conventional water balance assumptions. The findings reveal that hard rock aquifers, particularly weathered/fractured basalt aquifers in volcanic regions, exhibit high potential, while pyroclastic aquifers generally demonstrate lower potential. Concerns regarding high fluoride levels are identified in Mount Meru aquifers. Among sedimentary aquifers in the Mekelle area and Jifarah Plain, limestone intercalated with marl or dolomite rock emerges as having high potential. However, high TDS and high sulfate concentrations are quality issues in some of the areas, quite above the WHO’s and each country’s drinking water standards. The inter-basin groundwater flow, investigated in this study of Beles Basin, challenges the conventional water balance assumption that the inflow into a hydrological basin is equivalent to the outflow out of the basin, by emphasizing the importance of considering groundwater influx from neighboring basins. These insights contribute novel perspectives to groundwater balance and potential assessment studies, challenging assumptions about groundwater divides.

Despite the introduction of the perimeter blasting technique at the Tulawaka Gold Mine, the mine continued to suffer from an overbreak of mine development headings, with an average overbreak of 24% every 22 m, which is approximately twice the acceptable 10% overbreak. The causes of this problem include ineffective drilling practices and uneven and excessive charging of explosives, resulting in a slightly high powder factor of 3.94 kg/m 3 instead of 3.8 kg/m 3 , as per the design. The problem of overbreak resulted in ore dilution, a longer mine development cycle time and additional costs of approximately US$ 45 per cut, especially in mucking and hauling processes. This study proposed and recommended new drill and blast designs to solve this problem. Compared to the existing design, the proposed new drill design has a total of 12 fewer drill holes; this is a significant number of holes, which significantly reduces drilling costs. The proposed new blast design consumes approximately 25 kg less ANFO than the existing practice. Moreover, the study showed that large drives in the Star and Comet in the Geita Gold Mine suffer the most from the problem of ineffective advance per cut. One of the causes of ineffective advances per cut is the low amount of explosives used per cut compared to the planned amount.

This study aimed to investigate the hydrochemical and hydrogeochemical facies and mechanisms controlling groundwater quality from the northern and eastern parts of Kilwa district and Songosongo Island in Tanzania. Multifaceted methods were used to analyze the hydrochemical properties of water in relation to local geology and proximity to the Indian Ocean. The pH of the groundwater ranged from 5.18 to 7.56 with an average value of 6.64 which is slightly acidic. Electrical Conductivity (EC) ranged from 354 to 1429.50 mu S/cm with an average value of 1652.6 mu S/cm while Total Dissolved Solids (TDS) values varied from 170 to 1825 mg/L with an average value of 918.8 mg/L. The average values for Ca2+, Mg2+, Na+, and K+ were 36.9, 21.4, 152.5, and 13.31 mg/L, while for NO3-, Cl-, HCO3-, and SO42- were 2.1, 256.3, 156.6, and 45.8, respectively. The study found that groundwater closest to the ocean had elevated values of TDS, Na+, and Cl- and were more affected by seawater intrusion compared to those further inland. The dominant groundwater type was established to be Na-Cl mostly nearest to the ocean while Ca-Mg-Cl was more encountered towards the inland. The groundwater in the northern and eastern parts of Kilwa is mainly controlled by seawater intrusion and recharge water. The Neogene formations consisting of clay, silts, coastal sands, and alluvium had lower Na+, Cl-, EC, and TDS values than the Paleogene which is more influenced by marine sediments. Thus, these findings call for improved groundwater monitoring to track changes in water quality since several parameters including sodium, magnesium, chlorides, TDS, EC, and pH were higher than recommended values for drinking purposes. However, the majority of the water samples were suitable for human consumption.

•Appropriate validation methods ensure the reliability of groundwater potential maps.•125 scientific articles were reviewed, 85 % of articles contain validated maps.•In the articles studied, 10 methods with different parameters were used.•Field data reflecting aquifer productivity are more appropriate for validation.

Groundwater is a very important resource for socio-economic development. The uncertainty of where potential groundwater resources is located often causes some groundwater development projects to fail. It is common for water resources development projects hitting dry wells after heavy investments of resources. In Mpwapwa District, borehole drilling locations are uncertain, determined by trial-and-error techniques based on geophysical survey methods that involve the study of the behaviour of rock and soil types in specific geological locations. To reduce such uncertainty, this study used remote sensing and GIS-based Fuzzy Analytical Hierarchical Process (F-AHP) to simulate groundwater potential zones (GWPZ) in Mpwapwa District, Dodoma region, Tanzania. The F-AHP model was used to reclassify, weight, and rank various thematic maps, including lithology, soil types, drainage density, lineament, magnetic intensity, slope and elevation. The overall GWPZ map was created by combining the seven (7) ranking thematic map layers in a GIS environment. The resulting GWPZ map that was then validated using two methods: overlaying method and area under the curve (AUC) method. The resulting GWPZ map shows that 19%, 31%, 28% and 22% of the area are classified as very good, good, moderate, poor and very poor zones, respectively. The accuracy of the generated map is 72% using the overlaying method and 93% using the AUC method.

Groundwater recharge maps developed using GIS techniques are important tools that aid the identification of recharge zones. This map must be validated with field data. This study reviewed 63 articles published between 2007 and 2024 to examine the data used to validate these maps and identify the appropriate data for validation. About 50 % of articles reviewed contain non-validated maps, suggesting that many researchers did not do map validation. A total of 12 types of data have been identified to validate groundwater recharge maps, including electrical conductivity, total dissolved solids, stable isotope, and the magnitude of groundwater level fluctuations. Moreover, this review shows that 50 % (n = 6) of the identified data have high uncertainty and are therefore inappropriate for validation, including groundwater level, nitrate concentration, well yield, and aquifer transmissivity. Data reflecting groundwater residence time are more appropriate for validation.

This study investigates the localities of low and high F- groundwaters in the aquifer system on the flanks of Mount Meru to come up with guidelines to provide groundwater that can be used for drinking water supply without health impacts on the population. Our study focuses on parts of the flanks which were only partially or not at all covered by previous research. Results show that the groundwater chemistry of F--rich NaHCO3 alkaline groundwater in the area is controlled by dissolution of weathering aluminosilicate minerals, dissolution of F--bearing minerals, the precipitation of carbonate minerals as secondary products and the dissolution of magmatic gases. The low F- groundwaters which can be used for drinking water supply without health impacts under the WHO limit (1.5 mg/L) are the low-fluoride springs from the high altitude recharge areas on the eastern and north-western flanks of Mount Meru inside Arusha National Park, whereas on the western flank the groundwater meets the Tanzanian limit (4.0 mg/L). On the south-western flank, the shallow aquifer composed of alluvium deposits at lower elevations, shows F- values that meet the Tanzanian limit. One of the three investigated deep boreholes on this flank also meets the Tanzanian limit, suggesting a possibility of finding relatively low F- groundwaters in the deep aquifer. Yet, in general, the deposits at lower elevations are found to contain high to very high F- values, whereas the deposits at high elevations contain groundwater of low F- values. Thus, the internal texture and grain size of geological formations, the burial depth of these formations and the water residence times are the factors determining the groundwater mineralisation and F- concentrations in the area. The study identified that the deep hydrothermal system has influence on the high F- groundwaters on the eastern and north-eastern flanks of Mount Meru.

Estimating groundwater recharge, direct runoff and baseflow is essential for understanding groundwater resource availability and managing groundwater systems. This study estimates groundwater recharge, direct runoff and baseflow on two slopes of Mount Meru: the northern and southern slopes using the water-table fluctuation (WTF) method and baseflow separation technique. High-frequency groundwater level measurements in five shallow wells over three hydrological years from 2018 to 2021 were analysed, while streamflow data in four gauging stations over nine hydrological years from 2010 to 2019 were used. The results of the WTF method show that the aquifer undergoes an average recharge of 544 mm/year and 90 mm/year on the south-western and north-eastern slopes, respectively. On average, this recharge is about 53% and 13% of the annual rainfall on each slope. The baseflow results show that the aquifer on the south-eastern and north-western slopes recharges an average of 88 mm/year and 54 mm/year, respectively, which is on average about 12% and 7% of annual rainfall, respectively. In general, the high recharge on the south-western slope is attributed to the high rainfall, and the high hydraulic conductivity and high hydraulic diffusivity of the pyroclastic deposits compared to the debris avalanche deposits on the north-eastern slope. In addition, debris avalanche deposits show homogeneous recharge conditions, while pyroclastic deposits show heterogeneous recharge conditions. The WTF method can be useful to identify areas of preferential recharge so that preferential groundwater flow paths can be mapped for focused recharge of surface runoff during the rainy season.

The Dodoma region located in Central Tanzania is a semi-arid area characterised by scarce surface water resources. Because of climate change and dependence on groundwater resources in the Dodoma urban area, there is currently an increased demand for water due to low groundwater recharge and high groundwater withdrawals due to the growing population. There is therefore a need to explore potential deep aquifer systems around the Dodoma urban area to meet the increasing water demand. This study uses lithological logs, pumping tests, and electromagnetic survey data to delineate the subsurface lithologies to locate potential deep aquifer system in the area. Results show that the shallow aquifer system is unconfined in some areas with resistivity values ranging from 11 to 28 Omega m and semi-confined in other areas with resistivity values ranging from 19 to 27 Omega m. The unconfined aquifer extends up to 60 m, while the semi-confined aquifer extends between 50-55 m and 65-120 m. The study found a potential deep aquifer system at a depth of between 200 and 290 m, with resistivity values ranging from 11 to 20 Omega m. Currently, this deep aquifer system has not been exploited as most boreholes in the area are only up to 150 m deep. The main lithology in the study area is weathered and fractured granite, with different degrees of weathering and fracturing, indicating a hard-rock aquifer system. This study adds valuable knowledge on the location of potential deep aquifer systems in the area for proper groundwater utilisation and management.

The study focuses on assessing the suitability of groundwaters used for irrigation on the flanks of Mount Meru in Northern Tanzania and providing a map showing the spatial variability of irrigation water quality for proper irrigation and crop management in the area. Results of irrigation water quality index (IWQI) show that the groundwaters (F --rich NaHCO3 alkaline waters) used for irrigation on the eastern, northern, western, and south-western flanks of Mount Meru are not suitable for irrigation; only 1% (n = 1) of the inventoried groundwater points (n = 76) is classified as good for irrigation use, while 99% (n = 75) of the points are classified as poor to unsuitable for irrigation use. Hence, the study recommends the treatment of groundwaters used for irrigation in the study area by reducing the Na+ concentration and Total Alkalinity (HCO3- + CO32-) using appropriate quantities of amendments. This study would be helpful for water resources management in other similar geological settings.

This study uses classical solute geothermometry analysis to estimate the temperature and circulation depth of the geothermal reservoir around Mount Meru. Five springs affected by magmatic gases from a deep magmatic heat source are investigated; these include two hydrothermal springs. Results from silica geothermometers show that estimated reservoir temperatures range from 70 to 110 degrees C; this corresponds to a low-temperature hydrothermal system. Since Mount Meru is an active volcano, one would expect a high-temperature hydrothermal system; the low temperatures are ascribed to the mixing of hydrothermal and cold recharge waters. The geothermal reservoir is estimated to be about 1.3-1.4 km deep. Thus, the study shows that a low-temperature geothermal energy resource can be found on the eastern flank of Mount Meru.

Understanding of the aquifer structure and its hydraulic properties provides comprehensive knowledge for proper groundwater utilisation and management. This study delineated the aquifer structure using litho-hydrostratigraphical cross-sections, and estimated the hydraulic parameters using single well pumping tests for various locations on and around Mount Meru. Results show that, the aquifer system on the flanks of Mount Meru is a sloping aquifer with sloping beds. On the far east of the eastern flank, the aquifer is composed of debris avalanche deposits, while on the north-eastern and west flanks the aquifer is composed of weathered fractured lava, whereas on the south-western flank, the aquifer is composed of different layers: pyroclastics on the top, weathered fractured lava, weathered pyroclastics, and weathered fractured lava at the bottom. The aquifer is semi-confined on the north-eastern and western flanks; on the north-eastern flank, the overlying debris avalanche deposits acting as an aquitard, while on the western flank, the overlying layers: pyroclastics and unweathered lava acting as an aquitard and aquiclude, respectively. The aquifer is unconfined on the far east of the eastern flank and south-western flank. The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth, while variable, both at the shallow depth of hand-dug wells and the larger depth of boreholes, on the south-western flank; indicating aquifer heterogeneity. On the north-eastern flank, the topmost part of the aquifer, exploited by hand-dug wells, has a low transmissivity (T = 1.3 m2/d) and potential for smaller withdrawals for local water supply with limited consumption, while the upper part of the aquifer, captured by boreholes, has an intermediate transmissivity (T = 35 m2/d) and potential for local water supply, whereas the deeper part of the aquifer has a high transmissivity (T = 788 m2/d) with potential of somewhat regional importance. On the western flank, the aquifer has a very low transmissivity (T = 0.4 m2/d) and potential for local water supply with limited consumption. On the south-western flank, on average, the topmost part of the aquifer, exploited by hand-dug wells, has very low to intermediate transmissivity (range of T: 0.3-21 m2/d), leading to variable potential for smaller withdrawals for local water supply (private consumption), whereas the deeper part of the aquifer, captured by boreholes, has low to intermediate transmissivity (range of T: 9-43 m2/d) and potential for local water supply.

A water quality problem exists in populated areas along the flanks of Mt. Meru in northern Tanzania, with excessively high fluoride (F-) concentrations exceeding the WHO drinking water standards (1.5 mg/L). Little is known about the potential sources of F-among the various rocks types forming the Meru aquifers. Nineteen samples (Debris avalanche deposits (DAD n=4), lava flows n=6, brecciated lava n=4, pumice n=2, scoria n=1, ash n=1, carbonitic n=1) representative of the materials covering the slopes of Mt. Meru were characterized for their mineralogical, chemical, and total and water-soluble F- compositions. Mt. Meru is mainly composed of alkaline volcanic rocks of basaltic to phonolitic composition. The total F- analysis indicated that F-occurs in all rock types with a mean value varying per rock type from 0.6 to 3.2 g/kg. The DAD in the east and northwest of Mt.Meru contained the highest amount of F- (mean 3.1±0.17 g/kg), whilst the lava flow samples had the lowest mean value (0.6±0.25 g/kg). Water rock-interaction experiments further revealed the highest release of F- in the analyzed DAD samples, possibly associated with their weathering status that progressively converted the primary minerals into secondary clay-bearing minerals assemblage, and favoring F- release into the interacting water. Unlike DAD, pumice and ash have a moderately high level of total F- (1.76±0.04 g/kg) yet; release a minimal amount of it through leaching. Petrographic observations showed that the analyzed volcanic rocks consist of volcanic glass and rare F--bearing accessory minerals (amphibole, titanite, biotite, and apatite), among others. Using electron microprobe analysis, the F- concentrations were found to be as high as 3- 6.5 g/kg in the glassy groundmass and up to 4 g/kg, 5 g/kg, and 45 g/kg in accessory phases of titanite, amphibole, and fluorapatite, respectively. Comparing the abundance and the composition of the glassy groundmass with the mineral phases, the former harbors most of the total F-content. The findings of leaching experiments are congruent with past water quality which show that, low F- is found in water from lava and tephra-dominated areas at higher altitudes and Mt. Meru west, respectively. This new information could guide future explorations for safer locations to place wells for water consumption. Itcould also be of interest for other East African Rift sectors and similar volcanic settings. Keywords: Northern Tanzania, East African Rift, Meru volcano, fluoride contamination, volcanic rocks, leaching

The population of the semi-arid areas of the countries in the East African Rift Valley (EARV) is faced with serious problems associated with the availability and the quality of the drinking water. In these areas, the drinking water supply largely relies on groundwater characterised by elevated fluoride concentration (> 1.5 mg/L), resulting from interactions with the surrounding alkaline volcanic rocks. This geochemical anomaly is often associated with the presence of other naturally occurring potentially toxic elements (PTEs), such as As, Mo, U, V, which are known to cause adverse effects on human health. This study reports on the occurrence of such PTEs in the groundwater on the populated flanks of Mt. Meru, an active volcano situated in the EARV. Our results show that the majority of analysed PTEs (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Se, Sr, Pb, and Zn) are within the acceptable limits for drinking purpose in samples collected from wells, springs and tap systems, suggesting that there is no immediate health risk associated with these PTEs. However, some of the samples were found to exceed the WHO tolerance limit for U (> 30 μg/L) and Mo (> 70 μg/L). The sample analysis also revealed that in some of the collected samples, the concentrations of total dissolved solids, Na+ and K+ exceed the permissible limits. The concerning levels of major parameters and PTEs were found to be associated with areas covered with debris avalanche deposits on the northeast flank, and volcanic ash and alluvial deposits on the southwest flanks of the volcano. The study highlights the need to extend the range of elements monitored in the regional groundwater and make a more routine measurement of PTEs to ensure drinking water safety and effective water management measures.

Study region: Mount Meru located in Northern Tanzania.Study focus: Groundwater level monitoring is essential for uncovering the spatial-temporal variation of groundwater levels in a studied aquifer, helping discussions on the sustainable use and management of groundwater resources. This study analyses the spatial and temporal variability of groundwater level in the shallow aquifer system on the flanks of Mount Meru. Time series analysis of groundwater level measurements obtained in two hydrologic years: 2018-2019 and 2019-2020 is applied.New hydrological insights for the region: On the north-eastern flank of Mount Meru, at Ngarenanyuki, there is a rise of about 1.80 m between the static water levels in April 2018 and December 2020 in the shallow aquifer, whereas on the western flank, at Mamsa, there is a decrease of about 0.50 m between the static water levels in May 2018 and December 2020 in the shallow aquifer, this can be attributed to low/reduced recharge (due to very low hydraulic conductivity and semi-confined condition of the aquifer), or exploitation. Hence, the current pumping practices in the aquifer on the western flank should be restrained for sustainable groundwater management.

Groundwater development in coastal aquifers of southwest Bangladesh is challenged by both natural and anthropogenic activities resulting in a landward migration of marine waters and increase in the risk of seawater intrusion. In some cases, infiltration of dissolved evaporite salts in the shallow aquifer and presence of connate water in the deep aquifer (DA) are the sources of groundwater salinity other than modern seawater intrusion. A detail investigation of these sources is imperative for a sustainable development and management of coastal aquifers. This work investigates the hydrogeochemical processes affecting groundwater chemistry by interpreting conventional plots, ionic delta, HFE-diagram, stable isotopes, and geochemical modelling. There are three hydrogeological units delineated in this area: upper shallow aquifer (USA) (<100 m bgl), lower shallow aquifer (LSA) (100-200 m bgl) and DA (below 200 m bgl). The hydrochemistry data reveal that the median values of total dissolved solids of the aquifers have a decreasing trend from top to bottom: USA with 7012 mg/l, LSA with 2622 mg/l and DA with 787 mg/l. Sodium is the dominant cation in all waters. The dominant anion in DA is HCO3-, but in shallow aquifers Cl-. The main water type based on the classification of Stuyfzand (1989) is the brackish to saline NaCl type in the shallow aquifers. The Br-/Cl- ratio and relatively enriched δ18O values in these NaCl waters suggest an origin derived from evaporate dissolution. Reverse cation exchange during intrusion, replacing Na+ with Ca2+, results in CaCl and CaMix water types. These waters infiltrate into the LSA. The water in the DA is mainly fresh NaHCO3+ type which originated by cation exchange from infiltrating fresh water. Ca2+ was replaced by Na+ due to the cation exchange, the water became undersaturated with respect to calcite and secondary calcite dissolution caused elevated bicarbonate concentrations. Near the present-day shoreline and at larger depths, the NaHCO3+ type water mixes with connate water, increasing salinity. The enriched δ18O values in the DA suggest an origin in a warmer climate, implying that this water has infiltrated a long time ago, much farther inland, probably during the Holocene climatic optimum. It can be expected that the salinization of the shallow aquifers will continue to increase if evaporite deposition and seasonal flooding occur. For a sustainable use of the groundwater resource in this coastal region and to prevent from even further worsening of water quality in its shallow aquifers, it is advised to develop future exploitations in the DA. Key words: Groundwater chemistry; Stable isotope; Evaporite; Cation exchange; Calcite dissolution.