Rainfall Recharge Research Articles

A FCM Runoff Model for Small Rivers with Rainfall Recharge. 2. Parameterization and Verification

The specific features of the parameterization and verification of FCM model were analyzed, and the data published before, as well as new results of the authors’ field observations, are systematized. The parameterization algorithms and the results of model testing in different regions with the predominance of rain floods in river regime are described. The basis and empirical confirmation of some principal hypotheses of FCM are discussed and the so-called effect of basin buffer storage is considered. This most vivid manifestation of the nonlinearity of the extreme runoff formation is, though a rare, but principally important phenomenon in the formation of extraordinary rain floods.

Evaluation of the impact of the intensive exploitation of groundwater and the mega-drought based on the hydrochemical and isotopic composition of the waters of the Chacabuco-Polpaico basin in central Chile

A hydrogeochemical and isotopic study has been carried out to understand the hydrogeological functioning of a small alluvial aquifer in central Chile in a context of mega-drought and intensive exploitation of its waters. Additionally, two mine tailings dams from porphyry copper mining are situated in the area. The prolonged mega-drought, which has lasted for over thirteen years, has resulted in a significant decrease in rainfall recharge and a drop of up to 50 m in piezometric levels, although no serious groundwater contamination problems have yet been detected, except for a rise in nitrate contents (ranging between 23 and 45 mg/L NO3) attributed to return irrigation. Groundwaters are calcium-bicarbonate and calcium-sodium-bicarbonate in composition. The values of δ18O and δ2H of the alluvial aquifer indicate fractionation by evaporation that would be explained by the recirculation of water that occurs in the agricultural areas of the basin, where the excess irrigation water that go back to the aquifer presents fractionation by evaporation. The δ34S and δ18O of dissolved sulfate point to pyrite oxidation, which could be related to the pyrite present in the copper porphyry and recognized in the Andes Cordillera. The 87Sr/86Sr isotopic values of the alluvial aquifer waters are close to the isotopic fingerprint of the volcanic rocks of the Abanico Formation. However, the water from the wells located further downstream in the basin and close to the tailing dams show δ34S and δ18O of dissolved sulfate and 87Sr/86Sr consistent with Miocene intrusive mineralogies of the copper porphyry type. The groundwater chemistry does not show water seepage from the tailings dam. Therefore, a minor contribution of minerals related to the intrusive rocks is proposed, which would originate from the movement of fine particles by the wind from the dams to the valley floor. The 14C activities indicate that groundwater is recent.

Caves demonstrate decrease in rainfall recharge of southwest Australian groundwater is unprecedented for the last 800 years

Billions of people worldwide rely on groundwater. As rainfall in many regions in the future is projected to decrease, it is critical to understand the impacts of climate change on groundwater recharge. The groundwater recharge response to a sustained decrease in rainfall across southwest Australia that began in the late 1960s was examined in seven modern speleothems and drip waters from four caves. These show a pronounced increase or uptick in regional drip water and speleothem oxygen isotopic composition (δ18O) that is not driven by a change in rainfall δ18O values, but is in response to the shallow karst aquifers becoming disconnected from rainfall recharge due to regional drying. Our findings imply that rainfall recharge to groundwater may no longer be reliably occurring in this region, which is highly dependent on groundwater resources. Examination of the longer speleothem record shows that this situation is unprecedented over the last 800 years.

Determination of ecological flow thresholds for rainfall-recharging rivers based on multiple hydrological methods

Given the threats to the regional river ecological flow, including the sharp increase in per capita water demand, the increase in the number of hydraulic engineering, and the strong seasonal runoff of rainfall recharge channels, we clarified the appropriate ecological flow thresholds for the middle reaches of Bailong River of northwest China. Based on the monthly runoff data in the Wudu Hydrological Station of Bailong River from 1990 to 2020, seven suitable hydrological methods were used to couple the estimation of the ecological flow in the middle reaches of Bailong River, which were tested by runoff satisfaction level analysis, using quadratic fit and 95% confidence interval to determine the monthly ecological flow and threshold of the river in the study area. The results by using the single hydrological methods showed that the calculation results from the monthly minimum ecological runoff calculation method, the improved RVA method, the Tennant method, and the DC method were four better estimation methods, which had a satisfaction level of more than 90% in the whole year. The improved RVA method and the Tennant method were more suitable for the diversion power station whose main task aimed at power generation. Although the economic benefits of hydropower stations were better when the improved RVA method was used to calculate ecological flow, the calculation results from the improved RVA method were tested and analyzed by the Tennant method, which were extremely poor from November to April in the following year, and could not meet the minimum ecological water requirements for the biological community in the river channel. While the other five methods all meet this requirement. We suggest that the minimum ecological flow in the middle reaches of the Bailong River maintained at 27.28 m3⁄s, and the maximum retained at 116.33 m3⁄s. The calculation results were in line with the dynamics of runoff in the study area, which could improve the accuracy of water ecological protection. The calculation results of this study could be used for the middle reaches of the Bailong River and may provide a reference for follow-up ecological restoration research and management in similar ecological zones.

Integrating stakeholders' inputs to co-design climate resilience adaptation measures in Mediterranean areas with conflicts between wetland conservation and intensive agriculture

Designing sustainable management strategies in groundwater-dependent socio-economic systems in areas with scarce water resources and protected wetlands is a challenging issue. The high vulnerability of these systems to droughts will be exacerbated even further under future climate change (CC) and socio-economic scenarios. A novel integrated bottom-up/top-down approach is used to identify “climate resilient pathways”, from which to co-design adaptation strategies to reduce the impact of potential future CC and socio-economic scenarios. The approach followed two steps (1) the generation of local CC and socio-economic scenarios by downscaling global/regional climate models and (2) the identification and assessment of potential adaptation strategies through an iterative bottom-up/top-down approach. Top-down assessments of the impact of CC have been undertaken by propagating local scenarios within a chain of mathematical models based on expert criteria/assumptions. This allowed us to analyse of the physical vulnerability of the system under different potential CC and socio-economic scenarios by simulating them with a sequential modelling of rainfall–recharge, agriculture, and hydrological processes through a distributed groundwater finite difference model. These model results were discussed with the stakeholders at a first workshop, which aimed to identify potential adaptation strategies. The influence of the adaptation strategies on the future hydrological status was assessed by simulating them through the chain of models. These results were the inputs into the discussions at a second workshop, which aimed to validate and/or improve the results of the first workshop. The methodology was applied in the Upper Guadiana River Basin, where there is a long-standing conflict between wetland conservation and groundwater overexploitation for intensive agriculture. The future horizon 2016–2045 is analysed with the scenarios compatible with the emission scenario RCP4.5. The research has allowed us to conclude that groundwater pumping reduction would be the most robust and effective measure to reduce the impact of CC in the area.

Water competition among the coexisting Platycladus orientalis, Prunus davidiana and Medicago sativa in a semi-arid agroforestry system

Agroforestry has been widely used for the ecological restoration construction of semi-arid regions of the Chinese Loess Plateau. Investigating plant water sources is crucial for understanding the key ecohydrological processes of plant root water uptake and the water relations between coexisting plants. Clarifying the plant water use strategies can help to assess the sustainability of the vegetation restoration in agroforestry systems and provide references for the vegetation management. Thus, we investigated the water use characteristics of plants in an agroforestry system consisting of Platycladus orientalis, Prunus davidiana and Medicago sativa. The δD and δ18O of plant stem water and soil water in the 0–300 cm layer were measured. The MixSIAR model and proportional similarity (PS) were used to quantify the proportion of soil water absorbed by the plants in each layer and the hydrological niche overlap of plants. The results showed that the combined effects of rainfall recharge and evapotranspiration (ET) loss resulted in a decrease in soil water content (SWC) for the agroforestry system with increasing soil depth, and the SWC of the deep layer (80–300 cm) had minor variability (6.1–7.1%) throughout the study period. During the study period, due to the deep soil desiccation, P. orientalis, P. davidiana and M. sativa mainly utilized water from shallow (0–80 cm) soil layers, with a contribution rate of 65.4 ± 8.3%, 64.9 ± 7.7% and 73.0 ± 0.2%, respectively. The three coexisting plants relied on the unstable shallow soil water (recharged by rainfall) while the water use proportion of the deep soil layer was consistently low. This implies that the three plants were less resistant to drought stress, thus posing a threat to the stability and sustainability of the agroforestry system. Moreover, even in July and September with the high SWC in agroforestry, the partitioning of soil water among the three coexisting plants did not increase with increased ET loss. The three coexisting plants showed strong competition for soil water use, as indicated by the high values (0.69–0.97) of PS. Overall, the hydrological niche overlap of the coexisting plants in the agroforestry system resulted in low ecosystem stability. Density reduction or selection of suitable species is required to achieve sustainable vegetation restoration.

How far are groundwater resource assessments in India reliable?

AbstractThe article critically reviews the methodology adopted by the Central Ground Water Board (CGWB) for the assessment of groundwater resources in India. The authors developed a water balance equation that simulates the changes in annual and seasonal groundwater storages of an agricultural region, using a water accounting framework; they solved the developed equation using the data of annual and seasonal water level fluctuations for a wet year for Ludhiana district of Punjab to estimate different components of the water balance. The estimated values are used to test the robustness of the CGWB methodology for monsoon recharge. The annual groundwater storage change obtained from solving the water balance equation was compared with the observed change in annual groundwater storage and was found to closely tally. As per the water balance equation, the CGWB estimates of rainfall recharge conform to the annual water level fluctuations recorded by the agency and therefore are not reliable. Hence, we could infer that our methodology is superior to that of CGWB for estimating monsoon recharge. The validated equation was also used to estimate the recharge from rainfall during a dry year. Using these outputs in a simple groundwater balance equation, irrigation return flows were estimated for the wet and dry years. The equation was then extended to the Ahmednagar district of Maharashtra, a hard rock area, for estimating the surface water import during a wet year, the key unknown in the region's water balance. Hence, our methodology can be employed to estimate rainfall recharge for dry years using annual changes in groundwater storage and estimated consumptive uses of water, when the “WLF approach,” used by CGWB, fails, owing to the presence of an additional variable, that is, monsoon draft. For wet years, it can be used to arrive at the consumptive use of water for various purposes.

Model Test Analysis of Groundwater Level Fluctuations on Karst Cover Deformation Taking the Monolithic Structure of Guilin as an Example

Engineering practice and real-life cases show that the geological conditions of the Guilin overlying karst site are complex. In particular, the groundwater, which drives the accelerated formation of soil cavities, and the thickness of the overlying soil layer, which affects the speed of the groundwater subsidence process. Therefore, this paper is based on a physical model to evaluate the effects of groundwater level changes caused by different factors on the deformation of karst cover. The model tests are simulated for different cover thicknesses (6 cm, 9 cm, 12 cm, 15 cm, 18 cm) under rainfall and other recharge, cavity supply, and drainage conditions at the same density (1.40 g/cm3) and initial water content (30%), respectively. The results show that with the increase of rainfall and other recharge time, the basic change trend of different cover thicknesses is that the infiltration curve changes faster at the beginning and slows down at the end, but the thicker the cover, the slower the overall deformation; at a certain rate of cavity recharge and drainage, the thicker the cover, the smaller the deformation caused by the fluctuation of groundwater level. The cavity recharge makes the cover displacement obvious, in the order of 0.304 cm, 0.173 cm, 0.118 cm, 0.068 cm, and 0.056 cm. After the formation of the cavity, the rainfall, other recharge, and the cavity supply and drainage accelerate the destruction and deformation of the soil body and the upward development of the cavity. The research results provide theoretical support for the subsequent prevention and control of karst collapse in covered karst areas, and have certain practical engineering significance.

Analysis of Groundwater Storage Changes and Influencing Factors in China Based on GRACE Data

Groundwater is a primary freshwater resource for human consumption and an essential source for industry and agriculture. Therefore, understanding its spatial and temporal trends and drivers is crucial for governments to take appropriate measures to manage water resources. This paper uses Gravity Recovery and Climate Experiment (GRACE) satellite data and the Global Land Data Assimilation System (GLDAS) to derive groundwater storage anomalies (GWSAs) and to analyze the spatial and temporal trends of GWSA in different regions of China (Xinjiang, Tibet, Inner Mongolia, North China Plain, South China, and Northeast China). It used groundwater-level observation data to verify the accuracy of GWSA estimates and analyzed the drivers of regional GWSA changes. The results showed that: (1) GWSA in South China increased at a rate of 4.79 mm/a from 2003 to 2016, and GWSA in other regions in China showed a decreasing trend. Among them, the decline rates of GWSA in Xinjiang, Tibet, Inner Mongolia, North China Plain, and Northeast China were −6.24 mm/a, −3.33 mm/a, −3.17 mm/a, −7.35 mm/a, and −0.75 mm/a, respectively. (2) The accuracy of the annual-scale GWSA estimates was improved after deducting gravity losses due to raw coal quality, and the correlation coefficient between GWSA and groundwater levels monitored by observation wells increased. (3) In Xinjiang, the annual water consumed by raw coal mining, industrial, and agricultural activities had a greater impact on GWSA than rainfall and temperature, so these human activities might be the main drivers of the continued GWSA decline in Xinjiang. Water consumption by raw coal mining and industry might be the main drivers of the continued decline in GWSA in Inner Mongolia and the North China Plain. The increase in groundwater storage in South China was mainly due to the recharge of rainfall.

Assessing the Baseline Uranium in Groundwater around a Proposed Uraninite Mine and Identification of a Nearby New Reserve

The presence of uranium in groundwater is a cause of concern all over the world. In mineralized regions where elevated concentrations of uranium are possible in groundwater, mining activities can further degrade the water quality. Hence, it is essential to document the baseline uranium concentration in groundwater before the commencement of mining. This study was carried out with the objective of assessing the concentration of uranium in groundwater around a proposed uraninite mining site in the Gogi region, Karnataka, India. Gogi is a village in the Yadgir district of Karnataka where groundwater is the main source of water for domestic needs. The uranium mineralized zone in this region occurs along the major E-W trending Gogi-Kurlagere fault at a depth of about 150 m. Groundwater samples were collected every three months from January 2020 to October 2020 from 52 wells located in this area. The concentration of uranium in groundwater ranged from 1.5 ppb to 267 ppb. The USEPA and WHO have recommended a permissible limit of 30 ppb, while the Atomic Energy Regulatory Board of India has a limit of 60 ppb for the purpose of drinking water. Based on these permissible limits for uranium in drinking water, concentrations exceeded the limit in about 25% of wells within 20 km from the mineralized region. Wells present in the granitic and limestone terrain exhibited higher concentrations of uranium in this area. Uranium concentration in groundwater changes depending on the degree of weathering, lithology, and rainfall recharge. This study will serve as a baseline and will help to assess the impact of mining activities in this region in the future. In wells where the uranium concentration exceeds permissible limits, it is suggested not to use groundwater directly for drinking purposes. These sites need to be explored further for the possible presence of uranium-bearing minerals.

Modelling of hillslope storage under temporally varied rainfall recharge

Water storage inside hillslopes is a crucial issue of environment and water resources. This study separately built a numerical model and an analytical model employing a hillslope-storage equation to simulate the water storage in a sloping aquifer response to recharge. The variable width of hillslope was hypothetically represented by an exponential function to categorize the hillslope into three types: uniform, convergent, and divergent. An integral transform technique was introduced to derive the analytical solution whereas a finite difference method was employed for the numerical modelling. As a result, under the same scenario a gap existed between the two solutions to distinct forms of the water storage equation, and the gap decreases with a falling recharge rate for convergent hillslopes. Moreover, all outflows gradually approached one value based on different hillslopes under the same accumulative recharge amount for six typical rainfall recharge patterns. Particularly, while the recharge stops, the outflow decreases and then mildly rises for a long time for convergent hillslope because of the slow water release near the upstream boundary where the storage water is relatively abundant due to the widest width.

Evaluating the impacts of climate change and water over-abstraction on groundwater resources in Pacific island country of Tonga

Small low-lying Pacific Island countries are prone to climate change and water resources-related issues. The demand for water in Pacific Island countries has increased significantly due to population growth, industrialisation, tourism, and agricultural needs. Groundwater is utilised by most of the Pacific Island countries, and due to increasing demand, the majority of the Pacific Island countries practise over-abstraction. Climate change caused by natural means and over-abstraction of groundwater has led to saltwater intrusion into the coastal aquifers and other groundwater-related problems in several low-lying Pacific Island countries. In this study, groundwater salinity data collected over a 42-year duration from several abstraction wells in Tonga is linearly analysed to ascertain the impact of over-abstraction on groundwater resources. Climate change also affects rainfall and net recharge patterns. Hence, Tonga's long-term rainfall and net recharge patterns were linearly analysed. Also, to ascertain the climate change effect in Tonga, the sea level height and carbon dioxide emissions were linearly analysed using the data from 1993 to 2020 and 1960–2018, respectively. Quantitative data, linear regression and graphical linear fit techniques were used in this study for data analysis. The results from this study indicated that over-abstraction has caused saltwater intrusion more frequently and affected groundwater quality. An increasing salinity trend of 58% was observed from 1965 till 2007. It is also evident that the higher the abstraction rates, the higher the saltwater flux sipping into the coastal aquifers. Moreover, decreasing trends were also observed in rainfall (19%) and net recharge (37%) in Tonga between 1950 and 2006. This study also revealed that the sea level and carbon dioxide emissions have increased by 5.2% and 800%, respectively. This study provides insights into why controlling abstraction rates and acting against climate change is essential concerning groundwater. These insights will be helpful for groundwater resource managers, stakeholders, and policymakers in Tonga and the broad scientific community, in managing saltwater intrusions and preserving the water resource.

Assessment of groundwater salinity using principal component analysis (PCA): a case study from Mewat (Nuh), Haryana, India.

In the present study, principal component analysis (PCA) is used to investigate the processes controlling groundwater salinity in the Mewat (Nuh) district, Haryana, India. Twenty groundwater samples were collected from salinity-affected areas in the March-April months of years 2018 and 2019 and were analyzed for chemical variables pH, EC, Ca2+, Mg2+, Na+, K+, [Formula: see text], Cl-, SO42-, [Formula: see text], TDS, and total hardness. Three principal components were selected based on the eigen value, which explains 79.58% and 85.08% of the total variation in the years 2018 and 2019, respectively. The first principal component (PC-1) is identified with salinity, the second principal component (PC-2) with alkalinity, and the third principal component (PC-3) described the pollution. When the yearly comparison was made, the samples collected in 2019 were found to have an increased salinity compared to 2018, which shows an increased vulnerability to the aquifer of Mewat on account of the decline in rainfall recharge. It was also evident that declining recharge also triggered the recharge from other sources; thus, the impact of pollution is more pronounced in 2019 compared to 2018.

Integrated Surface Water and Groundwater Modeling in Arid Environment, Al-Lusub Watershed, Saudi Arabia

Coupling surface and groundwater for a better understanding of the hydrologic response in arid basins is essential for managing water resources. The study aims to integrate surface water (SW) and groundwater (GW) modeling in an arid environment and to identify groundwater sources at Hadat Ash-Sham farm station in the Al-Lusub watershed, located in the western part of Saudi Arabia. The curve number (CN) method for SW modeling is primarily used to estimate GW potential recharge based on a developed correlation equation between event-based rainfall and potential recharge, which is processed in the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) software. Monthly potential recharge is utilized to compute GW modeling in MODFLOW. Van Mullem’s equation is used to calculate hydraulic conductivity (K) from CN. The calibration of steady-state GW modeling reveals that the K (from Van Mullem’s equation) is within the range of measured K in the field. The transient groundwater modeling phase concludes that the groundwater system in the Al-Lusub watershed can be interpreted based on two different scenarios. The first is that an extra recharge from a nearby watershed flows through the geological structure into a downstream area. The second scenario involves potential recharge from surface water flowing on the Al-Lusub watershed’s mainstream bed. Validation reveals a strong relationship between predicted and observed water tables. The root mean square error (RMSE) for Scenarios 1 and 2 are 0.6 m and 0.7 m, respectively. Further investigation is needed to determine the region’s most common scenario.

Recharge variability in Australia's southeast alpine region derived from cave monitoring and modern stalagmite δ18O records

Oxygen isotopic (δ18O) variations in stalagmite records have the potential to provide new insights about past climates beyond the instrumental record. This paper presents the first high-resolution oxygen isotope time series of three coeval stalagmite records from the alpine region of south-eastern Australia covering the period 1922–2006 CE. We use extended surface and cave monitoring datasets, petrographic investigation, modelled recharge time series and farmed calcite precipitates to assess the controls on speleothem δ18O and investigate the coherence between three records from Harrie Wood Cave. The drip water response to recent interannual rainfall variability shows that cave drip water Cl−, δ18O and drip rate display a clear response to an increase in rainfall recharge. It is demonstrated that stalagmites from the same drip sites also record variability in interannual recharge, where an increase in δ18O values is observed with lower recharge, while a decrease in δ18O values correspond to higher recharge amounts. The three stalagmite δ18O records are in broad agreement, showing common responses to relatively higher recharge between 1945 and 1995 CE and the low recharge periods between 1937 and 1945 CE (World War II drought) and late 1996 to 2006 CE (beginning of the Millennium Drought). However, differences in the magnitude of the relative response of each stalagmite δ18O record varies. Based on evidence from our cave monitoring study and farmed calcites, we conclude that the differences between the three stalagmite records is attributed to variability in the contribution of preferential flows during recharge events and the store reservoir volume supplying the drip site. When the δ18O decreases in response to enhanced recharge, the speleothem δ13C also decreases, and this is interpreted to reflect a soil respiration response to changes in soil moisture availability due to recharge. Hence, stalagmite δ18O from the Australian alpine region can be applied to reconstruct periods of relatively higher and lower rainfall recharge and thus extend our knowledge of the timing and relative magnitude of droughts as well as past periods of higher recharge in this region.

Localized recharge processes in the NE Mekong Delta and implications for groundwater quality

Understanding recharge in the Mekong Delta is critical for the delta's groundwater resources, and requires the investigation of recharge processes at the local scale. In this study of the north eastern area of the Mekong Delta, time-series of environmental tracer data (δ18O, δ2H, major ions and 3H) and markers of rural pollution (NH4 and NO3) were used to highlight localized recharge and impacts on groundwater quality. Results highlighted new hydrological insights into recharge processes, including that the Pleistocene aquifer receives recent recharge (< 60 years), predominantly during high rainfall months (> 100 mm/month). However, due to shallow clay layers there are significant spatial variations in these recharge processes, which were observed in the seasonal fluctuation of groundwater δ18O values in groundwater. Wet season δ18O changes ranged from below analytical uncertainty (≤ 0.10 ‰) to up to 0.56 ‰, and the calculated fraction of rainfall contribution to the aquifer is ≤5 % to 16 %. Rainfall recharge via the acrisol soils results in low groundwater EC (20–55 μS/cm), acidic groundwater (pH 3.6–5.6), and may also have resulted in the low groundwater NO3 concentrations (≤ 5.3 mg NO3/L) at many sites due to adsorption, therefore delaying not reducing NO3 contamination. Site specific variations in nitrogen processes includes increased NO3 (to 29.7 mg/L) from fertiliser transfers or nitrification, and increased NH4 (to 1.4 mg/L) likely due to the recharge of irrigation waters. Unlike other recharge areas across the northern Mekong Delta, this north-eastern region provides a groundwater resource unaffected by arsenic contamination. Therefore, these results should inform on priority areas for protection from further contamination by rural anthropogenic activities.

Water stable isotopes reveal a complex rainfall to groundwater connectivity in central Honduras

The inter-mountainous region of central Honduras has been experiencing abrupt urban drinking water shortages during the last decade. Land use fragmentation and rainfall deficits have rapidly reduced surface water quality and quantity in this region. Here we present a 3-yr (2018–2020) tracer study within the headwaters of the Choluteca River basin (2949 km2). We sampled rainfall (weekly N = 156; daily N = 270), drilled wells (N = 166; up to ~300 m depth), boreholes (N = 70; ~4–12 m depth), and springs (N = 128) to assess the spatiotemporal connectivity between rainfall and mean groundwater recharge elevations (MREs). Clear W-shaped incursions characterized rainfall isotopic seasonality from the dry to the wet season. Air mass back trajectory analysis revealed three primary moisture sources: 73 % (east, Caribbean Sea), 17 % (southwest, Pacific Ocean), and 10 % (north; Gulf of Mexico). Groundwater sources exhibited a strong meteoric origin with evidence of secondary evaporation evolution, characterized by low d-excess values. MREs for the drilled wells ranged from 821 to 2018 m asl with a mean value of 1570 ± 150 m asl. Seasonal isotopic variability during dry-wet transitions and the influence of rapid infiltration limited the performance of the MRE method in springs and boreholes. MREs coincided primarily with coniferous forests, pasture, and crop areas, within regions of moderate to high transmissivity. These results are intended to guide the mapping and delineation of critical recharge areas in central Honduras to enhance municipal water regulations, effective environmental protection, and long-term conservation practices.

A Resilient and Nature-Based Drinking Water Supply Source for Saline and Arsenic Prone Coastal Aquifers of the Bengal Delta

Salinity causes a hostile environmental impact throughout the year in the coastal region of Bangladesh, and its severity increases day by day. Because of upstream freshwater flow reduction and massive groundwater extraction, salinity has increased substantially over the last three decades. Moreover, arsenic contamination in shallow groundwater makes the groundwater unsuitable for potable use. Consequently, the coastal area suffers from acute storage of safe water supply. Salinity also negatively impacts human activities, livelihood, agricultural production, and the aquatic ecosystem. Though the shallow aquifer contains high salinity and a small amount of Arsenic (As), the very shallow aquifer (within 3m to 8m) contains fresh water in many areas in the rainy season due to the direct recharge of rainwater. However, rainfall recharge varies significantly depending on the geological and hydrogeological settings. Specifically, up to 50% of annual rainfall is stored in shallow aquifers of Quaternary sands through direct infiltration. The research’s principal objective is to identify the safe and sustainable drinking water source in the arsenic and saline-prone coastal region. Groundwater samples were collected from the different locations of the study area during both dry and wet seasons and examined seasonal variations in groundwater table and salinity levels. The chemical analyses and Physico-chemical parameters indicate that the groundwater samples are suitable for drinking. Except for some groundwater samples from the wet season, the salinity of all samples was under the allowable limit for Bangladesh (&lt;2000 µS/cm), and the targeted aquifer was almost arsenic (50 µg/l) free. Therefore, a comprehensive analysis has been made to accomplish the study goals. Particularly, the groundwater’s electrical conductivity (EC) values of most samples were measured within the limit of fresh or brackish water (&lt;2000 μS/cm). Overall, the results indicate the prospect of a very shallow aquifer as a source of freshwater for drinking purposes throughout the year, considering both arsenic and salinity, which effectively solve the freshwater shortage, especially in the saline-arsenic prone area.

Estimation of Water Balance Parameters in Rogerm Catchment Area, Mangesh, Duhok Governorate, Kurdistan Region of Iraq

The analysis of some hydrological elements of the water balance of Rogerm catchment area which is in Mangesh subdistrict, Duhok Governorate about 45 km north-west of Duhok was conducted. The aimed area is around 179.5 km². The historical record of rainfall data in Mangesh Agricultural office stations were used to calculate the water balance parameters for the period 2012-2013 to 2020-2021. The average amount of rain is almost 783.5 mm, it falls through 56 days of eight rainfall months/year. The biggest amount of rain falls in March, it reaches 158.4 mm. In winter the rain is denser and it reaches 47.7% from the total of the rainy year. 46.1% of the total amount of rain falls during two days, which cause the surface runoff. Water surplus was between 77% - 78% and 18% ground water recharge of the total annual rainfall. The probability of return period of the water surplus each two years may be 50% from (565-907 mm/year) and 50% from (363-530 mm/year) consequently, while maximum and minimum probability of return period is (907 mm/year) and (363 mm/year) consequently of the water surplus for the coming year are 10% and 90% consequently

Determination of Groundwater Sensitivity Potential Using Geography Information System (GIS) Based DRASTIC Model: A Case Erzin Plain (South of Turkey)

Today, due to the rapidly increasing world population and urbanization, the amount of water is increasing exponentially in areas such as drinking, irrigation, energy, industry, etc. There is a great increase in the use of water in agriculture, especially due to the food needs of human beings. For this reason, human beings need water; They obtain water almost everywhere from above ground (springs, dams, ponds) and underground (drilling wells) water sources. Usage of groundwater is quite common in the plains, where surface water resources are insufficient. This situation; While increasing the use of pesticides and fertilizers for agricultural purposes due to irrigation, it also creates the risk of contamination of groundwater. In this study; contamination potential of groundwater in Erzin Plain was determined using Geography Information System (GIS)-based DRASTIC model. Seasonal and annual field sensitivity levels were determined by integrating current land use into this model. Accordingly, in the dry seasons of August-2006, November-2006, while the Mediterranean coast has high EC values in the vicinity of the Mediterranean coast, the area around the resort sites and the settlement area, the mountainous areas, the north of the plain and the west of Gokdere have low EC values. It has the lowest EC values by decreasing towards the north and northeast and other parts of the plain. In the study area; Although NO3 concentration varies seasonally, it is especially high in citrus growing segments with high permeability. On this change; Factors such as rainfall recharge, evaporation effect in the dry period, irrigation water recharge with the effect of land use, and the depth of groundwater depending on topography played an important role.