Artificial Recharge Techniques Research Articles

Multi-criteria analysis using satellite images and GIS for mapping groundwater recharge zones in Saudi Arabia: A case study of the Riyadh Region

Abstract Water scarcity is well pronounced in arid and semiarid regions where potential evapotranspiration exceeds precipitation. Saudi Arabia is one of the most water-scarce regions where there are 2 billion m3 of annual renewable freshwater resources, besides 24 billion m3 of freshwater withdrawal, especially from the aquifers with fossil water. In Saudi Arabia, floods often occur and the harvest of flood water for groundwater recharge became an issue of discussion; however, this requires determining groundwater recharge potential (GWRP) zones where water naturally percolates and feeds the depleted aquifers. This study aims to produce a detailed (digital) map for GWRP zones for the Riyadh Region by using a multicriteria approach where datasets were derived from satellite images (Landsat 7 ETM+, Spot-5, and Aster) associated with thematic maps and field surveys. The geo-information system (GIS) was also used to manipulate and integrate the geospatial data layers which represent the controlling factors on GWRP. Results show five classes of GWRP zones, where about 36,448 km2 (89.2% of the Riyadh Region) belong to high and very high GWRP. The resulting map will be key information for decision-makers to select suitable localities for groundwater artificial recharge techniques as an adaptive measure for the changing climate.

Geospatial Assessment of Managed Aquifer Recharge Potential Sites in Punjab, Pakistan

Groundwater is a precious natural resource that is vital to various aspects of life. Punjab is experiencing groundwater stress due to urbanization and population growth, leading to overuse and reduced aquifer recharge. Sustainable groundwater supplies can only be created through better management and artificial recharge techniques. This study uses multi-influencing factor, literature-based, and combined techniques to identify and characterize groundwater-managed aquifer recharge potential sites (GWMARPSs) in Punjab. There are limitations to the previous work in this field, and these factors have not been used to estimate GWRPSs in the study area. The study uses GIS and RS techniques to overlay twelve geo-informative layers, with rainfall being the most significant factor. High-quality data and observations from the field are incorporated into the model. The study classifies the GWMARPSs into five categories, with Punjab having 0.34%, 13.29%, 60.68%, 25.26%, and 0.43% of the least, poorly, moderately, well-, and highly suitable sites. Punjab’s southern regions are least suitable for recharge, while some areas in eastern and northern Punjab are well-suited for recharge. Alluvial plains, valleys, low-lying areas, and areas with volcanic landforms are classified as least to poorly suitable zones. Model predictions are validated using piezometric level data and ROC and exhibit good performance (AUC, 0.74). This study could serve as a baseline for future groundwater research.

Impact of climatic variability on groundwater resources in the Eastern Mitidja plain, Algeria

The aim of this study is to assess the main climatic characteristics and their impact on the hydrological regime at the watershed and the hydrodynamic functioning of the aquifer in the Eastern Mitidja plain (Algeria, 2,382 millions km2). In detail, specific objectives are to determine the recharge mode of the aquifer, to propose solutions for the groundwater overexploitation and to remedy the seawater problem in its northeastern part. The application of three statistical methods (Pettitt’s, Buishand’s U statistic and, Lee and Heghinian’s tests) and two drought indices (SPI and Ipmc) allowed identifying the wet and dry periods for the time interval 1906-2018. In addition, the piezometric maps analysis for the years 1973, 1981, 2015 and 2020 was carried out to investigate the hydrodynamic behavior of the study area and to determine the effect of the hydrological regime on the hydrogeological functioning of the aquifer. Results obtained by the application of the three statistical methods and two drought indices indicate two distinct periods. The first period is wet and it extends from 1906 to 1973, while the second period is dry and it goes from 1974 to 2018. It is characterised by a rainfall deficit between 15% and 19% compared to the previous period (1906-1973). Furthermore, a significant drawdown in the piezometric levels is observed from 1973 to 2020, varying between 10 and 80 m, that indicates a negative trend of piezometric levels. This drawdown coincides with the rainfall deficit noticed during the period 1973-2018. Also, seawater intrusion was observed in the northeastern part of the plain. To enhance groundwater management, an effective remediation strategy is to use an artificial recharge technique from the existing wastewater treatment plants in the region, complemented by stopping the pumping of wells in coastal zones that are affected by seawater intrusion supplemented by a hydro-chemical monitoring of the groundwater.

Rainwater Harvesting through Point Recharge Method for Efficient Recharge of Tube Wells for Sustainable Management of Groundwater Resources in Karnataka

Water is a precious natural resource for sustaining life, agriculture and environment. The dependability on groundwater has reached high in all time in recent decades due to reasons such as unreliable supplies from surface water due to vagaries of monsoon, increase in demand for domestic, agricultural and other purposes. Karnataka is largely dependent on groundwater to meet industrial, municipal, domestic and irrigation needs. So, Rainwater harvesting (RWH) forms an important component for development and management of water resources for domestic, agricultural, municipal and industrial uses. Management of scanty rain fall by rain water harvesting, Augmentation of depleting natural resources of water (deeper ground water table) and Management of poor-quality ground water and scope for conjunctive/domestic use is need of the hour. With increase in withdrawal of ground water, ground water (GW) table is declining at a rapid pace with an urgent need to recharge GW in addition to dilute poor quality ground water. Double ring technique of Groundwater Recharge consists of filtering the water at different layers using gradation materials generally the pebbles of different size with synthetic material wrapped around the casing pipe. By harvesting rain water and recharging into point recharge soaking infiltration gallery established at Irrigation Water Management Research Centre, (IWMRC) Belavatagi Tq: Navalagund has shown encouraging results as far as water quality, discharge and water table are concerned. The results of assessment of influence of ground water recharge through rainwater harvesting on ground water yield (lps), quality (dS/m) and fluctuations (feet bgl) during the year 2020, have shown that around 3.35 lakhs liters of water could be collected from rain water harvesting during the year 2020. Also, from point recharge through 7 recharge events (rain fall events from July to October 2020), it was observed that the considerable rise in the water table from more than 100 feet below ground level to around 22 feet below ground level, drastic reduction in groundwater salinity i.e. electrical conductivity (EC) of ground water from more than 10 dS/m to an average (EC) of 1.32 dS/m and tube well yield has significantly increased from 0.4 lps to around 2.4 lps. Therefore, Artificial recharge techniques through rainwater harvesting can be a better strategic approach to combat the emerging problems of water scarcity especially over exploitation of ground water and its quality deterioration.

Identification of Potential Groundwater Recharge Zones Using GIS Based Multi-Criteria and AHP Technique: A Case Study of Pune City, Western Maharashtra

With dwindling supply of surface water, Ground water is increasingly being used as a source of fresh water in many cities across the world. Consequently, there is an increasing need to evaluate groundwater potential of an area. Over the past few decades, Remote Sensing and GIS have been used for systematic investigations on potential recharge of aquifers. As in major cities of the world, the demand for water in Pune City is also increasing every year and demand outstrips the supply of surface water. This study delineated potential zones for artificial recharge across Pune City by using Multi-criteria analysis and the Analytical Hierarchy Process (AHP) techniques. Artificial recharge techniques especially the use of rainwater harvesting (RWH) are being deployed globally to augment supply of fresh water. Ground-water recharge is directly influenced by surface characteristics such as rainfall, geology, soil types, Land Use/Land Cover (LULC), drainage, lineaments/fractures, etc. Hence, six such parameters, namely, LULC, Slope, Soil texture, Rainfall, Drainage density, and Geology were considered to generate a groundwater recharge potential map. Based on the analysis, the study area was zoned into five classes, namely, low, moderate, good, very good and high groundwater potentials. About 45% of the city shows good to high potential for recharge. The results reveal that the high and good potential recharge zones lie to the western part of the city, whereas the central part (inner city) and the eastern part show medium to low potential for recharge. The results can help to identify areas for recharge and formulate a framework for systematic recharge of the existing aquifers in the area under study.

Hydrogeochemical Survey along the Northern Coastal Region of Ramanathapuram District, Tamilnadu, India

Ramanathapuram is a drought-prone southern Indian district that was selected for conducting a hydrogeochemical study. Groundwater samples from 40 locations were collected during January 2020 (pandemic interdiction according to COVID) and January 2021. The hydrogeochemical properties of the groundwater samples were evaluated and compared with drinking water regulations to assess their water quality. The order of cation dominance was as follows: Na+ > Ca2+ > K+ > Mg2+ in January 2020 and Na+ > Ca2+ > Mg2+ > K+ in January 2021 with respect to the mean value. The order of anion dominance was as follows: Cl− > HCO3− > SO42− > NO3− > F− in January 2020 and Cl− > SO42− > HCO3− > NO3− > F− in January 2021 with respect to the mean value. In the study area, the southern coastal region was identified as a groundwater-polluted zone through spatial analysis based on all analysis results. The irrigation water quality was analyzed using various calculated indices, such as Na% (percent sodium), SAR (sodium absorption ratio), PI (permeability index), MgC (magnesium risk), RSC (residual sodium concentration), and KI (Kelly ratio), demonstrating the suitability of the groundwater for irrigation in most parts of the study area. This was also confirmed by the Na% vs. EC Plot, USSL, and Doneen’s Plot for PI. In addition, the WQI results for drinking water and irrigation confirmed the suitability of the groundwater in most parts of the study area, except for the coastal regions. The dominant hydrogeologic facies of Na+-Cl−, Ca2+-Mg2+-SO42−, and Ca2+-Mg2+-Cl− types illustrated by the Piper diagram indicate the mixing process of freshwater with saline water in the coastal aquifers. Rock–water interaction and evaporation were the main controllers of groundwater geochemistry in the study area, as determined using the Gibbs plot. Ion exchange, seawater intrusion, weathering of carbonates, and the dissolution of calcium and gypsum minerals from the aquifer were identified as the major geogenic processes controlling groundwater chemistry using the Chadha plot, scatter plot, and Cl−/HCO3− ratio. Further, multivariate statistical approaches also confirmed the strong mutual relationship among the parameters, several factors controlling hydrogeochemistry, and grouping of water samples based on the parameters. Appropriate artificial recharge techniques must be used in the affected regions to stop seawater intrusion and increase freshwater recharge.

Mobilization and health risk assessment of fertilizer induced uranium in coastal groundwater

Uranium (U) in groundwater is hazardous to human health, especially if it is present in drinking water. The semiarid regions of southern India chiefly depend on groundwater for drinking purposes. In this regard, a comprehensive sampling strategy was adopted to collect groundwater representing different lithologies of the region. The samples were collected in two different seasons and analysed for major and minor ions along with total U in the groundwater. Two samples during pre monsoon (PRM) and seven samples during post monsoon (POM) had U > 30 μgL−1, which is above the World Health Organization's provisional guideline value. The high concentration of U (188 μgL−1) was observed in the alluvial formation though a few samples showed the release of U near the pink granite (39 μgL−1) and the concentration was low in the lateritic formation (10 μgL−1). The uranyl carbonato complexes UO2(CO3)22− and UO2(CO3)34− were associated with high pH which facilitated the transport of U into groundwater especially during POM. U3O8 is the major form observed in groundwater compared to either UO2 or UO3 in the both seasons. The uranium oxides were observed to be more prevalent at the neutral pH. Though U concentration increases with pH, it is mainly governed by the redox conditions. The principal component analysis (PCA) analysis also suggested redox conditions in groundwater to be the major process facilitating the U release mechanism regardless of the season. The POM season has an additional source of U in groundwater due to the application of nitrogenous fertilizers in the alluvium region. Furthermore, redox mobilization factor was predominantly observed near the coastal region and in the agricultural regions. The process of infiltration of the fertilizer-induced U was enhanced by the agricultural runoff into the surface water bodies in the region. Health risk assessment was also carried out by determining annual effective dose rate, cancer mortality risk, lifetime average daily dose and hazard quotient to assess the portability of groundwater in the study area. Artificial recharge technique and reducing the usage of chemical based fertilizers for irrigation are suggested as sustainable plans to safeguard the vulnerable water resource in this region.

Integrated urban water resources management strategy for a smart city in India

Abstract Economic growth of any nation like India depends on growth of cities. In India 31% of the total population exists in urban areas. The smart city mission of India was established with the objective to deliver the basic requirements of the citizens in a sustainable manner. Madurai city located at Peninsular India with a 1.4 million population was taken for this study. The objective was to develop an integrated urban water management strategy after analysing all the components of the urban water cycle such as rainfall, runoff, groundwater and wastewater. The population forecast for 2021 was carried out for the Local Planning Area of 726.34 km2 and the water demand was calculated as 109 Mm3/year. To meet the demand, runoff from the average rainfall was estimated as 393 Mm3/yr using the SCS-CN method. The storage capacity in the water bodies to store the surface water was estimated as 156 Mm3/yr and groundwater recharge potential was estimated as 22 Mm3/yr. The integrated urban water management strategy developed, shows that there is a huge potential for rainwater storage at the surface level and subsequent recharge through artificial recharge techniques.

Targeting groundwater potential zones using Electrical resistivity and GIS techniques in Kadavanar Sub-basin, South India

Geographical Information System techniques are widely used to determine suitable sites for groundwater recharge through artificial recharge techniques. The present research work is to identify suitable locations for constructing artificial recharge structures in the Kadavanar Sub-basin, South India. People in the Sub-basin mainly depend on the groundwater resources for drinking and irrigation purposes. Groundwater resources are often overexploited in many parts of this Sub-basin to meet the water demand leading to groundwater consumption. A lot of surfaces and sub-surface information and criteria are required for mapping the groundwater recharge zone. This is where the geographic information system [GIS] provides the right impetus besides the groundwater prospective zone to harness multilayered spatial data so that multi-criteria analysis is possible. This analysis integrates historic rainfall data analysis, groundwater level fluctuation, stream network, aquifer thickness, land use/land cover and basin slope. Drainage map, slope map and land use/land cover maps were prepared from satellite imageries. Vertical electrical sounding (VES) geophysical survey with Schlumberger electrode configuration was also conducted in the basin at 50 locations to map the aquifer thickness. Spatial variation maps for groundwater level and aquifer thickness were generated using GIS. Weighted aggregation method was used in this study to obtain groundwater recharge maps. Finally, multi-criteria analysis has been carried out to identify and assess the potential sites for groundwater recharge according to the associated weightages. It is established that GIS is best suited for the mapping of groundwater recharge zones. A similar study can be extended to any other hard-rock region facing water crises.

Status of seawater intrusion in coastal aquifer of Gujarat, India: a review

Seawater intrusion (SWI) is a universal concern, intensified and aggravated due to over-exploitation of groundwater, sea-level rise, and climate change in the coastal province. According to the Ghyben–Herzberg principle, the stability between freshwater and saltwater is caused by the density difference between the two, until the pressure equalizes. The keystone of India’s geography, economy, biodiversity, and the environment are its extended and vast coastline, which occupies the most precious as well as potential aquifer system. This review mainly fascinated on the status, knowledge, and vulnerability of SWI within the aquifers of the coastal region of Gujarat, India. Foregoing investigations reveal that the meteoric intensification in the salinity of coastal regions of Gujarat is the chief provenance of socioeconomic development and environmental degradation. Different studies are performed to analyze and mitigate the SWI problem. In this region, groundwater over-exploitation is the foremost driver of SWI. There are miscellaneous developmental and management skills and techniques to diminish the SWI in coastal regions of the world. Numerous models are fabricated and established to analyze and epitomize the complications associated with it. Numerical models suggest some valuable techniques to manage groundwater-related problems. This study also delivers some advanced management strategies such as dilution of salinewater by artificial recharge techniques, construction of physical barriers in the subsurface to reduce the intrusion etc. feasible to the coast of Gujarat.

A Conceptual Design Model to Groundwater Recharge in Dense Urban Area Roads

As increasing of Urbanization, the soil surface which is permeable through which groundwater recharge by infiltration can occur is reducing, this is resulting in much less groundwater recharge and greatly increased surface runoff. This Paper deals with the increasing of groundwater table utilizing of road runoff or stormwater through artificial recharge techniques. Infiltration devices that redirect surface runoff to the subsurface environment should be adopted, the infiltration system like infiltration trenches can be used to increase the groundwater table and the use of infiltration trenches has proven to be useful to reduce runoff in urban surface. By making continuous infiltration trenches in an area below the footpath and providing a filter media in it which consists of different layers of gravel and sand. Due to which filtered water goes inside the earth's surface and infiltration increases and the maximum portion of surface runoff go inside subsurface and stormwater management can be managed by using this technique. The methodology, applications, design & calculations are presented and discussed.

A study on ground water problems, artificial recharge techniques in Musunuru

Artificial groundwater recharge is a process of induced replenishment of the groundwater via the assist of human activities. It is far the planned, human activity of increasing the quantity of groundwater available via works designed to grow the natural replacement or percolation of surface water into the groundwater aquifers, resulting in a corresponding increase in the amount of groundwater available for the concept. In an area like Musunuru Mandal in Andhra Pradesh, there is a need for recharge of groundwater identified by Jal Shakti Abhiyan. This study explains the demand and consumption of water and estimates the water budget in Musunuru village. In this study, the major source of water for agriculture is rainfall or borewells (tube wells). To identify the water demand in the village and suggesting the best practice approach to reduce the risk of Musunuru with an experimental study on groundwater recharge techniques. Among all the recharge techniques this study chooses the low budget soak pit method with materials like a reused plastic drum and locally available construction materials in Musunuru. By using this proposed low budget soak pit method 85% of groundwater recharge contributes.

GPS Technology for Finding Suitable Place for Water Harvesting

Groundwater is a precious and scarce natural resource on the earth. Though Ranchi is blessed with prominent monsoon with an average rainfall of around 1430 mm; it experiences water scarcity in off monsoon seasons. Artificial recharge technique such as rainwater harvesting is essential to increase the groundwater level and to maintain the quality of water. The technique can be used effectively to trap the unutilized surface runoff and thereby increase the groundwater level. The present study has been conducted in the campus of a technical college in Ranchi, the capital city of Jharkhand state of India. The objective of this study is to demonstrate a simple but generally applicable water-harvesting model with finding pore points. Global positioning system was used for the survey, and ArcMap 10.1 software was used for the spatial analysis. The prominent sites were located by overlaying thematic maps of land use, soil, slope, runoff potential, soil permeability and stream order. Further, the role and scope of advertisement in bringing awareness of rainwater harvesting technology have been analysed. It has been found during the survey that people residing in the study area are hardly aware of such technology. Thus, the study helps depict the need for advertisement to promote rainwater harvesting technology.

Water Resources Management Through Flood Spreading Project Suitability Mapping Using Frequency Ratio, k-nearest Neighbours, and Random Forest Algorithms

Lack of water resources is a common issue in many countries, especially in the Middle East. Flood spreading project (FSP) is an artificial recharge technique, which is generally suggested for arid and semi-arid areas with two major aims including (1) flood mitigation and (2) artificial recharge of groundwater. This study implemented three state-of-the-art popular models including frequency ratio (FR), k-nearest neighbours (KNN), and random forest (RF) for determining the suitability of land for FSP. At the first step, suitable areas for FSP were identified according to the national guidelines and the literature. The identified areas were then verified by multiple field surveys. To produce FSP land suitability maps, several FSP conditioning factors such as topographical (i.e. slope, plan curvature, and profile curvature), hydrogeological (i.e. transmissivity, aquifer thickness, and electrical conductivity), hydrological (i.e. rainfall, distance from rivers, river density, and permeability), lithology, and land use were considered as input to the models. For the FR modelling, classified layers of the aforementioned variables were used, while their continuous layers were implemented in the KNN and RF algorithms. At the last step, receiver operating characteristic (ROC) curve was used to assess the ability and accuracy of the applied algorithms. Based on the findings, the area under the curve of ROC for the RF, KNN, and FR models was 97.1, 94.6, and 89.2%, respectively. Furthermore, transmissivity, slope, aquifer thickness, distance from rivers, rainfall, and electrical conductivity were recognized as the most influencing factors in the modelling procedure. The findings of this study indicated that the application of RF, KNN, and FR can be suggested for identification of suitable areas for FSP establishment in other regions.

Evaluating the impact of artificial groundwater recharge structures using geo-spatial techniques in the hard-rock terrain of Rajasthan, India

Groundwater levels in hard-rock areas in India have shown very large declines in the recent past. The situation is becoming more critical due to a paucity of rainfall, limited surface water resources and an increasing pattern of groundwater extraction in these areas. Consequently, the Ground Water Department with the aid of World Bank has implemented the water structuring programme to mitigate groundwater scarcity and to develop a viable solution for sustainable development in the region. The present study has been undertaken to assess the impact of artificial groundwater recharge structures in the hard-rock area of Rajasthan, India. In this study groundwater level data (pre-monsoon and post-monsoon) of 85 dug-wells are used, spread over an area of 413.59 km2. The weathered and fractured gneissic basement rocks act as major aquifer in the area. Spatial maps for pre- and post-monsoon groundwater levels were prepared using the kriging interpolation technique with best fitted semi-variogram models (Spherical, Exponential and Gaussian). The groundwater recharge is calculated spatially using the water level fluctuation method. The entire study period (2004–2011) is divided into pre- (2004–2008) and post-intervention (2009–2011) periods. Based on the identical nature of total monsoon rainfall, two combinations of average (2007 and 2009) and more than average (2006 and 2010) rainfall years are selected from the pre- and post-intervention periods for further comparisons. All of the water harvesting structures are grouped into the following categories: as anicuts (masonry overflow structure); percolation tanks; subsurface barriers; and renovation of earthen ponds/nadis. A buffer of 100 m around the intervention site is taken for assessing the influence of these structures on groundwater recharge. The relationship between the monsoon rainfall and groundwater recharge is fitted by power and exponential functions for the periods of 2004–2008 and 2008–2011 with R 2 values of 0.95 and 0.98, respectively. The average groundwater recharge is found to be 18% of total monsoon rainfall prior to intervention and it became 28% during the post-intervention period. About 70.9% (293.43 km2) of the area during average rainfall and more than 95% (396.26 km2) of the area during above-average rainfalls show an increase in groundwater recharge after construction of water harvesting structures. The groundwater recharge pattern indicates a positive impact within the vicinity of intervention sites during both average and above-average rainfall. The anicuts are found to be the most effective recharge structures during periods of above-average rainfall, while subsurface barriers are responded well during average rainfall periods. In the hard-rock terrain, water harvesting structures produce significant increases in groundwater recharge. The geo-spatial techniques that are used are effective for evaluating the response of different artificial groundwater recharge techniques.

Hydro-engineering solution for a sustainable groundwater management at a cross border region: case of Lake Nyasa/Malawi basin, Tanzania

A groundwater resources assessment has been carried out for the Lake Nyasa Basin east Africa, with reference to sub catchments further to the whole basin wise analysis, including quantification of potential yields from the aquifers. Numerical groundwater models, MODFLOW-SURFACT coupled with Visual MODFLOW, were used to assess sub-basin groundwater sustainability (Via “Zone Budget” software package). The model has been calibrated to observed hydraulic head and processed baseflow estimate. It is concluded that the aquifer system is sustained by episodic recharge and the long-term gaining storage which represents the maximum extractable volume. Future predictions of groundwater usage indicate that by 2035 the percentage of annual safe yield extracted will increase to between 11.3 and 103%. Model result suggests that there is a need to revise the current estimate of sustainable yield based on future climate change conditions and projected population growth, which would decrease spring flows substantially and decrease hydraulic head basin-wide. It also suggests that by 2035 some sub catchments will be nearly at or exceeding the annual safe yield leaving no room for socio-economic development, or the need to reduce existing socio-economic demands to meet domestic demands. Besides to improving the natural replenishment capacity through artificial recharge technique, the other option is to increase the percentage of total recharge allocated to the annual safe yield from 10% of the total annual recharge to 20% in these catchments. This provides a basis for management of individual groundwater scheme in sustaining livelihood activities or implications of policies and to develop a plan for potential groundwater extraction scenarios pertaining to water use and allocation.

Assessment of Sea Water Intrusion in Muthupettai Block

<div><p><em>Salt water intrusion into coastal aquifers is potentially a major problem in the coastal region of Muthupettai block in Thiruthuraipoondi taluk (Thiruvarur District, Tamil Nadu), hence in order to assess the vulnerability area, ground water study should be done. By the water quality variations sea water mixing index is assessed. Seawater mixing index is used to describe the vulnerability area and the extension of intrusion over the study area. Thematic maps of factors influencing the sea water intrusion were prepared and overlaid using Geographical Information System (GIS). By the vulnerability mapping, the suitable area for the remediation technique of sea water intrusion that should be practiced in the study area will be decided. Rain water harvesting and artificial recharge techniques are more useful as a tool in remediation of salt water intrusion. Estimation of surplus run-off is also very important in planning artificial recharge schemes.</em></p></div>

Geophysical and Hydrological Investigations of the Northern Wadis Area of Azraq Basin for Groundwater Artificial Recharge Purposes

Geophysical study and watershed hydrological delineation have been integrated at downstream of Alasra dam site Norh Azraq area to investigate their potential for artificial groundwater recharge. The total surface area of the watershed was found to be about 195 square kilometers. The estimated annual runoff volumes for the Alasra watershed ranged between 1.2 and 1.8 MCM. Moreover, the interpretation of Ten Time Domain Electromagnetic (TDEM) soundings suggested three principal subsurface layers. The top surface layer has an intermediate resistivity (90 - 110 Ohm·m) with a thickness ranging from a few meters to around 50 m. This layer was interpreted as superficial deposits. The second subsurface layer with variably high resistivity values is composed of unsaturated massive basalt layer and probably belongs to Madhala Olivine Phyric Basalt Formation (MOB). The large variations in resistivity could be ascribed to the degree of water saturation (as a result of groundwater recharge from the nearby harvested water dam), or lithological variations (clay content) and/or due to structural control. The third subsurface layer has low resistivity values (<10 Ω·m to 40 Ω·m) and was found at a depth ranging from 120 to 150 m. This layer could represent a saturated basalt layer with high clay contents. The subsurface structures and major faults have been identified. Based on the results of this study, a combination of surface and subsurface artificial groundwater recharge techniques is highly recommended.

Enhancement of groundwater potential by aquifer artificial recharge techniques: an adaptation to climate change

INTRODUCTION Climate change is already a reality affecting, in particular, several countries of the Mediterranean Sea. The impact of this change on water resources is very important; indeed, climate observations highlight periods of droughts and floods, which we call extreme events. To reduce the effect of these two phenomena on the quantitative degradation or lack of water resources due to changes in rainfall, artificial recharge techniques are a solution to adapting to this situation. The excess water generated by floods on watersheds could be retained in basins to be injected into the aquifer reservoir after the identification of suitable sites for groundwater recharge. The development of numerical tools can enhance the studies and the conceptions of aquifer artificial recharge operations. Indeed, these tools, particularly numerical models, by way of numerical simulations, can give the behaviour of response of the aquifer (water table) to the induced infiltration. In addition, the use of these numerical tools is an opportunity for synthesis of all data of the aquifer in order to establish a conceptual model first.

Climate change impact assessment in Veneto and Friuli Plain groundwater. Part II: A spatially resolved regional risk assessment

Climate change impact assessment on water resources has received high international attention over the last two decades, due to the observed global warming and its consequences at the global to local scale. In particular, climate-related risks for groundwater and related ecosystems pose a great concern to scientists and water authorities involved in the protection of these valuable resources. The close link of global warming with water cycle alterations encourages research to deepen current knowledge on relationships between climate trends and status of water systems, and to develop predictive tools for their sustainable management, copying with key principles of EU water policy. Within the European project Life+ TRUST (Tool for Regional-scale assessment of groundwater Storage improvement in adaptation to climaTe change), a Regional Risk Assessment (RRA) methodology was developed in order to identify impacts from climate change on groundwater and associated ecosystems (e.g. surface waters, agricultural areas, natural environments) and to rank areas and receptors at risk in the high and middle Veneto and Friuli Plain (Italy). Based on an integrated analysis of impacts, vulnerability and risks linked to climate change at the regional scale, a RRA framework complying with the Sources–Pathway–Receptor–Consequence (SPRC) approach was defined. Relevant impacts on groundwater and surface waters (i.e. groundwater level variations, changes in nitrate infiltration processes, changes in water availability for irrigation) were selected and analyzed through hazard scenario, exposure, susceptibility and risk assessment. The RRA methodology used hazard scenarios constructed through global and high resolution model simulations for the 2071–2100 period, according to IPCC A1B emission scenario in order to produce useful indications for future risk prioritization and to support the addressing of adaptation measures, primarily Managed Artificial Recharge (MAR) techniques. Relevant outcomes from the described RRA application highlighted that potential climate change impacts will occur with different extension and magnitude in the case study area. Particularly, qualitative and quantitative impacts on groundwater will occur with more severe consequences in the wettest and in the driest scenario (respectively). Moreover, such impacts will likely have little direct effects on related ecosystems – croplands, forests and natural environments – lying along the spring area (about 12% of croplands and 2% of natural environments at risk) while more severe consequences will indirectly occur on natural and anthropic systems through the reduction in quality and quantity of water availability for agricultural and other uses (about 80% of agricultural areas and 27% of groundwater bodies at risk).