The Damaging Effects of Abstracting the Deep Aquifers’Groundwater in Jordan-Quality Constraints

The deep aquifers in Jordan contain non-renewable and fossil groundwater and their extraction is quasi a mining process, which ends in the depletion of these resources. Although aquifers in the majority of groundwater basins in Jordan are vertically and horizontally interconnected stratification in different water quality horizons with generally increasing water salinity with the depth is observed. Many officials and planners advocate the extraction of deep salty and brackish water to be desalinated and used in household, industrial, and agricultural uses. In this article, the quality of the groundwater in the different deep aquifers and areas in Jordan is discussed. The results of this study show that the consequences of the deep groundwater exploitation are not restricted to depletion of the deep aquifers but also that the overlying fresh groundwater will, due to vertical and horizontal interconnectedness of the different aquifers, percolate down to replace the extracted deep groundwater. This will cause the down-percolating fresh groundwater to become salinized in the deep saline aquifers, which means that extracting the deep brackish and saline groundwater is not only an emptying process of the deep groundwater but also it is an emptying process of the fresh groundwater overlying them. The results allow to conclude that any extraction of the deep groundwater in areas lying to the north of Ras en Naqab Escarpment will have damaging impacts on the fresh groundwater in the overlying fresh groundwater aquifers. This article strongly advises not to extract the deep brackish and saline groundwater, but to conserve that groundwater as a base supporting the overlying fresh groundwater resources, and that will help in protecting the thermal mineralized water springs used in spas originating from these deep aquifers. The increasing water needs of the country can be covered by the desalination of seawater at Aqaba, which is the only viable option for Jordan at present and in the coming decades.

Submarine groundwater discharge enhances primary productivity in the Yellow Sea, China: Insight from the separation of fresh and recirculated components

Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutrient into coastal waters,and generally comprises two components:submarine fresh groundwater discharge(SFGD)and recirculated saline groundwater discharge(RSGD).The separate evaluation of SFGD and RSGD is extremely limited as compared to the conventional estimation of total SGD and associated nutrient fluxes,especially in marginal-scale regions.In this study,new high-resolution radium isotopes data in seawater and coastal groundwater enabled an estimation of SGD flux in a typical marginal sea of the Yellow Sea.By establishing 226Ra and 228Ra mass balance models,we obtained the SGD-derived radium fluxes,and then estimated the SFGD and RSGD fluxes through a two end-member model.The results showed that the total SGD flux into the Yellow Sea was equivalent to approximately 6.6 times the total freshwater discharge of surrounding rivers,and the SFGD flux accounted for only 5.2%–8.8%of the total SGD.Considering the nutrient concentrations in coastal fresh and saline groundwater,we obtained the dissolved inorganic nutrient fluxes(mmol m^(-2) yr^(-1))to be 52–353 for nitrogen(DIN),0.21–1.4 for phosphorus(DIP),34–226 for silicon(DSi)via SFGD,and 69–262 for DIN,1.0–3.9 for DIP,70–368 for DSi via RSGD,with the sum of nutrient fluxes equaling to(1.8–9.3)-fold,(1.3–5.6)-fold and(2.0–9.5)-fold of the riverine inputs.Compared to the conventional estimation of the total SGD flux,the nutrient fluxes derived from the separation of SFGD and RSGD were(1.6–2.1),(1.6–1.8)and(4.0–4.9)times lower for DIN,DIP and DSi,respectively,indicating that the estimates by separating SFGD and RSGD could be conservative and representative results of the Yellow Sea.Furthermore,we suggested that SGD played an important role in nutrient sources among all the traditional nutrient inputs sources,providing 15%–48%,33%–68%and 14%–43%of the total DIN,DIP and DSi input fluxes into the Yellow Sea,and the high nutrient stoichiometric ratios(i.e.,DIN/DIP)in SGD probably contributed to the increasing ratios in the Yellow Sea.In addition delivering large amounts of nutrient into the Yellow Sea,SGD would create primary productivity of 10–49,1.6–6.8 and 8.8–42 g C m^(-2)yr^(-1) based on N,P and Si,which were equivalent to 5.2%–27%,0.9%–3.7%and 4.7%–23%of the total primary productivity,respectively.In particular,the SFGD-derived DIN flux can be converted to primary productivity of 4.2–28 g C m^(-2)yr^(-1) thus demonstrating the disproportionately large role of SFGD in ecological environment of the Yellow Sea relative to its flux.Therefore,we conclude that SGD,particularly SFGD,plays an important role as a nutrient source for the Yellow Sea,and not only affects nutrient budgets and structures but also enhances the primary productivity.

Groundwater hydrochemistry and isotope geochemistry in the Turpan Basin, northwestern China

The Turpan Basin is located in the arid zone of northwestern China and is a typical closed inland basin surrounded by high mountains. It is one of the most arid regions in the world and, as a result, the groundwater in this area is very important for both domestic and agricultural uses. In the present study, the relationships of major elements（K＋, Na＋, Ca2＋, Mg2＋, HCO3-, SO42- and Cl-） and environmental isotopes（δ18O, δ2H and T） in groundwater were analyzed to investigate the evolution of the regional hydrochemistry within the Turpan Basin. The hydrochemistry results demonstrate that groundwater with high total dissolved solids（TDS） concentration is dominated by sodium chloride（Na-Cl） and sodium sulfate（Na-SO4） type water, whereas that with low TDS concentration（typically from near mountain areas） is dominated by calcium bicarbonate（Ca-HCO3） type water. The evolution of groundwater hydrochemistry within the Turpan Basin is a result of calcium carbonate precipitation, evaporation concentration, cation exchange and dissolution of evaporites（i.e. halite, mirabilite and gypsum）. Furthermore, evaporite dissolution associated with irrigation practice plays a key role in the groundwater salinization, especially in the central part of the basin. Environmental isotopes reveal that the groundwater is recharged by precipitation in the mountain areas and fast vertical infiltration of irrigation return flow. In the southern sub-basin the shallow groundwater and the deep groundwater is separated at a depth of about 40 m, with substantial differences in terms of hydrochemical and isotopic characteristics. The results are useful for decision making related to sustainable water resource utilization in the Turpan Basin and other regions in northwestern China.

The Mechanism of Groundwater Salinization and Its Control in the Yaoba Oasis,Inner Mongolia

The arid area is one of the most concerned areas among the water resources researchers and economists. Northwest China will be an important developing region of China in the 21st century. Yaoba is a well-irrigation oasis within this arid area, which is located in the Alxa area west of the Helan Mountains and next to the Tengger desert in the east. It has contributed greatly to the local stock raising and agriculture since its development in 1970. However, the groundwater which the oasis depends on to survive has been getting salinized gradually and more serious in recent years.

Distribution of groundwater salinity and formation mechanism of fresh groundwater in an arid desert transition zone

This study reviews the distribution of groundwater salinity in an arid desert transition zone. By combining field experiments and computer simulation models we make a comprehensive analysis of the formation mechanism of fresh groundwater in relation to the paleogeographic conditions of lithofacies, the geochemical characteristics of the aquifer media, salt deliverability in the vadose zone and prevailing hydrodynamic conditions. The results demonstrate that(1) the lacustrine facies deposition stratum of the Huanhe formation in the Cretaceous system provides a brackish-salt groundwater environment;(2) the average salinity of parent rocks are approximately 440 mg/kg and 4 371 mg/kg in the Quaternary eolian sand and the Cretaceous Huanhe formation respectively, suggesting that parent rocks are the principal controlling factor in the distribution of groundwater quality given that mineral and chemical composition of the eolian sand is simpler than that of the Huanhe formation;(3) average groundwater flow rates are approximately 0.25 m/d and 0.1 m/d in eolian sand and Huanhe formation aquifers respectively, indicating that hydrodynamic conditions play an important role in driving in the formation and evolution of fresh groundwater;(4) The salinity deliverability in the vadose zone overlying the aeolian sand and Huanhe formation aquifers are approximately 15.97 mg/L and 220.42 mg/L respectively, signifying that the combination of lithology and salt content of vadose zone, rainfall infiltration, evapotranspiration and concentration heavily influence the formation, distribution and evolution of groundwater quality. This study can provide a scientific basis for the sustainable development and utilization of groundwater resources in arid areas.

Hydrochemical evolution of groundwater in northwestern part of the Indo-Gangetic Basin,India:A geochemical and isotopic approach

The present study aims to understand the hydrochemical evolution of groundwater in the Ghaggar River Basin,representing a zone of excessive abstraction of groundwater in the northwestern Indo-Gangetic Basin.The study comprises a regional scale and high-resolution sampling of groundwater during preand post-monsoon seasons of 2013 and their analyses for major ions,δ^(18)O,δ^(2)H,and 3 H.Variation in hydrochemical and isotopic data is found both in spatial and vertical scales.The significant vertical variation of TDS,NO_(3)and K^(+)allowed the classification of the aquifer system into two major groups:shallow(depth<80 m bgl)and deep(depth>80 m bgl).The depthwise variations ofδ^(18)O andδ^(2)H support this categorization of the aquifers.The Ca-HCO_(3)and Ca-Mg-Na-HCO_(3)water facies with higher values of 3 H in the proximal part of the basin characterize recharge areas under humid conditions.The dominance of Mg-Na-HCO_(3)and Na-HCO_(3)facies in shallow and deep aquifers in central part of the basin,illustrate the intermediate to advanced stages of hydrochemical evolution in the system.Dominance of brackish Ca-Mg-Cl-SO_(4)and Na-Cl-SO_(4)water types in the discharge areas is due to the prevailing geological conditions and anthropogenic activities.Geochemical modelling supports the reverse cation exchange and mixing during lateral and vertical flows,weathering of silicate minerals,dissolution of crustal salts,and evaporative enrichment are the natural processes governing the evolution of groundwater chemistry along the flowpaths.The developed process-based conceptual model will aid in the formulation of a suitable plan for groundwater resource management in the region.

Hydrochemical Characteristics and the Suitability of Groundwater in the Coastal Region of Tangshan, China

Through collecting groundwater samples from the coastal region of Tangshan, China, the hydrochemical processes that affect the chemical composition of groundwater and the quality of resources were analyzed. Chemical constituents, factor analysis, and a graphic method were employed in this research. The results show that human activities obviously affect fresh groundwater. The deep groundwater distributed in the southern part of the region is severely affected by salinization, and the shallow groundwater in the north is also beginning to show the same deterioration. The chemical concentrations of the deep groundwater depend largely upon the water-rock interaction, the mixing of saline water and the ion exchange processes. With the exception of sample C-33, all the groundwater samples in the study area are suitable for drinking. Tests show that roughly half of the deep groundwater samples have at least one water quality index indicating that it is chemically doubtful or unsuitable for irrigation. Therefore, it is concluded that deep groundwater is becoming an unacceptable resource to irrigate areas located near the coastline because the groundwater quality in the study area is exhibiting signs of degradation. This study＇s findings contribute to a better understanding of groundwater resources in order to support regional management and protection.

Molecular Analysis of Dominant Microbial Populations in Heavily and Slightly Polluted Aquifers by a Seaside Landfill

The microbial populations were investigated in two groundwater samples, GW-H and GW-S, which represented heavily and slightly polluted aquifers by a seaside landfill. The concentrations of dissolved redox-relevant species suggested that iron-reduction/sulfate-reduction and denitrification were major redox processes for GW-H and GW-S. The dominant microbial populations were determined using restriction fragment length polymorphism analyses of 16S rRNA gene clone libraries. These microbes were then further studied by sequencing and phylogenetic analyses. The results indicate an obvious variation of the dominant populations between the two samples. The coexistence of sequences related to denitrifiers, sulfur-reducers, and methanotrophic bacteria was found in the GW-S sample, and a sequence associated with a sulfate-reducer was also found in the GW-H sample using molecular analyses. These results suggest that the molecular approach may be an important supplement to other approaches in characterizing the redox processes in polluted aquifers.