Decision support model for assessing aquifer pollution hazard and prioritizing groundwater resources management in the wet Pampa plain, Argentina

This paper gives an account of the implementation of a decision support system for assessing aquifer pollution hazard and prioritizing subwatersheds for groundwater resources management in the southeastern Pampa plain of Argentina. The use of this system is demonstrated with an example from Dulce Stream Basin (1,000 km² encompassing 27 subwatersheds), which has high level of agricultural activities and extensive available data regarding aquifer geology. In the logic model, aquifer pollution hazard is assessed as a function of two primary topics: groundwater and soil conditions. This logic model shows the state of each evaluated landscape with respect to aquifer pollution hazard based mainly on the parameters of the DRASTIC and GOD models. The decision model allows prioritizing subwatersheds for groundwater resources management according to three main criteria including farming activities, agrochemical application, and irrigation use. Stakeholder participation, through interviews, in combination with expert judgment was used to select and weight each criterion. The resulting subwatershed priority map, by combining the logic and decision models, allowed identifying five subwatersheds in the upper and middle basin as the main aquifer protection areas. The results reasonably fit the natural conditions of the basin, identifying those subwatersheds with shallow water depth, loam–loam silt texture soil media and pasture land cover in the middle basin, and others with intensive agricultural activity, coinciding with the natural recharge area to the aquifer system. Major difficulties and some recommendations of applying this methodology in real-world situations are discussed.     

Groundwater quality assessment in semi-arid regions using integrated approaches: the case of Grombalia aquifer (NE Tunisia)

As many arid and semi-arid regions in the Mediterranean Basin, the Grombalia coastal aquifer (NE Tunisia) is affected by severe groundwater exploitation and contamination. Therefore, quality assessments are becoming increasingly important as the long-term protection of water resources is at stake. Multidisciplinary investigations, like the one presented in this paper, are particularly effective in identifying the different origins of mineralization within an aquifer and investigating the impact of anthropogenic activities on groundwater quality. An integrated assessment, focused on the combined use of geostatistical, geochemical and isotopic (δ¹⁸O, δ²H and ³H) tools, was performed in the Grombalia aquifer between February and March 2014. The overall goal was to study the main processes controlling aquifer salinization, with special focus to nitrate contamination. Results indicate a persisting deterioration of water quality over the whole basin except the south-eastern zone juxtaposing the recharge area of the aquifer. Nitrate contents exceed the drinking water standard (50 mg/l) in 70% of groundwater samples, mainly due to the excessive use of fertilizers and urban activities. Stable isotope measurements showed the contribution of modern rainwater to aquifer recharge and proved the presence of evaporation contributing to the salinity increase. Tritium values of groundwater samples suggested two hypotheses: the existence of mixture between old and recent water or/and the existence of two recharge periods of the aquifer, pre- and post-nuclear weapons test. Principal component analysis confirmed the geochemical interpretation, highlighting that water-rock interaction evaporation effect and intensive anthropogenic activities constitute the main processes controlling the regional groundwater mineralization.     

Time Series Analysis to Monitor and Assess Water Resources: A Moving Average Approach

An understanding of the behavior of the groundwater body and its long-term trends are essential for making any management decision in a given watershed. Geostatistical methods can effectively be used to derive the long-term trends of the groundwater body. Here an attempt has been made to find out the long-term trends of the water table fluctuations of a river basin through a time series approach. The method was found to be useful for demarcating the zones of discharge and of recharge of an aquifer. The recharge of the aquifer is attributed to the return flow from applied irrigation. In the study area, farmers mainly depend on borewells for water and water is pumped from the deep aquifer indiscriminately. The recharge of the shallow aquifer implies excessive pumping of the deep aquifer. Necessary steps have to be taken immediately at appropriate levels to control the irrational pumping of deep aquifer groundwater, which is needed as a future water source. The study emphasizes the use of geostatistics for the better management of water resources and sustainable development of the area.     

Future groundwater extraction scenarios for an aquifer in a semiarid environment: case study of Guadalupe Valley Aquifer,Baja California,Northwest Mexico

Semiarid northwestern Mexico presents a growing water demand produced by agricultural and domestic requirements during the last two decades. The community of Guadalupe Valley and the city of Ensenada rely on groundwater pumping from the local aquifer as its sole source of water supply. This dependency has resulted in an imbalance between groundwater pumpage and natural recharge. A two-dimensional groundwater flow model was applied to the Guadalupe Valley Aquifer, which was calibrated and validated for the period 1984–2005. The model analysis verified that groundwater levels in the region are subject to steep declines due to decades of intensive groundwater exploitation for agricultural and domestic purposes. The calibrated model was used to assess the effects of different water management scenarios for the period 2007–2025. If the base case (status quo) scenario continues, groundwater levels are in a continuous drawdown trend. Some wells would run dry by August 2017, and water demand may not be met without incurring in an overdraft. The optimistic scenario implies the achievement of the mean groundwater recharge and discharge. Groundwater level depletion could be stopped and restored. The sustainable scenario implies the reduction of current extraction (up to about 50 %), when groundwater level depletion could be stopped. A reduction in current extraction mitigates water stress in the aquifer but cannot solely reverse declining water tables across the region. The combination of reduced current extraction and an implemented alternative solution (such as groundwater artificial recharge), provides the most effective measure to stabilize and reverse declining groundwater levels while meeting water demands in the region.     

Computation of groundwater resources and recharge in Chithar River Basin, South India

Groundwater recharge and available groundwater resources in Chithar River basin, Tamil Nadu, India spread over an area of 1,722 km² have been estimated by considering various hydrological, geological, and hydrogeological parameters, such as rainfall infiltration, drainage, geomorphic units, land use, rock types, depth of weathered and fractured zones, nature of soil, water level fluctuation, saturated thickness of aquifer, and groundwater abstraction. The digital ground elevation models indicate that the regional slope of the basin is towards east. The Proterozoic (Post-Archaean) basement of the study area consists of quartzite, calc-granulite, crystalline limestone, charnockite, and biotite gneiss with or without garnet. Three major soil types were identified namely, black cotton, deep red, and red sandy soils. The rainfall intensity gradually decreases from west to east. Groundwater occurs under water table conditions in the weathered zone and fluctuates between 0 and 25 m. The water table gains maximum during January after northeast monsoon and attains low during October. Groundwater abstraction for domestic/stock and irrigational needs in Chithar River basin has been estimated as 148.84 MCM (million m³). Groundwater recharge due to monsoon rainfall infiltration has been estimated as 170.05 MCM based on the water level rise during monsoon period. It is also estimated as 173.9 MCM using rainfall infiltration factor. An amount of 53.8 MCM of water is contributed to groundwater from surface water bodies. Recharge of groundwater due to return flow from irrigation has been computed as 147.6 MCM. The static groundwater reserve in Chithar River basin is estimated as 466.66 MCM and the dynamic reserve is about 187.7 MCM. In the present scenario, the aquifer is under safe condition for extraction of groundwater for domestic and irrigation purposes. If the existing water bodies are maintained properly, the extraction rate can be increased in future about 10 % to 15 %.     

典型水源地地下水污染风险评价

地下水污染是由含水层本身的脆弱性与人类活动产生的污染负荷造成的。污染物的荷载可以控制或改变,但是含水层的敏感性是本质的、天然的特性。污染风险不仅取决于相对稳定、不宜改变的含水层天然特征,还取决于主观的污染活动。因此,从地下水天然防污性能、地下水污染源荷载以及地下水社会效益3个方面评价了典型水源地地下水受污染的风险。     

Managed aquifer recharge by a check dam to improve the quality of fluoride-rich groundwater: a case study from southern India

In many regions around the globe, including India, degradation in the quality of groundwater is of great concern. The objective of this investigation is to determine the effect of recharge from a check dam on quality of groundwater in a region of Krishnagiri District of Tamil Nadu State, India. For this study, water samples from 15 wells were periodically obtained and analysed for major ions and fluoride concentrations. The amount of major ions present in groundwater was compared with the drinking water guideline values of the Bureau of Indian Standards. With respect to the sodium and fluoride concentrations, 38% of groundwater samples collected was not suitable for direct use as drinking water. Suitability of water for agricultural use was determined considering the electrical conductivity, sodium adsorption ratio, sodium percentage, permeability index, Wilcox and United States Salinity Laboratory diagrams. The influence of freshwater recharge from the dam is evident as the groundwater in wells nearer to the check dam was suitable for both irrigation and domestic purposes. However, the groundwater away from the dam had a high ionic composition. This study demonstrated that in other fluoride-affected areas, the concentration can be reduced by dilution with the construction of check dams as a measure of managed aquifer recharge.     

Numerical modelling of the environmental impact of landfill leachate leakage on groundwater quality – a field application

Waste disposal facilities are mainly responsible for the gradual quality degradation of subsurface freshwater reservoirs. The main objective of this work is to identify the groundwater contamination risk due to potential leachate leakage and seepage beneath the municipal landfill of the City of Patras in Greece. A groundwater and leachate mass transport model of the underlying aquifer was developed for this purpose. The derived simulation results indicate that, depending on the permeability of the soil at the location of leakage, the contamination risk for the groundwater can be high. In order to quantify the magnitude and the extent of the leakage, a risk assessment model for the leachate contaminant plume was developed. The risk assessment analysis shows that the municipal drinking wells are under high risk of contamination.     

A Methodology for Space-Time Classification of Groundwater Quality

Safeguarding groundwater from civil, agricultural and industrial contamination is matter of great interest in water resource management. During recent years, much legislation has been produced stating the importance of groundwater as a source for drinking water supplies, underlining its vulnerability and defining the required quality standards. Thus, schematic tools, able to characterise the quality and quantity of groundwater systems, are of very great interest in any territorial planning and/or water resource management activity.This paper proposes a groundwater quality classification method which has been applied to a real aquifer, starting from several studies published by the Italian National Hydrogeologic Catastrophe Defence Group (GNDCI).The methodology is based on the concentration values of several parameters used as indexes of the natural hydro-chemical water condition and of potential man-induced modifications of groundwater quality. The resulting maps, although representative of the quality, do not include any information on its evolution in time. In this paper, this “stationary” classification method has been improved by crossing the quality classes with three indexes of temporal behaviour during recent years. It was then applied to data from monitoring campaigns, performed in spring and autumn, from 1990 to 1996, in the plain of Modena aquifer (central Italy). The results are reported in the form of space-time classification table and maps.     

An attempt to evaluate the recharge source and extent using hydrogeochemistry and stable isotopes in North Henan Plain,China

A thorough understanding of groundwater recharge source, particularly its rate, is usually a prerequisite for effective water resources management. In this paper, we report the impact of Yellow River water seepage from the North Henan Plain, using both hydrogeochemical and stable isotopic analysis data. Seven Yellow River water samples, 10 groundwater samples from a river-parallel transect, and 36 groundwater samples from four different perpendicular transects to the Yellow River in the western, middle, and eastern plain were collected and analyzed. It inferred that cation exchange of Ca²⁺ and/or Mg²⁺ for Na⁺ occurred in groundwaters because of the dissolution of carbonate rocks. The hydrogeochemical results indicate that western piedmont lateral groundwater and the Yellow River are both important sources of groundwater recharge for the western transect of the North Henan Plain, while the former is a greater recharge source for the middle transect, and the latter is a greater recharge source for the eastern transect. Stable isotope data support Yellow River water incursion into the groundwater. The approximate distance (based on chloride concentration) from the Yellow River to border of the impact zone is17.43–23.40 km in the western plain, 52.46 km in the middle plain, and 49.82 km in the eastern plain.     

Response of groundwater to climate variation: fluctuations of groundwater level and well yields in the Halacli aquifer (Cankiri, Turkey)

The aim of this study was to investigate the response of groundwater level and well yields in the Halacli aquifer to climate variations in Central Anatolia, Turkey. The Halacli aquifer is a typical aquifer due to its vulnerability to the climate variations. The aquifer is shallow and its recharge area is small. The waters from rains and snow melts can rapidly infiltrate down to the groundwater body because the vadose zone is thin and formed from coarse material. Therefore, the groundwater system responds to the short-term recharges by raising its level. Although any exploitation did not occur, the groundwater levels have declined from 1989 to 1997. However, the groundwater levels began rising when the exploitation started in the summer of 1998. After the year 2000, although the amount and duration of yearly exploitation was constant, fluctuations of water level continued. Fluctuation of groundwater levels and well yields bewilders the water users and imperils the sustainable water management in the study area and also in arid and semi-arid regions of Turkey. In order to overcome this problem, behavior of groundwater level and discharges of the wells must be recorded and the water users must be informed about the current conditions and the possible trend in the future of the system.     

Hydrogeochemical features of groundwater of semi-confined coastal aquifer in Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran

Hydrogeochemical data of groundwater from the semi-confined aquifer of a coastal two-tier aquifer in Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran reveal salinization of the fresh groundwater (FGW). The saline groundwater zone is oriented at an angle to both Caspian Sea coastline and groundwater flow direction and extends inland from the coastline for more than 40 km. Spearman’s rank correlation coefficient matrices, factor analysis data, and values of C ratio, chloro-alkaline indices, and Na⁺/Cl^? molar ratio indicate that the ionic load in the FGW is derived essentially from carbonic acid-aided weathering of carbonates and aluminosilicate minerals, relict connate saline water, and ion exchange reactions. Saline groundwater samples (SGWS) (n?=?20) can be classified into two groups. SGWS of group 1 (n?=?17) represent the saline groundwater zone below the Caspian Sea level, and salinization is attributed essentially to (1) lateral intrusion of Caspian seawater as a consequence of (a) excessive withdrawal of groundwater from closely spaced bore wells located in the eastern part of the coastal zone and (b) imbalance between recharge and discharge of the two-tier aquifer and (2) upconing of paleobrine (interfaced with FGW) along deep wells. SGWS of this group contain, on average, 7.9 % of saltwater, the composition of which is similar to that of Caspian seawater. SGWS of group 2 (n?=?3) belong to the saline groundwater zone encountered above the Caspian Sea level, and salinization of the groundwater representing these samples is attributed to irrigation return flow (n?=?2) and inflow of saline river water (n?=?1).     

Application of drastic model and GIS: for assessing vulnerability in hard rock granitic aquifer

Geographic information system (GIS) has become one of the leading tools in the field of hydrogeological science that helps in assessing, monitoring, and conserving groundwater resources. Groundwater is a finite resource, which is being overexploited due to increase in demand over the years leading to decrease in its potentiality. In the present study, DRASTIC model has been used to prepare groundwater vulnerable zone in hard rock aquifer of granitic terrain. The main objective is to determine susceptible zone for groundwater pollution by integrating hydrogeological layers in GIS environment. The layers such as depth of aquifer, recharge, aquifer yield, soil type, topography, vadose zone, and transmissivity are incorporated in the DRASTIC model. The final output of the map shows that around 60% of the area falls under low to no risk of pollution zone. The high risk of pollution zones are mostly present towards the margin of southeastern periphery. The lower part of the basin as well as small area on northern side falls under moderate risk of pollution zone. For the assessment of groundwater pollution zone, 24 groundwater samples have been collected from different vulnerable zones. The chemical analysis of sample shows that the southeastern margin of basin has relatively high concentration of nitrate as compared to other parts of the basin. It is present in high pollution zone as well as moderate pollution zone. The present model can be used for assessment and management of groundwater.     

Long-term reclaimed water application effects on phosphorus leaching potential in rapid infiltration basins

Rapid infiltration basins (RIBs) are effective tools for wastewater treatment and groundwater recharge, but continuous application of wastewater can increase soil P concentrations and subsequently impact groundwater quality. The objectives of this study were to (1) investigate the effects of reclaimed water infiltration rate and "age" of RIBs on soil P concentrations at various depths, and (2) estimate the degree (percentage) of sorption equilibrium reached between effluent P and soil attained during reclaimed water application to different RIBs. The study was conducted in four contrasting cells of a RIB system with up to a 25 year history of secondary wastewater application. Soil samples were collected from 0 to 300 cm depth at 30 cm intervals and analyzed for water extractable phosphorus (WEP) and oxalate extractable P, Al, and Fe concentrations. Water extractable P and P saturation ratio (PSR) values were generally greater in the cells receiving reclaimed water compared to control soils, suggesting that reclaimed water P application can increase soil P concentrations and the risk of P movement to greater depths. Differences between treatment and control samples were more evident in cells with longer histories of reclaimed water application due to greater P loading. Data also indicated considerable spatial variability in WEP concentrations and PSR values, especially within cells from RIBs characterized by fast infiltration rates. This occurs because wastewater-P flows through surface soils much faster than the minimum time required for sorption equilibrium to occur. Studies should be conducted to investigate soil P saturation at deeper depths to assess possible groundwater contamination.     

Hydrochemical and geoelectrical investigation of the coastal shallow aquifers in El-Omayed area, Egypt

Monitoring and assessment of the coastal aquifers are becoming a worldwide concern for the need of additional and sustainable water resources to satisfy demographic growth and economic development. A hydrochemical and geoelectrical investigation was conducted in the El-Omayed area in the northwestern coast of Egypt. The aim of the study was to delineate different water-bearing formations, provide a general evaluation of groundwater quality, and identify the recharge sources in aquifers. Thirty-seven water samples were collected and chemically analyzed from the sand dune accumulations and oolitic limestone aquifers. Fifteen profiles of vertical electrical soundings (VESs) were obtained in the oolitic limestone aquifer to examine the variations of subsurface geology and associated groundwater chemistry. The groundwater reserves in the El-Omayed area are mainly contained in sand dune accumulations and oolitic limestone aquifers. The aquifer of sand dune accumulations contains freshwater of low salinity (average total dissolved solids (TDS)?=?974 mg/l). Groundwater of oolitic limestone aquifer is slightly brackish (average TDS?=?1,486 mg/l). Groundwater of these aquifers can be used for irrigation under special management for salinity control, and regular leaching as indicated by electrical conductivity and sodium adsorption ratio. Results of VES interpretation classified the subsurface sequence of oolitic limestone aquifer into four geoelectric zones, with increasing depth, calcareous loam, gypsum, oolitic limestone, and sandy limestone. Oolitic limestone constitutes the main aquifer and has a thickness of 12–32 m.     

Tailoring groundwater quality monitoring to vulnerability: a GIS procedure for network design

Monitoring networks aiming to assess the state of groundwater quality and detect or predict changes could increase in efficiency when fitted to vulnerability and pollution risk assessment. The main purpose of this paper is to describe a methodology aiming at integrating aquifers vulnerability and actual levels of groundwater pollution in the monitoring network design. In this study carried out in a pilot area in central Italy, several factors such as hydrogeological setting, groundwater vulnerability, and natural and anthropogenic contamination levels were analyzed and used in designing a network tailored to the monitoring objectives, namely, surveying the evolution of groundwater quality relating to natural conditions as well as to polluting processes active in the area. Due to the absence of an aquifer vulnerability map for the whole area, a proxi evaluation of it was performed through a geographic information system (GIS) methodology, leading to the so called “susceptibility to groundwater quality degradation”. The latter was used as a basis for the network density assessment, while water points were ranked by several factors including discharge, actual contamination levels, maintenance conditions, and accessibility for periodical sampling in order to select the most appropriate to the network. Two different GIS procedures were implemented which combine vulnerability conditions and water points suitability, producing two slightly different networks of 50 monitoring points selected out of the 121 candidate wells and springs. The results are compared with a “manual” selection of the points. The applied GIS procedures resulted capable to select the requested number of water points from the initial set, evaluating the most confident ones and an appropriate density. Moreover, it is worth underlining that the second procedure (point distance analysis [PDA]) is technically faster and simpler to be performed than the first one (GRID?+?PDA).     

Simulations of groundwater-surface water interaction and particle movement due to the effect of weir construction in the sub-watershed of the river Labe in the town of Děčín

Steady- and transient-state simulations of groundwater flow and particle movement in the sub-watershed of the river Labe in Dě?ín town was carried out using Visual MODFLOW software. The simulations were performed for calibration and for the scenarios that the change in the water level of the river Labe was undergoing. Steady-state simulation was carried out for the sake of calibration of model outputs. For transient simulation, two different scenarios were considered in order to investigate the response of the aquifer system to the stresses applied on surface water of the river. The simulation results have shown that the surface water and groundwater interactions, and the subsequent particle movement were affected by the stresses applied on the surface water in the river Labe. The first scenario involved the rapid recharge of surface water to the aquifer in the vicinity of the river while particles still move towards the river at the places far away from the river. At the end of the second scenario, particles still tend to move towards the river slowly and finally tend to stay within the aquifer as equilibrium of hydraulic gradient is reached between the surface and groundwater levels. The time series graphs of hydraulic heads at all observation wells show that the groundwater level in the surrounding aquifer rises significantly as a result of recharges from the river. The local water balance of the study area was calculated and expressed as the rates of water entering and leaving the system. At the end of the second scenario, the difference between the rate of flow into and out of the model area was 0.73 m³ day^?1.     

An analytical model for the assessment of pesticide exposure levels in soils and groundwater

The movement and degradation of pesticide residues in soils and groundwater are complex processes affected by soil physical, (bio)chemical, and hydrogeological properties, climatic conditions, and agricultural practices. This work presents a physically-based analytical model suitable for long-term predictions of pesticide concentrations in groundwater. The primary interest is to investigate the impact of soil environment, related physical and (bio)chemical processes, especially, volatilization, crop uptake, and agricultural practices on long-term vulnerability of groundwater to contamination by pesticides. The soil is separated into root and intermediate vadose zones, each with uniform properties. Transport in each soil zone is modeled on the basis of complete mixing, by spatial averaging the related point multiphase-transport partial differential equation (i.e., linear-reservoir models). Transport in the aquifer, however, is modeled by a two-dimensional advection-dispersion transport equation, considering adsorption and first-order decay rate. Vaporization in the soil is accounted for by assuming liquid-vapor phase partitioning using Henry's law, and vapor flux (volatilization) from the soil surface is modeled by diffusion through an air boundary layer. Sorption of liquid-phase solutes by crops is described by a linear relationship which is valid for first-order (passive) crop uptake. The model is applied to five pesticides (atrazine, bromacil, chlordane, heptachlor, and lindane), and the potential for pesticide contamination of groundwater is investigated for sandy and clayey soils. Simulation results show that groundwater contamination can be substantially reduced for clayey soil environments, where bio(chemical) degradation and volatilization are most efficient as natural loss pathways for the pesticides. Also, uptake by cross can be a significant mechanism for attenuating exposure levels in ground-water especially in a sandy soil environment, and for relatively persisting pesticides. Further, simulations indicate that changing agricultural practices can have a profound effect on vulnerability of groundwater to mobile and relatively persisting pesticides.     

MONITORING OF SPATIAL AND TEMPORAL HYDROCHEMICAL CHANGES IN GROUNDWATER UNDER THE CONTAMINATING EFFECTS OF ANTHROPOGENIC ACTIVITIES IN MERSIN REGION, TURKEY

The development of groundwater resources for water supply is a favored way in Turkey. The Berdan alluvial aquifer in Mersin is particularly productive, but little is known about the natural phenomena that govern the groundwater quality and the contamination sources in this region. During 2001 and 2002, water samples for chemical analysis were obtained from 27 wells and from two points of Berdan River and analyzed by ICP. Main chemical characteristics of sampled groundwater define two aquifers, which were also determined by hydrogeological investigations. The groundwater produced from some of the wells was affected by anthropogenic activities temporally and spatially by seawater intrusion. Berdan River is polluted with the wastewater discharges and river water also influences the groundwater quality.     

短时强降雨下平原区域浅层地下水入渗补给规律研究

以豫东平原惠北试验区为研究区域,根据研究区域包气带土壤蓄水库容、土壤前期含水量、地表径流、潜水蒸发量等资料数据计算地下水入渗补给规律,确定降雨对地下水的补给系数.研究结果显示:单次短时强降雨条件下,降雨强度与研究区域浅层地下水入渗补给系数呈反比例关系;当降雨强度一致时降雨量与研究区域浅层地下水入渗补给系数呈正比例关系,在降雨强度低于15 mm/h的条件下,降雨量主要用于补充包气带缺失的水分和土壤、作物、植物等的蒸发蒸腾消耗,无法对研究区域浅层地下水进行有效补给.