Comparison of Different Indicators for Groundwater Contamination by Seawater Intrusion on the Lebanese Coast

In order to evaluate the state of groundwater salination by seawater intrusion on the Lebanese coast, the region of Choueifat–Rmeyle, situated in the south of Mount-Lebanon, was chosen as a study zone. Overall, six wells were chosen and water sampling was done for three years starting from 1999 till 2002. Sampling was done on a monthly basis for ten months per year, from July till April. A complete physico-chemical analysis was done for all the water samples taken. Seawater intrusion in the Choueifat-Rmeyle region was studied through the interrelations between the chemical and physical constituents of groundwater. Results showed that the regions of Choueifat, Jiye and Rmeyle were subject to seawater intrusion. This intrusion was directly and simultaneously related to the pumping period and intensity but weakly linked to the quantity of rainfall. It was also related to the geologic nature of the study area. Furthermore, the actual intrusion in the study zone increases the already existing salinity problems. The salinity rates of wells water oscillated between 0.7 dS/m and 5.5 dS/m with the majority above 2 dS/m. This is leading to intolerable levels of water and soil salinity, inadequate for the cultivation of many crops, thus threatening their growth and production and reducing the agrodiversity in the region.     

Modeling Groundwater Flow and Seawater Intrusion in the Coastal Aquifer of Wadi Ham,UAE

Groundwater pumping from Kalbha and Fujairah coastal aquifer of the United Arab Emirates (UAE) has increased significantly during the last two decades to meet the agriculture water demands. Due to the lack of natural replenishment from rainfall and the excessive pumping, groundwater levels have declined significantly causing an intrusion of seawater in the coastal aquifer of Wadi Ham. As a result, many pumping wells in the coastal zone have been terminated and a number of farms have been abandoned. In this paper, MODFLOW was used to simulate the groundwater flow and assess the seawater intrusion in the coastal aquifer of Wadi Ham. The model was calibrated against a five-year dataset of historical groundwater levels and validated against another eleven-year dataset. The effects of pumping on groundwater levels and seawater intrusion were investigated. Results showed that reducing the pumping from Khalbha well field will help to reduce the seawater intrusion into the southeastern part of the aquifer. Under the current groundwater pumping rates, the seawater will continue to migrate inland.     

A Methodology to Analyse and Assess Pumping Management Strategies in Coastal Aquifers to Avoid Degradation Due to Seawater Intrusion Problems

Water Resources Management - In this paper we will focus on an interesting and complex problem, the analysis of coastal aquifer management alternatives in aquifers affected by seawater intrusion...     

Groundwater Vulnerability and the Reuse of Water,with Reference to Saudi Arabia

It is noted that an integrated water supply system incorporating surface water, groundwater and recycled water is essential and that in the definition of groundwater resources consideration should be given to the inclusion of some brackish and saline waters. The abstraction of groundwater in Saudi Arabia, irrespective of quality, is a mining operation so that increasing emphasis will need to be placed on desalinization and the recycling of sewage and industrial waste waters. Aspects of the reuse of such waters are discussed with respect to aquifer protection and aquifer value as a storage medium.     

Correction to: Monitoring and Predicting Saltwater Intrusion via Temporal Aquifer Vulnerability Maps and Surrogate Models

Water Resources Management -     

Evaluation of Vulnerability to Extreme Climatic Events in the Brazilian Amazonia: Methodological Proposal to the Rio Acre Basin

The southern border of the Brazilian Amazon is one of the most sensitive areas to deforestation in Brazil. In addition to problems related to changes in land use, new issues are emerging, including climate change and its negative effects on the regional hydrological cycle. In recent years considerable research has been undertaken focusing on climate change and its effects on Amazon Biodiversity, carbon cycle, fire incidence and even on regional water resources, but there is very little research linking territorial planning and public policies to prospective planning scenarios and climate change and the necessary adaptation or mitigation actions to address climate vulnerability. This study examines issues pertaining to social, economic and environmental vulnerability, including new challenges posed by climate change. Examples of environmental problems related to climate dynamics of the Rio Acre Basin are floods and dry periods such as the major drought of 2005 and the 2009 flood. The use of methodology for integrated assessment of vulnerability to river basins in Amazon Region constitutes a valuable instrument for territorial planning, since it takes into account both the challenges of poverty and the environmental fragility, as well the possible aggravations of extreme climatic events in the future.     

Comparison of Self-Organizing Map,Artificial Neural Network,and Co-Active Neuro-Fuzzy Inference System Methods in Simulating Groundwater Quality: Geospatial Artificial Intelligence

Water quality experiments are difficult, costly, and time-consuming. Therefore, different modeling methods can be used as an alternative for these experiments. To achieve the research objective, geospatial artificial intelligence approaches such as the self-organizing map (SOM), artificial neural network (ANN), and co-active neuro-fuzzy inference system (CANFIS) were used to simulate groundwater quality in the Mazandaran plain in the north of Iran. Geographical information system (GIS) techniques were used as a pre-processer and post-processer. Data from 85 drinking water wells was used as secondary data and were separated into two splits of (a) 70 percent for training (60% for training and 10% for cross-validation), and (b) 30 percent for the test stage. The groundwater quality index (GWQI) and the effective water quality factors (distance from industries, groundwater depth, and transmissivity of aquifer formations) were implemented as output and input variables, respectively. Statistical indices (i.e., R squared (R-sqr) and the mean squared error (MSE)) were utilized to compare the performance of three methods. The results demonstrate the high performance of the three methods in groundwater quality simulation. However, in the test stage, CANFIS (R-sqr?=?0.89) had a higher performance than the SOM (R-sqr?=?0.8) and ANN (R-sqr?=?0.73) methods. The tested CANFIS model was used to estimate GWQI values on the area of the plain. Finally, the groundwater quality was mapped in a GIS environment associated with CANFIS simulation. The results can be used to manage groundwater quality as well as support and contribute to the sustainable development goal (SDG)-6, SDG-11, and SDG-13.

     

Groundwater Circulation Well for Controlling Saltwater Intrusion in Coastal aquifers: Numerical study with Experimental Validation

Saltwater intrusion into coastal aquifers has become a prominent environmental concern worldwide. As such, there is a need to prepare and implement proper remediation techniques with careful planning of freshwater withdrawal systems for controlling saltwater intrusion in coastal marine and estuarine environments. This paper investigates the performance of groundwater circulation well (GCW) in controlling saltwater intrusion problems in unconfined coastal aquifers. The GCWs have been established as a promising in-situ remedial technique of contaminated groundwater. The GCW system creates vertical circulation flow by extracting groundwater from an aquifer through a screen in a single well and injecting back into the aquifer through another screen. The circulation flow induced by GCW force water in a circular pattern between abstraction and recharge screens and can be as a hydraulic barrier for controlling saltwater intrusion problem in coastal aquifers. In this study, an effort has been made to investigate the behavior of saltwater intrusion dynamics under a GCW. An experiment has been conducted in a laboratory-scale flow tank model under constant water head boundary conditions, and the variable-density flow and transport model FEMWATER is used to simulate the flow and transport processes for the experimental setup. The evaluation of the results indicates that there is no further movement of saltwater intrusion wedge towards the inland side upon implementation of GCW, and the GCW acts as a hydraulic barrier in controlling saltwater intrusion in coastal aquifers. The present study reveals the GCWs system can effectively mitigate the saltwater intrusion problem in coastal regions and could be considered as one of the most efficient management strategies for controlling the problem.

     

Assessing Groundwater Geospatial Variation Using Microgravity Investigation in the Arid Riyadh Metropolitan Area,Saudi Arabia: a Case Study

A combination of relative microgravity measurements at ground surface, and depth to water and water table measurements from adjacent wells were used to estimate geospatial variation of groundwater. A highly accurate portable Grav-Map gravimeter was used for gravimetric measurements at locations nearby a 42 well water table monitoring program. To efficiently correlate the two data sets, wells were clustered into five groups by geological unit and water saturation. Microgravity data was processed, interpreted, and correlated with both the depths to groundwater and the water table levels. Regression analyses revealed a strong negative correlation for microgravity and depth to groundwater in all five clusters; correlation coefficients varied between 0.70 and 0.97, and measured 0.78 over the entire study area. Microgravity values increased as groundwater depth decreased, likely because rising groundwater fills voids and fractures within soil and rocks, increasing rock density and therefore relative gravity. To validate the correlation, we superimposed a map of depths to water on the first derivative of microgravity measurements. The shallowest groundwater depths were positively related to the zero first derivatives, having intersection areas within a 75 % significance interval. Negative first derivatives covered the rest of the study area, with relative gravity decreasing with increasing groundwater depth. This technique can precisely and efficiently determine changes in subsurface geology and geospatial changes in depths to the groundwater table. Distances between microgravity stations should be small, to better detect small changes in gravity values, reflecting density contrasts underground.     

Sampling and Modeling Approaches to Assess Water Quality Impacts of Combined Sewer Overflows—The Importance of a Watershed Perspective

As part of the planning effort for combined sewer overflow (CSO) abatement, a combination of sampling and mathematical modeling was used to characterize both CSO and receiving water quality in the city of Buffalo, NY. Samples collected during storm events showed that while CSOs within the city boundary are a source of fecal coliform to the Buffalo River, higher concentrations enter the river from the upper watershed, upstream of the city. Loading estimates of Pb, Zn, Cu, and Hg were made for design storms and on an annual basis using a combined model and sampling approach. While the metals loads were quantifiable from the CSOs, the loads associated with the upper watershed discharge were greater, for example, by a factor of 3 to 18 times for the design storms. Continuous, automated sampling of conventional parameters at 15 minute time steps indicated that the river experienced non-compliant periods for dissolved oxygen. In some cases, low dissolved oxygen levels may be associated with CSO inputs, but the hydraulics of the river system also had an important negative impact on dissolved oxygen. In developing CSO abatement options for the Buffalo River, it is essential to recognize that there are other significant contaminant sources in the upper watershed that will continue to negatively impact water quality.     

Rainfall-Runoff Modeling: Comparison of Two Approaches with Different Data Requirements

Among several hydrological models developed over the years, the most widely used technique for estimating direct runoff depth from storm rainfall i.e., the United States Department of Agriculture (USDA) Soil Conservation Service’s (SCS) Curve Number (CN) method was adopted in the present study. In addition, the Muskingum method, which continues to be popular for routing of runoff in river network, was used in the developed model to route surface runoffs from different subbasin outlet points up to the outlet point of the catchment. SCS CN method in combination with Muskingum routing technique, however, required a detailed knowledge of several important properties of the watershed, namely, soil type, land use, antecedent soil water conditions, and channel information, which may not be readily available. Due to this complexity of semi-distributed conceptual approach (SCS CN method) and non-linearity involved in rainfall-runoff modeling, researchers also attempted another less data requiring approach for runoff prediction, i.e., the neural network approach, which is inherently suited to problems that are mathematically difficult to describe. The purpose of this study was to compare the rainfall-runoff modeling performance of semi-distributed conceptual SCS CN method (in combination with Muskingum routing technique) with that of empirical ANN technique. The models were coded in C language and to make them user friendly, a Graphical User Interface (GUI) was also developed in Visual Basic 6.0. The developed models were tested for Kangsabati catchment, situated in the western part of West Bengal, India. Monsoon data of 1996 to 1999 were used for calibration of the models whereas they were validated for another four years (1987, 1989, 1990, and 1993) monsoon data. Modeling efficiency (ME) and coefficient of residual mass (CRM) were used as performance indicators. Results indicated that for Kangsabati catchment, the empirical runoff prediction approach (ANN technique), in spite of requiring much less data, predicted daily runoff values more accurately than semi-distributed conceptual runoff prediction approach (SCS CN method).     

Geostatistical Assessment of Groundwater Nitrate Contamination with Reflection on DRASTIC Vulnerability Assessment: The Case of the Upper Litani Basin, Lebanon

Groundwater constitutes the largest single source of fresh water in many parts of the world and provides a risk buffer to sustain critical water demands during cyclic and prolonged dry periods, especially in semi-arid and arid regions. However, unprecedented socio-economical growths are threatening the viability of these precious resources through fast depletion of already critically low stocks accompanied by persistent degradation of water quality due to salinization, and contamination by pesticides and fertilizers, urban sewage and industrial waste. These circumstances are particularly true of the Upper Litani Basin (ULB), which houses over 500,000 of Lebanon’s 4 million population and provides the bulk of the country’s agricultural output. Uncontrolled urban, agricultural and industrial growths following a prolonged civil strife and foreign occupation have resulted in the deterioration of the quality of the basin’s surface water and potentially its groundwater resources. An assessment study of groundwater quality conditions in the ULB was conducted in support of efforts to manage water quality in the basin. Geostatistical analysis of groundwater nitrate levels was conducted using data collected through an extensive basin-wide water quality survey sponsored by the USAID and covered two periods representing the summer and winter periods. The results of analysis include maps of nitrate contamination and probability of exceedance of drinking-water nitrate regulatory limit. The results indicate a significant, widespread and persistent nitrates contamination of groundwater in the ULB. Nitrate levels in groundwater exceed standard limits for drinking water in many parts of the basin. These findings were examined with respect to those of a DRASTIC groundwater vulnerability assessment conducted by the USAID BAMAS project. Comparative analysis of the two assessments shed the light on several issues related to the application and interpretation of DRASTIC scores and the groundwater nitrate contamination process.     

Risk Assessment of Groundwater and its Application. Part II: Using a Groundwater Risk Maps to Determine Control Levels of the Groundwater

With the rapid development of economy, demand of water resources is becoming larger and larger, and over-exploitation of groundwater is common in many areas. Due to over-exploitation of groundwater over many years, a number of potential adverse hydrogeological problems have raised. To reduce such adverse effects, it is necessary to carry out strict groundwater management in over-exploited areas. And to achieve the strictest management of groundwater, it is critical to determine control levels of groundwater including the blue line levels (proper levels) and red line levels (warning levels). According to the establishment of evaluation model of shallow and deep groundwater exploitation and utilization risks, it can be observed that the groundwater level index factor is included in the evaluation index system in different groundwater function zones. Therefore, there is a corresponding relationship between the risk grade and groundwater level of different underground aquifers. The risk grade of different groundwater function zones in Tianjin is divided into five grades, which contributes to the risk management of groundwater, avoiding the arising of a wide range of risk management measure. However, to determine the key groundwater level, the standard of five grades cannot meet the requirements. The risk grades need to be divided more subtly. Hence, in this paper, the risk grade was divided according to the standard of sixteen grades based on that of five grades in the first place. The higher the grade is, the greater the risk. And then the occurrence frequency of risk grade for each aquifer was counted in each administrative district or country. The corresponding water level of the risk grade, whose occurrence frequency was the highest, served as the base level. The water level of groundwater that would be exploited and utilized in the future cannot be below this base level. In consequence, this water level that served as the red line level was the minimum requirement in the planning years, while the corresponding water levels of other risk grades that were inferior to this risk grade can all be seen as red line levels. And the planning period the long-term corresponding groundwater level of the aquifers under mining-banned condition can be used as blue line control levels of the different planning years. Finally, according to the determinate range of red line level change amplitude in each district or country, as well as the ultimate restoration aim of groundwater levels (blue line levels), corresponding measures were taken step by step to achieve the overall rising of groundwater levels. The obtained determinate control levels can provide a scientific basis for dynamic management of groundwater.     

The Water-Economy Nexus: a Composite Index Approach to Evaluate Urban Water Vulnerability

Resource scarcity is a driving force behind water conservation and reuse as urban areas seek strategies to adapt to population growth and environmental challenges. Although there are numerous indicators that examine urban water resource and demand characteristics, these approaches do not tie together how aspects like economic health, environmental conditions, and population growth correlate with local water conservation to demonstrate a city’s ability to cope with water resource vulnerability. This research develops a conceptual framework for the Water-Economy Index (WEI) which characterizes social, economic, and environmental dynamics of water reuse and conservation. The application specifically utilizes a principal component analysis (PCA) to evaluate how hydro-economic indicators (including water demand intensity, demand for recycled water, economic productivity of water, unemployment, and allocations of water resources) are correlated and can impact sustainability goals. The PCA method aggregates indicators into three groups: socio-economic, water allocation, and socio-environmental indicators. The most influential indicators within each group are economic productivity of water, wastewater reuse, and consumptive water demand, respectively. The WEI ranks of 49 cities are compared to identify shared traits across individual indicators and to demonstrate the application of the WEI for benchmarking. The results provide insight into the complex relationship between the characteristics of an urban area’s water demand and socio-economic performance.

     

Groundwater Modeling Under Variable Operating Conditions Using SWAT,MODFLOW and MT3DMS: a Catchment Scale Approach to Water Resources Management

This paper presents an integrated modeling approach by linking soil and water application tool (SWAT), modular finite difference groundwater flow (MODFLOW) and modular 3-dimensional multi-species transport (MT3DMS) models capable of predicting a groundwater system response, in terms of flow and salt concentrations, to current and future development conditions. SWAT, a semi-distributed hydrologic model, estimates the spatio-temporal distribution of groundwater recharge rates. These rates are then input to MODFLOW using an interface module developed that maps the HRU-based spatial resolution of SWAT outflows into the cell-based spatial structure of inputs to MODFLOW and MT3DMS. The integrated SWAT-MODFLOW-MT3DMS model is used in modeling Dehloran aquifer system located in the arid western region of Iran, experiencing changes in land-use, irrigation system and pumping locations and loads. The results illustrate the significance of the developed integrated modeling tool in quantifying the impact of changes in land and surface water resources on its subsurface water system.     

Application of GWQI to Assess Effect of Land Use Change on Groundwater Quality in Lower Shiwaliks of Punjab: Remote Sensing and GIS Based Approach

The groundwater resource is a multidimensional concept; it is defined by its location, its occurrence over time, its size, properties, conditions of accessibility, the effort required to mobilize it and therefore, all of which are to be considered in the context of demand. Groundwater, a renewable and finite natural resource, vital for man’s life, social and economic development and a valuable component of the ecosystem, is vulnerable to natural and human impacts. There is a great need for the assessment and monitoring of quality and quantity of groundwater resource required at local level to develop an exact scenario of watershed. In this study qualitative assessment of groundwater was done and a ground water quality index criterion was used to understand the suitability of groundwater for irrigation and drinking purpose in the study area. A GIS based multicriteria analysis was done by assigning weight to different water quality parameters. The water quality was grouped into six classes from very good to unfit for drinking. It was found that the in most part of the study area the water quality varied from moderate to good except in some areas where it is poor to unfit. An assessment of change in landuse and landcover was done from the year 1989 using Landsat data to year 2006 using LISS III satellite data. The change in LULC was correlated with water quality data and it was found that the areas around which rapid urbanisation as well as industrialisation is taking place showed poor to unfit groundwater in terms of quality.     

Delineating Capture Zone of a Pumping Well in a Slanting Regional Groundwater Flow to a Stream with a Leaky Layer

In this study, analytical and semi-analytical solutions are derived to delineate capture zone of a pumping well near a stream where a leaky layer exists between the aquifer and the stream. A groundwater regional flow is considered in the aquifer and allowed to have different angles with respect to the stream axis. Three critical pumping rates are introduced. At the first pumping rate, capture zone boundary tangents the interface between the aquifer and the leaky layer; called the in-homogeneity boundary. At the second pumping rate, capture zone boundary tangents the stream boundary and if the rate is increased, a part of pumped water would be withdrawn from the stream. The third pumping rate, which may be smaller or larger than the other two, is defined as the rate at which stream water begins to enter the leaky layer; it may or may not be captured by the pumping well. Four different capture zone configurations (cases) are analyzed for different values of pumping rates, groundwater flow directions, and leaky layer’s thickness and hydraulic conductivity. The first three cases analyze hydraulic situations whereby capture zone does not reach the stream, and hence, no pumped water is withdrawn from the stream. With the lowest pumping rate in the first case, no stream water enters the leaky layer. It enters the leaky layer but not the aquifer in the second, and enters the leaky layer and the aquifer in the third case. In the fourth case, where capture zone boundary intersects the stream, the fraction of pumped stream water to total pumped water is delineated.     

Evaluating the SWAT Model for Hydrological Modeling in the Xixian Watershed and a Comparison with the XAJ Model

Already declining water availability in Huaihe River, the 6th largest river in China, is further stressed by climate change and intense human activities. There is a pressing need for a watershed model to better understand the interaction between land use activities and hydrologic processes and to support sustainable water use planning. In this study, we evaluated the performance of SWAT for hydrologic modeling in the Xixian River Basin, located at the headwaters of the Huaihe River, and compared its performance with the Xinanjiang (XAJ) model that has been widely used in China. Due to the lack of publicly available data, emphasis has been put on geospatial data collection and processing, especially on developing land use-land cover maps for the study area based on ground-truth information sampling. Ten-year daily runoff data (1987?C1996) from four stream stations were used to calibrate SWAT and XAJ. Daily runoff data from the same four stations were applied to validate model performance from 1997 to 2005. The results show that both SWAT and XAJ perform well in the Xixian River Basin, with percentage of bias (PBIAS) less than 15%, Nash-Sutcliffe efficiency (NSE) larger than 0.69 and coefficient of determination (R²) larger than 0.72 for both calibration and validation periods at the four stream stations. Both SWAT and XAJ can reasonably simulate surface runoff and baseflow contributions. Comparison between SWAT and XAJ shows that model performances are comparable for hydrologic modeling. For the purposes of flood forecasting and runoff simulation, XAJ requires minimum input data preparation and is preferred to SWAT. The complex, processes-based SWAT can simultaneously simulate water quantity and quality and evaluate the effects of land use change and human activities, which makes it preferable for sustainable water resource management in the Xixian watershed where agricultural activities are intensive.     

Assessing Groundwater Contribution to Streamflow of a Large Alpine River with Heat Tracer Methods and Hydrological Modelling

The contribution of groundwater to streamflow in Alpine catchments is still poorly understood, despite the fact that it may heavily impact hydrological balance and stream habitats. This paper presents the results of a field campaign based on experiments with heat tracer methods to assess the hyporheic flow during the low‐flow period of a large Alpine river in Italy. These measurements were employed to validate a distributed hydrological model that can be used to asses river–groundwater interaction in both low‐flow and high‐flow conditions. The results show that groundwater may have a relevant role during low‐flow periods, by increasing river discharge and during floods, by subtracting direct run‐off that is stored in river banks. Copyright © 2015 John Wiley & Sons, Ltd.