Specifying the differentiated contribution of farmers to groundwater depletion in two irrigated areas in North Africa

Much attention has been paid to the issue of groundwater depletion linked to intensive groundwater-based agriculture in (semi-)arid areas. Often referred to as the “overexploitation” of aquifers, groundwater depletion is generally attributed to the entire agricultural sector without distinguishing between different uses and users. Although it expresses a general concern for future users, the ambiguous term of “overexploitation” does not acknowledge the contested nature of groundwater use and emerging inequalities. Also, the impact of inequality on groundwater depletion is rarely questioned. The aim of this article is to investigate how and by whom groundwater is depleted, and in turn, how unequal access to groundwater fuels the socioeconomic differentiation of farms and groundwater depletion. Based on a detailed analysis of groundwater use from a user perspective in two irrigated areas in North Africa (Morocco and Algeria), this study shows how the context of groundwater depletion exacerbates—and is exacerbated by—existing inequalities. The paper concludes that knowing how much is withdrawn, where, and by whom provides helpful information for more informed groundwater management by a better understanding of the response of users to declining groundwater conditions and the interests and incentives of different social categories of famers to contribute to groundwater management.     

Evaluation of the water resources potential at Dahaban region, western Saudi Arabia

Shallow renewable groundwater sources have been used to satisfy the domestic needs and the irrigation in many parts of Saudi Arabia. Increased demand for water resulting from accelerated development activities has placed excess stress on the renewable sources especially in coastal aquifers of the western region of Saudi Arabia. It is expected that the current and future development activities will increase the rate of groundwater mining of the coastal aquifer near the major city Jeddah and surrounding communities unless management measures are implemented. The current groundwater development of Dahaban coastal aquifer located at alluvial fan at the confluence of three major Wadis is depleting the shallow renewable groundwater sources and causes deterioration of its quality. Numerical models are known tools to evaluate groundwater management scenarios under a variety of development options under different hydrogeological regimes. In this study, two models are applied—the MODFLOW for evaluating the hydrodynamic behaviors of the aquifer and MT3D salinity distribution to the costal aquifer near Dahaban town. The models’ simulation evaluates two development scenarios—the impact of excessive abstraction and the water salinity variation keeping abstraction at its current or increases in levels with or without groundwater recharge taking place. The simulation evaluated two scenarios covering a 25-year period—keeping the current abstraction at its current and the other scenario is increasing the well abstraction by 50% for dry condition (no recharge) and wet condition (with recharge). The analysis reveals that, under the first scenario, the continuation of the current pumping rates will result in depletion of the aquifer resulting in drying of many wells and quality deterioration at the level of 2,500 ppm. The results are associated with the corresponding salinity distribution in the region. Simulation of salinity in the region is a density-independent problem as salt concentration does not exceed 2,000 ppm, which is little value compared with sea salinity that amounts to 40,000 ppm. It is not recommended to increase the pumping rate than the current values. However, for the purpose of increasing water resources in the region, it is recommended to install new wells in virgin zones west of Dahaban main road. Maps of high/low potential groundwater and maps of salinity zones (more or less than 1,000 ppm) are provided and could be used to identify zones of high groundwater potential for the four studied scenarios. The implemented numerical simulation of Dahaban aquifer was undertaken to assess the water resources potential in order to reduce the depletion of sources in the future.     

Hydrochemical evolution and variation of groundwater and its environmental impact at Sohag, Egypt

Groundwater resources of Sohag, Egypt are currently threatened by contamination from agricultural and urbanization activities. Groundwater in Sohag area has a special significance where it is the second source for fresh water used for agricultural, domestic, and industrial purposes. Due to growing population, agriculture expansion, and urbanization, groundwater quality assessment needs more attention to cope with the increasing water demand in this arid zones and limited water resources. The aim of this paper is to address the integrated role of geochemical processes, agriculture and urbanization in evolution of groundwater composition, and their impact on groundwater quality to help in management and protection of groundwater resources of study area using geochemical modeling techniques and geographical information systems. Spatial variation of groundwater hydrochemical properties, rock–water interaction, ion exchange, and assessment of groundwater quality were investigated. Results indicated that groundwater properties are varied spatially and its evolution in the study area is generally controlled by the prevailed geochemical processes represented by leaching, dissolution, and precipitation of salts and minerals, ion exchange, in addition to human activities represented by agriculture and urbanization as well as climatic and poor drainage conditions. Management alternatives should be followed in the study area to avoid degradation of groundwater quality and provide sustainable development.     

Impact of climate change on irrigation requirements in terms of groundwater resources

Climate change affects not only water resources but also water demand for irrigation. A large proportion of the world’s agriculture depends on groundwater, especially in arid and semi-arid regions. In several regions, aquifer resources face depletion. Groundwater recharge has been viewed as a by-product of irrigation return flow, and with climate change, aquifer storage of such flow will be vital. A general review, for a broad-based audience, is given of work on global warming and groundwater resources, summarizing the methods used to analyze the climate change scenarios and the influence of these predicted changes on groundwater resources around the world (especially the impact on regional groundwater resources and irrigation requirements). Future challenges of adapting to climate change are also discussed. Such challenges include water-resources depletion, increasing irrigation demand, reduced crop yield, and groundwater salinization. The adaptation to and mitigation of these effects is also reported, including useful information for water-resources managers and the development of sustainable groundwater irrigation methods. Rescheduling irrigation according to the season, coordinating the groundwater resources and irrigation demand, developing more accurate and complete modeling prediction methods, and managing the irrigation facilities in different ways would all be considered, based on the particular cases.     

Groundwater optimization model for sustainable management of the Valley of Puebla aquifer, Mexico

The Valley of Puebla aquifer (VPA), at the central region of Mexico, is subject to intensive exploitation to satisfy the urban and industrial demand in the region. As a result of this increased exploitation, a number of state and federal agencies in charge of water management are concerned about the problems associated with the aquifer (decline of groundwater table, deterioration in water quality, poor well productivity and increased pumping and water treatment costs). This study presents a groundwater management model that combines “MODFLOW” simulation with optimization tools “MODRSP”. This simulation–optimization model for groundwater evaluates a complex range of management options to identify the strategies that best fit the objectives for allocating resources in the VPA. Four hypothetical scenarios were defined to analyze the response of the hydrogeological system for future pumping schemes. Based on the simulation of flow with the MODFLOW program, promising results for the implementation of the optimization of water quantity were found in scenarios 3 and 4. However, upon comparison and analysis of the feasibility of recovery of the piezometric level (considering the policy of gradual reductions of pumping), scenario 4 was selected for optimization purposes. The response functions of scenario 4 were then obtained and optimized, establishing an extraction rate of 204.92 millions of m³/year (Mm³/year). The reduction in groundwater extraction will be possible by substituting the volume removed by 35 wells (that should be discontinued) by the same volume of water from another source.     

A GIS-index integration approach to groundwater suitability zoning for irrigation purposes

In recent decades, the high population growth has increased the demand for agricultural lands and products. Groundwater offers reliability and flexibility in access to water for irrigation purposes, especially in arid and semi-arid areas, such as Amol-Babol Plain, Iran. However, the quality and quantity of groundwater may not be suitable for irrigation purposes in all areas due to urbanizations, and intensive agricultural and industrial activities. Groundwater suitability zoning for irrigation purposes could be useful to improve water resources and land use planning, mostly in areas with water scarcity. Therefore, a GIS-based indices method is proposed to assess suitable zones for agricultural activities, integrating the irrigation water quality (IWQ) index and hydrogeological factors. IWQ index was utilized to assess groundwater quality based on salinity hazard, infiltration hazard, specific ions, and trace elements hazards, and miscellaneous effects such as pH, bicarbonate, and nitrate. The potential of the aquifer for irrigation water abstraction was investigated using hydrogeological surveys such as slope angle of the plain, hydraulic conductivity, and aquifer thickness. The groundwater suitability index classified most of the study area (more than 90 %) as “excellent” or “good” suitability zones for irrigation purposes. A limited area of around 5.6 % of the total area has moderate suitability for irrigation purposes due to the Caspian Seawater intrusion and the presence of fossil saline water. The proposed methodology provides useful information in order to allow irrigation management to prevent water and soil deterioration.     

The key role of supply chain actors in groundwater irrigation development in North Africa

The role played by supply chain actors in the rapid development of groundwater-based irrigated agriculture is analyzed. Agricultural groundwater use has increased tremendously in the past 50 years, leading to the decline of water tables. Groundwater use has enabled intensification of existing farming systems and ensured economic growth. This “groundwater economy” has been growing rapidly due to the initiative of farmers and the involvement of a wide range of supply chain actors, including suppliers of equipment, inputs retailers, and distributors of irrigated agricultural products. In North Africa, the actors in irrigated production chains often operate at the margin of public policies and are usually described as “informal”, “unstructured”, and as participating in “groundwater anarchy”. This paper underlines the crucial role of supply chain actors in the development of groundwater irrigation, a role largely ignored by public policies and rarely studied. The analysis is based on three case studies in Morocco, Tunisia and Algeria, and focuses on the horticultural sub-sector, in particular on onions and tomatoes, which are irrigated high value crops. The study demonstrates that although supply chain actors are catalyzers of the expansion of groundwater irrigation, they could also become actors in adaptation to the declining water tables. Through their informal activities, they help reduce market risks, facilitate credit and access to subsidies, and disseminate innovation. The interest associated with making these actors visible to agricultural institutions is discussed, along with methods of getting them involved in the management of the resource on which they depend.     

Urban and rural groundwater use in Zhengzhou, China: challenges in joint management

Groundwater plays an important role in the total water supply of much of China, particularly in the north. It has contributed substantially to both agricultural growth and urban and industrial expansion. However, overexploitation and poor management have contributed to infamous groundwater depletion problems and less publicized groundwater quality deterioration. One of the key challenges for China will be how to make groundwater use sustainable while still meeting increased food needs as well as the industrial and domestic demands of a rapidly urbanizing society. Zhengzhou City, one of China’s test cities for building a “water saving society” highlights both the difficulties and potential solutions to northern China’s joint rural and urban groundwater challenges. Based on secondary data and a primary survey of groundwater management in the region, this report provides an overview of Zhengzhou’s groundwater development and use as well as the ongoing institutional and policy reform processes within the water sector. The results highlight how a deepening of ongoing reforms, which simultaneously consider groundwater as an integral rural and urban issue and a fundamental economic and social asset, may improve groundwater outcomes, not only in Zhengzhou but in China, as the country’s economy and demography continue to change.     

Groundwater Environment of a Tropical East Flowing River of Western Ghats,Southern India

Abstraction of groundwater resources is increasing over the years to meet its ever-increasing demand for industrial, agricultural and domestic purposes throughout the world. The scenario is even worse in the east flowing rivers of the Western Ghats, where the demand of water is high under changing climatic conditions. Such situation may affect the groundwater resources of the river basin on a long run. The aim of the present study is to characterize the geochemistry of groundwater in Tamiraparani sub-basin through geochemical modeling and deduce the ionic interactions with the aid of geostatistical and multivariate statistical techniques. A total of 40 groundwater samples from shallow aquifers were collected randomly throughout the sub-basin for assessing its physicochemical parameters, which include physical properties of the water, major ions and nutrients. Two major hydrogeochemical facies were identified such as mixed Ca-Mg-Cl and Ca-HCO₃ groups. The nutrients derived from agricultural runoff, urban discharge and organic decomposition alters the nutrient level in the groundwater. The dissolution/precipitation of minerals such as calcite and dolomite controls the chemical constituents of the groundwater. The multivariate statistical analysis indicates that natural weathering of source rocks is the main contributors of ions in the groundwater followed by anthropogenic activities such as agricultural practices and urbanization. The insights obtained from this study can be helpful for sustainable groundwater management and long-term monitoring studies.     

The protection of groundwater dependent ecosystems in Otago, New Zealand

Surface waters (streams, rivers, and wetlands) are the most important groundwater dependent ecosystems (GDEs) in Otago, New Zealand. Pumping wells in the vicinity can deplete water in the GDE. In Otago, most of the surface water resources are allocated and a method, which would assist in the implementation of water management policy, is needed to acknowledge the strong hydraulic link between surface and shallow groundwater. A simplified method has been developed which derives a numerical relationship between the bore pumping rate and the distance between the bore and surface water body beyond which depletion is considered insignificant. A range of GDE depletion scenarios are examined at various combinations of hydraulic parameters to find a minimum distance for a given pumping rate, at which 90% of the modelled surface water depletion scenarios become less than a threshold GDE depletion after a specified time. A buffer zone, based on the minimum distance is placed around GDEs, and groundwater abstraction rights within the buffer are subject to stricter rules. Applicants wishing to abstract from bores within the buffer zone will need to address the environmental impact of the proposed activity on the GDE.     

吉林省西部潜水资源与生态环境风险分析

吉林省西部是我国主要粮食产区,但区内农业水利规划管理同时面临潜水资源与生态环境双重风险。近20年来,区内曾尝试多种水资源利用模式,但缺少不同模式应用效果的定量化对比。文章建立了不同水资源利用模式,对比分析各模式的水资源与次生盐碱化风险。以洮儿河流域为例,采用循环神经网络预测2019—2023年该地区大气降水和地表水对地下水补给量;通过随机数值模拟预测现状开采、连续干旱、无序开采、地下水库建设、节水灌溉、旱田改水田6种情形下,区内潜水水位空间分布特征。以防止次生盐碱化为目标,定义水位埋深上限为1 m;以含水介质厚度为参考,定义水位埋深下限为12 m。遴选适合吉林省西部地区地下水资源可持续利用模式。结果显示:无序开采是导致区内水资源枯竭的主要诱因;地下水库建设和旱改水工程有助于潜水资源维护,但长期运行可加剧生态环境风险。节水灌溉（净采强度为2.0×108～3.0×108 m3/a）是降低区内水资源风险和生态环境风险的最佳方式。文章采用的神经网络—随机模拟分析方法成功预测了地下水位变化驱动因子和地下水位中长期变化趋势,为我国干旱半干旱地区潜水资源利用方案制定提供了新方法。     

A semi-distributed groundwater recharge model for estimating water-table and water-balance variables

A semi-distributed groundwater recharge model is presented, which estimates water-table fluctuation and water-balance variables. The model is expressed by the water-balance concept linking atmospheric and hydrogeological parameters to different water uses (industrial, agricultural, domestic, etc). It was calibrated and validated using 5 years of data collected in the Dogo Plain in Japan. A 3-year dataset, from 2000 to 2002, was used in the calibration, while a 2-year dataset, from 2003 to 2004, was used for the validation. Calibration of the model was achieved by the shuffled complex evolution automatic optimization of model parameters to match simulated results with measured water-table depth. Square roots of relative error (R²) are 0.88 and 0.90 for calibration and validation processes, respectively. Monthly evolution of water storage change was then estimated and the water-table drawdown in different pumping scenarios was simulated. Finally, the groundwater-pumping amount planned by the government for future sustainable groundwater utilization was evaluated. The government-planned groundwater-pumping amount is feasible in most regions while the midstream region should be paid more attention. This study offers a scientific basis to control and prevent depletion of groundwater resources.     

Forecasting of groundwater level in hard rock region using artificial neural network

In hardrock terrain where seasonal streams are not perennial source of freshwater, increase in ground water exploitation has already resulted here in declining ground water levels and deteriorating its’ quality. The aquifer system has shown signs of depletion and quality contamination. Thus, to secure water for the future, water resource estimation and management has urgently become the need of the hour. In order to manage groundwater resources, it is vital to have a tool to predict the aquifer response for a given stress (abstraction and recharge). Artificial neural network (ANN) has surfaced as a proven and potential methodology to forecast the groundwater levels. In this paper, Feed-Forward Network based ANN model is used as a method to predict the groundwater levels. The models are trained with the inputs collected from field and then used as prediction tool for various scenarios of stress on aquifer. Such predictions help in developing better strategies for sustainable development of groundwater resources.     

Pumping-induced Well Hydraulics and Groundwater Budget in a Leaky Aquifer System with Vertical Heterogeneity in Aquitard Hydraulic Properties

In groundwater hydrology, aquitard heterogeneity is often less considered compared to aquifers, despite its significant impact on groundwater hydraulics and groundwater resources evaluation. A semi-analytical solution is derived for pumping-induced well hydraulics and groundwater budget with consideration of vertical heterogeneity in aquitard hydraulic conductivity (K) and specific storage (Ss). The proposed new solution is innovative in its partitioning of the aquitard into multiple homogeneous sub-layers to enable consideration of various forms of vertically heterogeneous K or Ss. Two scenarios of analytical investigations are explored: one is the presence of aquitard interlayers with distinct K or Ss values, a common field-scale occurrence; another is an exponentially depth-decaying aquitard Ss, a regional-scale phenomenon supported by statistical analysis. Analytical investigations reveal that a low-K interlayer can significantly increase aquifer drawdown and enhance aquifer/aquitard depletion; a high-Ss interlayer can noticeably reduce aquifer drawdown and increase aquitard depletion. Locations of low-K or high-Ss interlayers also significantly impact well hydraulics and groundwater budget. In the context of an exponentially depth-decaying aquitard Ss, a larger decay exponent can enhance aquifer drawdown. When using current models with a vertically homogeneous aquitard, half the sum of the geometric and harmonic means of exponentially depth-decaying aquitard Ss should be used to calculate aquitard depletion and unconfined aquifer leakage.     

Modeling of seawater intrusion in a coastal aquifer of Karaburun Peninsula,western Turkey

Seawater intrusion is a major problem to freshwater resources especially in coastal areas where fresh groundwater is surrounded and could be easily influenced by seawater. This study presents the development of a conceptual and numerical model for the coastal aquifer of Karareis region (Karaburun Peninsula) in the western part of Turkey. The study also presents the interpretation and the analysis of the time series data of groundwater levels recorded by data loggers. The SEAWAT model is used in this study to solve the density-dependent flow field and seawater intrusion in the coastal aquifer that is under excessive pumping particularly during summer months. The model was calibrated using the average values of a 1-year dataset and further verified by the average values of another year. Five potential scenarios were analyzed to understand the effects of pumping and climate change on groundwater levels and the extent of seawater intrusion in the next 10 years. The result of the analysis demonstrated high levels of electrical conductivity and chloride along the coastal part of the study area. As a result of the numerical model, seawater intrusion is simulated to move about 420 m toward the land in the next 10 years under “increased pumping” scenario, while a slight change in water level and TDS concentrations was observed in “climate change” scenario. Results also revealed that a reduction in the pumping rate from Karareis wells will be necessary to protect fresh groundwater from contamination by seawater.     

Groundwater quality assessment using integrated geochemical methods,multivariate statistical analysis,and geostatistical technique in shallow coastal aquifer of Terengganu,Malaysia

Extensive agricultural, residential, and industrial activities have increased demand for water supplies, which can lead to groundwater quality degradation. The integration of geochemical methods, multivariate statistical analysis, and geostatistical approaches were carried out on 169 groundwater samples to elucidate the regional factors and processes that influencing the geochemical composition of groundwater in coastal shallow aquifer of Terengganu, Malaysia. Hydrochemical modelling revealed that the abundance of Ca and Mg was contributed by carbonate and silicate weathering while higher HCO₃ and Cl were resulted from reverse ion exchange reaction. Therefore, the dominant hydrogeochemical facies of groundwater was Ca-Mg-HCO₃-Cl type. The influence of salinization resulting from seawater mixing to the groundwater was corroborated by Cl/HCO₃ ratio, which affected around 50.9% of the groundwater samples slightly or moderately. Spatial mapping using ordinary kriging found that the threat of sea water intrusion is more prominent in the major river confluence especially around Terengganu and Marang River in the northeast and Dungun and Kemaman River confluence in southeast of study area. Moreover, factor analyses concluded that salinization, anthropogenic activities, reverse ion exchange, weathering processes, agricultural impact, and seasonal variations were the factors that regulate 63% of the major ion chemistry in study area. Finally, these findings showed the importance of understanding the hydrochemical characteristics for effective utilization, aquifer protection, and prediction of changes to minimize the effects of salinization and reduce human pollution such as agriculture and urbanization. It is essential steps in order to safeguard the utilization of groundwater resources for future generations.     

Hydrogeology and sustainable future groundwater abstraction from the Agua Verde aquifer in the Atacama Desert,northern Chile

The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m³/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity.     

The weight of interaction of mining activities: groundwater in environmental impact assessment using fuzzy analytical hierarchy process (FAHP)

Mining operations threaten the environment if the monitoring and controlling steps are not implemented completely. One of the important methods for control of the environmental situation in the mining district is the environmental impact assessment (EIA) method, which is performed by matrix calculations. In this method, the environmental problem is broken into several parts as the Impacting Factors that is evaluated their influences on Environmental Components by the mathematical calculations. For these calculations, the weight of each Impacting Factor must be evaluated by using comprehensive scenarios that are involved all the predicable environmental issues. Based on literature, it has not been organized a comprehensive scenario about “Interference with groundwater” as an Impacting Factor yet. By consideration of the importance degree of groundwater and its role in supply the drinking water resource, it is felt to demand for an organization a developed scenario in relation with groundwater pollution in mining district. Therefore, the main aim of this study is developing a new scenario to weight the “Interference with groundwater” in EIA matrix. For this purpose, the 8 criteria and 63 subcriteria are defined and their weights are determined using the Fuzzy Analytic Hierarchy Process. The proposed scenario can be successfully evaluated the weight of “Interference with groundwater” Impacting Factor more exactly than the former one, because it considers 8 criteria and 63 subcriteria instead of 2 criteria in the former scenario. Finally, the application of proposed scenario is illustrated by an imaginary ideal case study. Such studies can be used by mining engineers and planners to design an appropriate environmental plan for the mining districts.     

Intervention scenarios to manage seawater intrusion in a coastal agricultural area in Oman

The Batinah coastal plain in northern Oman has experienced a severe deterioration of groundwater quality due to seawater intrusion as a result of excessive groundwater abstraction for agricultural irrigation. Upgrading all farms to fully automated irrigation technology based on soil moisture sensors may significantly reduce the water demand and lead to recovering groundwater levels. This study compares the effects of smart irrigation technology, recharge dams, and a combination of both on seawater intrusion in the coastal aquifer of the Batinah. A groundwater flow and transport model is used to simulate the effect of reduced pumping rates on seawater intrusion for various intervention scenarios over a simulation period of 30 years, and an economic analysis based on cost-benefit analysis is conducted to estimate the potential benefits. Results indicate that a combination of smart irrigation and recharge dams may prevent further deterioration of groundwater quality over the next 30 years. In conjunction with increased efficiency, this combination also generates the highest gross profit. This outcome shows that the problem of seawater intrusion needs to be tackled by a comprehensive, integrated intervention strategy.     

Groundwater–wetlands interaction in coastal lagoon of Almería (SE Spain)

Water resources management in coastal wetlands requires the degree of interdependence between groundwater and terrestrial ecosystems to be known. This is especially so in semiarid areas where surface inflows are restricted, marine influence is marked and the evaporation rate is high. Thus, chemistry of surface waters is very variable in the Cerrillos-Punta Entinas wetlands system. Using classical hydrogeochemical tools, the main processes that favor a diversity of water types were described, related to: presence of salt deposits on the lagoon beds, marine origin of the water, and local influence of groundwater. All these factors make it difficult to establish what reference conditions should be used to define “good” water quality of the surface waters—as required by the Water framework directive—and to understand the influence of groundwater on these coastal wetlands. Knowledge about the influence of the different interaction of these factors on the hydrogeochemical dynamics is required for the sustainable management of this protected natural site.