A quantitative assessment of groundwater resources in the Middle East and North Africa region

The Middle East and North Africa (MENA) region is the world’s most water-stressed region, with its countries constituting 12 of the 15 most water-stressed countries globally. Because of data paucity, comprehensive regional-scale assessments of groundwater resources in the MENA region have been lacking. The presented study addresses this issue by using a distributed ArcGIS model, parametrized with gridded data sets, to estimate groundwater storage reserves in the region based on generated aquifer saturated thickness and effective porosity estimates. Furthermore, monthly gravimetric datasets (GRACE) and land surface parameters (GLDAS) were used to quantify changes in groundwater storage between 2003 and 2014. Total groundwater reserves in the region were estimated at 1.28 × 10⁶ cubic kilometers (km³) with an uncertainty range between 816,000 and 1.93 × 10⁶ km³. Most of the reserves are located within large sedimentary basins in North Africa and the Arabian Peninsula, with Algeria, Libya, Egypt, and Saudi Arabia accounting for approximately 75% of the region’s total freshwater reserves. Alternatively, small groundwater reserves were found in fractured Precambrian basement exposures. As for groundwater changes between 2003 and 2014, all MENA countries except for Morocco exhibited declines in groundwater storage. However, given the region’s large groundwater reserves, groundwater changes between 2003 and 2014 are minimal and represent no immediate short-term threat to the MENA region, with some exceptions. Notwithstanding this, the study recommends the development of sustainable and efficient groundwater management policies to optimally utilize the region’s groundwater resources, especially in the face of climate change, demographic expansion, and socio-economic development.     

Estimating potential for exploitation of karst aquifer: case example on two Serbian karst aquifer

Rational use of karst water resources depends considerably on the existence of a successful approach to estimating karst groundwater potential for exploitation. The term groundwater potential for exploitation involves the application of regulatory measures affecting natural outflow regime. Generally, the concept of controlling the artificial discharge regime is based on two principles. The first one, the “borrowing” of water from deeper (storage) part of storage, is based mainly on the construction of groundwater wells. The second one, considers increasing dynamic reserves by providing additional artificial water storage thereby controlling the groundwater discharge regime, is based on the construction of underground dams. This paper examines how these two concepts can be used to increase potential groundwater usage from two karst springs in Serbia—St. Petka and Peru?ac. The ability to potentially increase the amount of karst ground water available for future exploitation may facilitate and give important directions to the future research.     

A comparison of stochastic and deterministic downscaling methods for modelling potential groundwater recharge under climate change in East Anglia, UK: implications for groundwater resource management

Groundwater resource estimates require the calculation of recharge using a daily time step. Within climate-change impact studies, this inevitably necessitates temporal downscaling of global or regional climate model outputs. This paper compares future estimates of potential groundwater recharge calculated using a daily soil-water balance model and climate-change weather time series derived using change factor (deterministic) and weather generator (stochastic) methods for Coltishall, UK. The uncertainty in the results for a given climate-change scenario arising from the choice of downscaling method is greater than the uncertainty due to the emissions scenario within a 30-year time slice. Robust estimates of the impact of climate change on groundwater resources require stochastic modelling of potential recharge, but this has implications for groundwater model runtimes. It is recommended that stochastic modelling of potential recharge is used in vulnerable or sensitive groundwater systems, and that the multiple recharge time series are sampled according to the distribution of contextually important time series variables, e.g. recharge drought severity and persistence (for water resource management) or high recharge years (for groundwater flooding). Such an approach will underpin an improved understanding of climate change impacts on sustainable groundwater resource management based on adaptive management and risk-based frameworks.     

Sustainable groundwater development in the coastal Tra Vinh province in Vietnam under saltwater intrusion and climate change

Three-dimensional transient groundwater flow and saltwater transport models were constructed to assess the impacts of groundwater abstraction and climate change on the coastal aquifer of Tra Vinh province (Vietnam). The groundwater flow model was calibrated with groundwater levels (2007–2016) measured in 13 observation wells. The saltwater transport model was compared with the spatial distribution of total dissolved solids. Model performance was evaluated by comparing observed and simulated groundwater levels. The projected rainfalls from two climate models (MIROC5 and CRISO Mk3.6) were subsequently used to simulate possible effects of climate changes. The simulation revealed that groundwater is currently depleted due to overabstraction. Towards the future, groundwater storage will continue to be depleted with the current abstraction regime, further worsening in the north due to saltwater intrusion from inland trapped saltwater and on the coast due to seawater intrusion. Notwithstanding, the impact from climate change may be limited, with the computed groundwater recharge from the two climate models revealing no significant change from 2017 to 2066. Three feasible mitigation scenarios were analyzed: (1) reduced groundwater abstraction by 25, 35 and 50%, (2) increased groundwater recharge by 1.5 and 2 times in the sand dunes through managed aquifer recharge (reduced abstraction will stop groundwater-level decline, while increased recharge will restore depleted storage), and (3) combining 50% abstraction reduction and 1.5 times recharge increase in sand dune areas. The results show that combined interventions of reducing abstraction and increasing recharge are necessary for sustainable groundwater resources development in Tra Vinh province.

     

Climate change and groundwater resources in Mekong Delta,Vietnam

Groundwater resources have considerable influences on the human population and socioeconomic development of Vietnam and the Mekong River Delta (MRD). This paper presents an overview of the relationship between climate change and groundwater in the MRD, including the challenges, strategies and technical measures. Our results showed that groundwater levels are related to other climate and hydrological variables (i.e., rainfall, river levels, etc.); therefore, the impacts of climate change on the groundwater resources of the Mekong delta are significant, especially on groundwater recharge. Based on the results of this study, it is recommended that groundwater development in the future should focus on reducing groundwater harvesting, enhancing groundwater quantity by establishing artificial works and exploiting surface water. This study suggests that the Artificial Neural Network (ANN) model is an effective tool for forecasting groundwater levels in periods of 1 month and 3 months for aquifers in the natural and tidal regime areas of the delta.     

我国气候变化对地下水资源影响研究的主要进展

为了推动我国关于气候变化对地下水影响的深入研究,列举了关于气候变化对地下水影响的研究方法,包括包气带和含水层环境示踪技术,研究地下水及其沉积物的物理化学指标,地表水-地下水耦合数值模拟技术等;综述了我国华北地区(北京市、滹沱河流域、海河流域、滦河下游地区、黄淮海平原、临汾盆地、鄂尔多斯盆地、黄河下游地区、大同盆地、北方岩溶泉域)、西北地区(塔里木下游地区、三工河流域、阿克苏河绿洲、黑河流域、石羊河流域、河西走廊、巴丹吉林沙漠)和东北地区(吉林中部平原地区、三江平原)等典型区域气候变化(气温、降水、蒸发)对地下水水位、补给量与排泄量(泉流量、开采量)、水化学成分、水温、同位素组成的影响;提出了气候变化条件下合理利用和管理地下水资源的若干对策,包括减缓温室效应引起的全球气候变暖对未来地下水资源产生不利影响,定量化研究气候变化和地下水之间的相互关系,应用高新技术开展地下水资源脆弱性的研究,充分利用灌区地下含水层的调蓄作用,通过地表水与地下水的联合利用控制水盐平衡、涵养地下水源,节约农业、工业和生活用水等。     

地下水对气候变化的敏感性研究进展

地下水是人类生活、生产、生态用水的重要水源。地下水含水层的补给及其开发利用是水资源可持续开发利用与管理的重要组成部分。浅层地下水的补给主要受制于气候变异与变化。气候变化影响研究从地表水扩展至地下水不仅有利于正确地评估可利用的淡水资源,而且对于改进气候模型,更完整的描写水文循环有重要的科学意义。自21世纪以来,欧美等国开始研究不同时空尺度的地下水补给的定量估算方法,并在气候变化对水资源影响的研究中,考虑了气候变化与人类活动对地下水补给的影响。目前在我国,无论对地下水观测资料的诊断分析,或对地下水补给模型的研制都尚属空白或起步阶段。本文对当前国际上研究地下水补给以及地下水对气候变化敏感性的研究现状予以综述,目的是为了推动我国关于气候变化对水资源影响的深入研究。     

Effect of the groundwater contribution, the climatic change, and the human-induced activities on the hydrological behavior of discharge playas: a case study Sidi El Hani discharge playa, Tunisian Sahel

This study is meant to provide an insight into how discharge playas, which are strongly influenced by a regional salty groundwater flow regime, such as the discharge playa of Sidi El Hani, would respond to the climatic variability and to the materials coming from the subsurface of the Sahel area. In order to choose the appropriate method, a special care was given in this paper to different methods of investigation of the groundwater contribution in water and salt budgets of saline systems. The hydrogeological map of the surrounding aquifers proved their convergence toward Sidi El Hani discharge playa. As consequence of the dominance of a salty groundwater contribution, the climate variability may be considered minor. Accordingly, the model proposed by this study showed the dominance of the salty water coming from the hydrogeology at the expense of the fresh water coming from the climatic contribution. Moreover, according to the adopted model, the effect of the human-induced activity on the hydrogeological contribution such as the installation of dams in the Tunisian center and the overexploitation of the phreatic aquifer of Kairouan was judged increasing the convergence of Kairouan aquifer towards Sidi El Hani discharge playa. On the other hand, the consumption of salt reserves from the discharge playa tends to decrease its salinization.     

Assessing the effects of climate change on the hydrological regime of the Limay River basin

The electricity generation capacity in the Limay River basin is approximately 26% of the total electrical power generation in Argentina. Assessing the potential effects of climate change on the hydrological regime of this basin is an important issue for water resources management. This study explores the presence of trends in streamflow series, evaluates climate sensitivity and studies the effects on the flow regime of predicted changes in precipitation in the basin. In order to identify and quantify changes in observed streamflow series, the Mann–Kendall test, with a modification for autocorrelated data, and an estimator of the magnitude of the trend are applied. In order to evaluate the sensitivity of streamflow to changes in climate, the concept of elasticity is used. Precipitation elasticity of streamflow is used to quantify the sensitivity of streamflow to changes in precipitation and is estimated using a power law model and a linear statistical model in two sub-basins, Aluminé and Nahuel Huapi. The effects on flow regime of the predicted changes in precipitation under different scenarios are studied. Climatic results for different scenarios of growth in greenhouse gases from some General Circulation Models are used as inputs into the proposed models. The analysis identifies decreasing trends in mean and minimum annual flows and in the low flow season. The estimates of the precipitation elasticity imply that changes in precipitation produce similar changes in streamflow and the climatic results for different scenarios show that the variations are moderate.     

Impact of climate change on waterlogging and salinity distributions in Huai Khamrian subwatershed, NE Thailand

Regional climate models project significant changes in temperature and rainfall over the Greater Mekong Subregion over the twenty-first century. The potential impacts of climate change on areas affected by waterlogging and shallow saline groundwater in Northeast Thailand was investigated using the variable density groundwater model SEAWAT supported with recharge estimates derived from the hydrologic model HELP3. The focal area is the 154 km² Huai Kamrian subwatershed. Changes in groundwater salinity and waterlogging areas at the middle and end of this century were predicted using the calibrated model. These predictions used the dynamically downscaled PRECIS regional climate change scenarios generated by ECHAM4 GCM A2 and B2 scenarios. Recharge rates are predicted to increase as a result of the higher intensity of rainfall. Shallow watertable areas are projected to increase by approximately 23 % from existing conditions during the middle of the century and up to 25 % by the end of this century. Although the precise rate and timing of climate change impacts are uncertain, all of the scenarios clearly point towards an extension in the area of waterlogging and area affected by shallow saline groundwater areas. Given that areas affected by shallow saline watertables are predicted to expand for both climate change scenarios as well as for the base case, it is concluded that climate change will have a significant impact on the area affected by salinity and waterlogging areas for both climate change scenarios. Evaluation of management options that explore the adaptation to saline environments and to means to reduce salt affected areas are required.     

Effects of climate change on the groundwater system in the Grote-Nete catchment,Belgium

The effects of climate change on the groundwater systems in the Grote-Nete catchment, Belgium, covering an area of 525 km², is modeled using wet (greenhouse), cold or NATCC (North Atlantic Thermohaline Circulation Change) and dry climate scenarios. Low, central and high estimates of temperature changes are adopted for wet scenarios. Seasonal and annual water balance components including groundwater recharge are simulated using the WetSpass model, while mean annual groundwater elevations and discharge are simulated with a steady-state MODFLOW groundwater model. WetSpass results for the wet scenarios show that wet winters and drier summers are expected relative to the present situation. MODFLOW results for wet high scenario show groundwater levels increase by as much as 79 cm, which could affect the distribution and species richness of meadows. Results obtained for cold scenarios depict drier winters and wetter summers relative to the present. The dry scenarios predict dry conditions for the whole year. There is no recharge during the summer, which is mainly attributed to high evapotranspiration rates by forests and low precipitation. Average annual groundwater levels drop by 0.5 m, with maximum of 3.1 m on the eastern part of the Campine Plateau. This could endanger aquatic ecosystem, shrubs, and crop production.     

Climate change and groundwater resources in Thailand

The average temperature of Thailand is projected to increase by 2-3 °C, and the annual rainfall is projected to increase by 25% and up to 50% in certain areas. The climate change in future is expected to provide changes in hydrological cycle and therefore impacts the groundwater resources too. In this study, we analyzed the general climate change trends and reviewed the groundwater conditions of Thailand. The climate changes, hydrologic variability and the impact of climate change on groundwater sustainability are also discussed based on a national groundwater monitoring program. Currently, there are 864 groundwater monitoring stations and 1 524 monitoring wells installed in Thailand. Moreover, the impact of climate change on groundwater-dependent systems and sectors is also discussed according to certain case studies, such as saline water intrusion in coastal and inland areas. Managing aquifer recharge and other projects are examples of groundwater adaptation project for the future.     

Understanding the past to interpret the future: comparison of simulated groundwater recharge in the upper Colorado River basin (USA) using observed and general-circulation-model historical climate data

In evaluating potential impacts of climate change on water resources, water managers seek to understand how future conditions may differ from the recent past. Studies of climate impacts on groundwater recharge often compare simulated recharge from future and historical time periods on an average monthly or overall average annual basis, or compare average recharge from future decades to that from a single recent decade. Baseline historical recharge estimates, which are compared with future conditions, are often from simulations using observed historical climate data. Comparison of average monthly results, average annual results, or even averaging over selected historical decades, may mask the true variability in historical results and lead to misinterpretation of future conditions. Comparison of future recharge results simulated using general circulation model (GCM) climate data to recharge results simulated using actual historical climate data may also result in an incomplete understanding of the likelihood of future changes. In this study, groundwater recharge is estimated in the upper Colorado River basin, USA, using a distributed-parameter soil-water balance groundwater recharge model for the period 1951–2010. Recharge simulations are performed using precipitation, maximum temperature, and minimum temperature data from observed climate data and from 97 CMIP5 (Coupled Model Intercomparison Project, phase 5) projections. Results indicate that average monthly and average annual simulated recharge are similar using observed and GCM climate data. However, 10-year moving-average recharge results show substantial differences between observed and simulated climate data, particularly during period 1970–2000, with much greater variability seen for results using observed climate data.     

基于地表水-地下水耦合模型的未来气候变化对西北干旱区水资源影响研究——以黑河中游为例

基于物理过程的地表-地下水耦合模型能全面、系统地刻画流域水循环过程,并为水资源管理提供详细信息。同时,未来水资源的变化趋势受到气候变化的影响显著,在未来气候情景下水资源如何变化将影响水资源管理措施。本文以黑河中游盆地为例,基于地表水-地下水耦合模型GSFLOW,评估区域水资源对气候变化的响应,预测未来气候情景(CMIP5)下区域水资源变化趋势,为西北干旱区水资源管理提供参考。研究表明:(1)GSFLOW模型能很好地模拟黑河中游盆地复杂的水循环过程。(2)在中等排放强度(RCP4.5)下,平均每年降水上升0.6 mm,温度上升0.03℃,地下水储量减少0.38亿m3;在高排放强度(RCP8.5)下,降水上升0.8 mm,温度上升0.06℃,地下水储量减少0.34亿m3。     

潜水地下水动态成因类型的综合判别方法——以三江平原松花江流域为例

传统地下水动态类型的判别方法存在受人为主观因素影响大、易产生多解性等问题。为提高地下水动态成因类型判断的可靠性,本文提出了基于水文地质条件定性分析与实测数据定量分析相结合的综合判别方法。根据研究区的气象、水文及水文地质条件等,将地下水各补给项及排泄项对地下水动态的影响进行定量化,对动态数据进行相关分析及逻辑判断,辨识出对地下水位动态贡献最大的补给项和排泄项,并依此确定地下水动态的成因类型。基于该方法,以三江平原松花江流域2011年及2015年相同的57个地下水观测点为例,结合地下水位埋深、地下水位、河水位、降水量、观测井距河流的距离、包气带岩性等资料,将研究区地下水动态成因类型共划分为水文型、降水入渗型、降水入渗-蒸发型、降水入渗-径流型、降水入渗-开采型和人工开采型6种类型;对比2011年及2015年研究区地下水动态类型的变化,降水入渗型、降水入渗-径流型等天然地下水动态成因类型占比减少,而受人类活动影响的地下水动态成因类型占比增加,表明人工开采活动对地下水动态的影响日益增强。相比根据地下水动态曲线特征确定动态成因类型的传统定性分析方法,本研究提出的综合判别方法能够在充分考虑水文地质...     

Impact of changing climate and land use on the hydrogeology of southeast Australia ∗

Anthropogenic climate change is the Earth's most serious large-scale environmental concern. While the projected changes of global temperatures, rainfall and surface water have been modelled in a sophisticated manner, the impact on groundwater resources is much less well constrained. In southeast Australia, the decrease in rainfall amount and an increase in temperature that are predicted by climate models are generally assumed to reduce the amount of recharge to the groundwater systems. However, the increase in recharge that has resulted from clearing of the native vegetation will almost certainly produce a greater impact on the groundwater system, increasing quantity and potentially improving quality. Additionally, the impact on recharge of changes to rainfall frequency rather than just total amount is not well documented. Overall our understanding of the impacts of climate change on groundwater systems is insufficiently advanced to make firm predictions. Indirect impacts of climate change, particularly the projected increased demand for groundwater or surface water to supplement surface water supplies also will have a major impact that may be greater than the direct effect of climate change.     

大庆油田西部地区地下水动态监测网优化设计

大庆油田地下水动态监测,网（用水文地质定性方法建立）历经30多年的开采，需要进行定量优化设计，本次研究采用卡尔曼滤波技术与地下水流系统确定－－随机性数值模型相耦合的方法，首先对现有监测网进行质量评价，计算结果表明：监测网在漏斗区（地下水集中开采区）应增加监测孔的数目，调整监测孔的位置，为此，我们拟订了6套12个备选方案，从中选取了由88个监测孔组成的监测网，此监测网无论从监测目标上还是经费上都是最优的。     

Response of the groundwater system in the Guanzhong Basin (central China) to climate change and human activities

The Guanzhong Basin in central China features a booming economy and has suffered severe drought, resulting in serious groundwater depletion in the last 30 years. As a major water resource, groundwater plays a significant role in water supply. The combined impact of climate change and intensive human activities has caused a substantial decline in groundwater recharge and groundwater levels, as well as degradation of groundwater quality and associated changes in the ecosystems. Based on observational data, an integrated approach was used to assess the impact of climate change and human activities on the groundwater system and the base flow of the river basin. Methods included: river runoff records and a multivariate statistical analysis of data including historical groundwater levels and climate; hydro-chemical investigation and trend analysis of the historical hydro-chemical data; wavelet analysis of climate data; and the base flow index. The analyses indicate a clear warming trend and a decreasing trend in rainfall since the 1960s, in addition to increased human activities since the 1970s. The reduction of groundwater recharge in the past 30 years has led to a continuous depletion of groundwater levels, complex changes of the hydro-chemical environment, localized salinization, and a strong decline of the base flow to the river. It is expected that the results will contribute to a more comprehensive management plan for groundwater and the related eco-environment in the face of growing pressures from intensive human activities superimposed on climate change in this region.     

Impact of climate change on groundwater recharge in a small catchment in the Black Forest, Germany

Temporal and spatial changes of the hydrological cycle are the consequences of climate variations. In addition to changes in surface runoff with possible floods and droughts, climate variations may affect groundwater through alteration of groundwater recharge with consequences for future water management. This study investigates the impact of climate change, according to the Special Report on Emission Scenarios (SRES) A1B, A2 and B1, on groundwater recharge in the catchment area of a fissured aquifer in the Black Forest, Germany, which has sparse groundwater data. The study uses a water-balance model considering a conceptual approach for groundwater-surface water exchange. River discharge data are used for model calibration and validation. The results show temporal and spatial changes in groundwater recharge. Groundwater recharge is progressively reduced for summer during the twenty-first century. The annual sum of groundwater recharge is affected negatively for scenarios A1B and A2. On average, groundwater recharge during the twenty-first century is reduced mainly for the lower parts of the valley and increased for the upper parts of the valley and the crests. The reduced storage of water as snow during winter due to projected higher air temperatures causes an important relative increase in rainfall and, therefore, higher groundwater recharge and river discharge.     

Climate change and groundwater resources in Cambodia

Climate change has become a major global concern and threatens the security of natural environmental resources, including groundwater, especially for Cambodia. In this study, literature reviews related to climate change and groundwater resources in Cambodia were evaluated to address the impact of climate change on the groundwater environment. In Cambodia, global climate change will likely affect available water resources by driving changes in the groundwater recharge and usage pattern. Despite a general increase in the mean annual rainfall, a reduction in rainfall is anticipated during the dry season, which could lead to shortages of fresh water during the dry season. The impact of climate change on water resource environments can significantly affect national economic development. Thus, strategic management plansfor groundwater in response to climate change should be established to ensure the security of water resources in Cambodia.