Maximizing the management of groundwater resources in the Paris–Abu Bayan reclaimed area,Western Desert,Egypt

The Paris–Abu Bayan area located along the Darb El Arbaein road is involved in the New Valley Project in the Egyptian Western Desert (EWD) as part of ongoing efforts since the 1960s. In this dryland area, groundwater stored in the Nubian Sandstone Aquifer System (NSAS) serves as the only water resource for a number of different uses. A major concern is the significant groundwater withdrawals from 74 pumped wells since the beginning of agricultural activities in 2000. The recent rapid expansion of agricultural activity and the lack of sufficient groundwater recharge as a result of unplanned groundwater development have led to severe stress on the aquifer. Field measurements have shown a rapid decline in groundwater levels, creating a crisis situation for this sole source of water in the area. In this study, mathematical modeling of the groundwater system (single aquifer layer) of the Paris–Abu Bayan reclaimed area was implemented using MODFLOW to devise a new strategy for the sustainable use of groundwater, by applying a number of scenarios in a finite-difference program. The conceptual model and calibration were developed by generating and studying the hydrogeological records, NSA parameters, production wells, and water level measurements for 2005 and 2012. Three management scenarios were applied on the calibrated model to display the present and future stresses on this aquifer over a 30-year period (2012–2042). The results clearly show a high decline in the heads of the NSA, by about 13.8 m, due to the continuous withdrawal of water (first scenario: present conditions, 102,473 m³/day). In the second scenario, the water level is expected to decrease significantly, by about 16 m, in most of the reclamation area by increasing the pumping rates by about 25% (over-pumping) to meet the continuous need for more cultivation land in the area. To reduce the large decline in water levels, the third plan tests the aquifer after reducing the water withdrawal by approximately 25%, applying modern irrigation systems, and suggesting two new reclaimed areas in the northeastern and northwestern parts (areas 1 and 2), with 20 new wells, at 500 m³/day/well. The results in this case show that groundwater levels are slightly decreased, by about 9.5 m, while many wells (especially the new wells in the northern part) show a slight decrease in groundwater levels (0.8 m). The results comparison shows that the groundwater level in the modeled area is lowered by 0.3 m/year with an increase in the number of wells to 94 and increased cultivation area by about 18% (third scenario), versus 0.45 m/year and 0.60 m/year recorded for the first and second scenarios, respectively. Therefore, based on the results, the third scenario is recommended as a new strategy for improving groundwater resource sustainability in the region.     

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.     

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.     

Spatio-temporal analysis of groundwater levels and projection of future trend of Agra city,Uttar Pradesh,India

Access to water resources is one of the major challenges being faced worldwide. Water scarcity, particularly groundwater resource, is the major ubiquitous concern for the country. Almost half of the country is reeling under severe ground water crisis due to anthropogenic and natural reasons (basalt rock surface). Agra region situated in the western part of Uttar Pradesh state of India has a semi-arid climate. The study area, which has a history of water scarcity since medieval ages, has seen a spurt of acute water shortage in recent times owing to the expansion of a very dense built-up area and excessive haulage accompanied by decline in rainfall. A study was under taken for identifying the trends in pre- and post-monsoon groundwater levels for Agra city, Uttar Pradesh. Pre-monsoon and post-monsoon groundwater depth data of 16 observation wells for the 2007–2016 period were collected and analyzed using ARC GIS 10.2 software. The rainfall trend during the study period was also studied to understand its role in groundwater fluctuation level. Statistical tests like Mann-Kendall, Sen’s slope estimator, and linear regression model were applied to understand the trend and rate of change in groundwater level. The land use/land cover map of the study area was integrated with groundwater map to have a primary understanding of the spatial trend of groundwater scenario of the study area. The result obtained is quite alarming for the city’s groundwater scenario. Results showed that the groundwater levels had significantly declined during 2007–2016. Average rates of water level decline were 0.228 and 0.267 m/year during pre- and post-monsoon seasons, respectively. There was a rapid decline in water level between 2008 and 2009 and between 2013 and 2014. The average rate of decline of pre- and post-monsoon groundwater level in the city during this period is 0.32 and 0.30 m/year, respectively. Significant decrease in groundwater level is found in 84.21% of wells for pre- and post-monsoon as obtained through Mann-Kendall analysis at 95% confidence level. During pre-monsoon season, the rate of decline according to Sen’s slope estimator varied between 0.74 and 2.05 m/year. Almost similar picture of decline is portrayed through linear regression slope wherein the computed rate of decline varied between 0.75 and 2.05 m/year. During post-monsoon, the rate of decline according to Sen’s slope varied between 0.13 and 1.94 m/year. Similar trend statistic is obtained through linear regression method where the declining rate is between 0.14 and 1.91 m/year. Comparison of the three statistical tests indicates similar nature of declining trend. The result of this research raises concern about the future of groundwater resources in Agra city. The findings of this study will assist planners and decision-makers in developing better land use and water resource management.     

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.     

An integrated study on the characterization of freshwater lens in a coastal aquifer of Southern India

The hydrogeochemical characterization of groundwater helps to assess the trend of salinization and freshening of the groundwater. The present study was carried out to understand the lateral and vertical variation of groundwater salinity and the process of salinization and freshening of the groundwater in a coastal aquifer comprising a freshwater lens. The partially isolated unconfined aquifer selected for the present study is lying just south of the Chennai City, one of the densely populated cities on the east coast of South India. Critical problems affecting this aquifer include a thin aquifer which is connected/surrounded by saltwater on all the sides, overexploitation of the groundwater, surface impermeabilization due to increasing residential areas, and destruction of existing dune morphology by conversion of barren land to the residential area which causes a reduction in their barrier effect to seawater intrusion. The process of salinization and freshening of the groundwater was studied and monitored by using electrical resistivity survey and hydrogeochemical analysis. The vertical electrical sounding was carried out at 17 locations, and 400 water samples were collected and analyzed from 50 locations during the period from August 2008 to May 2010 for this study. The apparent resistivity values were analyzed and compared with groundwater quality to demarcate the zone of seawater intrusion. The regional flow direction of the groundwater is westward and eastward with respect to the central stretch and groundwater level ranges from 4.96 m MSL at the dune morphology to 0 m MSL along the boundary on all the sides. Base exchange index indicates that salinization trend in the northern part of the study area is due to the extensive groundwater pumping which increases the possibility of seawater intrusion. The increase of base exchange index towards southern part indicates a better groundwater quality of the aquifer due to proper land use practices. A strong trend of quality alteration is clearly visible from the base exchange index in response to the seasonal change between monsoon and dry season. In the western side, the monsoonal variation in the salinization and freshening of the groundwater was not noticed; however, the salinity is slightly higher than freshwater due to the presence of clay.     

A groundwater flow model for overexploited basaltic aquifer and Bazada formation in India

Recent changes in land use practices, such as increase in orange orchards in central India, has put undue pressure on the groundwater resources. Excess withdrawal from the aquifers has resulted in groundwater table decline. The stage of groundwater development in some watersheds has reached 155.85 %, converting these into overexploited watersheds. In the present research paper, a groundwater flow model has been developed to evaluate the groundwater system in a basaltic terrain with Bazada formation. A conceptual model has been developed and calibrated for steady and transient states and the sensitivity analysis was carried out. Future predictions, for current scenario where present practices are continued and for scenario with 20 % reduction in groundwater draft have been made, to select the best strategy for mitigating the problem. The modeling results show that the decline in groundwater level in basaltic and Bazada unconfined aquifers will result into drying up (water level more than 15 m bgl) of 243 km² area by 2020. To restore the groundwater level, it is simulated that the groundwater draft rate must be reduced by 20 % for next 10 years. It may be achieved by adopting groundwater management strategies, particularly for irrigation sector.     

In situ infiltration test using a reclaimed abandoned river bed: managed aquifer recharge in Shijiazhuang City,China

Managed aquifer recharge (MAR) is necessary for water resources management in arid and semiarid regions. Infiltration rate is often a decisive limiting factor in site selection for MAR. In order to avoid scale effects in the application of infiltration rate parameters, the largest in situ infiltration test in China was undertaken between August 19 and August 30, 2009 to measure the infiltration rate of the field selected for MAR in Shijiazhuang City, China. The in situ test lasted for 10 days, and about 1.82 × 10⁷ m³ of water was introduced into the infiltration field. Groundwater level variations were monitored during the test. Monitoring showed that the infiltration rate of surface water was 1.5 m/day, which means that about 10–15 × 10⁸ m³/a of water could be injected into the target aquifer. Also, groundwater level variations showed that the northern part of the infiltration field had a higher infiltration rate, as predicted, and the test result supplied a sound foundation for validation of the groundwater numerical simulation, which will be of benefit for future predictions of the response of the groundwater level to artificial recharge engineering. Finally, an artificial recharge plan was proposed based on the infiltration test results and the water source conditions, which would be useful for the development of MAR programs and management of local water resources.     

Assessment of water level threshold for groundwater restoration and over-exploitation remediation the Beijing-Tianjin-Hebei Plain

The Beijing-Tianjin-Hebei Plain (BTHP) is the political, economic and cultural center of China, where groundwater is the main source of water supply to support social and economic development. Continuous overdraft of the resources has caused a persistent decline of groundwater level and formed a huge cone of depression at a regional scale. This paper addresses current groundwater situation over the BTHP area. The paper also delineates the groundwater flow field, using groundwater level data, in order to provide an effective method for the restoration of groundwater level and associated water resources management. Based on the analysis of multiple factors, such as groundwater level, soil salinization, ground subsidence, groundwater recharge and storage, urban underground space security, formation of fractures, and seawater intrusion, the threshold for groundwater level restoration is defined, and some measures for groundwater over-exploitation management are accordingly proposed. The study shows that: (i) Since the 1980s to 2020, shallow groundwater level in the western part of the BTHP area has dropped by 25 m to 60 m, while the cumulative decline of deep groundwater in the central and eastern regions is in the range of 40–80 m; (ii) The water table of the shallow groundwater within the depression zone over the Western Piedmont Plain should be controlled in the range of 15–30 m below ground level (mbgl), while the depth of groundwater level in large and medium-sized urban areas should be controlled within 20–30 mbgl. The groundwater level in the resource preservation area should be controlled within 10–15 mbgl, and the groundwater level in the area with identified soil salinization in the central and eastern plain should be controlled within 3–10 mbgl. However, for the deep groundwater in the central and eastern plainwater, the main focus of the resources management is to control the land subsidence. The water level in the severe land subsidence area should be controlled within 45–60 mbgl, and in the general subsidence area should be controlled within 30–45 mbgl; (iii) Based on the water level recovery threshold and proposed groundwater overdraft management program, if the balance of abstraction and recharge is reached in 2025, the shallow groundwater abstraction needs to be gradually reduced by about 2×10⁸ m³. Meanwhile, the ecological water replenishment of rivers through the South-to-North Water Transfer Project should be increased to 28.58×10⁸ m³/a, and the deep groundwater abstraction needs to be gradually reduced by 2.24×10⁸ m³. To reach the target of shallow groundwater level in 2040, surface water replacement is recommended with a rate of 25.77×10⁸ m³/a and the ecological water replenishment of rivers in the South-to-North Water Diversion Project should reach 33.51×10⁸ m³/a. For deep groundwater recovery, it is recommended to replace the deep freshwater extraction with the utilization of shallow salt water by 2.82×10⁸ m³ , in addition to the amount of 7.86×10⁸ m³ by water diversion. The results are of great significance to the remediation of groundwater over-exploitation, the regulation of water resources development and utilization, and ecological protection in Beijing-Tianjin-Hebei plain.     

Modelling the response of shallow groundwater levels to combined climate and water-diversion scenarios in Beijing-Tianjin-Hebei Plain,China

A three-dimensional groundwater flow model was implemented to quantify the temporal variation of shallow groundwater levels in response to combined climate and water-diversion scenarios over the next 40 years (2011–2050) in Beijing-Tianjin-Hebei (Jing-Jin-Ji) Plain, China. Groundwater plays a key role in the water supply, but the Jing-Jin-Ji Plain is facing a water crisis. Groundwater levels have declined continuously over the last five decades (1961–2010) due to extensive pumping and climate change, which has resulted in decreased recharge. The implementation of the South-to-North Water Diversion Project (SNWDP) will provide an opportunity to restore the groundwater resources. The response of groundwater levels to combined climate and water-diversion scenarios has been quantified using a groundwater flow model. The impacts of climate change were based on the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model dataset for future high (A2), medium (A1B), and low (B1) greenhouse gas scenarios; precipitation data from CMIP3 were applied in the model. The results show that climate change will slow the rate of decrease of the shallow groundwater levels under three climate-change scenarios over the next 40 years compared to the baseline scenario; however, the shallow groundwater levels will rise significantly (maximum of 6.71 m) when considering scenarios that combine climate change and restrictions on groundwater exploitation. Restrictions on groundwater exploitation for water resource management are imperative to control the decline of levels in the Jing-Jin-Ji area.     

Groundwater simulation using a numerical model under different water resources management scenarios in an arid region of China

Groundwater plays an important role in the economic development and ecological balance of the arid area of northwest China. Unfortunately, human activity, for example groundwater extraction for irrigation, have resulted in excessive falls in groundwater level, and aquifer overdraft in the oasis, disrupting the natural equilibrium of these systems. A groundwater numerical model for Minqin oasis, an arid area of northwest China, was developed using FEFLOW software to simulate regional groundwater changes under transient conditions. The vertical recharge and discharge (source/sink terms) of the groundwater models were determined from land-use data and irrigation systems for the different crops in the different sub-areas. The calibrated model was used to predict the change for the period from 2000 to 2020 under various water resources management scenarios. Simulated results showed that under current water resources management conditions groundwater levels at Minqin oasis are in a continuous drawdown trend and groundwater depth will be more than 30 m by 2020. Reducing the irrigation area is more effective than water-saving irrigation to reduce groundwater decline at Minqin oasis and the annual groundwater budget would be −0.978 × 10⁸ m³. In addition, water-diversion projects can also reduce the drawdown trend of groundwater at Minqin oasis, and the groundwater budget in the Huqu sub-area would be in zero equilibrium if the annual inflow into the oasis was enhanced to 2.51 × 10⁸ m³. Furthermore, integrative water resources management including water-diversion projects, water-saving irrigation, and reducing the irrigation area are the most effective measures for solving groundwater problems at Minqin oasis.     

Variations in groundwater levels and quality due to agricultural over-exploitation in an arid environment: the phreatic aquifer of the Souf oasis (Algerian Sahara)

Groundwater is a major source of supply for domestic and agricultural purposes, especially in arid and semi-arid regions. In this study, we followed the variations in water levels in the Souf oasis in the Algerian Sahara by measuring depths to groundwater across 65 points during the period from 2010 to 2015. Additionally, electrical conductivity (EC) was measured for assessing variations in groundwater salinity in the same groundwater monitoring network over the same time interval. The results from these investigations indicated that there are significant and continuous declines in the groundwater level across all study areas throughout the period of investigation. This is especially the case in the northern part of the study area where the water table declined by up to 18.2 m in Ghamra in 2015. Additionally, this study has indicated that the rate of decline of groundwater levels has increased from 0.29 m/year as an average in 2011 to 2.37 m/year in 2015, where the situation has become alarming. As a consequence of this, the depth to groundwater now exceeds 2 m over more than 77% of the study area, and only about 17% of the study area now has a water table depth that lies within the optimal depth interval for extractive uses (between 1 and 2 m). This decline in groundwater levels has been accompanied by a significant increase in the electrical conductivity values (salinity) of this water, and there is a strong correlation between these variables (R > 0.99). This alarming situation has been caused by the continuous over-exploitation and unsustainable management of this limited resource, especially by the agricultural sector. For a long time, this critical situation led to the demise of the agricultural world heritage cultivation system (Ghout) due to the increasing salinity of groundwater. Two solutions are proposed to manage the effects of groundwater depletion in the area: firstly, rationalizing groundwater use through effective groundwater allocation management measures, and secondly by implementing the reuse of treated wastewater as an alternative water source for agricultural use. This latter measure could be in two ways: either by direct use in irrigation to relieve pressure on the phreatic aquifer, or by artificial recharge of the phreatic aquifer.     

Statistical analysis of groundwater level variability across KwaZulu-Natal Province,South Africa

This paper reports the results of analysis of groundwater level changes and its relationship with rainfall across KwaZulu-Natal (KZN) Province of South Africa. The study used 32 groundwater level monitoring sites and 15 selected rainfall stations located across the province. The Mann–Kendall test was used to explore the presence of trends in groundwater level and rainfall data at 10% significance level. The slope of the trend was estimated using Sen’s slope estimator. To understand the cause–effect relationship between rainfall and groundwater level changes, the cumulative rainfall departure (CRD) was computed at the respective rainfall stations influencing the groundwater monitoring site. The results show variable but a general decreasing trend. The variability of the groundwater level trends was analyzed based on water management areas (WMA): (1) both groundwater level and rainfall have a decreasing trend for the entire record period in the Usuthu–Mhlathuzi WMA. Groundwater level around Tembe and Mbazwana areas declined by 0.7 and 2.7 m, respectively. Areas around Richards Bay experienced a reduction between 0.7 and 6.3 m from 2004 to 2015. During the same period, the rainfall within the WMA decreased by 26, 6 and 18% from the mean around Tembe, Mbazwana and Richards Bay, respectively; (2) The northern sector of the uThukela WMA, around Dundee and Newcastle exhibited groundwater level increase by about 1.5 m between 2004 and 2010 but later declined by 1.2 m from 2014 to 2015. The rainfall increased by 8% from 2004 to 2010, and decreased by 22% at the end of 2015. The central part of the uThukela WMA, around Tugela Ferry and Greytown, experienced groundwater level and rainfall reductions of 3.2 m and 15%, respectively, during the entire record period; (3) Within the Mvoti–uMzimkulu WMA in the vicinity of Maphumulo, groundwater level decline by 11 m from 2005 to 2011. However, it recovered by 8 m between 2012 and 2013 following an increase in rainfall by 21%. Areas around Durban exhibited increasing trend from 2005 to 2008 in response to an increasing rainfall amount by about 13% for the same period. The reduction in rainfall by 21% from 2012 to 2015 resulted in a decline of groundwater level by 0.4 m. The steady decline in groundwater levels across the province appears to be a response to prolonged reduction in rainfall, which consequently reduced the amount of groundwater recharge reaching the aquifer. The general response of groundwater levels to changes in rainfall across the province has a lag time from 1 to 4 months.     

Groundwater flow in a transboundary fault-dominated aquifer and the importance of regional modeling: the case of the city of Querétaro,Mexico

The city of Querétaro, located near the political boundary of the Mexican states of Querétaro and Guanajuato, relies on groundwater as it sole water supply. Groundwater extraction in the city increased from 21?×?10⁶ m³/yr in 1970 to 104?×?10⁶ m³/yr in 2010, with an associated drawdown of 100 m in some parts of the aquifer. A three-dimensional numerical groundwater-flow model has been developed that represents the historical evolution of the aquifer’s potentiometric levels and is used to simulate the effect of two scenarios: (1) a 40 % reduction in the extraction rate from public water supply wells in early 2011 (thus reducing the extraction to 62?×?10⁶ m³/yr), and (2) a further reduction in 2021 to 1?×?10⁶ m³/yr. The modeling results project a temporary recovery of the potentiometric levels after the 40 % reduction of early 2011, but a return to 2010 levels by 2020. If scenario 2 is implemented in 2021, the aquifer will take nearly 30 years to recover to the simulated levels of 1995. The model also shows that the wells located in the city of Querétaro started to extract water from part of the aquifer beneath the State of Guanajuato in the late 1970s, thus showing that the administrative boundaries used in Mexico to study and develop water resources are inappropriate, and consideration should be given to physical boundaries instead. A regional approach to studying aquifers is needed in order to adequately understand groundwater flow dynamics.     

西北地区地下水水量-水位双控指标确定研究——以民勤盆地为例

地下水是西北内陆河流域干旱半干旱地区重要的供水水源、生态因子和环境因子。当前缺乏针对西北干旱半干旱地区特点的地下水水量和水位双控管理指标确定方法研究,无法为西北地区开展流域水资源管理生态保护提供技术支撑。本研究基于地下水可持续利用和生态保护的原则,提出了一套确定西北地区地下水水量-水位双控指标的技术方案。采用“以位定量”的思路,依据指标监测井代表的不同地下水功能区的地下水管理水位,确定水位指标区间值;将通过天然植被排泄的地下水量作为不可袭夺的排泄项,以数值模拟方法预报求解满足水位指标约束的地下水开采量,计算水量指标区间值。以民勤盆地为研究区开展示例研究,依据技术方案计算得到水位指标的下限阈值为埋深5.00～49.37 m,上限阈值为埋深0.00～5.00 m,水量指标上限为6 000×104 m3/a,下限为10 000×104 m3/a。采用2012—2016年区内实际开采量和监测水位变化趋势进行验证,当开采量在水量指标区间内运行时,水位也基本在水位指标区间内变化。该技术方法可以为西北地区开展双控管理提供一定的技术支撑。     

Use of water balance calculation and tritium to examine the dropdown of groundwater table in the piedmont of the North China Plain (NCP)

The groundwater table in the piedmont plain was only about 1–2 m in depth in the 1950s and 1960s, but it lowered dramatically afterwards to about 25–27 m in depth (currently 21–23 m above sea level) due to overpumping of groundwater and drought in the region. This change has adversely affected the sustainable development and food supply of this important agricultural area. The groundwater table at Luancheng Experimental Station of the Chinese Academy of Sciences, located in the piedmont, dropped from 39.36 m in 1975 to 21.47 m above sea level in 1999, at an average rate of 0.72 m/year. Water balance components, such as daily rainfall, pan-evaporation, and evapotranspiration (by lysimeter after 1995) have been recorded since the 1970s, and they were used as variants to simulate monthly water table change based on a physically based statistical model. Groundwater samples were collected during the period 1998–2001, and tritium was measured in the laboratory to trace the groundwater flow from the Taihang Mountains to the piedmont. A reasonable exploitation rate of 150 mm/year was obtained from the model by assuming the annual water table is constant. The recharge and groundwater flow from the Taihang Mountains plays an important role in the water balance of the piedmont area, and it was estimated to be about 112.5 mm/year by using the variation of tritium with the depth, which followed a good exponential function. The simple water balance calculation indicated that the water table could recede at a rate of 0.8 m/year, which is close to the actual situation.     

A spatio-temporal three-dimensional conceptualization and simulation of Dera Ismail Khan alluvial aquifer in visual MODFLOW: a case study from Pakistan

Dera Ismail Khan (DIK) is situated in the Lower Indus Basin of Pakistan. The land use has been changed in the canal command area due to irrigation activities near the Indus River. To check the current status and predict the groundwater levels in the area, the unconfined aquifer has been simulated in Visual MODFLOW for a period of 35 years, i.e., from 1985 to 2020. The 2900-km² area has been modeled with a grid of 500 by 500 m and the depth set to 100 m. The aquifer in the study area has been divided vertically and laterally into three and ten zones, respectively, for the characterization. Water wells and streams were used as the sinks and hydrologic boundaries, respectively. The model was successfully calibrated in steady and the non-steady state. The simulation revealed that the whole simulation can be divided into two phases, i.e., before and after the construction of the Chashma Right Bank Canal (CRBC), whereas the results were summarized in the form of water table depth maps and groundwater budget calculations. To determine the groundwater sustainability, a conjunctive use scenario has been employed to simulate the aquifer dynamics till 2020. The simulation revealed incremental drawdowns till the end.     

Regional groundwater flow model for Abu Dhabi Emirate: scenario-based investigation

Despite the continuous increase in water supply from desalination plants in the Emirate of Abu Dhabi, groundwater remains the major source of fresh water satisfying domestic and agricultural demands. Groundwater has always been considered as a strategic water source towards groundwater security in the Emirate. Understanding the groundwater flow system, including identification of recharge and discharge areas, is a crucial step towards proper management of this precious source. One main tool to achieve such goal is a groundwater model development. As such, the main aim of this paper is to develop a regional groundwater flow model for the surficial aquifer in Abu Dhabi Emirate using MODFLOW. Up to our knowledge, this is the first regional numerical groundwater flow model for Abu Dhabi Emirate. After steady state and transient model calibration, several future scenarios of recharge and pumping are simulated. Results indicate that groundwater pumping remains several times higher than aquifer recharge from rainfall, which provides between 2 and 5% of total aquifer recharge. The largest contribution of recharge is due to subsurface inflow from the eastern Oman Mountains. While rainfall induced groundwater level fluctuation is absent in the western coastal region, it reaches a maximum of 0.5 m in the eastern part of the Emirate. In contrast, over the past decades, groundwater levels have declined annually by 0.5 m on average with local extremes spanning from 93 m of decline to 60 m of increase. Results also indicate that a further decrease in groundwater levels is expected in most of Emirate. At other few locations, upwelling of groundwater is expected due to a combination of reduced pumping and increased infiltration of water from nonconventional sources. Beyond results presented here, this regional groundwater model is expected to provide an effective tool to water resources managers in Abu Dhabi. It will help to accurately estimate sustainable extraction rates, assess groundwater availability, and identify pathways and velocity of groundwater flow as crucial information for identifying the best locations for artificial recharge.     

Numerical simulation of the effect of heavy groundwater abstraction on groundwater–surface water interaction in Langat Basin, Selangor, Malaysia

The paper aims at evaluating the interaction between ground and surface water along the Langat River in Malaysia through the development of a numerical simulation. Malaysia has been experiencing a rapid economic growth since the last few decades, driven by many factors such as agriculture, industry, and the like. The demand for water in these sectors has increased so tremendously that surface water has been utilized in conjunction to groundwater. Approximately 18,184 m³ of water per day is obtained from the aquifer to supply to the steel factory. There are also workshops, petroleum stations, and houses in the area thus causing the water quantity and quality to degrade. In terms of quantity, the pumping activity has altered the interaction between the groundwater and surface water. Therefore, a numerical model was proposed and two aquifer layers were simulated, with the first layer being approximately >20 m in depth and the second layer >100 m. The recharge estimated from the tank model was input into the groundwater modeling. The effects of the surface water to the aquifer were included in the simulation by defining the river conductance, river bed, and river level. The calibrated model (error about 0.9 m) was achieved and applied to predict the flow pattern in its natural state without the pumping and with the pumping states. As a result, in the first scenario, the stream was in an effluent condition influenced by the groundwater from the northeast to the west. A hyporheic flow occurred and was observed from the contour map. The flow system was changed in the second scenario when the pumping activity was included in the simulation. The groundwater lost its original function but received leakage from the stream near the pumping sites. The findings of this study will help the local authorities and other researchers to understand the aquifer system in the area and assist in the preparation of a sustainable groundwater management.     

Water table fluctuation analyses and associated empirical approach to predict spatial distribution of water table at Yeşilköy/AgiosAndronikos aquifer

The groundwater of the deep Ye?ilköy aquifer is the only water resource for agricultural and domestic consumption at the Karpaz Peninsula of Cyprus, which stretches approximately 100 km from the northeast of capital Nicosia to the northern tip of Cyprus. During the last decade, over-pumping and following dry periods have depleted the groundwater resources and the water surface elevation of the aquifer has dropped. The aim of this study is to understand the behavior of the Ye?ilköy aquifer in the last decade for the proper management of groundwater resources. This has been achieved based on well survey and field survey studies, monitoring programs followed by pumping tests, and safe yield analysis. Most of the research effort has been focused on field and well survey studies to quantify agricultural water consumption and abstraction rates from the aquifer. A long-term groundwater level monitoring program, short-term continuous groundwater monitoring and pumping tests provided information for the regression analyses while deriving a sixth order polynomial relationship between the period parameter and the head parameter. The equation was helpful to predict the short-term behavior of the water level when the present hydrogeological conditions prevail. The pumping test results satisfied the hydraulic properties of calcarenite formation yielding T = 1,782 m²/day and S = 0.0012. The results of safe yield analysis show that the annual deficit of the aquifer is 0.496 million cubic meters (MCM), which is equivalent to a 0.6 m drop in groundwater levels per year. Finally, the resultant annual safe yield of the aquifer is estimated as 0.84 MCM.