Recharge and discharge controls on groundwater travel times and flow paths to production wells for the Ammer catchment in southwestern Germany

Travel times and flow paths of groundwater from its recharge area to drinking-water production wells will govern how the quality of pumped groundwater responds to contaminations. Here, we studied the 180 km² Ammer catchment in southwestern Germany, which is extensively used for groundwater production from a carbonate aquifer. Using a 3-D steady-state groundwater model, four alternative representations of discharge and recharge were systematically explored to understand their impact on groundwater travel times and flow paths. More specifically, two recharge maps obtained from different German hydrologic atlases and two plausible alternative discharge scenarios were tested: (1) groundwater flow across the entire streambed of the Ammer River and its main tributaries and (2) groundwater discharge via a few major springs feeding the Ammer River. For each of these scenarios, the groundwater model was first calibrated against water levels, and subsequently travel times and flow paths were calculated for production wells using particle tracking methods. These computed travel times and flow paths were indirectly evaluated using additional data from the wells including measured concentrations of major ions and environmental tracers indicating groundwater age. Different recharge scenarios resulted in a comparable fit to observed water levels, and similar estimates of hydraulic conductivities, flow paths and travel times of groundwater to production wells. Travel times calculated for all scenarios had a plausible order of magnitude which were comparable to apparent groundwater ages modelled using environmental tracers. Scenario with groundwater discharge across the entire streambed of the Ammer River and its tributaries resulted in a better fit to water levels than scenario with discharge at a few springs only. In spite of the poorer fit to water levels, flow paths of groundwater from the latter scenario were more plausible, and these were supported by the observed major ion chemistry at the production wells. We concluded that data commonly used in groundwater modelling such as water levels and apparent groundwater ages may be insufficient to reliably delineate capture zones of wells. Hydrogeochemical information relating only indirectly to groundwater flow such as the major ion chemistry of water sampled at the wells can substantially improve our understanding of the source areas of recharge for production wells.     

Artificial groundwater recharge to a semi-arid basin: case study of Mujib aquifer,Jordan

Mujib watershed is an important groundwater basin which is considered a major source for drinking and irrigation water in Jordan. Increased dependence on groundwater needs improved aquifer management with respect to understanding deeply recharge and discharge issues, planning rates withdrawal, and facing water quality problems arising from industrial and agricultural contamination. The efficient management of this source depends on reliable estimates of the recharge to groundwater and is needed in order to protect Mujib basin from depletion. Artificial groundwater recharge was investigated in this study as one of the important options to face water scarcity and to improve groundwater storage in the aquifer. A groundwater model based on the MODFLOW program, calibrated under both steady- and unsteady-state conditions, was used to investigate different groundwater management scenarios that aim at protecting the Mujib basin. The scenarios include variations of abstraction levels combined with different artificial groundwater recharge quantities. The possibilities of artificial groundwater recharge from existing and proposed dams as well as reclaimed municipal wastewater were investigated. Artificial recharge options considered in this study are mainly through injecting water directly to the aquifer and through infiltration from reservoir. Three scenarios were performed to predict the aquifer system response under different artificial recharge options (low, moderate, and high) which then compared with no action (recharge) scenario. The best scenario that provides a good recovery for the groundwater table and that can be feasible is founded to be by reducing current abstraction rates by 20% and implementing the moderate artificial recharge rates of 26 million(M)m³/year. The model constructed in this study helps decision makers and planners in selecting optimum management schemes suitable for such arid and semi-arid regions.     

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.     

A hybrid multiple criteria decision-making model for the sustainable management of aquifers

In this study, a hybrid multiple criteria decision-making (HMCDM) model was proposed for prioritizing scenarios for managing groundwater use from an aquifer. Three scenarios, including the construction of subsurface dams, the use of artificial recharge and reducing groundwater use by 5% and 10% were considered to assess the most sustainable development approach. The examined MCDM models were: simple additive weighting (SAW); and MTAHP which is a hybridization of the modified TOPSIS and the analytic hierarchy process models. The criteria proposed for determining the order preference of the scenarios included the sustainable development index (I_U) and a modified water exploitation index as well as economic, social and environmental indices. To assess the technical and economic impacts of the management scenarios, modeling of the aquifer was simulated for a 3-year period using these scenarios. The results of the assessment indicated that the scenario of water withdrawal reduction by 10% was the best scenario determined in MTAHP followed by a reduction in groundwater withdrawal by 5%, the use of artificial recharge and the construction of a subsurface dam, respectively. The difference between the results of MTAHP and SAW models was in their first and third ranks, in such a way artificial recharge scored the first rank in SAW model and the third rank in MTAHP model, also withdrawal reduction by 10% scored third rank in SAW model and first rank in MTAHP model. The results of these two models have demonstrated that the construction of a subsurface dam in Shahrekord aquifer is not an appropriate management option. According to the results of this study, MTAHP models can be applied for ranking feasible management scenarios in aquifers using the redefined sustainable development and modified groundwater exploitation indices introduced in this study.     

Optimal Groundwater Development in Coastal Aquifers Near Beihai, China

INTRODUCTIONThe city of Beihai,located on the south coast ofGuangxi,China,relies heavily on groundwater for its potablewater supply and agricultural irrigation.With rapid increasein population (for instance,from 134 0 0 0 in 1987to 47930 0in1995 ) and in developm ent program s,the demand for freshwater has been growing. Approxim ately 170 0 0 0 m3/ d ofgroundwater has been pumped from the productive coastalaquifers in recent years.Contamination of the fresh water inthe coastal aquifers b…     

A method to estimate the artificial recharge capacity of the Crestatx aquifer (Majorca, Spain).

This paper presents a method for the feasibility of an artificial recharge scheme in a limestone aquifer. A 3D digital groundwater flow model was developed and calibrated to gain a better understanding of the aquifer dynamics and to estimate its capacity for artificial recharge. Several scenarios, based on different pumping alternatives, were tested over a 30 year period. The results were then analysed by yearly input-output balances. Worst case scenario model output suggests that implementing the scheme might ensure a sustainable use of the aquifer in the future.     

Hydrology models approach to estimation of the groundwater recharge: case study in the Bulgarian Danube watershed

The groundwater (GW) makes an important part of a region runoff. GW bodies playing the role of accumulating reservoirs regulate the GW discharge enabling the river flow to have more uniform long-term distribution. Along with other important advantages, the GW offers the users stable water abstraction rate independent from the recharge rate. The GW recharge quantification belongs to the uneasy tasks in the water resource management. Applying the conventional methods needs multiyear observation records of the variation of the groundwater body (GWB) characteristics. The employment of hydrology models avoids that necessity but requires great amount of data related to the soil hydraulic properties, the land topography and cover of the GWB watershed and long-term records of the climatic effects. The paper presents an introduction of the mathematical model CLM3 into the GW recharge estimation problem. It is a complex and advanced model with adequate interpretation of the water-related processes in the soil and on the land surface under atmospheric effects. The input is available from NCEP/NCAR reanalysis atmosphere data and the International Geosphere-Biosphere Program (IGBP) data base. The model is applied to GW recharge assessment of the Bulgarian Danube district for the year 2013. The obtained monthly and yearly total district values and the areal distribution of the infiltration intensity are matched to the existing field observation-based estimates. The study shows that the CLM3 model approach leads to encouraging results. The method comes very useful with GWB lacking regime observation data as well as for GW recharge prognostic assessments under climatic scenarios.     

Climate and irrigation scenario analyses using three-dimensional numerical modelling: a case study of the Nasia sub-basin in the White Volta Basin,Ghana

A groundwater resource characterisation and assessment model was developed for Nasia river sub-basin in the White Volta Basin, Ghana. The model is useful to policymakers for planning and sustainable management of groundwater resources in the basin for domestic and irrigation purposes. A conceptual model was constructed that characterized boundary conditions and hydrostratigraphy, and estimated recharge rates and hydraulic and storage parameters. From current understanding of the hydrogeological dynamics, three hydrostratigraphic layers were delineated. The conceptual model was converted to a three-dimensional steady-state groundwater flow model using MODFLOW. Recharge rates estimated from the base model indicate a minimum of 1.1% and maximum of 6.2% of the total rainfall. The hydraulic conductivity ranged between 0.20 and 15 m/day. Four possible scenarios were simulated: (1) increased population, (2) climate variations (reduced recharge), (3) increased abstraction for irrigation, and (4) worst-case scenario which is a combination of the first three scenarios. Results from scenarios 1 and 2 indicated that, under such conditions, the groundwater resources could be sustained and no significant effect on any of the water budget indicators was observed. For scenario 3, there was significant drop in hydraulic head in the central portions of the study area. The scenario 4 simulation indicated that there was significant reduction in groundwater levels and groundwater discharge into streams under these stressors. Such reduction can affect stream levels in the basin and, subsequently, the ecosystem. These findings are valid within the limits of uncertainty in the hydrogeological data that were used in this study.

     

GIS based groundwater modeling study to assess the effect of artificial recharge: A case study from Kodaganar river basin,Dindigul district,Tamil Nadu

Groundwater is a dynamic and replenishable natural resource. The numerical modeling techniques serve as a tool to assess the effect of artificial recharge from the water conservation structures and its response with the aquifers under different recharge conditions. The objective of the present study is to identify the suitable sites for artificial recharge structures to augment groundwater resources and assess its performance through the integrated approach of Geographic Information System (GIS) and numerical groundwater modeling techniques using MODFLOW software for the watershed located in the Kodaganar river basin, Dindigul district, Tamil Nadu. Thematic layers such as geology, geomorphology, soil, runoff, land use and slope were integrated to prepare the groundwater prospect and recharge site map. These potential zones were categorized as good (23%), moderate (54%), and poor (23%) zones with respect to the assigned weightage of different thematic layers. The major artificial recharge structures like percolation ponds and check dams were recommended based on the drainage morphology in the watershed. Finally, a threelayer groundwater flow model was developed. The model was calibrated in two stages, which involved steady and transient state condition. The transient calibration was carried out for the time period from January 1989 to December 2008. The groundwater model was validated after model calibration. The prediction scenario was carried out after the transient calibration for the time period of year up to 2013. The results show that there is 15 to 38% increase in groundwater quantity due to artificial recharge. The present study is useful to assess the effect of artificial recharge from the proposed artificial structures by integrating GIS and groundwater model together to arrive at reasonable results.     

河流-含水层系统数值模拟方法探讨

地表水与地下水转化量的模拟预测一直是区域水资源评价和管理中的难题。提出了一种基于河流越流系数的处理方法,即将转化量计算模型同三维地下水数值模型完全耦合,能够预测在有人工干预条件下,地表水与地下水转化量的变化趋势。提出的方法适合多含水层系统的情形。实例研究表明,提出的河流-含水层系统模拟方法原理简单,易于实现,可以推广应用。     

控制海水入侵的地下水多目标模拟优化管理模型

为实现滨海含水层地下水开采-回灌方案优化、控制海水入侵面积和降低海水入侵损失等多重管理目标,建立了海水入侵条件下地下水多目标模拟优化管理模型SWT-NPTSGA。模拟模型采用基于变密度流的数值模拟程序SEAWAT来模拟海水入侵过程。优化模型采用小生境Pareto禁忌遗传混合算法NPTSGA来求解,该算法在保证多目标权衡解的收敛性和计算效率的前提下,能维护整个进化群体的全局多样性。将SWT-NPTSGA程序应用于一个理想滨海含水层地下水开采方案和人工回灌控制海水入侵的优化设计中,结果表明该管理模型能够同时处理最大化总抽水流量、最小化人工回灌总量和最小化海水入侵范围等3个目标函数之间的权衡关系。通过采用人工回灌海水入侵区的减灾策略,既能增加滨海地区的供水量,又可减少海水入侵的范围,由此进一步验证了模型的有效性和可靠性。     

济南岩溶泉域地下水可持续开采方案分析

济南岩溶泉域是济南市重要饮用水源地,泉水又是济南市市民消闲和吸引游客的亮丽景观。但是多年来开采地下水已引起泉水出现间歇性断流。本文在对水资源规划分析基础上,设计了4个地下水资源开采方案:现状方案、增加补给量方案、减少开采量方案和增补减开联合方案。运用地下水流数值模型模拟了4个方案对泉群地下水水位及泉水流量动态变化的影响,最终确定了泉域地下水可持续开采方案,为泉水持续喷涌和地下水开发利用提供了科学依据。     

Investigation of discharge-area groundwaters for recharge source characterization on different scales: the case of Jinan in northern China

Discharge-area groundwater in Jinan, a typical karst region in northern China, was investigated by studying both the hydrological and chemical processes evolving from the recharge in mountainous terrains to the karst-spring outflows in the metropolitan area. Large-scale exploitation of karst groundwater has led to a disturbing trend in the ever-decreasing spring outflow rates and groundwater level. There is insufficient information about the Jinan karst aquifers, which provide the main water sources to meet human demand and to sustain spring outflow. The coupling of hydrological and chemical processes quantifies the flow system through aqueous chemistry characterization of the water sources. This approach is used to study the groundwater flow discharges in different locations and geological settings. The potentiometric data indicated limited vertical connectivity between distinct hydrogeological units and alteration of the recharge regime by the faults and by artificial exploitation. Shallow groundwater primarily belongs to the local flow system, with high nitrate concentration and enriched stable isotopic contents. Thermal groundwater has high concentrations of chloride and total dissolved solids, derived from a regional flow system with the highest recharge altitudes and long residence time. Non-thermal karst water may be attributed to the intermediate flow system, with uniform HCO₃–Ca(Mg) facies and low nitrate concentration. This work highlighted discharge as a fingerprint of groundwater flow conditions and provides a better insight into the hydrogeological system.     

Assessment of factors influencing groundwater-level change using groundwater flow simulation,considering vertical infiltration from rice-planted and crop-rotated paddy fields in Japan

Assessing factors that influence groundwater levels such as land use and pumping strategy, is essential to adequately manage groundwater resources. A transient numerical model for groundwater flow with infiltration was developed for the Tedori River alluvial fan (140 km²), Japan. The main water input into the groundwater body in this area is irrigation water, which is significantly influenced by land use, namely paddy and upland fields. The proposed model consists of two models, a one-dimensional (1-D) unsaturated-zone water flow model (HYDRUS-1D) for estimating groundwater recharge and a 3-D groundwater flow model (MODFLOW). Numerical simulation of groundwater flow from October 1975 to November 2009 was performed to validate the model. Simulation revealed seasonal groundwater level fluctuations, affected by paddy irrigation management. However, computational accuracy was limited by the spatiotemporal data resolution of the groundwater use. Both annual groundwater levels and recharge during the irrigation periods from 1975 to 2009 showed long-term decreasing trends. With the decline in rice-planted paddy field area, groundwater recharge cumulatively decreased to 61 % of the peak in 1977. A paddy-upland crop-rotation system could decrease groundwater recharge to 73–98 % relative to no crop rotation.     

Effects of rainwater-harvesting-induced artificial recharge on the groundwater of wells in Rajasthan, India

In light of the increasing deterioration of groundwater supplies in Rajasthan, India, rainwater harvesting practices in southern Rajasthan were studied to determine the effects of artificially recharged groundwater on the supply and quality of local groundwater. A physical and geochemical investigation utilizing environmental tracers (δ¹⁸O and Cl^–), groundwater level and groundwater quality measurements, and geological surveys was conducted with two objectives: (1) to quantify the proportion of artificially recharged groundwater in wells located near rainwater harvesting structures and (2) to examine potential effects of artificial recharge on the quality of groundwater in these wells. A geochemical mixing model revealed that the proportion of artificial recharge in these wells ranged from 0 to 75%. Groundwater tracer, water table, and geological data provided evidence of complex groundwater flow and were used to explain the spatial distribution of artificial recharge. Furthermore, wells receiving artificial recharge had improved groundwater quality. Statistical analysis revealed a significant difference between the water quality in these wells and wells determined not to receive artificial recharge, for electrical conductivity and SO ₄ ^– . The findings from this study provide quantitative evidence that rainwater harvesting structures in southern Rajasthan influence the groundwater supply and quality of nearby wells by artificially recharging local groundwater.     

Groundwater simulation studies of parts of Western Yamuna Canal Command area, Haryana for planning sustainable development

A single layer mathematical model was developed to simulate the hydrogeological condition and groundwater flow in an area of about 2536 Sq km, which forms part of the WYC Command area. The model was run both for the steady state and for the transient state. The model was then successfully calibrated. The calibration results were recorded qualitatively and quantitatively. The results of the calibrated model were analyzed. Two Scenarios developed alonwith six scenarios created earlier, in another modeling study, were analyzed to find out a sustainable solution for optimal utilization of surface and ground water. The two Scenarios developed show that a viable solution will be reduction in pumping and regulated surface water supply. This will ameliorate water logging in the nearby areas. The reduction in pumping and thereby, reduction of return flow recharging groundwater can be achieved by improving water use efficiency and modifying/changing cropping pattern. These strategies can be successfully implemented, through mass awareness programmes, involving the farmers, who have to implement the programme, along with all the other stake holders. Ultimately reduction of groundwater pumping can be achieved through strict groundwater regulation. Direct recharge by way of seepage through canal can be reduced by lining the unlined canals and proper repair and maintenance of the already lined canals. But this has to be tested through a pilot project vis-a-vis economic viability of this lining, as seepage may be indirectly helping groundwater recharge in areas without water logging. Further to increase the availability of surface water and augment recharge of groundwater, the surface run off from the precipitation, can be utilized in various ways to reduce to decline of groundwater level.     

地铁施工对济南白泉泉群流量的影响

为研究地铁建设对济南白泉泉群的影响，在综合分析白泉泉域地质、水文地质条件的基础上，假定研究区岩溶强径流带位置及水力性质，利用FEFLOW软件建立地下水流数值模型。以规划地铁M1号线为研究对象，分析了济南东站、梁王站、梁王东站分别施工及3个站同时施工4种情景下，采用施工降水或施工降水+人工回灌两种施工方式对白泉泉群流量的影响。结果表明：单独采用施工降水的施工方式使得白泉泉群流量衰减，其中3个站同时施工对泉流量的影响最大，泉流量最大衰减达5.48%；各站分别施工时，济南东站对泉流量影响最大，泉流量较未施工时减少了0.043×10⁴ m³/d。采用施工降水+人工回灌的施工方式，能够有效缓解泉流量的衰减，各车站施工时的泉流量衰减由仅施工降水时的2.26%~5.48%降低至0.08%~1.21%。岩溶强径流带有利于地下水形成优势径流，促进白泉泉群补给，一定程度上缓解因地铁施工引起的泉流量衰减。     

Assessing the influence of climate change and inter-basin water diversion on Haihe River basin,eastern China: a coupled model approach

The modeling of changes in surface water and groundwater in the areas of inter-basin water diversion projects is quite difficult because surface water and groundwater models are run separately most of the time and the lack of sufficient data limits the application of complex surface-water/groundwater coupling models based on physical laws, especially for developing countries. In this study, a distributed surface-water and groundwater coupling model, named the distributed time variant gain model–groundwater model (DTVGM-GWM), was used to assess the influence of climate change and inter-basin water diversion on a watershed hydrological cycle. The DTVGM-GWM model can reflect the interaction processes of surface water and groundwater at basin scale. The model was applied to the Haihe River Basin (HRB) in eastern China. The possible influences of climate change and the South-to-North Water Diversion Project (SNWDP) on surface water and groundwater in the HRB were analyzed under various scenarios. The results showed that the newly constructed model DTVGM-GWM can reasonably simulate the surface and river runoff, and describe the spatiotemporal distribution characteristics of groundwater level, groundwater storage and phreatic recharge. The prediction results under different scenarios showed a decline in annual groundwater exploitation and also runoff in the HRB, while an increase of groundwater storage and groundwater level after the SNWDP’s operation. Additionally, as the project also addresses future scenarios, a slight increase is predicted in the actual evapotranspiration, soil water content and phreatic recharge. This study provides valuable insights for developing sustainable groundwater management options for the HRB.     

Land use change scenarios and associated groundwater impacts in a protected peri-urban area

Land use changes in peri-urban areas are usually associated with significant impacts on groundwater resources due to alteration of the recharge regime as well as through the establishment of pollution sources. Quantifying the aforementioned impacts and assessing the vulnerability of the groundwater resources is an important step for the better management and protection of the aquifers. In the present study, a physically based, distributed hydrologic model has been used to identify the impacts from specific land use change scenarios in the protected area of Loutraki catchment. A vulnerability assessment method has been also implemented to provide a decision support tool to the land planning authorities and also hydrologic mitigation measures for the sustainable development of the area have been proposed. The hydrologic impacts of the land use scenarios include a 5% reduction in the annual recharge of the study aquifer for scenario 1 (doubling of the current urban areas) and 7% decrease for scenario 2 (tripling of the current urban areas). Nevertheless, these impacts can be minimised if small-scale artificial recharge infrastructure is developed and the land planning measures suggested through the vulnerability and recharge maps will be followed.     

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.