Depletion risk assessment of the Nossana Spring (Bergamo, Italy) based on the stochastic modeling of recharge

A hydrogeological study of the Nossana Spring (Val Seriana, Bergamo, Italy) is presented with the aim of assessing the spring’s depletion risk. In the last few years, the discharge of the Nossana Spring showed a decreasing trend, similar to the trend of many other springs in the Prealpine Region. The study was carried out using a groundwater flow model to simulate the depletion curve of the spring in different recharge conditions. The simulations have shown that the depletion curve of the Nossana Spring depends on the recharge during the previous season. As a result, a negative exponential relation giving the spring depletion curve as a function of the recharge was obtained. This relation was also used to statistically calculate the actual probability of the occurrence of a deficiency in water resources, which for the present day is equal to 2%. Finally, the effect of climate change was considered, showing in the next 100 years a flat decline of about 40% in the average spring discharge and a considerable shortening of the critical length (the time to reach the critical discharge at which supply problems occur) in the dry season, which will be halved by the end of the century.     

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。     

Goodenough Spring, Texas, USA: Discharge and water chemistry of a large spring deeply submerged under the binational Amistad Reservoir

Goodenough Spring (Texas, USA) is a large spring near the border of the American state of Texas and the Mexican state of Coahuila, discharging into the international Amistad Reservoir on the river Rio Grande (Rio Bravo). Discharge was routinely measured from 1928 until 1968 to partition the flow of the river between the two countries in accordance with water-use treaties. Samples were analyzed for water-quality parameters in 1967–1968 prior to inundation under 45 m of Amistad Reservoir in 1968. Subsequently, discharge has been estimated indirectly by the International Boundary and Water Commission (IBWC). For the first direct measurements of the spring in 37 years, velocity and cross-sectional measurements were made and water samples collected in the summer of 2005 using advanced self-contained underwater breathing apparatus (SCUBA) techniques. Spring discharge was calculated at 2.03 m³ s^–1, approximately one-half of the historical mean of 3.94 m³ s^–1. In situ and laboratory analyses of samples for temperature, pH, dissolved oxygen, specific conductance, alkalinity, nitrate-nitrogen, dissolved solids, chloride, sulfate, fluoride, phosphorus, calcium, sodium, potassium, magnesium, and iron showed the water quality to be very good for human consumption and crop irrigation. Measurement values are relatively unchanged from those reported 37 years prior.     

Characterization of the hydrogeology of the sacred Gihon Spring, Jerusalem: a deteriorating urban karst spring

The Gihon Spring, Jerusalem, is important for the major monotheistic religions. Its hydrogeology and hydrochemistry is studied here in order to understand urbanization effects on karst groundwater resources, and promote better water management. High-resolution monitoring of the spring discharge, temperature and electrical conductivity, was performed, together with chemical and bacterial analysis. All these demonstrate a rapid response of the spring to rainfall events and human impact. A complex karst system is inferred, including conduit flow, fissure flow and diffuse flow. Electrical conductivity, Na⁺ and K⁺ values (2.0 mS/cm, 130 and 50 mg/l respectively) are very high compared to other nearby springs located at the town margins (0.6 mS/cm, 15 and <1 mg/l respectively), indicating considerable urban pollution in the Gihon area. The previously cited pulsating nature of the spring was not detected during the present high-resolution monitoring. This phenomenon may have ceased due to additional water sources from urban leakage and irrigation feeding the spring. The urbanization of the recharge catchment thus affects the spring water dramatically, both chemically and hydrologically. Appropriate measures should therefore be undertaken to protect the Gihon Spring and other karst aquifers threatened by rapid urbanization.     

北方岩溶大泉流量动态模拟及其管理

在充分研究晋祠泉流量动态的基础上,分析了影响晋祠泉流量的主要因素,并利用时间序列分析方法,建立了晋祠泉流量动态的模拟模型,在此基础上,提出煤矿排水管理曲线图的方法来管理晋祠泉域岩溶水资源。     

疏干开采条件下晋祠岩溶水系统的水箱模型

根据晋祠岩溶水系统的水均衡要素,建立晋祠岩溶水系统水箱模型及水均衡方程。使用晋祠岩溶水系统的补给量、排泄量和岩溶水位等数据建立晋祠岩溶水贮量的亏缺量与岩溶水位间的关系,采用非线性回归分析建立泉流量与岩溶水位的关系,并利用这两个关系替换水均衡方程中的未知量,从而求解所建水箱模型。通过1981至2006年的岩溶水位、亏缺量、泉流量数据检验所建模型,并以绝对误差的绝对值及线性相关系数评价模型的模拟效果。结果表明岩溶水位、亏缺量、泉流量模拟结果的误差均小于0.5,多数误差值小于0.01,线性相关系数均大于0.7,说明所建模型能够较准确地在以年为单位的时间尺度上模拟泉流量、岩溶水位和亏缺量的变化。该模型考虑了人工补给量、管井开采量及煤矿排水量等人为因素,可用于宏观的地下水资源保护及管理。      

Assessing hydro-morphological changes in Mediterranean stream using curvilinear grid modeling approach - climate change impacts

The objective of this work was the estimation of time-space hydraulic (water depth, flow velocity) and morphological (sediment transport and bank erosion) characteristics in the downstream part of a Mediterranean stream under current and future climatic conditions. The two-dimensional hydraulic model MIKE 21C was used, which has been developed specifically to simulate 2D flow and morphological changes in rivers. The model is based on an orthogonal curvilinear grid and comprises two parts: (a) the hydrodynamic part and (b) the morphological changes part. The curvilinear grid and the bathymetry file were generated using a very high-resolution DEM (1 m × 1 m). Time series discharge data from a hydrometric station introduced in the hydrodynamic part of the model. Regarding the morphological part of the model, field measurements of suspended sediment concentration and of bank erosion were used. The model was calibrated and verified using field data that were collected during high and low flow discharges. Model simulation was in good agreement with field observations as indicated by a variety of statistical measures. Next, for predicting the riverbank change, future meteorological data and river flow data for the next 10 years (2017–2027) were employed. These data series were created according to a lower and a higher emission climate change scenario. Based on the results, an increase in rainfall intensity may cause significant changes in river banks after 10 years (more than 5 m of soil loss in river meanders). Using the obtained simulation results, extreme hydrological events such as floods transporting large sediment loads and changes in river morphology can be monitored. The proposed methodology was applied to the downstream part of the Koiliaris River Basin in Crete, Greece.     

Simulation of spatial and temporal trends in nitrate concentrations at the regional scale in the Upper Dyle basin,Belgium

Models are the only tools capable of predicting the evolution of groundwater systems at a regional scale, by taking into account a large amount of information. This study presents the association of a water balance model (WetSpass) with a groundwater flow and solute transport model (SUFT3D, saturated and unsaturated flow and transport in 3D) in order to simulate the present and future groundwater quality in terms of nitrate in the Upper Dyle basin (439 km²) Belgium. The HFEMC (hybrid finite element mixing cell) method implemented in the SUFT3D code is used to model groundwater flow and nitrate transport. Spatially distributed recharge, modelled with WetSpass, is considered for prescribing the recharge to the groundwater flow model. The feasibility of linking the WetSpass model with the finite-elements SUFT3D code is demonstrated. Time evolution and distribution of nitrate concentration are then simulated using the calibrated model. Nitrate inputs are spatially distributed according to land use. The spatial simulations and temporal trends are compared with previously published data on this aquifer and show good results.     

Impact of Preboreal to Subatlantic shifts in climate on groundwater resources on the Arabian Peninsula

A large-scale numerical flow and transport model was developed for the central-eastern arid part of the Arabian Peninsula. The model was applied to a region with freshwater resources dating back to more humid periods of the past, which are faced with overexploitation today. Model inflow was based on infiltration around wadi beds and groundwater recharge. Inflow was balanced by natural outflows, such as evaporation from sabkhas, spring discharge, and discharge to the sea. Two models were developed: (1) a short-term present-day model to estimate effective model parameters, and (2) a long-term model to study the development of the groundwater resources during the Mid- and Late Holocene and the natural response of the groundwater system to changes in climate. Hydraulic model parameters (hydraulic conductivity and specific storage) were assigned with respect to geological structures. Hydraulic parameters were estimated with an inverse PEST model by calibrating against observed depression cones cause by groundwater abstraction. Sensitivity analysis demonstrated that estimated model parameters were associated with a high uncertainty at a certain distance from agricultural areas when calibration data were lacking. A long-term model starting 10,000 years BP was calibrated by spring discharge and palaeo-groundwater levels and validated using measured ¹⁴C groundwater ages. The long-model predicted that groundwater levels adapted in response to changes in precipitation. During the Mid-Holocene, which was characterized by an intensification of the monsoon season, groundwater levels increased by 10 m on the mainland within the shallow aquifers and adapted quickly to higher recharge rates. The deeper aquifers were less affected by changes in climate. Along the present-day coastline, the groundwater level rose by about 25 m due to the declined sea level in the Mid-Holocene. During this period, surface run-off was possible as groundwater levels temporarily reached the ground surface. The natural groundwater budget reacted sensitively to changes in climate. Between 10 and 3 ka, groundwater storage occurred. During the Late Holocene, at 3 ka, natural depletion of the groundwater system began, which still prevails today.     

柳林泉域降水补给的时滞研究

柳林泉位于山西省柳林县东川河河谷,是中国北方最大的岩溶泉之一.1984～2005 年间的平均流量为 3.29 m3/s.流域内的大气降水是泉水的主要补给来源.根据柳林泉域水文地质条件的灰色系统特征,通过对泉域降水补给的时滞问题研究,提出了带有时滞的灰色关联分析模型.在此基础上,运用该模型对泉域不同地区的降水量与泉水流量进行了时滞分析.结果表明,柳林泉域不同区域的降水对柳林泉域的补给时滞存在差异.离石、中阳和方山的降水时滞分别为 3 a、4 a 和 6 a.该方法可应用于山西省其它岩溶大泉的岩溶水动态分析.     

3D modeling and monitoring of karst system as a base for its evaluation and utilization: a case study from eastern Serbia

Beljanica Mountain in eastern Serbia is a part of the Carpathian Balkan arch (northern Alpine branch). It covers an area of about 300 km² and consists mostly of Jurassic and Cretaceous limestones. Numerous surface karst features, long caves and several large karstic springs located in Beljanica’s piedmont along the contact of karstic and non-karstic rocks are all indicators of an intense karstification. Currently, the large karstic water reserves of Beljanica Mountain are not properly utilized because of their distance from main consumers, the objection by national water managers that the springs lack a stable and sufficient discharge particularly during recession periods. Due to its unpolluted and high quality water, the area is a great prospect for future water supply, and provides an opportunity for artificial regulation and for the design and implementation of specific tapping structures. This paper includes an analysis of the created 3D ArcGIS model of karst interior and its correlation with historical and newly collected data of spring discharges and groundwater physico-chemical characteristics. The results of karst aquifer monitoring (both quantitative and qualitative) are linked with the results of extensive field geological and speleological survey of the upper non-saturated part of the karst (such as sinkholes, pits and caves) and with the investigation of the permanently saturated deeper part of the aquifer (including the diving methods). The model of karst interior is based on the data from the 69 caves, 15 sinks and 1,682 dolines (sinkholes) surveyed. The total length of the karst channels network, calculated using the GIS model and presented in a 3D environment, is 647 km. The catchment areas of five major springs that drain the areas are estimated to range from only 7 km² (Malo Vrelo Spring) to 124 km² (Vrelo Mlave Spring). The groundwater exploitable reserves of Beljanica karst aquifer are estimated to be over 4 m³/s. The waters are low mineralized, unpolluted and have a great potential for water supply.     

Investigation of karst hydrological processes by using grey auto-incidence analysis

The karst hydrological processes are the response of karst groundwater system to precipitation. The precipitation penetrates through the vadose zone, the subsequent groundwater pressure wave propagates to a spring outlet, and then, the spring discharge changes. This paper proposes a grey auto-incidence analysis for studying the karst hydrological processes. The method can detect the periodicity of a time series, for example, precipitation and spring discharge. Then the approach is applied to Liulin Springs Basin, China. The results show that the auto-incidence degree of precipitation reaches to the maximum (i.e., 0.816) when time delay equals to 8 years. The auto-incidence degree of spring discharge reaches to the maximum (i.e., 0.865) when time delay equals to 3 years. These results show that the periodicity of precipitation is 8 years, and of spring discharge is 3 years. The difference of periodicity between the precipitation and the spring discharge reveals that the processes of precipitation recharging groundwater and groundwater transport are regulated or controlled by karst aquifer. Because of heterogeneity of karst aquifer, the quick flow and base flow occur during the groundwater propagation, which causes the periodicity of spring discharge is not coincidence with of precipitation.     

Numerical modelling assessment of climate-change impacts and mitigation measures on the Querença-Silves coastal aquifer (Algarve,Portugal)

Predicted changes in climate will lead to seawater intrusion in the Querença-Silves (QS) coastal aquifer (south Portugal) during the coming century if the current water-resource-management strategy is maintained. As for much of the Mediterranean, average rainfall is predicted to decrease along with increasing seasonal and inter-annual variability and there is a need to understand how these changes will affect the sustainable use of groundwater resources. A density-coupled flow and transport model of the QS was used to simulate an ensemble of climate, water-use and adaptation scenarios from 2010 to 2099 taking into account intra- and inter-annual variability in recharge and groundwater use. By considering several climate models, bias correction and recharge calculation methods, a degree of uncertainty was included. Changes in rainfall regimes will have an immediate effect on groundwater discharge; however, the effect on saltwater intrusion is attenuated by the freshwater–saltwater interfaces’ comparatively slow rate of movement. Comparing the effects of adaptation measures demonstrates that the extent of intrusion in the QS is controlled by the long-term water budget, as the effectiveness of both demand and supply oriented measures is proportional to the change in water budget, and that to maintain the current position, average groundwater discharge should be in the order of 50 × 10⁶ m³ yr^?1.     

Streamflow modeling in a fluctuant climate using SWAT: Yass River catchment in south eastern Australia

Hydrological models play vital roles in understanding and management of surface water resources. The physically based distributed model Soil and Water Assessment Tool (SWAT) was applied to a small catchment in south eastern Australia to determine its ability to mimic low and high streamflows. The model was successfully calibrated using 1993–2002 streamflow data and validated using 2003–2011 data with a combination of manual and auto-calibration techniques for both monthly and daily time steps. Sensitivity analysis indicated that curve number for moisture condition II (CN2) is the most sensitive parameter for both time steps. In general, the model performance statistics indicated “very good” agreement between measured and simulated discharges for both calibration and validation periods. The model was able to satisfactorily simulate both low and high flows of the Yass River. Analysis of water balance components indicated that more than 90 % of the rainfall is lost as evapotranspiration and about 45 % of the streamflow is base flow. The calibrated and validated SWAT model can be used to analyze the effect of climate and land use changes on catchment wide hydrologic process.     

Comparison of age distributions estimated from environmental tracers by using binary-dilution and numerical models of fractured and folded karst: Shenandoah Valley of Virginia and West Virginia, USA

Measured concentrations of environmental tracers in spring discharge from a karst aquifer in the Shenandoah Valley, USA, were used to refine a numerical groundwater flow model. The karst aquifer is folded and faulted carbonate bedrock dominated by diffuse flow along fractures. The numerical model represented bedrock structure and discrete features (fault zones and springs). Concentrations of ³H, ³He, ⁴He, and CFC-113 in spring discharge were interpreted as binary dilutions of young (0–8  years) water and old (tracer-free) water. Simulated mixtures of groundwater are derived from young water flowing along shallow paths, with the addition of old water flowing along deeper paths through the model domain that discharge to springs along fault zones. The simulated median age of young water discharged from springs (5.7  years) is slightly older than the median age estimated from ³H/³He data (4.4  years). The numerical model predicted a fraction of old water in spring discharge (0.07) that was half that determined by the binary-dilution model using the ³H/³He apparent age and ³H and CFC-113 data (0.14). This difference suggests that faults and lineaments are more numerous or extensive than those mapped and included in the numerical model.     

Quantitative and qualitative simulation of groundwater by mathematical models in Rafsanjan aquifer using MODFLOW and MT3DMS

Agriculture sector by using 80% of freshwater is the greatest water consumer in Iran. Excessive use of agricultural fertilizers in last decade, caused accumulation of enormous amounts of salts and subsequence declined the physical properties of soil. In desert and dry regions such as Rafsanjan plain, use of the groundwater resources is more than the surface water resources. Therefore, information about the quality of these resources remains a necessary task for optimum management, protection of water resources, and stopping the future damages. In this study, the groundwater quantity and quality of Rafsanjan plain was investigated by MODFLOW and MT3DMS. The presented quantitative model for this aquifer was compared by observed data and calibrated. This model was used to predict a 10-year period. Results show that water elevation decreases approximately 15 m for 10 years to come in this plain. Qualitative model results show that most quality parameters will increase. Electrical conductivity will increase more than other parameters. As values of this parameter will reach 16,000 µs/l for next 5 years. Therefore, we suggest that exploitation of water from these resources should be reduced and discharge from some of agricultural wells stop; also we suggested that recharge to groundwater resources should be increased and agricultural activities should be limited or improved using of modern irrigation systems in this plain.     

Integrating Monte Carlo and hydrodynamic models for estimating extreme water levels by storm surge in Colombo,Sri Lanka

The prediction of high extremes in sustained water level is very important for coastal engineering design and planning. The recorded historical water level datasets in Colombo, Sri Lanka, are not long enough for the traditional frequency analysis in predicting extreme water levels, such as 50-, 100- and 200-year extreme water levels. In this study, the integrated ADCIRC + SWAN hydrodynamic model and Monte Carlo model have been applied to predict extreme water level in Colombo station of Sri Lanka. The meteorological driving forces of cyclone storm surge are simulated by Monte Carlo stochastic model. The calibrated ADCIRC model with SWAN wave model is used to simulate the potential surge setups with the driving forces generated by Monte Carlo model. By ranking the maximum high water levels in each storm surge procedure, the estimation on extreme high water levels for the desired return period is proposed in this study. The estimated extreme high water levels with return period of 50, 100 and 200 years are 1.28, 1.40 and 1.50 m correspondingly. The estimated extreme high water levels are recommended for engineering design and planning.     

济南岩溶泉域泉群区水化学与环境同位素研究

本文通过对济南岩溶泉域排泄区地下水样品的分析,采用主要离子(Cl、NO_3、Mg、Ca、HCO_3、SO_4)、微量元素(Br、Ba、Sr)、氢氧同位素(~2H和~(18)O)、硫同位素(~(34)S)等示踪因子的综合研究方法,结合岩溶泉域实际水文地质条件,揭示了济南泉水的水文地球化学特征、枯丰期水化学动态和环境同位素特征,确定了泉水在枯、丰水期不同的补给来源及补给途径。研究显示,泉群区出流的泉水可以分为三组,黑虎泉出流的路径是经奥陶系灰岩直接出流,趵突泉是经奥陶系灰岩与第四系沉积层出流地表,而五龙潭泉、珍珠泉和53号井则是在灰岩和侵入岩体的接触地带及第四系沉积层较薄弱处涌出地表;在丰水期地下水是混合补给,包括来自奥陶系岩溶水直接补给和硅酸盐岩裂隙水的间接补给,而在枯水期地下水主要由奥陶系岩溶水直接补给;泉群区地下水中的S主要来源于燃煤,而且有不断增加的趋势。     

Initial assessment of recharge areas for large karst springs: a case study from the central Zagros Mountains,Iran

Sousan Spring emerges from the Keyno Anticline, Zagros Mountains (Iran), and the mean annual discharge is ~24 m³/s. Geological and hydrochemical evaluations suggest that the spring recharge is from the limestone Ilam-Sarvak Formation (Cretaceous) but the Mafaroon Fault, a major thrust feature, influences the regional groundwater flow path by juxtaposing other strata. Geological, geochemical, stable isotope and water balance studies were employed to interpret this behavior. Using the isotope data, the sources and elevations of the recharge area were found. Temporal variations of the isotopic data were compared with variations of electrical conductivity (EC). Unexpectedly, high EC was associated with a relative increase of discharge and depletion of δ¹⁸O. Several hypotheses were investigated and approximate water balance studies employed for validation. It was found that an elongated catchment on the Keyno Anticline plus a lesser catchment on a pair of parallel anticlines recharge the aquifer. While the long groundwater flow path along the Keyno Anticline plus guidance by Mafaroon Fault and the adjacent Garou shaly strata lead to increased EC in the Sousan Spring at the end of the dry season, a flow pulse from two adjoining anticlines (Mahalbakh and Shirgoon) arrives at the same time to increase the discharge and deplete the δ¹⁸O signal. Apparently the spring did not experience true base flow conditions during the recorded hydrological year. Although the spring response to specific precipitation events was similar to typical karst aquifers, standard interpretation of recession curves and related coefficients will not be practical at Sousan.     

Characterization of a Pleistocene thermal spring in Mozambique

A hydrogeological study was conducted with the objective to investigate the only currently known hot spring of Sofala Province in Mozambique with respect to the origin of the water, the discharge, and its chemical composition. Field investigations comprised a general land use survey, mapping of sediment and water temperatures, discharge measurements and on-site water chemistry as well as sampling for further chemical analyses and groundwater dating. Thermal water discharge occurs along a 100 m long NE–SW zone with water temperatures ranging from 42 to 64.5°C. The thermal water is a low-mineralized sodium-chloride-sulfate water enriched in phosphate, fluorine and nickel. The silica geothermometer, the silica concentration of 43 mg/kg and the ratios of Br/Cl and I/Cl of 2.5?×?10^–3, suggest that the thermal water stems from approximately 5,000 m depth and had a long residence time with silicate rocks. This points towards Gorongosa Mountain as the water source area. ¹⁴C dating suggests a groundwater age of 11,000 years.