Estimating Groundwater Withdrawal in Poorly Gauged Agricultural Basins

A method is presented for estimating the annual groundwater withdrawal based on water balance resulting from surface and groundwater hydrological considerations. The unknown groundwater losses of the aquifer are estimated from the groundwater level fluctuations, the specific yield and the groundwater withdrawal prior to the installation of the irrigation network. The meteorological and hydrometric data are used in the Sacramento hydrological conceptual model for the estimation of the stored groundwater volume, via minimization of the difference between the simulated and measured stream discharge. Following the installation of the network due to poorly kept field records, an initial estimation of the groundwater withdrawal is made based on the fluctuations of the groundwater level, the specific yield, and the annual precipitation. The monthly stored groundwater volume is verified against the volume obtained during the recharge of the basin (November–April). The difference between the groundwater volume and the measured discharge of the basin (May–October) is in agreement with the initial estimation of the groundwater withdrawal. This method is applied successfully in an agricultural basin on the island of Crete, Greece and its novelty lies in the fact that it can be used in basins where groundwater withdrawal is not known or data is incomplete.     

Identification of Strong Karst Groundwater Runoff Belt by Cross Wavelet Transform

Karst aquifers are highly heterogeneous and exhibit hierarchical permeability structures or flow paths. Conduits and fractures typically account for less than 1 percent of the porosity of the aquifer, but more than 95 percent of the permeability. For the purposes of karst groundwater resources management, as well as of protection strategies against potential contamination, identifying the strong karst groundwater runoff belt of an entire aquifer system is generally more important than information about a specific spring. In this project, we introduce cross wavelet transform to analyze the relation between precipitation and spring discharge, and then identify the strong karst groundwater runoff belt. In highly concentrated karst areas, the precipitation signal can penetrate an aquifer relatively easily and will readily affect spring discharge. The precipitation and spring discharge are thus closely related, and the cross wavelet transform coefficients are large. Conversely, in areas of low karst concentration, the cross wavelet transform coefficients are small. We applied the method to Niangziguan Springs Basin in China to detect the strong karst groundwater runoff belt. Results showed that Pingding County and Yangquan City have a high degree of karstification (i.e. the strong karst groundwater runoff belt), Xiyang County and Shouyang County have a moderate degree of karstification, and Yuxian County, Heshun County, and Zuoquan County have a low degree of karstification. The results agree with the geological structure of Niangziguan Springs Basin.     

基于EMD-LSTM耦合模型的趵突泉岩溶地下水水位预测应用

由于岩溶地下水具有强烈的非线性及非平稳波动特征,水位预测结果容易产生较大误差。针对岩溶地下水水位预测精度较差的问题,提出一种EMD-LSTM耦合模型,首先采用经验模态分解（EMD）将趵突泉岩溶地下水水位分解为5个分量（4个本征模函数项和1个残余项）,以此消除水位数据的非平稳波动性;同时构建长短期记忆（LSTM）神经网络模型,并将与地下水水位动态变化密切相关的降水量（表征含水层补给项）和月平均气温值、月最高气温值、月最低气温值、水汽压值（表征含水层排泄项）作为输入项分别对5个分量进行预测,最终将分量预测结果累加获得地下水水位预测值。结果表明：EMD能够显著消除岩溶地下水水位的非平稳波动特征;EMD-LSTM耦合模型可有效提高岩溶地下水水位的预测精度,其均方根误差相比于LSTM神经网络模型、ARIMA模型分别减小了27.86%和59.94%。总体来说,本文所提出的EMD-LSTM耦合模型具有较强的可靠性和稳定性,可为岩溶地下水水位的精确预测提供借鉴。     

Local and Regional Water Flow Quantification in Groundwater-dependent Wetlands

Runoff, groundwater recharge and discharge, and surface water–groundwater interaction are the main driving forces of wetlands. The quantification of such flows is crucial information in the restoration and management of groundwater-dependent wetlands. The objective of this work is to quantify groundwater inflow at the level of the hydrogeological basin, which discharges into the wetland in the coastal plain of the Río de la Plata (Argentina). It also aims at evaluating whether such inflow is affected by groundwater exploitation in the high plain adjacent to the wetland. On the basis of water level data, a model of hydrological behaviour was developed and then a numerical simulation to quantify groundwater inflow was carried out. The evolution of groundwater levels was analyzed considering three situations: one of them in natural conditions and two others under different groundwater exploitation conditions. In the first case, the inflow originates in the recharge from precipitation, in the local groundwater discharge from the adjacent high plain and in the regional one from the semi-confined aquifer. The exploitation of the semi-confined aquifer in the high plain causes the formation of a cone of depression which modifies the hydrodynamics of the wetland in the area adjacent to the extraction wells. The quantification of flows shows that groundwater exploitation in areas of the basin located out of the wetland may cause the volume of water flowing into the wetland through groundwater discharge to decrease by approximately 25 %. The importance of considering discharge wetlands as part of regional hydrogeological systems should be highlighted, mainly as regards the management of natural resources.     

A Piecewise Grey System Model for Study the Effects of Anthropogenic Activities on Karst Hydrological Processes

Sustainable groundwater development must rely on a good understanding of hydrological processes, especially under effects of anthropogenic activities. This paper develops a piecewise analysis based on grey system model for study effects of anthropogenic activities on hydrological processes. The time series of precipitation and spring discharge were segmented into three time periods depending on whether variations are due to climate variation: the predevelopment stage, the transition stage, and the new equilibrium stage. Then we modeled hydrological process of the predevelopment stage and new equilibrium stage by the grey system model. By comparing the model results, we can quantify the effects of human activities on hydrological processes. We applied the model to Liulin Springs China. The results indicated that the hydraulic response time of the spring discharge to precipitation from the predevelopment stage to the new equilibrium stage, ranges from less than 1 year to up to 4 years. The results revealed that human activities slow the groundwater flow. GM (1,N) models of Liulin Springs discharge showed that the driving coefficients of precipitation to the spring discharge decreased from 0.012272 in the predevelopment stage to 0.007753 in the new equilibrium stage, which means that groundwater recharge ability has reduced about 36.82 %. Human activities in Liulin Springs have drastically changed the groundwater system. Piecewise grey system model is a robust method for hydrological process simulation.     

SIMULATION OF THERMAL TRANSPORT IN AQUIFER： A GWHP SYSTEM IN CHENGDU, CHINA

With an established convection-dispersion model for the thermal transport in aquifer, the thermal transport processes in an unconfined aquifer of a Groundwater Heat Pump (GWHP) system in Chengdu, China, are simulated with double-well intervals and cooling-load design fluctuations in summer running period under special groundwater flow and heat source conditions, and the stage-characteristics of the thermal transport in the aquifer are investigated in the running cycle (1 year) numerically. The results show that the thermal transport in the aquifer is closely related to the distance between pumping and injecting wells and the cooling-load design fluctuations, especially, to the cycling water volume. The thermal transport in the aquifer sees different characteristics in the two states in the pumping-recharging stages in summer/winter and the storing stages in spring/autumn. With the hydro-geologic theory and the numerical model, the effect of the groundwater-flow on the thermal transport in the unconfined aquifer is discussed.     

Chemical and Isotopic Tracer Evaluation of Water Mixing and Evaporation in a Dammed Texas River During Drought

The interaction between drought and river regulation is monitored to better understand river flow mixing, evaporation and surface‐groundwater exchange in changing regional climates and in increasingly regulated waterways. This study compared Brazos River stable isotope (δ¹⁸O and δD) and electrical conductivity values with reservoir, creek and aquifer samples in the Brazos watershed, the largest watershed in Texas. The combination of tributaries, rainfall and the Brazos River Alluvium Aquifer, on the one hand, and the Lake Whitney reservoir, on the other hand, represent endmembers of dilute run‐off water and evaporated saline water, respectively. A simple isotope mixing model that uses monthly river discharge, Lake Whitney discharge, historical monthly precipitation δ¹⁸O and pan evaporation accurately reconstructs river δ¹⁸O (±0.5‰ on average). Data and isotope balance modelling support continued evaporation of ¹⁸O‐enriched Lake Whitney water as it flows downstream, although the most evaporation took place in Lake Whitney. The difference between river and precipitation δ¹⁸O, or Δ¹⁸O_RIV‐_PPT, here a measurement of degree of evaporation, ranged from ?0.1‰ for a small creek, to 1.7‰ for the Brazos River, to at least 2.7‰ in Lake Whitney. This study indicates that drought in regulated rivers may enhance reservoir discharge dominance in river flows during peak drought conditions when combined run‐off and baseflow dominance would be expected in a similar undammed river. Copyright © 2016 John Wiley & Sons, Ltd.     

Identification of Groundwater Contamination Sources Using Meshfree RPCM Simulation and Particle Swarm Optimization

In this study, a simulation-optimization (SO) model is presented by coupling a meshfree based simulator using radial point collocation method (RPCM) and particle swarm optimization (PSO) as optimizer to identify the unknown groundwater contaminant sources from the measured/simulated contaminant concentration data in the aquifer. To demonstrate the approach, two case studies have been presented. The first example is a hypothetical case which simulates the contaminant releases from several disposal sites in an aquifer during four years release period. The second case considered is a field study where leaching of contaminant, during their storage, from disposal sites at several locations in the aquifer leads to contamination of the groundwater. The goal in both cases was to reconstruct the contaminant release history from the disposal sites and their magnitudes from the given historical concentration data at a few observation wells in the aquifer. It was observed that the source identification model could reconstruct the release histories from the waste disposal sites in both the cases accurately. This study demonstrated that PSO based optimization model with a meshfree flow and transport simulator can be effectively used for groundwater contaminant source identification problems.     

ANALYTICAL SOLUTION OF GROUNDWATER FLUCTUATIONS IN ESTUARINE AQUIFER

1.INTRODUCTIONTide-induced head fluctuations are a naturalphenomenon in a coastal aquifer[1-3].For an un-confined aquifer,groundwater level changes corre-sponding to the tidal waves.As the tidal propagateinland,their amplitude is attenuated and phase-shifts occur.A typical damping distance for tidalwater table fluctuation in an unconfined aquifer isseveral hundred meters whereas the tidal influenceon a confined aquifer can extended landward byseveral thousand meters[2,4].According to thef…     

THEORETICAL ESTIMATION OF GROUNDWATER DISCHARGE AND ASSOCIATED NUTRIENT LOADING TO A LAKE WITH GENTLE SLOPE BOTTOM

A simple estimation model of groundwater discharge and nutrient flux from nearshore unconfined aquifer to lake was studied. It was supposed that the aquifer was permeable isotropic homogeneously and its thickness approximated to the depth of lake. Distribution of the hydraulic gradient and the specific discharge along the transect of the discharge zone were discussed. Results show that the groundwater discharge patterns vary with the inclination angle of lakeshore bottom. For a shallow lake with gentle slope bottom, the rate of discharge of groundwater to lake is not constant across a discharge zone, but the discharge is concentrated in a narrow portion of the littoral zone where the Dupuit assumptions are invalid. The width of the discharge zone is correlative with aquifer thickness and slope of the lake bottom. The distribution functions of hydraulic gradient and groundwater discharge rates accord exponentially with offshore distance.     

基于泉群流量与降水量相关性的明水泉域岩溶水强径流带识别

运用皮尔逊相关系数法分析了明水泉域各水文站月尺度最佳降水滞时,依据最佳降水滞时在旬尺度和日尺度条件下分别计算了 2006-2013年泉群流量与各水文站降水量的皮尔逊相关系数,得出与泉群流量关系相对密切的水文站点,从而识别出明水泉域强径流带.结果表明:各水文站最佳降水滞时均为5个月;明水站、闫家域站和旭升站降水量变化与泉...     

涞源岩溶地下水系统泉水量变化特征分析

涞源泉泉域是一个全封闭式泉排型岩溶水系统,泉水利用对当地工农业生产发挥了重要作用.通过对涞源岩溶地下水系统特征分析,利用地表水系列资料,采用基流分割法、相关系数法等,计算出泉水量系列资料.由降水补给地下水,再以泉水的形式排泄,在此过程中使水量在时间上滞后,而且水量趋于平稳,泉水量年极值比为7.33,变差系数为0.34,年内分配变化幅度平缓.由降水—入渗—地下径流—泉水排出的过程,水资源经过地下岩溶调节作用,有利于水资源的开发利用,而且对水质也起到净化作用.研究和分析岩溶地下水径流量变化特征,为合理利用泉水资源提供科学依据.     

不同降水情景下天津市地下水位的时空变化特征

为了定量模拟和评价不同降雨情景下天津市不同含水层地下水位时空变化情况,通过对天津市水文地质条件的分析和已获取的资料建立地下水系统的三维数值模拟模型,并利用已知的地下水位动态数据对模型进行拟合与检验,确定模型的可靠性。然后利用模型对常态条件下(地下水开采量维持不变,50%频率下的降水量)和极端气候条件下(地下水开采量维持不变,95%频率下的降水量)天津市地下水位的时空变化特征进行预测和评价,分析不同含水层地下水位对两种情景的动态响应机制。结果表明:两种方案下10 a后的地下水流场特征较为相近,地下水流向也基本一致,地下水位均有所下降,在开采量不变情况下,降水量的减少对承压含水层的影响较为有限。     

陡河流域地表水与地下水转化关系

通过对陡河流域地表水-地下水水样的氢氧同位素分布特征进行分析,发现研究区河岸带第Ⅰ含水层除了受大气降水、灌溉回归水入渗补给外,还接受河水早期的渗漏补给,第Ⅱ含水层对第Ⅲ含水层有越流补给,第Ⅱ含水层同时也受大气降水和灌溉回归水的影响,而远离河岸带的第Ⅳ含水层与上覆各含水层稳定同位素组成显著不同,河岸带水库附近的第Ⅳ含水层可能受地表水库渗漏影响。河岸带地下水与地表水水力联系的变迁严格受河岸带地下水水位变化控制,如景庄子剖面的地下水埋深为5m,雨季时河水补给地下水,旱季时地下水补给河水,而靠近地下水漏斗中心的越河乡剖面地下水水位埋深达25m,其常年受地表水补给。     

Groundwater contributions to surface water in the Assiniboine Delta Aquifer (ADA): A water quantity and quality perspective

In the Lake Winnipeg Basin (LWB), at both basin and regional scales, there are currently gaps regarding the significance of groundwater as a mediator of nutrient and contaminant fluxes to Lake Winnipeg. During 2018, surface water and groundwater samples were collected from various locations across the largest sand and gravel aquifer (Assiniboine Delta Aquifer [ADA]; 3800 km²) in the LWB as well as from surface water courses flowing above this aquifer. The samples collected during spring and fall were analyzed for anions and cations as well as for a series of isotopic and geochemical tracers (e.g. water isotopes, carbon 14, artificial sweeteners, pesticides, etc.). The results reveal that groundwater and the small watercourses flowing above the ADA have a similar chemical composition, which is in contrast with the chemical composition of the main watercourse flowing above the aquifer (Assiniboine River [AR]). When corroborated with stream discharge measurements this indicates that groundwater plays a significant role at local scale in controlling both the flow and the chemical composition of the AR tributaries. Nitrate showed low to non-detectable concentrations in both groundwater and surface water. With respect to groundwater, this could be related to the reducing conditions in the deeper aquifer in conjunction with relatively large groundwater travel times of up to 2400 years.     

Operational Prediction of Groundwater Fluctuation in South Florida using Sequence Based Markovian Stochastic Model

The ecosystem of South Florida is characterized by a vast wetland system, karst surficial hydrogeology, and extended coastal boundary. The ecosystem is poised under risks of: ecological failure due to increased fragmentation by urbanization; groundwater flow disruption because of sinkhole formation; and intrusion of oceanic water with decreasing water table head because of drought or over pumping. It was found important to synthesize the spatiotemporal state of the groundwater hydrology and also develop a forecasting model to support the intensive management and monitoring in place. In this study, an objective was set to develop a stochastic sequence model capable of forecasting groundwater levels on a monthly span at a daily time scale. The groundwater level simulation was conceptualized as a sequence of daily fluctuating states of magnitudes and patterns that has a defined probability of occurrence. The model setup involved representation of daily fluctuation magnitudes in ten states and pattern changes in three states. The sequential occurrence of states of magnitudes and patterns at each time step was used for estimation of the transitional probabilities and employed in a hidden Markov model frame work for ensemble generation and estimation of posterior probabilities. A realization was chosen based on the highest maximum likelihood ratio of 90% and smallest root mean square error of 0.05–0.12 m against the historical data. A monthly forecasting at daily time step was done dynamically incorporating observed data at each time step and revising prior and posterior probability estimation in the hidden Markov model formulation. A case study was conducted at three well sites, which are situated at three different hydrogeologic settings. The model not only reproduced annual groundwater fluctuation patterns but also forecasted preceding monthly fluctuations at maximum likelihood ratio above 90% and root mean square error below 0.15 m. A further study was recommended first to analyze break point parametric estimation for seasonal analysis, and secondly to integrate the approach in other hydrological models for the purpose of synthetic groundwater fluctuation generation.     

GIS-Based Groundwater Management Model for Western Nile Delta

The limited availability of renewable fresh water is a major constraint on future agriculture and urban development in Egypt. The main water resource that Egypt has been depending on is the River Nile. Nowadays, the role of groundwater is steadily increasing and will cover 20% of the total water supply in the coming decades especially in the reclaimed areas along the desert fringes of the Nile Delta and Valley. Abstraction from groundwater in Egypt is dynamic in nature as it grows rapidly with the expansion of irrigation activities, industrialization, and urbanization. One of these areas is the Western Nile Delta in which the groundwater is exploited in many localities. To avoid the deterioration of the aquifer system in this area, an efficient integrated and sustainable management plan for groundwater resources is needed. Efficient integrated and sustainable management of water resources relies on a comprehensive database that represents the characteristics of the aquifer system and modeling tools to achieve the impacts of decision alternatives. In this paper, a GIS-based model has been developed for the aquifer system of the Western Nile Delta. The GIS provides the utilization of analytical tools and visualization capabilities for pre-and post-processing information involved in groundwater modeling for the study area. The developed model was calibrated for steady state and transient conditions against the historical groundwater heads observed during the last 20 yr. The calibrated model was used to evaluate groundwater potentiality and to test two alternative management scenarios for conserving the aquifer system in Western Nile Delta. In the first scenario, reducing the surface water inflow while increasing the annual abstraction from groundwater by about 450 million m³ and improving the irrigation system could increase the net aquifer recharge by about 5.7% and reduce the aquifer potentiality by about 91%. Constructing a new canal as a second management scenario could increase the annual aquifer potentiality by about 23%. The GIS-based model has been proven to be an efficient tool for formulating integrated and sustainable management plan.     

潮汐引起滨海承压含水层地下水位变化的数值模拟

海潮波动可以引起海岸带地下水位发生波动。建立基于有限差分法的滨海地区一维承压含水层地下水运动数值模型。通过将潮汐波动概化为正弦波,模拟滨海地区地下水位随潮汐波动的变化。结果表明,受海潮影响的滨海含水层地下水位与海潮有相似的波动特征,但变幅减小,受海潮的影响程度与离海岸的距离有关,随着离海岸距离的增加地下水位的变幅及潮汐效率呈负指函数衰减,地下水位对海潮的滞后时间随距离呈线性增加。例如,当承压含水层导水系数为31．25m^2／h、储水系数为4．5×10^-4及海潮振幅为2．5m、周期为24．7h时,在距离海岸500m处,振幅为1．35268m,潮汐效率为0．54107,滞后时间为1．825h。在距海岸达4389m以远时可以认为地下水位不受海潮波动的影响。     

Groundwater Level Forecasting in a Shallow Aquifer Using Artificial Neural Network Approach

Forecasting the ground water level fluctuations is an important requirement for planning conjunctive use in any basin. This paper reports a research study that investigates the potential of artificial neural network technique in forecasting the groundwater level fluctuations in an unconfined coastal aquifer in India. The most appropriate set of input variables to the model are selected through a combination of domain knowledge and statistical analysis of the available data series. Several ANN models are developed that forecasts the water level of two observation wells. The results suggest that the model predictions are reasonably accurate as evaluated by various statistical indices. An input sensitivity analysis suggested that exclusion of antecedent values of the water level time series may not help the model to capture the recharge time for the aquifer and may result in poorer performance of the models. In general, the results suggest that the ANN models are able to forecast the water levels up to 4 months in advance reasonably well. Such forecasts may be useful in conjunctive use planning of groundwater and surface water in the coastal areas that help maintain the natural water table gradient to protect seawater intrusion or water logging condition.     

基于相关分析法的滦河冲洪积扇浅层地下水埋深预测研究

根据研究区降水量和地下水埋深资料,分析降水量和地下水水位变幅的变化特征,用Excel软件绘制不同连续时段内的研究区平均降水量累计值与地下水水位变幅之间的相关图222张,选出两者相关程度高的趋势线,建立相关图模型,利用模型预测研究区每月26日平均地下水埋深,为地下水资源的合理开发利用和优化配置提供科学依据.