地下水源热泵含水层热量运移数值模拟

应用数值模拟方法对地下水源热泵采能条件下地温场的演化及含水层贮能效率进行了研究.以某水源热泵工程为例,通过对渗流影响区的温度输运方程、地下水渗流方程的耦合求解,得出了温度场分布,分析了不同工况下的地下含水层温度变化,并计算了含水层的热存储效率.结果表明:温度场中等温线的变化趋势可反映出贮能含水层因贮能水抽取和回灌温度不同导致的温度场的变化.     

基于水源热泵的地下含水层的温度场分析

地下水源热泵采能是20世纪90年代开始得到大力推广,利用该技术提出低品位、分布零散、无法直接利用的地热能源,并将其转化成高品味、高利用价值的能源。基于水源热泵分析了含水层中热量运移的数学模型的假设、模型建立、地下水流动方程、含水层中热量运移的基本数学模型的数值解法;在对井抽灌系统地温场的简析中,分析了对井系统的物理模型、对井系统的地温场表现,这一研究对于进一步推广地下水源热泵技术具有一定的理论指导意义。     

洛阳市地下水源热泵应用研究

介绍了地下水源热泵技术的发展状况及其优缺点,分析了洛阳市的水文地质特征、地下水资源状况,以及地下水源热泵的使用现状和应用前景等.提出应开展地下水源热泵的地下水开采与回灌的优化组合、回灌效果、建设场地的水文地质条件的调查和评价、地下水回灌对水井的化学堵塞机理和回灌井井管腐蚀、地下水开采过程中的控制沉降和地下水污染研究,以及地温空调井使用、回灌、含水层水位、水量、水质、水温等监测研究.     

热应力作用下的有效压力对多孔介质渗透系数的影响

渗透系数是地下水水力学和岩土力学中的一个重要参数，渗透系数的大小与含水层骨架所承受的有效应力关系密切。含水层储能过程中回灌水的温度与背景温度不同，固体骨架温度变化产生的热应力将导致有效应力的变化。本文结合含水层储能过程的特点，通过实验和理论推导，着重研究了存在热应力作用时回灌过程中的有效应力对渗透系数的影响。研究表明，在温差较小的情况下，热应力对渗透系数影响很小。该结论对含水储能过程中的流动与传热特性研究有指导意义。     

用于大规模区域供冷的地下含水层输运海洋冷量技术模拟

利用沿海地下含水层结构输运冷媒水,传递来自海洋的冷量,以构筑大中型城市地区性节能的建筑空调系统,从而实现大规模区域的廉价空调供冷。应用控制容积法和交替方向隐式求解方法,对含水层中的热量运移进行数值模拟,研究分析热弥散系数、岩层比热容及水力传导系数对热量运移过程的影响。研究证明,该方案有效降低了含水层中的地下水温度;借助大流量、大扬程的抽水井将冷媒水过量注入地下,能够有效控制地面沉降,促成已沉降地面的微量回升。此技术是一项符合可持续发展原则的地区性空调技术,具有节约能源、保护环境的积极意义。     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

基于随机行走的海岛地下水流替代模型构建方法

地下水是海岛重要的淡水资源。为了解决海岛地下水管理实践中遇到的模型计算成本过高以及现有替代模型黑箱性问题,本文提出基于随机行走的海岛地下水流替代模型构建方法。通过GPU并行随机行走算法分别建立海岛的人工增储含水层、分层越流含水层、随机非均质含水层的替代模型,并与相应海岛含水层解析解或数值解进行对比,验证随机行走替代模型在不同海岛含水层模型中的适用性和可靠性,分析潮汐动态边界对海岛分层含水层的影响,最后评估行走元数量对替代模型误差及计算成本的影响。     

大坝和堤防渗漏快速探测的浅层地温测量方法

本文论述了地下水资源勘探开发和流动地下水成因地质灾害防治中地下水存在状态模式的根本区别：前者认为地下水是“层状均一”分布,后者认为沿着某些构造薄弱部位以“流脉”状分布。“流脉”状分布的地下水温度和1m深正常地温的差别可以引起足够大小的温度异常。因此,可以利用浅层地温测量来探查具有一定埋深和规模的流动地下水,为防治灾害提供科学依据。浅层地温受到地表气温的日、年变化、地形变化,高程变化和地貌变化等的影响,应对实测值进行相应校正。天津市于桥水库大坝进行1m深地温现场测量,经各项改正后,推测出大坝渗漏的路径和部位,与实际观测资料和现象吻合。     

直流充电法在测定大屯煤矿地下水流速与流向中的应用

以大屯煤矿井筒检查孔为例,应用直流充电法测定其第四系含水层地下水的水平流速与流向.根据实测数据获取地下水等电位线的变化情况,运用矢量合成和数学公式,计算得出地下水的流速为6.88 m/d,流向为南偏东45°,结果与测区第四系含水层地下水径流情况基本相符,验证了此方法在测定地下水流速与流向应用中的准确性和可靠性,对矿区工程施工和安全生产具有重要的参考意义.     

基于井水位潮汐响应探讨含水层的水力特征及其变化

为了科学地认识应力荷载对地下水渗流运动规律的影响,揭示井孔-含水层系统与地震活动的响应关系,以华蓥山断裂带附近的大足井和北碚井为例,基于潮汐响应推求观测段含水层水力特征参数,探讨汶川地震对含水层水力特征及地下水流运动状态的影响,并对其变化机制进行解释。结果表明：大足井附近含水层中地下水运动以径向流为主,利用潮汐径向流模型计算出含水层水平渗透系数与以往抽水试验的结果基本一致;北碚井孔-含水层系统中地下水垂向流和径向流并存,引入越流含水层系统模型得到越流系数范围为1.5×10-8~2.5×10-8 s-1;汶川地震后,北碚和大足井水位均发生了阶降变化且含水层中地下水垂向流运动增强,分析认为原因是该区域侏罗系砂岩含水层在较大范围内存在着统一的水力联系,且局部裂隙发育,倾角较大,地震导致含水层发生膨胀变形和裂隙疏通,在重力作用下地下水顺层或沿裂隙通道流动。研究结果有助于提高对含水层受力变形与渗流相互作用的认识,进一步深化井孔-含水层系统对地震活动响应机制的研究     

分布式光纤温度示踪识别裂隙地下水流动研究进展

识别地下水渗流通道和流动状态,是预测裂隙介质中地下水流动行为的基本前提,也是目前裂隙地下水研究的热点问题之一。由于具备较强时空连续性、高分辨率、监测便捷、成本低廉等优点,基于分布式光纤测温(DTS)的温度示踪正逐渐成为裂隙地下水流动特征识别的重要手段,在识别地下水流动状态、钻孔间连通裂隙分布甚至裂隙水力性质等方面取得了许多新的进展。在阐述DTS原理的基础上,综述了基于DTS的温度示踪试验方法及其在裂隙地下水特征识别研究中的应用进展,重点归纳了该方法的各种试验手段、应用方式与适用范围,并指出了钻孔中的垂向流动是研究人员应用温度示踪试验时需重点关注的因素。将基于DTS温度示踪的多种试验手段结合运用及其与其他示踪方法协同运用,是未来需要进一步研究的重点方向。基于DTS的温度示踪方法有助于提升对裂隙介质中地下水渗流及热运移机理的认识,在涉及裂隙地下水的深部地质工程如高放核废物地质处置选址评价、增强型地热资源开发等研究中具有广阔的应用前景。     

基于示踪试验的岩溶管道及水力参数定量解析

以云南省丽江九子海洼地-甘泽泉一带岩溶地下水示踪试验为例,探究示踪试验在岩溶地下水通道研究中的应用。根据研究区水文地质条件,分析了地下水连通性及流场特征、推测岩溶通道位置,并结合Qtracer2计算模型对示踪剂穿透曲线（BTC）进行定量分析,同时也得出了岩溶管道结构参数及水力参数。试验结果表明,九子海洼地-甘泽泉一带存在水力联系,且还有其他岩溶通道存在。由此可判定地下水处于缓速紊流状态。Qtracer2程序可以实现示踪剂穿透曲线（BTC）的定量解析。      

浅层地热能不同开发方案对深层地下淡水咸化效应研究

为了保证浅层地热能可持续开发,同时控制深层承压淡水咸化,需评价浅层地热能开发对深层地下水咸化控制效应。基于地下水渗流、热量运移和溶质运移理论,以江苏省地质工程勘察院(南通分院)地下水源热泵系统为研究对象,建立松散孔隙地下水系统渗流—热量运移—溶质运移多场耦合数值模型,模拟预测了第Ⅰ承压含水层浅层地热能开发过程中地下水系统水位、温度、水化学浓度的演化规律,通过增大利用温差和减小夏季灌采比优化浅层地热能开发利用方案,定量评价增大利用温差和减小夏季灌采比对热贯通和深层地下淡水咸化的控制效应。结果表明：增大利用温差和减小夏季灌采比能有效缓解热贯通和深层淡水咸化的发展趋势,增大利用温差对深层地下淡水咸化的控制效应更为显著,减小夏季灌采比对热贯通的控制效应更为显著。     

Inclined Physical Subsurface Barriers for Saltwater Intrusion Management in Coastal Aquifers

Saltwater intrusion (SWI) has a negative environmental impact on groundwater quality in coastal areas. Therefore, effective management strategies are required to preserve fresh groundwater resources. Historically, vertical barriers have been exclusively considered in both numerical studies and practical applications. The novelty of this study consists in investigating the SWI mitigation effectiveness of inclined physical subsurface barriers (PSBs), and specifically cutoff walls (CWs) and subsurface dams (SDs). An initial benchmark analysis of the Henry problem was performed. Following verification, the proposed model was applied to a real case study - the Biscayne aquifer (Southeastern Florida, USA). The model simulations run for different scenarios considering the vertical placement of the PSB, an inclined placement of the PSB according to different slopes (1/4, 1/2 and 1/1, at sea- and landside) and the combination of the best scenario. The results showed that CWs are more effective in limiting SWI in comparison with SDs. The most positive impact in both cases was achieved for a slope of 1/4, indicating that a moderate vertical inclination of the PSB better preserve coastal groundwater resources. The model presented in this work can be a valuable tool for policy makers in predicting the coastal aquifer response. However, a comprehensive cost–benefit analysis is required to further account for the feasibility and the economic costs related to the construction of inclined PSBs.

     

Groundwater Allocation Using a Groundwater Level Response Management Method—Gnangara Groundwater System, Western Australia

The Gnangara groundwater system (Gnangara system) is an important source of groundwater for Perth, Western Australia: in the order of 350 GL of groundwater is abstracted annually. The Gnangara system also sustains groundwater dependent ecosystems (GDEs), mostly wetlands and native vegetation. Declining groundwater levels across the system have led to impacts on a number of key GDEs. Western Australia’s Department of Water recently prepared a Water Management Plan for the Gnangara system. Allocation limits were reviewed as part of the plan preparation. To assist in reviewing allocation limits, an adaptive Groundwater Level Response Management (GWLRM) methodology was developed and implemented. This paper describes the methodology and its application to the Gnangara system. The methodology was developed to be used as a corrective tool for the short- and medium-term, to assist in achieving long-term sustainability of groundwater management in the context of changing climate and declining groundwater levels. The GWLRM methodology is based on groundwater storage depletion and can be applied to existing allocation limits as an interim tool to assist in making management decisions aimed at recovering groundwater resources. The key to the GWRLM correction is that it will direct water allocation towards sustainable levels on the basis of measured trends. Allocations corrected through application of the GWRLM would therefore represent interim and improved water allocation figures. GWLRM can also identify potential problem areas where the principles or calculations used for long-term sustainable groundwater allocation would need to be reviewed. For the Gnangara system, the calculated storage changes or GWLRM corrections were considered together with results of predictive modelling as part of an expert panel process to derive a more sustainable interim groundwater allocation regime while further research is being completed.     

Assessing Groundwater Contribution to Streamflow of a Large Alpine River with Heat Tracer Methods and Hydrological Modelling

The contribution of groundwater to streamflow in Alpine catchments is still poorly understood, despite the fact that it may heavily impact hydrological balance and stream habitats. This paper presents the results of a field campaign based on experiments with heat tracer methods to assess the hyporheic flow during the low‐flow period of a large Alpine river in Italy. These measurements were employed to validate a distributed hydrological model that can be used to asses river–groundwater interaction in both low‐flow and high‐flow conditions. The results show that groundwater may have a relevant role during low‐flow periods, by increasing river discharge and during floods, by subtracting direct run‐off that is stored in river banks. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Impacts of urban areas and urban growth on groundwater in the Great Lakes Basin of North America

The Great Lakes Basin (GLB) holds vast reserves of groundwater, the great majority of which eventually drains to the lakes. Urban growth significantly affects both the quality and quantity of this groundwater and thereby represents a potential threat to the long-term viability of the Great Lakes hydrologic system. Urban areas import, manufacture, store, transport, and utilise large volumes of chemicals, a proportion of which inevitably finds its way to the shallow sub-surface. In many cases, potentially polluting chemicals are applied directly to urban surfaces (e.g. as road salts, fertilizers and pesticides), are stored in the subsurface (e.g. gasoline tanks) or are released to the subsurface (e.g. septic systems). Because most of the basin's larger urban areas rely almost exclusively on lake-based supplies, very little attention is given to the accumulation of contaminants in shallow urban groundwaters and the serious risks they pose. Assessment of the problem is complicated by the widespread use of urban fill and a complex network of drains, pipes and tunnels that create “urban karst”, a shallow artificial aquifer, unique to urban settings, that exerts a major, yet often unpredictable influence on groundwater flow and contaminant transport. Management of ground water pollution, and its impact on the receiving Great Lakes, will require rigorous audits of all urban sources of contamination together with the development and calibration of groundwater flow and transport models that will enable the fate of urban pollutants to be reliably predicted even when groundwater is not used for supply.     

Water Resources Sustainability Indicator: Application of the Watershed Characteristics Approach

The quantification of the renewable flux (i.e. sustainable limit) of the hydrologic system is the prerequisite for transitioning from unsustainable to sustainable water resources management. The application of the Watershed Characteristics Approach to estimate the renewable flux of the hydrologic system was demonstrated using Minnesota’s (USA) Twin Cities Metropolitan Area (TCMA). The methodology quantified the relationships between landscape properties and water balance characteristics, resulting in the development of functioning hierarchical hydrogeological units with corresponding recharge rates. This renewable flux is a key quantitative characteristic for the assessment of a sustainability indicator. The key indicator of sustainable water use is the ratio of the renewable capacity of the hydrologic system to the water use by humans and the environment. By incorporating water use estimates for the TCMA relative to the calculated recharge rates, sustainability indicators for groundwater and total flux were calculated for the metropolitan area. As far back as the 1890s, declines in TCMA groundwater levels have been observed, which correspond to the unsustainable groundwater extraction estimates identified in the results of this study. The non-stationary characteristics of urban watersheds influenced by ongoing land use/land cover changes as illustrated in this paper, emphasizes the need for conservative hydrologic planning to achieve sustainable water management. This approach can also be applied to other metropolitan areas as a hydrologic tool for decision-makers to design sustainable water policy and prevent the over-extraction of the water flowing through the hydrologic system.     

基于温度时间序列分析的水库 下泄低温水入渗速度研究

用温度作为示踪剂,基于饱和多孔介质一维稳态水热运移方程,运用时间序列分析法推求入渗速度,分析该方法的适用条件和范围,以及对热力参数选取的敏感性。以浙江省新安江下游河段为例,通过分析河岸带潜流区不同深度温度传感器的温度分布曲线相位和振幅变化,研究地表水和地下水的交换特征。结果表明流速较低时,入渗速度对不同深度的振幅变化较敏感,入渗速度接近±1×10^-5 m/s时,相位差的变化对入渗速度的影响最大。监测时段内试验区的入渗速度大致为2.22×10^-5~4.39×10^-5 m/s,入渗速度的数值均为正值,即在监测时段内均为地表水补给地下水。时间序列分析法对河床冲刷和沉积较不敏感,适用于较复杂的水流条件,且在一定程度上克服热弥散度的误差。