Asymptotic analysis of cross-hole pneumatic injection tests in unsaturated fractured tuff

We present a new method to interpret three-dimensional pressure interference tests, which is based on an asymptotic analysis of late time pressure transient data. The approach yields reliable estimates of equivalent permeability and porosity without resorting to type-curve fitting or numerical inverse models. This is accomplished by analyzing the late-time behavior of type-curve solutions for pressure interference tests. We use our approach to infer the permeability and porosity of fractured tuff from cross-hole pneumatic injection test data. Their values are found to be in good agreement with those inferred from more complicated methods of data analysis. We analyze the statistical properties of the estimated equivalent permeability and porosity and observe a weak correlation between the two.     

Numerical inverse interpretation of single-hole pneumatic tests in unsaturated fractured tuff

A numerical inverse method was used to interpret simultaneously multirate injection and recovery data from single-hole pneumatic tests in unsaturated fractured tuff at the Apache Leap Research Site near Superior, Arizona. Our model represents faithfully the three-dimensional geometry of boreholes at the site, and accounts directly for their storage and conductance properties by treating them as high-permeability and high-porosity cylinders of finite length and radius. It solves the airflow equations in their original nonlinear form and yields information about air permeability, air-filled porosity and dimensionless borehole storage coefficient. Some of this is difficult to accomplish with analytical type-curves. Air permeability values obtained by our inverse method agree well with those obtained by steady-state and type-curve analyses.     

Maximum likelihood Bayesian averaging of airflow models in unsaturated fractured tuff using Occam and variance windows

We use log permeability and porosity data obtained from single-hole pneumatic packer tests in six boreholes drilled into unsaturated fractured tuff near Superior, Arizona, to postulate, calibrate and compare five alternative variogram models (exponential, exponential with linear drift, power, truncated power based on exponential modes, and truncated power based on Gaussian modes) of these parameters based on four model selection criteria (AIC, AICc, BIC and KIC). Relying primarily on KIC and cross-validation we select the first three of these variogram models and use them to parameterize log air permeability and porosity across the site via kriging in terms of their values at selected pilot points and at some single-hole measurement locations. For each of the three variogram models we estimate log air permeabilities and porosities at the pilot points by calibrating a finite volume pressure simulator against two cross-hole pressure data sets from sixteen boreholes at the site. The traditional Occam’s window approach in conjunction with AIC, AICc, BIC and KIC assigns a posterior probability of nearly 1 to the power model. A recently proposed variance window approach does the same when applied in conjunction with AIC, AICc, BIC but spreads the posterior probability more evenly among the three models when used in conjunction with KIC. We compare the abilities of individual models and MLBMA, based on both Occam and variance windows, to predict space–time pressure variations observed during two cross-hole tests other than those employed for calibration. Individual models with the largest posterior probabilities turned out to be the worst or second worst predictors of pressure in both validation cases. Some individual models predicted pressures more accurately than did MLBMA. MLBMA was far superior to any of the individual models in one validation test and second to last in the other validation test in terms of predictive coverage and log scores.     

A constitutive model for water flow in unsaturated fractured rocks

A conceptual model for describing effective saturation in fractured hard rock is presented. The fracture network and the rock matrix are considered as an equivalent continuum medium where each fracture is conceptualized as a porous medium of granular structure and the rock matrix is assumed to be impermeable. The proposed model is based on the representation of a rough‐walled fracture by an equivalent porous medium, which is described using classical constitutive models. A simple closed‐form equation for the effective saturation is obtained when the van Genuchten model is used to describe saturation inside fractures and fractal laws are assumed for both aperture and number of fractures. The relative hydraulic conductivity for the fractured rock is predicted from a simple relation derived by Liu and Bodvarsson. The proposed constitutive model contains three independent parameters, which may be obtained by fitting the proposed effective saturation curve to experimental data. Two of the model parameters have physical meaning and can be identified with the reciprocal of the air entry pressure values in the fractures of minimum and maximum apertures. Effective saturation and relative hydraulic conductivity curves match fairly well the simulated constitutive relations obtained by Liu and Bodvarsson. Copyright © 2008 John Wiley & Sons, Ltd.     

Miocene rhyolitic welded tuff infilling a funnel-shaped eruption conduit Shiotani, southeast of Matsue, SW Japan

 At Shiotani, SW Japan, rhyolitic welded tuff forms a steep-sided funnel-shaped body, confined by Paleogene granitic rocks to an elliptical area 1–1.5 km across. The Shiotani welded tuff is pervasively welded and foliated concordantly with the contact that dips inward at angles of 70–90°. In contrast, nearby contemporary volcaniclastic deposits are non-welded and gently inclined. Near the contact with the granite, the tuff is plastically deformed and shows lineations that plunge inward at angles of 40–65°. Lithic and crystal clasts in the rheomorphic outer part are rotated in a plane normal to the foliations and parallel to the lineations indicating downward flow of the welded tuff. The geometry and internal structures suggest that the Shiotani welded tuff was emplaced and welded in a funnel-shaped eruption conduit. Upon collapse of a plinian or phreatoplinian eruption column, the majority of the conduit-filling pyroclasts probably fell back en masse into the conduit. Heat and steam from underlying magma and diffusion of interstitial volatiles into the glass perhaps reduced the viscosity of juvenile pyroclasts and facilitated welding in the conduit, especially at deep levels. The hot welded pyroclasts then flowed down the conduit wall during welding compaction and retreat of the magma. These processes resulted in increased welding toward the contacts and welding foliations concordant with the steep wall. Emplacement of nearby correlative volcaniclastic mass-flow deposits in a shelf to upper bathyal environment suggests a possibility that, when active, the Shiotani conduit was under the sea. Welding compaction would occur even under the sea provided that the steam generated in the upper part of the conduit fill prevented water access. Received: 28 February 1996 / Accepted: 5 May 1997     

隧道磁共振测深超前探测模型参数不确定度分析方法研究

地面磁共振方法探测地下水趋于成熟.随着研究的深入,磁共振技术在隧道超前探测方面也开展了应用.然而,由于隧道空间特殊环境限制,获取的磁共振信号信噪比极低,解释结果中各参数的确定性值得深思.基于这一问题,本文提出隧道磁共振测深超前探测模型参数不确定度分析方案,实际工作前,根据不同探测目标要求及环境噪声水平,优化仪器装置参数设计,提高解释结果准确性.本文首先在地面磁共振探测理论基础上,推导了考虑天线铺设角度影响的隧道矩形线圈激发场计算表达式,模拟了隧道准全空间磁共振测深正演响应.其次,基于后验模型协方差矩阵,计算模型参数标准偏差因子,划分参数不确定度等级.最后,构建三层含水模型,将第二层含水体作为观测目标.在仿真合成数据的基础上,分别探讨了电阻率、含水量、水体厚度、线圈边长、匝数、线圈旋转角度以及噪声水平等参数对目标含水体测定的影响.通过对比分析,得到如下结论：当探测目标前方地层的电阻率小于10 Ωm时,目标含水体的不确定度随着该电阻率的增大而降低;当该电阻率大于10 Ωm时,其不影响目标含水体的不确定度;目标体前方地层含水量的增大能够明显增加目标含水体的不确定度;目标层电阻率以及含水量对该层含水体的不确定度几乎不造成影响;目标层厚度越大其含水体的确定度越高;线圈边长和匝数的增大都能在很大程度上降低含水体的不确定度;线圈的偏转角度不影响目标体的不确定度;磁共振信号中噪声的幅度越大,含水体参数的不确定度越大.本文的研究结论有助于提高隧道磁共振探测数据反演参数的准确性,同时能够为实际探测提供预先优化参数的分析方案.

     

隧道磁共振测深超前探测模型参数不确定度分析方法研究

地面磁共振方法探测地下水趋于成熟.随着研究的深入,磁共振技术在隧道超前探测方面也开展了应用.然而,由于隧道空间特殊环境限制,获取的磁共振信号信噪比极低,解释结果中各参数的确定性值得深思.基于这一问题,本文提出隧道磁共振测深超前探测模型参数不确定度分析方案,实际工作前,根据不同探测目标要求及环境噪声水平,优化仪器装置参数设计,提高解释结果准确性.本文首先在地面磁共振探测理论基础上,推导了考虑天线铺设角度影响的隧道矩形线圈激发场计算表达式,模拟了隧道准全空间磁共振测深正演响应.其次,基于后验模型协方差矩阵,计算模型参数标准偏差因子,划分参数不确定度等级.最后,构建三层含水模型,将第二层含水体作为观测目标.在仿真合成数据的基础上,分别探讨了电阻率、含水量、水体厚度、线圈边长、匝数、线圈旋转角度以及噪声水平等参数对目标含水体测定的影响.通过对比分析,得到如下结论：当探测目标前方地层的电阻率小于10 Ωm时,目标含水体的不确定度随着该电阻率的增大而降低;当该电阻率大于10 Ωm时,其不影响目标含水体的不确定度;目标体前方地层含水量的增大能够明显增加目标含水体的不确定度;目标层电阻率以及含水量对该层含水体的不确定度几乎不造成影响;目标层厚度越大其含水体的确定度越高;线圈边长和匝数的增大都能在很大程度上降低含水体的不确定度;线圈的偏转角度不影响目标体的不确定度;磁共振信号中噪声的幅度越大,含水体参数的不确定度越大.本文的研究结论有助于提高隧道磁共振探测数据反演参数的准确性,同时能够为实际探测提供预先优化参数的分析方案.     

Development and demonstration of a structured hydrological feature coding system for Europe

Abstract

Validation of large amounts of digital hydrological data and eventual exchange of data between various organisations can benefit from the development of a structured hydrological feature coding system. In this article we describe the development of such a system and present its implementation in the CCM2 structured hydrological feature data set, covering Europe to the Urals and including Turkey. We discuss the coding of river basins, catchments, lakes and rivers. The proposed coding system is largely inspired by the work of Otto Pfafstetter with additions for coding oceans, seas, islands and lakes. Furthermore the coding system can be transferred to features that geometrically intersect the coded hydrological features and we propose some rules on how to establish this transfer.

Citation de Jager, A. L. & Vogt, J. V. (2010) Development and demonstration of a structured hydrological feature coding system for Europe. Hydrol. Sci. J. 55(5), 661–675.     

Site characterization in densely fractured dolomite: comparison of methods

One of the challenges in characterizing fractured-rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete-fracture approaches to aquifer characterization. There are two near-vertical sets of fractures at the site; near-horizontal bedding-plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of approximately 10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short-interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short-interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions. Comparison of distributions of hydraulic head and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured-carbonate aquifer, a characterization approach using traditional long-interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid.     

Modelling potential hydrological impact of abandoned underground mines in the Monday Creek Watershed,Ohio

Abandoned underground mines (AUM) have caused dramatic environmental effects that are closely linked to regional sustainability. This paper explores the potential hydrological impact of AUM in the Monday Creek Watershed, a typically mined area in Appalachian region, using the Soil and Water Assessment Tool (SWAT 2005) model and Sequential Uncertainty Fitting (SUFI‐2), calibrated at both the global and local scales. The locally calibrated model better incorporates those key parameters relevant to AUM for specific sub‐basins and hydrologic response units. Data from the years 2003–2004 were used for calibration and 2005–2006 for validation. The results were quite satisfactory; both the coefficient of determination (R²) and the Nash–Sutcliffe efficiency statistic were over 0.80. The potential influences of AUM were assessed by modelling an alternative scenario assuming no AUM for the period 2003–2009. Results show that the hydrological process of lateral subsurface flow plays a dominant role in linking AUM to overall watershed hydrology. The potential hydrological impact of AUM is an increased annual lateral flow of 82.1%, and a decrease in annual surface flow by 15%, leading to an increase of 16.9% in annual water yield for the Monday Creek Watershed. The seasonal fluctuation of water yield has a similar trend to lateral flow, decreasing from March to August and increasing from August to January. Higher volume, higher flow peaks and higher recession constants characterized the hydrograph of daily streamflow from AUM. The results indicate that more emphasis should be put on lateral flow for further study of acid mine drainage and flooding control in those watersheds with AUM. Copyright © 2012 John Wiley & Sons, Ltd.     

导电大地上航空电磁系统校准

航空电磁系统校准是开展实际测量工作的基础,校准情况直接影响数据处理和解释.传统校准方法通常假设在自由空间中进行,忽略导电大地耦合影响.然而,实际工作中很难找到绝对高阻的校准场地,导电大地对系统校准和观测数据的影响无法忽视.本文以频率域航空电磁系统为例,对导电大地上航电系统校准技术和校准误差改正方法进行研究.我们首先推导了层状导电大地上水平共面和直立共轴线圈系统的校准公式,结果表明导电大地对航电系统校准尤其是水平共面装置的高频信号影响很大.针对校准过程中大地电导率已知的情况,本文采用非线性方程求解技术一次性确定校准线圈位置和Q值;在没有任何辅助信息情况下,也可直接利用实测数据计算校正因子进行迭代求解.测试结果表明该方法快速、准确、有效.考虑到系统相位和增益调整直接影响观测数据,本文提出了航空电磁数据校准误差的改正算法.实测数据误差改正结果表明,导电大地对高频信号影响严重,校准误差改正后的航空电磁数据与实际地质资料更好吻合.

     

Understanding the hydrological system dynamics of a glaciated alpine catchment in the Himalayan region using the J2000 hydrological model

This paper provides the results of hydrological modelling in a mesoscale glaciated alpine catchment of the Himalayan region. In the context of global climate change, the hydrological regime of an alpine mountain is likely to be affected, which might produce serious implications for downstream water availability. The main objective of this study was to understand the hydrological system dynamics of a glaciated catchment, the Dudh Kosi River basin, in Nepal, using the J2000 hydrological model and thereby understand how the rise in air temperature will affect the hydrological processes. The model is able to reproduce the overall hydrological dynamics quite well with an efficiency result of Nash–Sutcliffe (0.85), logarithm Nash–Sutcliffe (0.93) and coefficient of determination (0.85) for the study period. The average contribution from glacier areas to total streamflow is estimated to be 17%, and snowmelt (other than from glacier areas) accounts for another 17%. This indicates the significance of the snow and glacier runoff in the Himalayan region. The hypothetical rise in temperature scenarios at a rate of +2 and +4 °C indicated that the snowmelt process might be largely affected. An increase in snowmelt volume is noted during the premonsoon period, whereas the contribution during the monsoon season is significantly decreased. This occurs mainly because the rise in temperature will shift the snowline up to areas of higher altitude and thereby reduce the snow storage capacity of the basin. This indicates that the region is particularly vulnerable to global climate change and the associated risk of decreasing water availability to downstream areas. Under the assumed warming scenarios, it is likely that in the future, the river might shift from a ‘melt‐dominated river’ to a ‘rain‐dominated river’. The J2000 model should be considered a promising tool to better understand the hydrological dynamics in alpine mountain catchments of the Himalayan region. This understanding will be quite useful for further analysis of ‘what‐if scenarios’ in the context of global climate and land‐use changes and ultimately for sustainable Integrated Water Resources Management in the Himalayan region. Copyright © 2012 John Wiley & Sons, Ltd.     

Environmental flow assessment in a lake-marsh system with reverse seasonal hydrological patterns

Environmental flow (e-flow) assessment is essential for the ecological protection and restoration of lake-marsh systems. Previous studies on e-flow assessment for lake-marsh systems focused on lake-marsh systems with natural seasonal hydrological patterns (i.e., low water level in winter and high water level in summer). However, they have not considered lake-marsh systems with reverse seasonal hydrological patterns (i.e., high water level in winter and low water level in summer). The reverse seasonal hydrological patterns impose seriously negative impacts on waterbirds, because the hydrological patterns could lead to limited plant germination in spring and massive plant death in summer, leaving few plants available as food for waterbirds in winter, and could consequently reduce the sheltering and forageable areas for waterbirds. This study took Hongze Lake Wetland National Nature Reserve in China as the study area. Based on the habitat requirements of waterbirds, the sheltering and forageable areas for waterbirds under different water-depth and aquatic plant distribution scenarios were calculated. By exploring the impacts of reverse seasonal hydrological processes on waterbird habitats, we determined the necessary e-flows for lake-marsh systems with reverse seasonal hydrological patterns to meet the needs of waterbird habitat. The results showed that the water level of Hongze Lake should be controlled to 13.0–13.1 m in March, 12.5–12.6 m in July, and 12.9–13.0 m in October, which can meet the needs of waterbirds for both shelter and foraging.     

Identification of a karst hydrological system in the Dinaric karst (Yugoslavia)

Abstract

The construction of a reservoir on the Neretva River resulted in the flooding of three springs which now function as ponors (swallow-holes). In the first phase, they discharged 28 m³ s^?1 of water from the full reservoir. All the water that was lost through these ponors appeared some 1 km downstream from the dam in a group of springs. Most of these springs were, in the natural state, only temporary, and during the dry period their discharge was approximately 1 m³ s^?1. In order to reduce the losses from the reservoir, some reclamation works were carried out resulting in a decrease of the losses by only 6 m³ s^?1. Detailed hydrogeological and hydrological analyses were performed with the objective of identifying the karst system, i.e. to determine the position of the karst channels. The definition of the position and dimensions of the karst channels through which the greatest quantities of water are lost from the reservoir was carried out according to the definition of the hydrograph recession curves and the discharge curves of a group of downstream springs. The recession part of the hydrograph was defined by applying a new expression for the Maillet formula. Thus, it became possible to define not only the transport characteristics of the karst mass but also its retention characteristics.     

鄱阳湖湖泊流域系统水文水动力联合模拟

本文以鄱阳湖湖泊流域系统为研究对象,鉴于该湖泊流域系统尺度较大,下垫面自然属性呈现高度空间异质性且具有流域-平原区-湖泊不同机制的水文水动力过程,为了真实描述湖泊流域间的水文水动力联系及反映不同过程间的作用机制,构建了鄱阳湖湖泊流域联合模拟模型.该模型基于自主研发的流域分布式水文模型WATLAC和湖滨平原区产流模型以及水动力模型MIKE 21 3个不同功能子模型的连接来实现该复杂系统的模拟.模型的联合采用输入-输出驱动及子模型的顺序执行进程,即将五大子流域与平原区入湖径流量作为输入条件来驱动湖泊水动力模型,模拟湖泊水位对流域入湖径流量的响应.以2000-2005年鄱阳湖流域6个水文站点的河道径流量、流域基流指数以及湖泊4个站点的水位资料来率定模型,其中各站点日径流量拟合的纳希效率系数E_ns为0.71~0.84,确定性系数R²介于0.70~0.88之间,而湖泊各站点水位拟合的纳希效率系数E_ns变化为0.88~0.98,确定性系数R²为0.96~0.98,均取得令人满意的率定结果.本文提出的鄱阳湖湖泊流域系统水文水动力联合模拟模型能较为理想再现湖泊水位对流域降雨-径流过程的响应.水位模拟结果进一步表明,该联合模型能用来获取重要的水动力空间变化特征.该模型可作为有效工具定量揭示湖泊流域系统水文水动力过程对气候变化和流域人类活动的响应.     

Hydraulic characterization and hydrological behaviour of a pilot permeable pavement in an urban centre,Brazil

Considering all the alterations on hydrology and water quality that urbanization process brings, permeable pavement (PP) is an alternative to traditional impermeable asphalt and concrete pavement. The goal of the PP and other low impact development devices is to increase infiltration and reduce peak runoff flows. These structures are barely used in Brazil aiming stormwater management, one of the big hydrological issues in cities throughout the country, with increasing urbanization rates. The main objective of this paper is the hydraulic characterization of a PP and the assessment of its hydrological efficiency from the point of view of the infiltration process. The study focuses on a pilot area in a parking lot in an urban area (Recife, Brazil). Soil elements filling the voids between concrete elements were sampled (particle size density, water contents) and tested with water infiltration experiments at several points of the 3 m × 1.5 m surface pilot area. Beerkan Estimation of Soil Transfer parameters algorithm was applied to the infiltration experiment data to obtain the hydraulic characteristics of the soil composing the PP surface layer, the concrete grid pavers (with internal voids filled with natural soil) permeability being neglected. Results show that the soil hydraulic characteristics vary spatially within the pilot area and that the soil samples have different hydraulic behaviours. The hydraulic characteristics derived from Beerkan Estimation of Soil Transfer parameters analysis were implemented into Hydrus code to simulate runoff, infiltration and water balance over a year. The numerical simulation showed the good potential of the PP for rainfall–runoff management, which demonstrates that PP can be used to retrofit existing parking infrastructure and to promote hydrological behaviour close to natural soils. Copyright © 2016 John Wiley & Sons, Ltd.     

Zero-stress,cylindrical wave functions around a circular underground tunnel in a flat,elastic half-space: Incident P-waves

The zero-stress boundary conditions at the surface of the half-space in the presence of surface and sub-surface cavities for in-plane, incident cylindrical P- and SV-waves have always posed challenging problems. The outgoing cylindrical P- and SV-waves can be represented by Hankel functions of radial distance coupled with the sine and cosine functions of angle. Together, at the half-space surface the P- and SV-wave functions are not orthogonal over the semi-infinite radial distance from 0 to infinity. Thus, to simultaneously satisfy the zero in-plane, normal, and shear stresses, an approximation of the geometry is often made. This paper presents an analytical formulation of the boundary-valued problem, where the Hankel wave functions are expressed in integral form, changing the representation from cylindrical to rectangular coordinates, so that the zero-stress boundary conditions at the half-space surface can be applied in a more straightforward way.     

A sensor array system for profiling moisture in unsaturated rock and soil

As the scope of hydrologic investigations extend deeper into the subsurface profile, and increasingly include fractured rock, there is a growing need for techniques that can accurately monitor saturation changes at a high spatial and temporal resolution in this environment. We have developed a technique, the Electrical Resistance Sensor Array System (ERSAS), to track moisture dynamics in vadose zone regions that include both fractured rock and soil. The performance of ERSAS was compared with the time domain reflectometry (TDR) technique under controlled and field conditions. We found that ERSAS was effective in determining patterns of saturation changes along vertical soil/rock profiles. Because of the small size of individual sensors, it was able to resolve travel times associated with a wetting front and peak saturation better than TDR. In addition, ERSAS is significantly cheaper than the TDR system, and the sensor arrays are relatively easier to install in the subsurface profile. Published in 2011 by John Wiley & Sons, Ltd.