Inverse modelling of aquifer parameters in basaltic rock with the help of pumping test method using MODFLOW software

The origin and movement of groundwater are the fundamental questions that address both the temporal and spatial aspects of ground water run and water supply related issues in hydrological systems. As groundwater flows through an aquifer, its composition and temperature may variation dependent on the aquifer condition through which it flows. Thus, hydrologic investigations can also provide useful information about the subsurface geology of a region. But because such studies investigate processes that follow under the Earth's shallow, obtaining the information necessary to answer these questions is not continuously easy. Springs, which discharge groundwater table directly, afford to study subsurface hydrogeological processes.The present study of estimation of aquifer factors such as transmissivity (T) and storativity (S) are vital for the evaluation of groundwater resources. There are several methods to estimate the accurate aquifer parameters (i.e. hydrograph analysis, pumping test, etc.). In initial days, these parameters are projected either by means of in-situ test or execution test on aquifer well samples carried in the laboratory. The simultaneous information on the hydraulic behavior of the well (borehole) that provides on this method, the reservoir and the reservoir boundaries, are important for efficient aquifer and well data management and analysis. The most common in-situ test is pumping test performed on wells, which involves the measurement of the fall and increase of groundwater level with respect to time. The alteration in groundwater level (drawdown/recovery) is caused due to pumping of water from the well. Theis (1935) was first to propose method to evaluate aquifer parameters from the pumping test on a bore well in a confined aquifer. It is essential to know the transmissivity (T = Kb, where b is the aquifer thickness; pumping flow rate, Q = TW (dh/dl) flow through an aquifer) and storativity (confined aquifer: S = bS_s, unconfined: S = S_y), for the characterization of the aquifer parameters in an unknown area so as to predict the rate of drawdown of the groundwater table/potentiometric surface throughout the pumping test of an aquifer. The determination of aquifer's parameters is an important basis for groundwater resources evaluation, numerical simulation, development and protection as well as scientific management. For determining aquifer's parameters, pumping test is a main method. A case study shows that these techniques have been fast speed and high correctness. The results of parameter's determination are optimized so that it has important applied value for scientific research and geology engineering preparation.     

抽水试验中不同位置自动水位计响应数据应用分析

抽水试验中,动水位数据采集记录及处理分析对水文地质参数计算具有重要意义。近年来自动水位计被广泛用于抽水试验,通过传感器压强水头变化值获取水位降深。因井管内水流动会产生水头损失,自动水位计安放位置不同会导致获取的井水位降深不同,不同于传统方法测得的井水面降深,对水文地质参数计算将产生一定影响,因此如何合理放置自动水位计以及在参数计算中如何应用其获取的水位降深都亟待开展试验研究。在黑河流域第四系大厚度含水层地区,选择典型单层试验孔和利用分层封隔技术实现的一孔同径多层抽水孔开展试验研究,在动水位以下抽水试验层段上部、中部、下部以及潜水泵上部和下部分别放置自动水位计进行了系统的数据采集分析。结果表明:抽水试验中因井管内水流沿程水头损失及速度水头差异导致不同位置自动水位计获得压强水头变化值不同,本次试验实测到井筒内不同部位井损值;井损值在潜水泵进水口处最大,随距潜水泵距离的增大而减小,为避开井筒内较大水头损失对参数计算的影响,自动水位计宜优选安放在潜水泵上部接近动水位位置;在单孔抽水试验中利用稳定流公式计算水文地质参数时,自动水位计获取水位降深含井损不可忽略,需通过多落程抽水试验数据分析扣除后使用。同时,抽水试验中自动水位计不同位置获取数据的处理分析方法为更好地理解井中水头损失提供了依据。     

硬岩水文地质参数井同径止水与分层抽水试验研究

针对传统施工程序无法解决坚硬岩石止水环隙很小（仅3 mm）钻孔的同径止水及分层抽水试验问题,以山西某水文地质参数井为研究对象,采用现场和室内综合试验的方法,对同径止水方案、材料、技术、分层抽水等工艺进行研究。结果表明:（1） 同径止水装置经过特殊的“外掏内缩”设计与制作,使止水外环间隙由3 mm增大到8.5 mm,解决了“极小止水环隙”下的同径止水问题;经抽水检验,止水效果良好。（2） 在孔外一系列试验的基础上,定制的止水材料和选择的止水组合与本孔的适应性强,下管风险小,实施过程相当顺利。（3）专门设计的分层导水管路,其上串接的隔离封水胶球与止水套管柱内设置的锥形隔水接头相互契合,封水可靠,形成了两套独立的导水管路,满足了上、下含水层分层抽水试验的工况。研究结果可为类似水文地质参数井开展同径止水或分层抽水试验研究提供参考。     

Water table fluctuation analyses and associated empirical approach to predict spatial distribution of water table at Yeşilköy/AgiosAndronikos aquifer

The groundwater of the deep Ye?ilköy aquifer is the only water resource for agricultural and domestic consumption at the Karpaz Peninsula of Cyprus, which stretches approximately 100 km from the northeast of capital Nicosia to the northern tip of Cyprus. During the last decade, over-pumping and following dry periods have depleted the groundwater resources and the water surface elevation of the aquifer has dropped. The aim of this study is to understand the behavior of the Ye?ilköy aquifer in the last decade for the proper management of groundwater resources. This has been achieved based on well survey and field survey studies, monitoring programs followed by pumping tests, and safe yield analysis. Most of the research effort has been focused on field and well survey studies to quantify agricultural water consumption and abstraction rates from the aquifer. A long-term groundwater level monitoring program, short-term continuous groundwater monitoring and pumping tests provided information for the regression analyses while deriving a sixth order polynomial relationship between the period parameter and the head parameter. The equation was helpful to predict the short-term behavior of the water level when the present hydrogeological conditions prevail. The pumping test results satisfied the hydraulic properties of calcarenite formation yielding T = 1,782 m²/day and S = 0.0012. The results of safe yield analysis show that the annual deficit of the aquifer is 0.496 million cubic meters (MCM), which is equivalent to a 0.6 m drop in groundwater levels per year. Finally, the resultant annual safe yield of the aquifer is estimated as 0.84 MCM.     

Global curve-fitting for determining the hydrogeological parameters of leaky confined aquifers by transient flow pumping test

Proper management of groundwater resources requires an accurate evaluation of the parameters (hydraulic properties) that control the movement and storage of groundwater. Hydrogeological parameters are the basis of groundwater evaluation, modeling, and management and so on. A global curve-fitting method incorporating pumping test data and water table recovery data was introduced in the present study. The principal and procedures of the method were elucidated in detail. The drawdown and recovery data from two sets of transient flow pumping test conducted in no. 2 water source site of Shizuishan city were used to verify the calculation accuracy of the proposed method. The hydrogeological parameters were also estimated with traditional type curve-fitting method on the basis of formula derived by Hantush and Jacob. The hydrogeological parameters calculated by the two methods were compared and the results show that the parameters obtained by the global curve-fitting method are a little bigger than but very close to those obtained by the traditional type curve-fitting method. The proposed method which possesses three major advantages is feasible and reliable in aquifer parameter identification. A comparative study on various methods for parameter identification is required and expected in future study.     

某地下空间承压含水层抽水试验及成果分析

由于地下水突涌风险,地下空间在施工作业中有必要通过抽水试验确定承压含水层的水文地质参数。依据勘察报告的初步评价,基坑开挖15.5m时,场地内第⑦1层承压含水层有可能产生突涌,为确保工程安全施工,需开挖前进行承压含水层抽水试验,取得场地承压含水层水文地质参数及降水引起的沉降特征,为地下空间设计和施工提供可靠依据。本次布设抽水井、观测井、分层沉降标组、孔隙水压力观测孔及地面沉降观测点,依据抽水试验技术要求获取渗透系数、抽水影响半径等相关水文地质参数。最后,针对工程场地内承压水情况及特点进行分析,提出基坑开挖时的承压水降压建议方案。     

超深涌水钻孔的钻探工艺及水文地质试验方法研究

C4Z—G-05孔为某铁路高黎贡山隧道工程勘察钻孔,钻孔深度1075．5m。钻探过程中分别在孔深288～400m和611～724m穿过落差大于100m的断裂构造破碎带,并出现涌水及漏水现象,施工难度大,水文地质试验难以进行。据此,采取了合理的施工顺序,并根据钻进时的机械设备及钻进情况及时调控钻进参数;针对不同的地层,选用不同的泥浆类型,从而顺利的完成了该孔钻探工作。在水文地质试验中,对松散层潜水,采取了抽水试验,对两个断裂带,适时的运用观测涌水量和压力水头及涌水试验的方法,并选择适宜的计算公式,较好的完成了该孔的水文地质参数的计算工作．取得了良好的效果。     

Numerical simulation and evaluation of groundwater resources in a fractured chalk aquifer: a case study in Zinder well field,Niger

Groundwater is often a unique water source for agriculture, industry and domestic use for local inhabitants in semi-arid African continent owing to shortage of surface water and rainfall. It is of significance to quantify and assess the groundwater resources for local sustainable development in order to correctly evaluate groundwater resources of Zinder well field with fractured media in Zinder, Niger. A conceptual model of hydrogeology was set up by a geological and hydrogeological survey. For simulating the real conditions, a large multi-well pumping test with designed pumping rate was conducted. In addition, a two-dimensional finite-element transient flow model was developed to simulate groundwater flow at the site. Results show that generally good agreements have been found between the simulated and observed hydrogeology heads for the test. The hydraulic parameters were obtained from the pumping test. A 11-year prediction of groundwater resources has been made under three exploitation schemes, respectively, and it indicates that the well field can offer 7,000 m³/day when the aquifer remains confined. An optimal scheme of exploitation is provided.     

单井与群井结合抽水试验在地面沉降实测中的应用研究

以天津市某工程项目抽水试验数据为实测基本资料,目的是确定地基土的渗透性和富水性,计算含水层的水文地质参数,并实时监测试验期间地面沉降监测结果。结果表明,单井和群井抽水试验在抽水过程中,地面高程呈现出下降的趋势,累计达到最大沉降量,达到23. 57 mm,随着抽水时间较短和抽水时间较长等原因,在地面具有附加荷载时,沉降变大。因此,试验实时监测可以有效预防存在问题,为工程的设计与施工提供安全的风险控制。     

小范围群井与单井抽水试验推求水文地质参数的比较分析

小范围岩溶区水文地质参数的推求是一项困难的工作.过去常常定性选取抽水孔与观测孔,利用单井抽水试验资料进行推求,这样往往造成推求误差过大.该文通过建立多层次多目标系统模糊决策模型,分别定量的优选了干扰井群抽水试验的最佳观测孔和单井抽水试验的最佳抽水试验单井;并运用了井群概化的方法,采用干扰井群抽水试验资料推求小范围水文地质参数,并且与单井抽水 试验资料推求的参数进行了比较分析,经分析应用方法取得了较好的效果.     

抽水试验在城市轨道交通工程勘察中的运用

地下工程建设中不可避免地遇到地下水的控制问题,正确的水文地质参数是准确预测基坑涌水量进而进行地下水控制的前提.文章以郑州地铁5号线经开第八大街站的现场抽水试验为基础,通过1个抽水试验孔、2个观测孔进行了 3个不同水位降深的抽水试验,以更精确地确定含水层的水文地质参数,为深基坑地下水控制设计和施工提供重要的基础数据,对类...     

Estimating transmissivity using empirical and geostatistical methods in the volcanic aquifers of Upper Awash Basin, central Ethiopia

Transmissivity (T) is a basic hydraulic parameter of an aquifer that is utilized in most groundwater flow equations to understand the flow dynamics and is generally estimated from pumping tests. However, the cost of performing a large number of aquifer tests is expensive and time consuming. The fact that specific capacity (S _c) is correlated with hydraulic flow properties of aquifers simplifies parameter estimation mainly because specific capacity values are more abundant in groundwater databases than values of transmissivity and they offer another approach to estimate hydraulic parameters of aquifers. In this study, an empirical relation is derived using 214 pairs of transmissivity and specific capacity values that are obtained from pumping tests conducted on water wells penetrating the complex volcanic aquifers of Upper Awash Basin, central Ethiopia. Linear and logarithmic regression functions have been performed and it is found that the logarithmic relationship predicting transmissivity from specific capacity data has a better correlation (R = 0.97) than the linear relationship (R = 0.79). The two parameters are log-normally distributed, in which the logarithmic relation is also better statistically justified than the linear relation. Geostatistical estimations of the transmissivity were made using different inputs and methods. Measured and supplemented transmissivity data obtained from estimates using the derived empirical relation were krigged and cokrigged, spherical and exponential models were fitted to the experimental variograms. The cross-validation results showed that the best estimation is provided using the kriging procedure, the transmissivity field represented by the measured transmissivity data and the experimental variogram fitted with the exponential model. Based on the geostatistical approach, the transmissivity map of the aquifer is produced, which will be used for groundwater flow modeling of the study area that will follow this analysis.     

Multi-scale aquifer characterization and groundwater flow model parameterization using direct push technologies

Direct push (DP) technologies are typically used for cost-effective geotechnical characterization of unconsolidated soils and sediments. In more recent developments, DP technologies have been used for efficient hydraulic conductivity (K) characterization along vertical profiles with sampling resolutions of up to a few centimetres. Until date, however, only a limited number of studies document high-resolution in situ DP data for three-dimensional conceptual hydrogeological model development and groundwater flow model parameterization. This study demonstrates how DP technologies improve building of a conceptual hydrogeological model. We further evaluate the degree to which the DP-derived hydrogeological parameter K, measured across different spatial scales, improves performance of a regional groundwater flow model. The study area covers an area of ~60 km² with two overlying, mainly unconsolidated sand aquifers separated by a 5–7 m thick highly heterogeneous clay layer (in north-eastern Belgium). The hydrostratigraphy was obtained from an analysis of cored boreholes and about 265 cone penetration tests (CPTs). The hydrogeological parameter K was derived from a combined analysis of core and CPT data and also from hydraulic direct push tests. A total of 50 three-dimensional realizations of K were generated using a non-stationary multivariate geostatistical approach. To preserve the measured K values in the stochastic realizations, the groundwater model K realizations were conditioned on the borehole and direct push data. Optimization was performed to select the best performing model parameterization out of the 50 realizations. This model outperformed a previously developed reference model with homogeneous K fields for all hydrogeological layers. Comparison of particle tracking simulations, based either on the optimal heterogeneous or reference homogeneous groundwater model flow fields, demonstrate the impact DP-derived subsurface heterogeneity in K can have on groundwater flow and solute transport. We demonstrated that DP technologies, especially when calibrated with site-specific data, provide high-resolution 3D subsurface data for building more reliable conceptual models and increasing groundwater flow model performance.     

大型抽水试验的水文地质意义

本文以山东省东阿县下马头水源地为实例,探讨了大型抽水试验的主要水文地质意义,包括:确定地下水的主要补给来源及方向,抽水影响范围及程度,水源地岩溶含水层的富水性及供水保证能力,水源地附近地下水与地表水之间的水力联系,水源地附近主要断裂构造的水力性质,水源地抽水对下游水源地的影响以及水文地质参数与水源地地下水允许开采量计算。     

基于AquiferTest的抽水试验参数计算方法分析

抽水试验是水文地质勘查中最常用的水文地质试验,通过抽水试验,可准确计算水文地质参数。本文根据在河南豫东地区进行的抽水试验,分别用AquiferTest软件计算抽水试验参数和人工求参,进而进行对比分析得出:传统的人工求参,计算结果较为准确,可靠,但因人而异,有不唯一性;用AquiferTest软件计算抽水试验参数,规范、可比性好。本文最后还对参数取值问题进行了分析对比。     

Complementary use of tracer and pumping tests to characterize a heterogeneous channelized aquifer system in New Zealand

The combined use of pumping and tracer test data enabled the derivation of equivalent average hydraulic conductivities (K_avg) for each test in a heterogeneous channelized alluvial aquifer, whereas K values of the preferential flow paths were two orders of magnitude higher. Greater and earlier drawdown was generally observed along preferential flow lines in a pumping test, within an array of 21 wells. The study aim was to characterize hydraulic properties of a channelized aquifer system in New Zealand by combining tracer and pumping test data. Estimates were able to be made of the percentage of highly permeable channels within the profile (～1.2%), effective porosity that reflected the maximum fraction of highly permeable channels within the aquifer (?_eff–pc ～0.0038), and flows through highly permeable channels (～98%) and the sandy gravel matrix material (～2%). Using ?_eff–pc, a tracer test K_avg value (～93 m/day) was estimated that was equivalent to pumping test values (～100 m/day), but two orders of magnitude smaller than K calculated solely from transport through permeable channels (K_pc ～8,400 m/day). Derived K values of permeable and matrix material were similar to values derived from grain size distribution using the Kozeny-Carman equation.     

单井稳定流抽水试验中水位恢复曲线的作用分析

单井稳定流抽水试验是目前煤炭勘探中获取水文地质参数、查明水文地质条件的主要方法之一。由于其获取的水文地质参数相对于非稳定流抽水试验简单直接而被广泛应用,但所计算的含水层渗透系数比实际往往偏小,且易忽视对水位恢复资料的分析研究与利用。通过对安徽淮南、淮北煤田近10年来水文地质勘探单孔稳定流抽水试验资料的分析与研究,论述了单井稳定流抽水参数计算的过程和存在的不足,强调了绘制水位恢复曲线的作用,提出了单井稳定流抽水渗透系数计算结果的采用方法和建议。进而使井田水文地质条件评价、矿井涌水量预测更加客观、真实。     

The bailer test: a simple effective pumping test for assessing borehole success

A new pumping test method has been designed around the practical requirements of those working in rural water-supply projects in developing countries. The bailer test needs only simple equipment and can be completed in under 1 h. The test involves removing 20–50 bails from a borehole over a 10-min period and then measuring the recovery. The test is analysed using large-diameter-well analysis (which accounts for well storage) and is appropriate for testing low productivity aquifers (transmissivity 0.1–10 m² d^–1), where water levels are shallow (<20 m depth). The bailer test was developed and trialled in a rural water supply project in Nigeria where it was found to predict similar transmissivity to 5-h constant rate tests (r²=0.9). Analysis of the test was further simplified to provide guidelines for field staff such as community health workers. The likelihood of a borehole sustaining a handpump for 250 people can be indicated by measuring the maximum drawdown and time for 50 and 75% recovery from a bailer test and comparing to a simple table. This simplified test is now being used in this and other rural water-supply projects, and has been modified to indicate whether a borehole can sustain higher yields for small-scale irrigation.     

基于实测埋深与开采量的抽水试验参数拟合

抽水试验是确定含水层参数及了解水文地质条件的一项重要方法,采用非稳定流直线图解法和水位恢复法对某水源地的抽水试验资料进行分析计算,根据水源地运行后的水位以及出水量资料来分析确定其水文地质参数。     

基于多源数据的弱透水层水文地质参数反演研究

弱透水层是含水层系统的重要组成部分,其水文地质参数的准确获取一直以来都是研究难点,传统室内试验难以克服应力状态及环境变化对土层参数的影响,因此如何在原位状态下评价其水文地质参数有着重要意义。选取呼和浩特盆地某淤泥层为研究对象,基于抽水试验和溶质运移试验获得的多源数据,采用基于控制体积有限差分法的非结构化网格（Unstructured Grid）方法,建立三维地下水流-溶质运移耦合模型,对弱透水层水文地质参数进行反演。结果显示:模型计算的抽水井中水位和溶质浓度变化规律与实际观测数据能够较好拟合,模型识别出的抽水含水层渗透参数（4.8 m/d）与通过解析法计算得出的结果（4.17 m/d）相近,建立的数值模型符合实际水文地质条件;反演得到淤泥质弱透水层垂向渗透系数为1.2×10?4 m/d、储水率为1.0×10?5 m?1。基于多源数据的参数反演方法可为弱透水层参数研究提供借鉴。