A Simple, Low-Cost Method to Monitor Duration of Ground Water Pumping

Monitoring ground water withdrawals for agriculture is a difficult task, while agricultural development leads frequently to overexploitation of the aquifers. To fix the problem, sustainable management is required based on the knowledge of water uses. This paper introduces a simple and inexpensive direct method to determine the duration of pumping of a well by measuring the temperature of its water outlet pipe. A pumping phase is characterized by a steady temperature value close to ground water temperature. The method involves recording the temperature of the outlet pipe and identifying the different stages of pumping. It is based on the use of the low-cost and small-size Thermochron iButton temperature logger and can be applied to any well, provided that a water outlet pipe is accessible. The temperature time series are analyzed to determine the duration of pumping through manual and automatic posttreatments. The method was tested and applied in South India for irrigation wells using electricity-powered pumps. The duration of pumping obtained by the iButton method is fully consistent with the duration of power supply (1.5% difference).     

A simple correction for slug tests in small-diameter wells

A simple procedure is presented for correcting hydraulic conductivity (K) estimates obtained from slug tests performed in small-diameter installations screened in highly permeable aquifers. Previously reported discrepancies between results from slug tests in small-diameter installations and those from tests in nearby larger-diameter wells are primarily a product of frictional losses within the small-diameter pipe. These frictional losses are readily incorporated into existing models for slug tests in high-K aquifers, which then serve as the basis of a straightforward procedure for correcting previously obtained K estimates. A demonstration of the proposed procedure using data from a series of slug tests performed in a controlled field setting confirms the validity of the approach. The results of this demonstration also reveal the detailed view of spatial variations in K that can be obtained using slug tests in small-diameter installations.     

Innovative Sampling Techniques for Ground Water Monitoring at Hazardous Waste Sites

The authors have recently used several innovative sampling techniques for ground water monitoring at hazardous waste sites. Two of these techniques were used for the first time on the Biscayne Aquifer Super-fund Project in Miami, Florida. This is the largest sampling program conducted so far under the U.S. Environmental Protection Agency (EPA) Superfund Program.
One sampling technique involved the use of the new ISCO Model 2600 submersible portable well sampling pump. A compressed air source forces water from the well into the pump casing and then delivers it to the surface (through a pulsating action). This pump was used in wells that could not be sampled with surface lift devices.
Another sampling technique involved the use of a Teflon manifold sampling device. The manifold is inserted into the top of the sampling bottle and a peristaltic pump creates a vacuum to draw the water sample from the well into the bottle. The major advantage of using this sampling technique for ground water monitoring at hazardous waste sites is the direct delivery of the water sample into the collection container. In this manner, the potential for contamination is reduced because, prior to delivery to the sample container, the sample contacts only the Teflon, which is well-known for its inert properties.
Quality assurance results from the Superfund project indicate that these sampling techniques are successful in reducing cross-contamination between monitoring wells. Analysis of field blanks using organic-free water in contact with these sampling devices did not show any concentration at or above the method detection limit for each priority pollutant.     

Electronic acquisition of hydrologic data from intensively instrumented hillslopes

A new concept in recording data from a large network of transducers in the field is described. Each transducer is equipped with an addressable switching unit enabling parallel connection by a single four wire cable and sequential interrogation from a micro-computer controlled data logger. A simple water level transducer suitable for both large stilling wells and piezometers, which returns an audio frequency signal with pulse width proportional to water level, is described. The use of audio frequency signals enables telephone grade circuits to be used and avoids many of the problems associated with direct current signals, whether current or voltage, commonly used at present. A field installation of 30 piezometers, a tipping bucket raingauge, a weir-stage recorder and logger controlled water sampler is described and examples given of the data collected from a single piezometer transect during a major storm event.     

Monitoring Well Completion Evaluation with Borehole Geophysical Density Logging

Grout continuity and the location of the bentonite seal and sand pack in PVC-cased monitoring wells can be evaluated with cased-hole geophysical density logs. This method relies upon density contrasts among various completion conditions and annular materials. Notably, the lack of annular material behind pipe (i.e., void space) creates a low-density zone that is readily detected by borehole density measurements.
Acoustic cement bond logging has typically been applied to the evaluation of cement in the annular space of completed oil and gas production wells, and in some cases to ground water monitoring wells. These logs, however, can only be obtained in the fluid-filled portion of the borehole, and their interpretation is severely hindered by the presence of the micro-annulus between casing and cement. The influence of the micro-annulus on cement bond logs can be mitigated in steel-cased wells by pressurizing the wellbore during acquisition of the log, but this procedure is not feasible in PVC-cased monitoring wells. The micro-annulus does not affect cased-hole density logs or their interpretation.
Empirical measurements made in the laboratory with density probes provide information on their depths of investigation and response to specific completion conditions. These empirical data, and general knowledge of the density of annular completion materials (sand, bentonite, cement), are used to support interpretations of cased-hole density logs acquired in the field. Three field examples demonstrate the applicability of geophysical density logs to the evaluation of PVC-cased monitoring well completions.     

Monitoring well interception with fractures in clayey till

When using monitoring wells for investigation of contaminant sources in clayey till, there is a high risk that fractures may cause mobile contaminants to bypass the monitoring wells. This paper indicates that the probability of interception between monitoring wells and hydraulic conductive fractures is often significantly less than 50%. Based on a field experiment and application of a calibrated discrete fracture matrix diffusion numerical model (FRAC3Dvs), the paper also evaluates pesticide-monitoring results for different positions of monitoring well screen relative to fractures. For well screens situated 0.25 and 2 m from a conductive fracture, the first concentrations of the pesticide metabolite (2,6 dichlorobenzamide, "BAM") would be measured two years and 18 years, respectively, after the contaminant had been transported into an underlying aquifer. In this way, underlying aquifers may be subjected to contamination by downward moving contamination without being observed in monitoring wells in the till.     

Data-Worth Assessment for a Three-Dimensional Optimal Design in Nonlinear Groundwater Systems

Groundwater model predictions are often uncertain due to inherent uncertainties in model input data. Monitored field data are commonly used to assess the performance of a model and reduce its prediction uncertainty. Given the high cost of data collection, it is imperative to identify the minimum number of required observation wells and to define the optimal locations of sampling points in space and depth. This study proposes a design methodology to optimize the number and location of additional observation wells that will effectively measure multiple hydrogeological parameters at different depths. For this purpose, we incorporated Bayesian model averaging and genetic algorithms into a linear data-worth analysis in order to conduct a three-dimensional location search for new sampling locations. We evaluated the methodology by applying it along a heterogeneous coastal aquifer with limited hydrogeological data that is experiencing salt water intrusion (SWI). The aim of the model was to identify the best locations for sampling head and salinity data, while reducing uncertainty when predicting multiple variables of SWI. The resulting optimal locations for new observation wells varied with the defined design constraints. The optimal design (OD) depended on the ratio of the start-up cost of the monitoring program and the installation cost of the first observation well. The proposed methodology can contribute toward reducing the uncertainties associated with predicting multiple variables in a groundwater system.     

How informative are stream level observations in different geographic regions?

Simple runoff models with a low number of model parameters are generally able to simulate catchment runoff reasonably well, but they rely on model calibration, which makes their use in ungauged basins challenging. In a previous study it has been shown that a limited number of streamflow measurements can be quite informative for constraining runoff models. In practice, however, instead of performing such repeated flow measurements, it might be easier to install a stream level logger. Here, a dataset of 600+ gauged basins in the USA was used to study how well models perform when only stream level data, rather than streamflow data, are available. A runoff model (the HBV model) was calibrated assuming that only stream level observations were available, and the simulations were evaluated on the full observed streamflow record. The results indicate that stream level data alone can already provide surprisingly good model simulation results in humid catchments, whereas in arid catchments some form of quantitative information (e.g. a streamflow observation or a regional average value) is needed to obtain good results. These results are encouraging for hydrological observations in data scarce regions as level observations are much easier to obtain than streamflow measurements. Based on runoff modelling, it might even be possible to derive streamflow time series from the level data obtained from loggers, satellites or community‐based approaches. Copyright © 2016 John Wiley & Sons, Ltd.     

Design, Installation, and Uses of Combination Ground Water and Gas Sampling Wells

Waste disposal sites with volatile organic compounds (VOCs) frequently contain contaminants that are present in both the ground water and vadose zone. Vertical sampling is useful where transport of VOCs in the vadose zone may effect ground water and where steep vertical gradients in chemical concentrations are anticipated. Designs for combination ground water and gas sampling wells place the tubing inside the casing with the sample port penetrating the casing for sampling. This physically interferes with pump or sampler placement. This paper describes a well design that combines a ground water well with gas sampling ports by attaching the gas sampling tubing and ports to the exterior of the casing. Placement of the tubing on the exterior of the casing allows exact definition of gas port depth, reduces physical interference between the various monitoring equipment, and allows simultaneous remediation and monitoring in a single well. The usefulness and versatility of this design was demonstrated at the Idaho National Engineering and Environmental Laboratory (INEEL) with the installation of seven wells with 53 gas ports, in a geologic formation consisting of deep basalt with sedimentary interbeds at depths from 7.2 to 178 m below land surface. The INEEL combination well design is easy to construct, install, and operate.     

Instrumentation Design and Installation for Monitoring Air Injection Ground Water Remediation Technologies

An in situ instrumentation bundle was designed for inclusion in monitoring wells that were installed at the Wasatch Trailer Sales site in Layton, Utah, to evaluate in situ air sparging (IAS) and in-well aeration (IWA). Sensors for the bundle were selected based on laboratory evaluation of accuracy and precision, as well as consideration of size and cost. SenSym pressure transducers, Campbell Scientific Inc. (CSI) T-type thermocouples, and dissolved oxygen (DO) probes manufactured by Technalithics Inc. (Waco, Texas), were selected for each of the 27 saturated zone bundles. Each saturated zone bundle also included a stirring blade to mix water near the DO probe. A Figaro oxygen sensor was included in the vadose zone bundle. The monitoring wells were installed by direct push technique to minimize soil disruption and to ensure intimate contact between the 18 inch (46 cm) long screens and the soil. A data acquisition system, comprised of a CSI 21X data logger and four CSI AM416 multiplexers, was used to control the stirring blades and record signals from more than 70 in situ sensors. The instrumentation performed well during evaluation of IAS and IWA at the site. However, the SenSym pressure transducers were not adequately temperature compensated and will need to be replaced.     

The Hydropunch™: An In Situ Sampling Tool for Collecting Ground Water from Unconsolidated Sediments

The Hydropunch™ is a stainless steel and Teflon® sampling tool that is capable of collecting a representative ground water sample without requiring the installation of a ground water monitoring well. To collect a sample, the Hydropunch (Patent #4669554) is connected to a small-diameter drive pipe and either driven or pushed hydraulically to the desired sampling depth. As the tool is advanced, it remains in the closed position, which prevents soil or water from entering the Hydropunch. Once the desired sampling depth is obtained, the tool is opened to the aquifer by pulling up the drive pipe approximately 1.5 feet (0.46m). In the open position, ground water can flow freely into the sample chamber of the tool. When the sample chamber is full, the Hydropunch is pulled to the surface. As the tool is retracted, check valves close and trap the ground water in the sample chamber. At the surface the sample is transferred from the Hydropunch to an appropriate sample container. The tool is a fast, inexpensive alternative for collecting ground water samples from a discrete interval. It is excellent for vertical profiling or defining the areal extent of a contaminant plume.     

A New Multilevel Ground Water Monitoring System Using Multichannel Tubing

A new multilevel ground water monitoring system has been developed that uses custom-extruded flexible 1.6-inch (4.1 cm) outside-diameter (O.D.) multichannel HOPE tubing (referred to as Continuous Multichannel Tubing or CMT) to monitor as many as seven discrete zones within a single borehole in either unconsolidated sediments or bedrock. Prior to inserting the tubing in the borehole, ports are created that allow ground water to enter six outer pie-shaped channels (nominal diameter = 0.5 inch [1.3 cm]) and a central hexagonal center channel (nominal diameter = 0.4 inch [1 cm]) at different depths, facilitating the measurement of depth-discrete piezometric heads and the collection of depth-discrete ground water samples. Sand packs and annular seals between the various monitored zones can be installed using conventional tremie methods. Alternatively, bentonite packers and prepacked sand packs have been developed that are attached to the tubing at the ground surface, facilitating precise positioning of annular seals and sand packs. Inflatable rubber packers for permanent or temporary installations in bedrock aquifers are currently undergoing site trials. Hydraulic heads are measured with conventional water-level meters or electronic pressure transducers to generate vertical profiles of hydraulic head. Ground water samples are collected using peristaltic pumps, small-diameter bailers, inertial lift pumps, or small-diameter canister samplers. For monitoring hydrophobic organic compounds, the CMT tubing is susceptible to both positive and negative biases caused by sorption, desorption, and diffusion. These biases can be minimized by: (1) purging the channels prior to sampling, (2) collecting samples from separate 0.25-inch (0.64 cm) O.D. Teflon sampling tubing inserted to the bottom of each sampling channel, or (3) collecting the samples downhole using sampling devices positioned next to the intake ports. More than 1000 CMT multilevel wells have been installed in North America and Europe to depths up to 260 feet (79 m) below ground surface. These wells have been installed in boreholes created in unconsolidated sediments and bedrock using a wide range of drilling equipment, including sonic, air rotary, diamond-bit coring, hollow-stem auger, and direct push. This paper presents a discussion of three field trials of the system, demonstrating its versatility and illustrating the type of depth-discrete data that can be collected with the system.     

地震地下流体井水位、水温观测数据集

地震地下流体井水位、水温观测是地震地球物理台网主要观测手段,其数据集包含水位、水温测项的原始数据、预处理数据、产品数据和均值类数据,可为地震监测预报研究提供重要的数据支撑,用于前兆异常、同震响应、区域应力变化特征、含水层参数反演、观测机理等研究。地下流体井水位、水温数据集不仅可为地震预测预报和科学研究提供服务,而且在国民经济建设领域具有重要的应用价值。     

Monitoring strategies at phreatic wellfields: a 3D travel time approach

Ground water quality networks for monitoring phreatic drinking water wellfields are generally established for two main purposes: (1) the short-term safeguarding of public water supply and (2) signaling and predicting future quality changes in the extracted ground water. Six monitoring configurations with different well locations and different screen depths and lengths were evaluated using a numerical model of the 3D ground water flow toward a partially penetrating pumping well in a phreatic aquifer. Travel times and breakthrough curves for observation and pumping wells were used to judge the effectiveness of different design configurations for three monitoring objectives: (1) early warning; (2) prediction of future quality changes; and (3) evaluation of protection measures inside a protection zone. Effectiveness was tested for scenarios with advective transport, first-order degradation, and linear sorption. It is shown that the location and especially the depth of the observation wells should be carefully chosen, taking into account the residence time from the surface to the observation well, the residual transit times to the extraction well, and the transformation and retardation rates. Shallow monitoring was most functional for a variety of objectives and conditions. The larger the degradation rates or retardation, the shallower should the monitoring be for effective early warning and prediction of future ground water quality. The general approach followed in the current study is applicable for many geohydrological situations, tuning specific monitoring objectives with residence times and residual transit times obtained from a site-specific ground water flow model.     

Field and synthetic experiments for virtual source crosswell tomography in vertical wells: Perth Basin,Western Australia

It is common for at least one monitoring well to be located proximally to a production well. This presents the possibility of applying crosswell technologies to resolve a range of earth properties between the wells. We present both field and synthetic examples of dual well walk-away vertical seismic profiling in vertical wells and show how the direct arrivals from a virtual source may be used to create velocity images between the wells. The synthetic experiments highlight the potential of virtual source crosswell tomography where large numbers of closely spaced receivers can be deployed in multiple wells. The field experiment is completed in two monitoring wells at an aquifer storage and recovery site near Perth, Western Australia. For this site, the crosswell velocity distribution recovered from inversion of travel times between in-hole virtual sources and receivers is highly consistent with what is expected from sonic logging and detailed zero-offset vertical seismic profiling. When compared to conventional walkaway vertical seismic profiling, the only additional effort required to complete dual-well walkaway vertical seismic profiling is the deployment of seismic sensors in the second well. The significant advantage of virtual source crosswell tomography is realised where strong near surface heterogeneity results in large travel time statics.     

京津冀地区井水温度的数字化观测及其地震前兆监测效能的评估

较为系统的分析了北京、 天津、 河北地区井水温度观测现状及年、 月、 日不同层次上的动态特征, 及其在相关的地震前兆监测中发挥效能的可能性做了宏观的评估。 评估结果表明, 74.7%井的水温观测正常运行, 58.6%的井在地震中期或中短期的前兆监测发挥效能, 67.8%的井在地震短期前兆监测发挥效能, 41.2%的井在地震短临前兆监测中有可能发挥一定效能。 文中还提出了进一步发挥井水温度观测监测效能的若干建议。     

基于微震特性的相对震级技术研究及应用

随着非常规气藏的开采开发,微地震监测成为压裂效果评估的关键技术.四川盆地非常规油气藏开采开发处于早期,井网密度极低导致在压裂井附近难以找到匹配深井作为观测井,而地面、浅井等替代观测方式面临无法有效探测微地震信号的风险.微地震事件能量弱和辐射的方向性使得观测方位预判及有效监测距离的评估成为微地震监测成败的关键因素.本文提出一种基于压裂微地震能量辐射模式和地层传播特征的相对震级计算技术,模拟微地震事件能量辐射模式及在地层传播过程中的动力学特征,达到评估微地震相对震级与检波器方位、地层传播距离的非线性关系的目的.通过理论分析和实际微地震监测资料验证,该方法能有效地解决微地震监测最佳观测方位的优选和有效传播距离的评估问题.     

An Inexpensive, Multi-Use, Dedicated Pump for Ground Water Monitoring Wells

A simple, inexpensive sampling pump has lately come into use in ground water monitoring. The pump is referred to as an inertial pump; its only downhole components are a foot valve connected to a length of tubing or pipe. The operating principle of the pump is based on the inertia of a column of water within the riser tubing. Ground water is drawn through the foot valve and up the riser tubing by rapid up and down movements of the tubing. This pumping method is not new, but has only recently been applied to monitoring wells. Foot valves are available in a variety of materials and sizes and can be used in monitoring wells as small as 19mm (3/4 inch) I.D. Flexible polyethylene or Teflon® tubing, and in some cases stainless steel tubing or rigid PVC pipe, is used as the riser. The inertial pump satisfies most of the criteria normally cited for an "ideal" sampling device. The pump is easy to operate, reliable, durable, portable, and virtually maintenance-free. It can be operated manually from as deep as 40m or from as deep as 60m using a motor drive. The pump is inexpensive, and therefore suitable for use as a dedicated sampling pump. Recent tests have shown the pump to be suitable for sampling volatile organics. The inertial pump has a high flow capacity and performs well in silty/sandy environments, which makes it useful for developing and purging monitoring wells. It may also be used to perform field hydraulic conductivity tests.     

A rapid method for hydraulic profiling in unconsolidated formations

Information on vertical variations in hydraulic conductivity ( K ) can often shed much light on how a contaminant will move in the subsurface. The direct-push injection logger has been developed to rapidly obtain such information in shallow unconsolidated settings. This small-diameter tool consists of a short screen located just behind a drive point. The tool is advanced into the subsurface while water is injected through the screen to keep it clear. Upon reaching a depth at which information about K is desired, advancement ceases and the injection rate and pressure are measured on the land surface. The rate and pressure values are used in a ratio that serves as a proxy for K . A vertical profile of this ratio can be transformed into a K profile through regressions with K estimates determined using other techniques. The viability of the approach was assessed at an extensively studied field site in eastern Germany. The assessment demonstrated that this tool can rapidly identify zones that may serve as conduits for or barriers to contaminant movement.