Radial Collector Research Articles

Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

Abstract. This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. Robin boundary conditions are adopted to describe fluxes across the streambeds. The head solution for the point sink is derived by applying the methods of finite integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length, and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow for the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

Hydraulic characterization of laterals as applied to selected radial collector wells at Belgrade groundwater source

The paper examines the possibility of hydraulic characterization of radial well laterals in a manner that does not require prior hydrodynamic analysis by simulating groundwater extraction conditions on a numerical model. The first step of the proposed approach is to assess the groundwater level regime formed in the capture zone when the well is operating, which is indicative of the functional condition of the laterals and the aquifer potential in terms of groundwater availability. Then the efficiency of the laterals is examined through the hydraulic function of the skin zone, depending on its filtration properties. An expression for groundwater flow from the aquifer to the laterals (commonly used to simulate laterals on a hydrodynamic model) is employed to define representative values of the conductance coefficient of the skin zone (as an indicator of colmation), and then applied to several wells at Belgrade Groundwater Source. The present research shows that a conductance coefficient of [Ks/ds]=1.0?10-4 s-1 can be considered as the threshold value in relation to which the effects of colmation of well laterals are exhibited, which is consistent with the results reported by researchers who studied the effect of skin zone conductance on the occurrence and nature of the so-called early drawdown at radial collector wells. In addition to gaining insight into the present condition of the laterals, the proposed approach can be used to study the progress of colmation at different points in time and to quantify the effectiveness of regeneration of laterals.

Updated 'budapest method' for revitalizing radial collector wells and applicability to Belgrade's water supply source

Belgrade's water supply source is faced with the complex issue of halting a continuing decline in radial well capacity. It is possible to counteract the problem by replacing worn-out laterals. Past research has provided a basis for undertaking radial well revitalization activities. One of the questions that remained unanswered was how to overcome structural limitations - shallow emplacement of laterals. In Budapest, an innovative revitalization procedure, applying a modified Ranney method, has been used effectively for about 15 years. The laterals are installed below the bottom of the original well shaft and the screen pipes have bridge-like slots. The possibility of applying this method at Belgrade's water supply source is substantial.

Characteristic groundwater level regimes in the capture zones of radial collector wells and importance of identification (Case study of Belgrade Groundwater Source)

Assessment of the operating modes of radial collector wells reveals that the pumping levels in the well caissons are very low relative to the depth/elevation of the laterals, which is a common occurrence at Belgrade Groundwater Source. As a result, well discharge capacities vary over a broad range and groundwater levels in the capture zones differ even when the rate of discharge is the same. Five characteristic groundwater level regimes are identified and their origin is analyzed using representative wells as examples. The scope and type of background information needed to identify the groundwater level regime are presented and an interpretation approach is proposed for preliminary assessment of the aquifer potential at the well site for providing the needed amount of groundwater.

양식장 용수 추가 확보를 위한 수압파쇄 적용성 평가

Feasibility tests for the hydraulic fracturing were conducted in order to secure additional saline groundwater for irrigating to the land-based aquaculture farm. Two boreholes were placed to the aquaculture farm A and B, respectively. A hydraulic fracturing using single packer was applied to major fracture zones within two boreholes. To identify effects of hydraulic fracturing on securing additional saline groundwater, some selective methods including well logging methods, pumping tests, and groundwater quality analysis were commonly applied to the boreholes before and after the hydraulic fracturing. Enlarging/creating fracture zones, increasing water contents in bedrock near boreholes, and increasing transmissivity were observed after the hydraulic fracturing. Even though the hydraulic fracturing could be an alternative to secure additional saline groundwater to the land-based aquaculture farm, salinity of the groundwater did not meet optimal thresholds for each fingerling in two farms: Fresh submarine groundwater discharge flowed the more into borehole of the farm A that resulted in decreasing a salinity value. Increased saline groundwater quantity in the borehole of the farm B rarely affect to the salinity. Although salinity problem of groundwater limited its direct use for the farms, the mixing with seawater could be effectively used for the fingerlings during the early stage. A horizontal radial collector well placed in the alluvial layer could be an alternative for the farms as well.

Design of filter pack and well screen for the horizontal gallery of radial collector well considering soil distribution in riverside alluvium

Design of filter pack and well screen for the horizontal gallery of radial collector well considering soil distribution in riverside alluvium

Evaluation of impacts of radial arm configurations on performance and efficiency of radial collector wells using a detailed numerical modeling technique

Evaluation of impacts of radial arm configurations on performance and efficiency of radial collector wells using a detailed numerical modeling technique

Hydrodynamic simulation and analysis of groundwater regime as impacted by radial collector wells: A case study of Belgrade's water supply source

The currently prevalent practice in hydrodynamic research is to assess radial wells by constructing a hydrodynamic model. Numerical modeling codes tended to limit the possibility of realistically representing the structural characteristics of a radial well (shaft and laterals), along with the groundwater abstraction mechanism via the known groundwater level within the laterals and the calibrated coefficient of their conductivity. Such limitations were offset by various boundary condition modeling techniques in order to produce a so-called 'representative' depiction of the radial well, which did not fail to affect the results. The objective of the present research is to assess the simulation of radial wells in MODFLOW- USG code, based on a numerical method of finite volumes. One of the radial wells at Belgrade's water supply source was selected for the case study, given that a complex groundwater regime change had been registered within its zone of influence. The results indicate that the method can be applied to simulate virtually all aspects and operational conditions of this type of well, with the highest level of representativeness.

방사형집수정의 수평집수관에서 지질특성과 취수량의 상관관계 분석

본 연구에서는 창원시 강변여과수 개발사업(2단계)에서 얻어진 자료들을 이용하여 대수층의 수리전도도와 방사형집수정의 수평집수관에서 산출되는 유량과의 상관관계를 규명하고자 하였다. 연구지역인 낙동강 중하류 모래자갈층에서 수평적으로 채취한 미고결 퇴적물의 시료를 이용하여 경험식에 의한 수리전도도를 산정하였다. 여러 경험식을 이용하여 연구지역에서 수리전도도를 산정한 결과, Beyer식에 의한 수리전도도가 가장 적합한 것으로 판정되었다. 산정된 수리전도도는 0.083 ~ 0.264 cm/s의 범위, 평균 0.159 cm/s로 나타내고 있어 연구지역의 대수층 특성은 모래자갈층에 투수성이 양호한 것으로 나타났다. 산정된 수리전도도와 실측자료에 의한 스크린 내 지하수의 유입속도 및 유량과의 상관관계를 분석하고자 회귀분석을 실시하였다. 회귀분석 결과, 수리전도도와 지하수의 유입속도 및 유량은 약 72 %의 높은 상관관계를 가지는 것으로 나타났고, 각 변수들 간에 실측자료와의 검증에서도 약 72 %가 일치하는 것으로 분석되어 선형 회귀식은 높은 적합성을 나타내었다. 본 연구의 결과로서 선형 회귀식을 이용하여 수리전도도에 의한 방사형집수정의 수평집수관에서 산출되는 유량의 추정이 가능하고, 연구지역과 유사한 대수층에서 적용이 가능할 것이라고 사료된다. This study was performed to investigate the correlation between hydraulic conductivity and the flow rate of an aquifer, with the flow rate calculated from the laterals of the radial collector well using data obtained by the development project of riverbank filtration (Second Phase) in Changwon City. The hydraulic conductivity was empirically calculated from unconsolidated sediments collected from a sandy gravel layer along the middle-to-downstream sections of the Nakdong River. The Beyer equation produced the most suitable hydraulic conductivity from the various empirical formulas employed. The calculated hydraulic conductivity ranged from 0.083 to 0.264 cm/s, with an average value of 0.159 cm/s, suggesting that the aquifer in the study area possesses a high permeability with a good distribution of sandy gravel. The relationship between the calculated hydraulic conductivity in the aquifer and the entrance velocity into the screen, the flow rate was analyzed through the linear regression analysis. From the result of regression analysis, it showed that the hydraulic conductivity and the entrance velocity into the screen and the flow rate have a linear regression equation having about 72% of the high correlation. The result of verification in the measured data between each variable showed a high suitability from being consistent with the approximately 72% in the linear regression analysis. This study demonstrates that the groundwater flow rate can be estimated within the laterals of the radial collector well using a linear regression equation, if the hydraulic conductivity of the aquifer is known. This methodology could thus be applicable to other aquifers with hydraulic conductivity and permeability parameters similar to those in the present study area.

Aquifer Characteristics of the Intake Wells on Damodar River near Raniganj, West Bengal, India

Since the British period the Damodar River has been the main source of water supply in Raniganj, Asansol and Durgapur area of West Bengal State in India. Afterwards since nineties, the drinking water demand was increasing rapidly with the population rise. There has been a considerable scarcity in water supply especially in summer months. Recently, to augment the water supply situation, considering future demand and population rise, a hydro-geological study has been carried out during dry period at different locations on the river bed. The observation were undertaken in and around the existing pumping area on Damodar river located in the southern part of Raniganj. This research is aimed at assessing the yield test at exploratory bored wells to find out the minimum quantity of water available to design radial collector wells at three different locations with respect to their drawdown, transmissibility and storativity. Secondly, a field method for the mechanical analysis of bore well log material of the study area was attained to determine the material size and the required artificial gravel packing. On the basis of the field study and investigations, data collection, collasion and analysis, this paper has been prepared highlighting the characteristics of the aquifer, the location of the intake wells and yield of the bed.

Evaluation of unconfined aquifer parameters from flow to partially penetrating wells in Tailan River basin, China

Effective evaluation, management and abstraction of groundwater resources of any aquifer require accurate and reliable estimates of its hydraulic parameters. This study, therefore, looks at the determination of hydraulic parameters of an unconfined aquifer using both analytical and numerical approaches. A long-duration pumping test data obtained from an unconfined aquifer system within the Tailan River basin in Xinjiang Autonomous Region in the northwest of China is used, in this study, to investigate the best method for estimating the parameters of the aquifer. The pumping test was conducted by pumping from a radial collector well and measuring the response in nine observation wells; all the wells used in the test were partially penetrating. Using two well-known tools, namely AquiferTest and MODFLOW, as an aid for the analytical and numerical approaches, respectively, the parameters of the aquifer were determined and their outputs compared. The estimated horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific yield for the analytical approach are 38.1–50.30 m/day, 3.02–9.05 m/day and 0.204–0.339, respectively, while the corresponding numerical estimates are 20.50–35.24 m/day, 0.10–3.40 m/day, and 0.27–0.31, respectively. Comparing the two, the numerical estimates were found to be more representative of the aquifer in the study area since it simulated the groundwater flow conditions of the pumping test in the aquifer system better than the analytical solution.

Simulation of horizontal well performance using Visual MODFLOW

A proposed horizontal well or radial collector well installation in shallow aquifers to enhance water withdrawal rates in Pintu Geng well field in Kelantan, Malaysia was simulated using the Drainage Package of MODFLOW groundwater model. The modelling exercise aimed at identifying an optimum pumping rate that would safely achieve the desired drawdown of less than 2 m in an area of 300 m radius surrounding the Pintu Geng horizontal collector well. The model also would serve as a basis for the design of the horizontal well components. High degree of grid refinement for the well location is needed to simulate the real field installation. However, for the purpose of designing water withdrawal systems, it is important to obtain the correct production rate of these wells for a given drawdown. A transient groundwater flow model was calibrated and validated with few assumptions of the horizontal well hydraulic properties. The model demonstrates that under natural flow condition at −3 m depth, the six collectors (drains) tap a volume of 19,200–43,700 m3/day. A steady-state model was also developed to predict the capture zone delineation. Attention is also given to the impact of the well installation to the surrounding 300 m radius by inspecting the degree of the drawdown.

Milojevic 경험식을 활용한 주요 국가하천 유역에서 방사형집수정의 강변여과수 취수가능량 평가

The pumping capacity of riverbank filtration using radial collector wells at the Geum, Yeongsan, Seomjin, and Nakdong rivers was evaluated using Milojevic's equation. Assessment of the radial collector wells' pumping capacity in riverbank filtration was carried out using a case study in which one set of collector wells is installed in the watershed of each river. Nakdong River was evaluated to have the highest pumping capacity for riverbank filtration. The areas capable of producing over 10,000 <TEX>$m^3$</TEX> per day were found mostly in the Nakdong River.

An analytical solution for a radial collector well near a stream with a low-permeability streambed

Summary Radial collector wells are often constructed near a stream to obtain more water and produce smaller drawdown in comparison with traditional vertical wells. This paper aims at developing a mathematical model for describing head distributions induced by pumping in a radial collector well near a stream in an unconfined aquifer. A low permeable streambed between the stream and the aquifer is considered. The first-order free surface equation is used to describe the movement of water table. A point-sink solution of the model is developed first by a general transform combining Fourier sine and cosine transforms and then by Fourier transform and Laplace transform. The transient solution of head distributions for different well types such as the horizontal well or radial collector well can be obtained by integrating the point-sink solution along the well. Based on Darcy’s law and the developed solution, an equation for temporal stream depletion rate describing filtration from the stream is then obtained. The steady-state solutions for filtration can be obtained from the transient solution when neglecting the exponential term associated with time. It is found that steady-state filtration depends only on the ratio of streambed permeability over aquifer permeability. Steady-state filtration equals water extraction from a well when the ratio is larger than 10−2. The streambed is regarded as completely impermeable when the ratio is less than 10−7. Additionally, the lowest water table happens near the well before occurrence of filtration. The lowest water table moves landward and away from the well after filtration occurs.

Interpretation of Pumping Test with Radial Collector Well Using a Reservoir Model

AbstractThis study proposes a reservoir model for evaluation of aquifer parameters from a long duration pumping test conducted with a radial collector pumping well and nine observation wells in an unconfined aquifer in the Tailan River basin of China. The proposed model, based on the concept of double continuum, was used to conceptualize the pumping test site into conduit and porous reservoirs coupled by a linear flow exchange for simulating flow during the pumping test. The set of model equations developed from the concept were solved by an iterative method. The model-simulated hydraulic heads agree reasonably well with the observation heads in both the pumping and observation wells at an average normalized root mean square error of 10.99 and 8.06%, respectively, during pumping but were weaker in the recovery period. This notwithstanding, the specific yield estimates compare well with the range obtained for a numerical modeling of the entire aquifer basin. Significantly, the model was applied successfull...

Hydraulic analysis of a radial collector well for riverbank filtration near Nakdong River, South Korea

A radial collector well is used for the extraction of a large amount of groundwater without causing a deep drawdown at the well’s center, and it is appropriate for the supply of municipal water through riverbank filtration (RBF). Flow path changes caused by water extraction through a radial collector well were simulated to estimate the amount of river water induction at a RBF site associated with Nakdong River in South Korea. The structure of the screened horizontal arms of a radial collector well was examined with respect to effective riverbank filtration. The relative ratio of the river water induced to the radial collector well compared to the total groundwater extraction was estimated to be 27–52%. The amount of induced river water varies with the distance of a horizontal arm from the river, indicating that the location and structure of the collector well is significant for RBF. In all simulation cases, the maximum drawdown of the groundwater level near the collector well was 2.1 m, which is not significant considering the substantial pumping rate at the study site. It was concluded that RBF radial collector wells can be used at the study site for a sustainable water supply.

Groundwater abstraction through river-bed collector well: a case study based on geophysical and hydrological investigation

Owing to lack of rational basis, design of radial collector (RC) well often becomes a confusing task for the designers arising out of a wide difference between the anticipated yield and the observed yield from RC wells. In this study, a long-term pumping test was carried out at three different sites (near Kharagpur City, India) on Kasai river bed and in its close proximity in order to design sub-surface RC well for water supply to Kharagpur City. The appropriate hydrological approaches were employed to estimate values of aquifer parameters, viz. storage coefficient (S) and coefficient of transmissibility (T) for the aforesaid sites under study, which were found to be in the ranges of 0.00129–0.068 and 810–2573 m3/day-m, respectively. This article reports the rationality of design methods of sub-surface RC well, based on image theory and model study, which was adequately supported with geophysical investigations. An RC well-system was designed following the aforesaid two methods and was constructed at the proposed Site-II, which was found to be the most favourable one based on remote sensing survey, geophysical studies, and hydrological investigations. In the trial operating stage of the RC well, commissioned at Site II, the observed yield was compared with the designed (predicted) values. Trial field (yield) test data at Site II showed that the designed yield of 24 million litres per day (MLD) based on model study was closer to field data (21 MLD) than that (8 MLD) obtained based on image theory.

A Modeling Framework for the Design of Collector Wells

We present results of a design study performed for the Saylorville Wellfield in Iowa, which is owned and operated by the Des Moines Water Works. The purpose of this study was to estimate wellfield capacity and provide a preliminary design for two radial collector wells to be constructed in the outwash aquifer along the Des Moines River near Saylorville, Iowa. After a field investigation to characterize the aquifer, regional two-dimensional and local three-dimensional, steady-state groundwater flow modeling was performed to locate and design the wells. This modeling was the foundation for design recommendations based on the relative performance of 12 collector well designs with varying lateral numbers, elevations, screen lengths, and orientations. For each site, alternate designs were evaluated based on model estimates of the capacity, the percent of surface water captured, and the production per unit length of screen. Many of our results are consistent with current design practices based on experience and intuition, but our methods allow for a quantitative approach for comparing alternate designs. Although the results are site-specific, the framework for evaluating the hydraulic design of the Saylorville radial collector wells is broadly applicable and could be used at other riverbank filtration sites. In addition, many of the conclusions from this design study may apply at other sites where construction of radial collector wells is being considered.

Several natural indicators of radial well ageing at the Belgrade Groundwater Source, part 1

Over time, the radial collector wells of the Belgrade Groundwater Source, located in the alluvial sediments of the Sava River, exhibit a decline in discharge and a reduction in operating efficiency due to well ageing. An increase in hydraulic losses at the lateral screens, due to chemical and biochemical clogging, has been identified as the primary cause. Certain hydrogeological, hydrochemical and microbiological parameters reflect the well-ageing process and can, therefore, be considered as its indicators. An indicator-based determination of scale is an important aspect in the selection of appropriate well locations, structural characteristics, and maintenance approaches. Well ageing was studied over a period of 5 years (2005-2009). The objective was to investigate the causes of well ageing. The correlations established between the groundwater redox potential, the total iron concentration in groundwater, the grain-size distribution of the aquifer, and well discharge, are presented in the paper.

A model of seepage field in the tailings dam considering the chemical clogging process

The radial collector well, an important water drainage construction, has been widely applied to the tailings dam. Chemical clogging frequently occurs around the vertical shaft in radial collector well due to enough dissolved oxygen and some heavy metals in groundwater flow of tailings dam. Considering the contribution of water discharge from both vertical shaft and horizontal screen laterals and chemical clogging occurring around vertical shaft well, a new model was developed on the basis of Multi-Node Well (MNW2) package of MODFLOW. Moreover, two cases were calculated by the newly developed model. The results indicate that the model considering chemical clogging occurring around the vertical shaft well is reasonable. Owing to the decrease in hydraulic conductivity caused by chemical clogging, the groundwater level in dam body increases constantly and water discharge of radial collector well declines by 10–15%. For ordinary vertical well, it decreases by 30%. Therefore, chemical clogging occurring around radial collector well can arouse increases of groundwater level, and influence dambody safety.