Groundwater Velocity Research Articles

HydrogeoEstimatorXL: an Excel-based tool for estimating hydraulic gradient magnitude and direction

HydrogeoEstimatorXL is a free software tool for the interpretation of flow systems based on spatial hydrogeological field data from multi-well networks. It runs on the familiar Excel spreadsheet platform. The program accepts well location coordinates and hydraulic head data, and returns an analysis of the area flow system in two dimensions based on (1) a single best fit plane of the potentiometric surface and (2) three-point estimators, i.e., well triplets assumed to bound planar sections of the potentiometric surface. The software produces graphical outputs including histograms of hydraulic gradient magnitude and direction, groundwater velocity (based on a site average hydraulic properties), as well as mapped renditions of the estimator triangles and the velocity vectors associated with them. Within the software, a transect can be defined and the mass discharge of a groundwater contaminant crossing the transect can be estimated. This kind of analysis is helpful in gaining an overview of a site’s hydrogeology, for problem definition, and as a review tool to check the reasonableness of other independent calculations.

Darcy and Apparent Velocities of Groundwater in Phreatic Aquiferous Formations in Kumba– Cameroon: Determined by use of Trigger-Tube Tracer Test Method in Dug Wells

Kumba with a population of about 144,413 people is the capital of Meme Division, in the Southwest region is one of the largest cocoa cash crop producing areas in Cameroon. The inhabitants depend mostly on groundwater through dug wells. It has a hot and humid equatorial climate with annual rainfall 2298-3400 mm and annual temperature 27° C with a short dry season (December to March) and a long rainy season (April to November). There is a need for a good understanding of the hydraulic properties of the aquiferous formations for the planning and management of the groundwater resources of this area. Twenty-one hand-dug wells at different sites in Kumba were tested using sodium chloride (NaCl) as a conservative tracer, by use of the trigger-tube tracer test method. Field estimations of groundwater flow and groundwater velocities in the phreatic aquiferous formation in Kumba through by trigger tube tracer tests gave Darcy velocities ranging from 19.63 m/d at Krammar to 634.13 m/d at Dallas and apparent velocities ranging from 39.26 m/d at Krammar to 1268.27 m/d at Dallas. The trigger tube tracer tests carried out in some dug wells in Kumba reveals significant spatial variations in groundwater velocities and groundwater flow velocities which are relatively poor at Krammar and good at Dallas. The huge spatial variations in groundwater flows and groundwater velocities imply that groundwater flows at different rates, directions, and at different rates in different sections of the phreatic aquiferous formation in Kumba, probably due to spatial variations in permeability and existence fractures acting as groundwater conduits. Areas with low groundwater velocities like Krammar have lower permeabilities compared to those around PS Kumba Town, Dallas and CCAS. This suggests spatial variations in formation types, facies changes (transgressive and regressive), thickness and layering.

Natural Attenuation Capacity Indicators for Groundwater Remediation to the Northeastern Cairo

The natural attenuation capacity of groundwater is considered to be an important factor for remediation purpose, it is also important for surveying suitability in the early phases of siting hazardous facilities. The present work has been devoted to explore the natural attenuation capacity of the groundwater system northeast Cairo. Some indicators (hydrogeological, hydrochemical and isotopic) have been insighted to explore the system retardability against contaminant dispersion. Groundwater flow and contaminant transport have been pointed out using GOD index which varied from 0.04 to 0.28 reflecting high protectability. The isotopic contents (18O, 3H, and 14C) showed a general comply with the GOD index and helped to delineate the sectors of high contaminate attenuation ability. Kelly index inferred significantly high adsorption potential on the aquifer clay content. The calcite and dolomite tend to precipitate on the aquifer contact providing a chance for specific contaminants to coprecipitate. The Eh-pH relation of the studied groundwater samples indicates high oxidation conditions and openness of the system. The attenuation capacity has been determined mathematically, it assumes the dispersive, advective, sorptive, and degradative processes acting on a solute in a one-dimensional flow system. The value of attenuation capacity increases by decreasing groundwater velocity and completely vanishes at a certain high velocity; determined for the relevant radioactive contaminants.

Borehole thermal energy storage systems under the influence of groundwater flow and time-varying surface temperature

A 3D finite element model of circular borehole cluster connected in series is used as a response model to generate normalized transfer functions of a borehole thermal energy storage system under the influence of ground surface temperature variations and groundwater flow. Two response functions are obtained by convolving transfer functions of the system's outlet fluid temperature with two incremental input functions describing the temperature variation of the inlet and outlet fluid and variations of the ground surface temperature. Superposition is applied to obtain the resulting fluid temperature with respect to thermal inputs at the inlet fluid and the ground surface over the course of ten years and results are compared for various groundwater velocities. This work demonstrates that the combined effect of groundwater flow and ambient air temperature variations can significantly decrease the performance of a BTES system. The methodology used can be extended to simulate complex system.

Hydrogeology of conglomerate fractured-rock aquifers: an example from the Portofino's Promontory (Italy)

The Portofino promontory is characterised by springs supplying Camogli, Portofino and Santa Margherita Ligure towns. This research concerns a hydrogeological preliminary study of the Caselle springs, located in the San Fruttuoso valley at 325 m asl.Water circulation occurs in discontinuities of Portofino Conglomerate and has been investigated by scientific studies since the late Nineteenth Century. The flow of Caselle springs has been monitored, while the climatic parameters recorded in the Mount Portofino weather station have allowed a first comparison between rains and outflows.The hydrogeological water balance has allowed assessing a loss due to evapotranspiration of 627 mm and an outflow of 753 mm. The evaluation of the recharge area permitted to calculate outflows between 4 and 13 l/s: adopting an infiltration rate of 0.7, obtained infiltration values are comparable with the measured flow rates. The answer to the rains of hydrogeological parameters shows a ground-water velocity of 10-6 m/s; protecting the aquifer from potential sources of pollution is therefore deemed as essential, taking into account that over 80,000 hikers per year walk upon the recharge area.

Determination of aquifer hydrodynamic parameters: a key tool for the design of an Open-loop Groundwater Heat Pump System

Open-loop groundwater geothermal heat pumps (GWHP) represent an interesting technology that is expected to contribute significantly to the reduction of primary energy use for buildings heating and cooling needs especially in urban context. In the GWHP's design phases the geological and hydrogeological parameters must be accurately determined in order to maximize efficiency and minimize installation costs.Physical properties of the aquifer such as the porosity and the thermal parameters of the aquifer framework have been usually obtained through field and laboratory geotechnical testing. Hydrogeological and hydraulic parameters of the exploited aquifer such as hydraulic conductivity and the storativity are usually obtained through pumping test.As reported in literature, the prevailing component of the heat transfer in the aquifer induced by the water re-injection is related to the advection and therefore the determination of the real field groundwater velocity in transient and steady conditions is fundamental in the modelling of the thermal plume especially in the GWHP plant design phases. To this aim the pumping tests appear to be among the most useful field hydrogeological investigations to be performed in most cases. Such tests can also provide suitable information related to the aquifer productivity (specific discharge rate) and therefore can permit to assess if the GWHP plant requirement can be satisfied in terms of groundwater sustainable withdrawals. A real field pilot plant aimed to supply energy needs to the Architecture Faculty building of the Politecnico di Torino (NW Italy) is presented and discussed.

Impacts of elevated dissolved CO2 on a shallow groundwater system: Reactive transport modeling of a controlled-release field test

One of the risks that CO2 geological sequestration imposes on the environment is the impact of potential CO2/brine leakage on shallow groundwater. The reliability of reactive transport models predicting the response of groundwater to CO2 leakage depends on a thorough understanding of the relevant chemical processes and key parameters affecting dissolved CO2 transport and reaction. Such understanding can be provided by targeted field tests integrated with reactive transport modeling. A controlled-release field experiment was conducted in Mississippi to study the CO2-induced geochemical changes in a shallow sandy aquifer at about 50m depth. The field test involved a dipole system in which the groundwater was pumped from one well, saturated with CO2 at the pressure corresponding to the hydraulic pressure of the aquifer, and then re-injected into the same aquifer using a second well. Groundwater samples were collected for chemical analyses from four monitoring wells before, during and after the dissolved CO2 was injected. In this paper, we present reactive transport models used to interpret the observed changes in metal concentrations in these groundwater samples. A reasonable agreement between simulated and measured concentrations indicates that the chemical response in the aquifer can be interpreted using a conceptual model that encompasses two main features: (a) a fast-reacting but limited pool of reactive minerals that responds quickly to changes in pH and causes a pulse-like concentration change, and (b) a slow-reacting but essentially unlimited mineral pool that yields rising metal concentrations upon decreased groundwater velocities after pumping and injection stopped. During the injection, calcite dissolution and Ca-driven cation exchange reactions contribute to a sharp pulse in concentrations of Ca, Ba, Mg, Mn, K, Li, Na and Sr, whereas desorption reactions control a similar increase in Fe concentrations. After the injection and pumping stops and the groundwater flow rate decreases, the dissolution of relatively slow reacting minerals such as plagioclase drives the rising concentrations of alkali and alkaline earth metals observed at later stages of the test, whereas the dissolution of amorphous iron sulfide causes slowly increasing Fe concentrations.

A Methodological Approach to Assess the Dissolution of Residual LNAPL in Saturated Porous Media and Its Effect on Groundwater Quality: Preliminary Experimental Results

In this paper, we present a simple methodological approach to assess the dissolution behaviour of residual light nonaqueous phase liquid (LNAPL) sources entrapped in saturated porous media and to estimate the actual risk to human health by water ingestion related to their presence in the subsurface. The approach consists of collecting experimental data on the release kinetics through lab-scale column tests and including these data in a modified version of the analytical model used to describe the groundwater ingestion pathway in risk analysis. The approach was applied to different test scenarios using toluene as a model compound and three types of porous media, i.e. glass beads and two sandy soils with slightly different textures. The experimental results showed that the concentration of toluene in the eluted water was far from the solubility value after a limited number of pore volumes. Furthermore, different behaviour was observed for the three types of porous media. In particular, higher residual saturation and a slower dissolution rate were observed for the soil characterized by the finest texture. This behaviour suggests that the release rate is inversely proportional to the total residual saturation due to the reduction in the porosity available for water flow and the permeability of the porous media. Using these data in a modified risk-based model showed that a remarkable reduction of the hazard index related to the water ingestion pathway can be achieved for a relatively high groundwater velocity and a small contamination source.

Quantification of exploitable shallow geothermal energy by using Borehole Heat Exchanger coupled Ground Source Heat Pump systems

In previous studies, the amount of exploitable shallow geothermal energy was estimated by assuming a uniform temperature drop of 2–6°C in the aquifer. In this work, a more comprehensive numerical model has been employed to evaluate the available amount of shallow geothermal energy by using Borehole Heat Exchanger coupled Ground Source Heat Pump systems. Numerical experiments have been performed by simulating the long-term evolution of the subsurface temperature field, which is subject to the operation of borehole heat exchangers and varying parameters like subsurface thermal conductivity and groundwater flow velocity. The concept of equivalent temperature drop is proposed as an auxiliary quantity for the subsurface. With the help of this parameter, a procedure has been established to quantify the amount of shallow geothermal potential. Following this approach, a realistic equivalent temperature reduction is found to be from −1.8 to −4.4°C in the subsurface over a period of 30years. This can be translated to an annual extractable geothermal energy value in a unit surface area, and it ranges from 3.5 to 8.6kWhm−2a−1. The exact value is site specific and heavily depends on the soil thermal conductivity, groundwater velocity, and borehole arrangement.

Shallow subsurface temperature in the environs of El-Nubaria canal, northwestern Nile Delta of Egypt: implications for monitoring groundwater flow system

Borehole temperatures from 47 wells were utilized to comprehend the spatial subsurface thermal regime in the study area. The recharge regions are situated in reclaimed desert lands (southern and southwestern parts) and have high subsurface temperatures, whereas the discharge areas are situated in the old agricultural lands (northern and northeastern parts) and have lower subsurface temperatures. This thermal system is attributed to differences in the surface air temperature where higher values are recorded in the developed desert (Wadi El-Natrun station average annual 23.15 °C) and the lower values in the old agricultural land (Damanhour station average annual 20.37 °C). The geothermal gradient is low in the recharge area (average 0.0198 °C/m) and high in the discharge area (average 0.0343 °C/m). The effect of the irrigation canals as gaining or losing streams on the thermal system decreases gradually and disappears at 90 m below sea level. Two-dimensional groundwater flow and heat transport models were simulated to estimate the vertical groundwater flow velocity and predict the factors controlling the groundwater flow system. Permeability was the most sensitive parameter during the simulation process. The assessed vertical linear groundwater velocities are, up to 3.2 mm/day in the main recharge region toward the southwestern course, up to 2.4 and 2 mm/day under El-Bustan and El-Hager canals, respectively, and up to 1.4 mm/day in the contact between the reclaimed desert and the old agricultural lands. The average vertical linear groundwater discharge velocities are, more than 2.4 mm/day in the southwestern corner, 0.8 and 0.6 mm/day in the northeastern and northern directions, respectively and 1.2 and 2.4 mm/day under El-Nubaria and Ferhash canals, respectively.

Solute dispersion in a semi-infinite aquifer with specified concentration along an arbitrary plane source

Mathematical modeling is carried out to investigate the behavior of solute transport in groundwater with non-point sources of contamination i.e., plane and line sources. Generalized form of plane is considered to study the most general case for non-point sources. Using the hyper-plane concept, the closed-form solution is derived for line sources in two-dimensions as well as the point source in one-dimension as special cases of the general plane source contamination problem. The domain is considered semi-infinite and the velocity of groundwater is in the positive direction of the axes. The three-dimensional advection-dispersion equation (ADE) with non-point source of contamination is solved analytically using the Laplace transform technique. The obtained solution is validated numerically using the finite difference technique. The proposed general solution of the three-dimensional ADE may be of interest to researchers working in surface water and vadose zone hydrology areas as well.

Estimating groundwater velocity using apparent resistivity tomography: A sandbox experiment

The electrical resistivity tomography (ERT) technique can estimate groundwater velocity to within 5% of the pre-set groundwater velocity. The apparent conductivity obtained by the ERT technique is linearly related to the groundwater conductivity, as described by Archie's law. Gaussian-like profiles of the tracer concentration were demonstrated with the ERT technique, and the estimated dispersion coefficient was between 0.0015 and 0.0051 cm2/sec. In terms of monitoring changes in groundwater conductivity, the ERT technique has two major advantages over monitoring wells: (1) it measures a larger area and provides more representative results; and, (2) it does not withdraw groundwater samples, and therefore does not affect the groundwater flow. The objective of this research is to measure groundwater velocity with the ERT technique using only one well. The experiments in this research were divided into two parts. The first part evaluated the accuracy and repeatability of the ERT technique using a dipole-dipole array, and the second part estimated the groundwater velocity in a sandbox using the ERT technique. The length, width, and height of the sandbox, which was made of acrylic, were 1.5, 5, and 1.0 m, respectively. The ERT sandbox was sequentially filled with 5-cm layers of the silica sand to a total height of 70 cm. A total of 32 electrodes spaced every 5-cm were installed in the center of the sandbox. Three monitoring wells were installed along the line of the electrodes. Both no-flow and constant flow (NaCl solution with electrical conductivity and concentration of 5,000 μs/cm and 2.456 g/L, respectively) tracer experiments were conducted.

Sensitivity analyses of the theoretical equations used in point velocity probe (PVP) data interpretation

Point velocity probes (PVPs) are dedicated, relatively low-cost instruments for measuring groundwater speed and direction in non-cohesive, unconsolidated porous media aquifers. They have been used to evaluate groundwater velocity in groundwater treatment zones, glacial outwash aquifers, and within streambanks to assist with the assessment of groundwater-surfaced water exchanges. Empirical evidence of acceptable levels of uncertainty for these applications has come from both laboratory and field trials. This work extends previous assessments of the method by examining the inherent uncertainties arising from the equations used to interpret PVP datasets. PVPs operate by sensing tracer movement on the probe surface, producing apparent velocities from two detectors. Sensitivity equations were developed for the estimation of groundwater speed, v∞, and flow direction, α, as a function of the apparent velocities of water on the probe surface and the α angle itself. The resulting estimations of measurement uncertainty, which are inherent limitations of the method, apply to idealized, homogeneous porous media, which on the local scale of a PVP measurement may be approached. This work does not address experimental sources of error that may arise from the presence of cohesive sediments that prevent collapse around the probe, the effects of centimeter-scale aquifer heterogeneities, or other complications related to borehole integrity or operator error, which could greatly exceed the inherent sources of error. However, the findings reported here have been shown to be in agreement with the previous empirical work. On this basis, properly installed and functioning PVPs should be expected to produce estimates of groundwater speed with uncertainties less than ±15%, with the most accurate values of groundwater speed expected when horizontal flow is incident on the probe surface at about 50° from the active injection port. Directions can be measured with uncertainties less than 15° with the most accurate measurements occurring when the flow angles are relatively low – on the order of 20°. At still lower flow angles, quantitation may suffer due to experimental limitations related to tracer delivery. However, useful qualitative assessments of α may still be possible under these conditions.

Groundwater response to serial stream stage fluctuations in shallow unconfined alluvial aquifers along a regulated stream (West Virginia, USA)

Groundwater response to stream stage fluctuations was studied in two unconfined alluvial aquifers using a year-long time series of stream stages from two pools along a regulated stream in West Virginia, USA. The purpose was to analyze spatial and temporal variations in groundwater/surface-water interaction and to estimate induced infiltration rate and cumulative bank storage during an annual cycle of stream stage fluctuation. A convolution-integral method was used to simulate aquifer head at different distances from the stream caused by stream stage fluctuations and to estimate fluxes across the stream–aquifer boundary. Aquifer diffusivities were estimated by wiggle-matching time and amplitude of modeled response to multiple observed storm events. The peak lag time between observed stream and aquifer stage peaks ranged between 14 and 95 hour. Transient modeled diffusivity ranged from 1,000 to 7,500 m2/day and deviated from the measured and calculated single-peak stage-ratio diffusivity by 14–82 %. Stream stage fluctuation displayed more primary control over groundwater levels than recharge, especially during high-flow periods. Dam operations locally altered groundwater flow paths and velocity. The aquifer is more prone to surface-water control in the upper reaches of the pools where stream stage fluctuations are more pronounced than in the lower reaches. This method could be a useful tool for quick assessment of induced infiltration rate and bank storage related to contamination investigations or well-field management.

Regional aquifer hydrogeochemistry in the confined aquifer system below the Boom Clay (NE Belgium): data analysis and modelling

Abstract Geochemical data from the deep aquifer system below the Boom Clay in NE Belgium have been collected and reinterpreted. The data were obtained between 1980 and 2014 within the framework of radioactive waste disposal studies. Currently, groundwater in the deep aquifer system mainly ranges between NaHCO 3 type and NaCl type. Because of the low groundwater velocity in this aquifer system, re-equilibration with the mineralogical composition of the host formations generally occurs. The main geochemical indicators point out that the current formation waters are a mixture between the original saline marine porewaters and freshwater recharge. SE–NW gradients of increasing ion concentrations are observed and can be explained in agreement with the pattern of natural groundwater flow. Calcite dissolution and cation exchange are still ongoing in this freshening aquifer system. A low sulphate content in the deep aquifer system indicates sulphate reduction associated with organic matter degradation. Inverse modelling along a flow path using PHREEQC generally confirms the reactions that have been derived in the data analysis.

Using radon-222 to study coastal groundwater/surface-water interaction in the Crau coastal aquifer (southeastern France)

Radon has been used to determine groundwater velocity and groundwater discharge into wetlands at the southern downstream boundary of the Crau aquifer, southeastern France. This aquifer constitutes an important high-quality freshwater resource exploited for agriculture, industry and human consumption. An increase in salinity occurs close to the sea, highlighting the need to investigate the water balance and groundwater behavior. Darcy velocity was estimated using radon activities in well waters according to the Hamada "single-well method" (involving comparison with radon in groundwater in the aquifer itself). Measurements done at three depths (7, 15 and 21 m) provided velocity ranging from a few mm/day to more than 20 cm/day, with highest velocities observed at the 15-m depth. Resulting hydraulic conductivities agree with the known geology. Waters showing high radon activity and high salinity were found near the presumed shoreline at 3,000 years BP, highlighting the presence of ancient saltwater. Radon activity has also been measured in canals, rivers and ponds, to trace groundwater discharges and evaluate water balance. A model of the radon spatial evolution explains the observed radon activities. Groundwater discharge to surface water is low in pond waters (4 % of total inputs) but significant in canals (55 l/m(2)/day).

Use of a Three-Dimensional Reactive Solute Transport Model for Evaluation of Bioreactor Placement in Stream Restoration.

A three-dimensional groundwater flow and multispecies reactive transport model was used to strategically design placement of bioreactors in the subsurface to achieve maximum removal of nitrate along restored stream reaches. Two hypothetical stream restoration scenarios were evaluated over stream reaches of 40 and 94 m: a step-pool scenario and a channel re-meandering scenario. For the step-pool scenario, bioreactors were placed at locations where mass fluxes of groundwater and nitrate were highest. Bioreactors installed over 50% of the total channel length of a step-pool scenario (located to intercept maximum groundwater and nitrate mass flux) removed nitrate-N entering the channel at a rate of 36.5 kg N yr (100 g N d), achieving about 65% of the removal of a whole-length bioreactor. Bioreactor placement for the re-meandering scenario was designed using a criterion of either highest nitrate mass flux or highest groundwater flux, but not both, because they did not occur together. Bioreactors installed at maximum nitrate flux locations (53% of the total channel length) on the western bank removed nitrate-N entering the channel at 62.0 kg N yr (170 g N d), achieving 85% of nitrate-N removal of whole-length bioreactors for the re-meandering scenario. Bioreactors installed at maximum groundwater flux locations on the western bank along approximately 40% of the re-meandering channel achieved about 65% of nitrate removal of whole-length bioreactors. Placing bioreactors at maximum nitrate flux locations improved denitrification efficiency. Due to low groundwater velocities, bioreactor nitrate-N removal was found to be nitrate limited for all scenarios.

Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand

The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW=12K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7×10−4Lhr−1m−2) and hydrogen evolution rate constant (1.4 nanomolLhr−1m−2) were independent of nZVI concentration above 10g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H2 evolution was explained by differences in pH and Eh at each nZVI mass loading; PCE reactivity increased when solution Eh decreased, and the H2 evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime.

Investigation on groundwater velocity based on the finite line heat source seepage model

Groundwater seepage can improve the heat transfer performance of borehole ground heat exchanger (BGHE), and the corresponding velocity is the significant parameter which shows the degree of seepage role. The paper presents the mathematical model while groundwater flows through BGHE, and the comparisons between pure conduction and the combined heat transfer including conduction and convection are made. Points are set around borehole to test the temperature response at different time and then the goal functions containing both model results and test results are established. Next, the back calculation method is employed to obtain the value and orientation of velocity and therefore the convection role can be expressed. The reasonable points’ locations along both depth and radial directions are analyzed; the comparisons of points’ temperature responses are made according to the variation of seepage orientation and value. The relativity between points’ locations and velocity value is discussed to make the calculation result acceptable. In addition, a number of trials are made to check the validity of back calculation method. The temperature response curves of points are shown and the characteristics embodied are investigated. Accordingly, the finite line heat source seepage model is significant to realize groundwater velocity.

Point dilution tests to calculate groundwater velocity: an example in a porous aquifer in northeast Italy

ABSTRACTThe point dilution test is a single-well technique for estimating horizontal flow velocity in the aquifer surrounding a well. The test is conducted by introducing a tracer into a well section and monitoring its decreasing concentration over time. When using a salt tracer, the method is easy and inexpensive. Traditionally, the horizontal Darcy velocity is calculated as a function of the rate of dilution and is based on the simple assumption that the decreasing tracer concentration is proportional both to the apparent velocity into the test section and to the Darcy velocity in the aquifer. In this article, an alternative approach to analyse the results of point dilution tests is proposed and verified using data acquired at a test site in the middle Venetian plain, northeast Italy. In this approach, the one-dimensional equilibrium advection–dispersion equation is inverted using the CXTFIT model to estimate the apparent velocity inside the test section. Analysis of the field data obtained by the two approaches shows good agreement between the methods and suggests that it is possible to use the equilibrium advection–dispersion equation to estimate apparent velocity over a wide range of velocities.Editor D. Koutsoyiannis; Associate editor K. Heal