Estimation Of Hydraulic Properties Research Articles

Disentangling slope‐scale spatial variability of saturated hydraulic conductivity in the black soil region of northeast China using noise‐assisted multivariate empirical mode decomposition

AbstractReliable estimates of saturated hydraulic conductivity (Ks) are usually difficult to obtain, as Ks is regulated by a variety of soil processes acting at different spatial scales that may obscure each other's impacts. We hypothesized that these scale‐specific relationships could be well characterized with the aid of the noise‐assisted multivariate empirical mode decomposition (NA‐MEMD), thereby serving as a solid foundation for an accurate Ks prediction. The objective was to evaluate whether the incorporation of NA‐MEMD could improve the estimation of Ks based on the multiscale associations it unraveled. On a typical slope transect of 860 m in the black soil region of northeast China, Ks, mollic epipedon thickness, bulk density, soil organic carbon content, total (ϕ) and effective porosities (ϕe), and particle size distribution were investigated at every 20 m. Prior to NA‐MEMD, Ks was most strongly correlated with ϕe, and the linear regression models based on ϕe solely were satisfactory for Ks estimation at the scale of investigation. Adding other predictors significantly improved Ks prediction in calibration, but impaired it in validation. Upon decomposition by NA‐MEMD, Ks was found to be significantly associated with each attribute at two scales of oscillation at least. Summing up the estimates of each Ks component derived from the properties at the equivalent oscillation scales, the results outperformed the traditional multiple linear regressions made at the investigation scale, when the same sets of predictors were used. The application of NA‐MEMD, moreover, could save the tedious measurements of ϕe and ϕ. Excluding these two porosity‐related properties, Ks estimates obtained by incorporating NA‐MEMD were statistically similar or even better than those involving them before NA‐MEMD. These findings demonstrate the great potential of NA‐MEMD in untangling scale‐dependent relationships of Ks with various processes and hold important implications for future estimations of Ks and other hydraulic properties in the black soil region of northeast China and similar regions.

Estimation of hydraulic conductivity in a watershed using sparse multi-source data via Gaussian process regression and Bayesian experimental design

Enhanced water management systems depend on accurate estimation of subsurface hydraulic properties. However, geologic formations can vary significantly, so information from a single source (e.g., widely spaced boreholes) is insufficient in characterizing subsurface aquifer properties. Therefore, multiple sources of information are needed to complement the hydrogeology understanding of a region. This study presents a numerical framework in which information from different measurement sources is combined to characterize the 3D random field in a multi-fidelity prediction model. Coupled with the model, a Bayesian experimental design was used to determine the best future sampling locations. The Upper Sangamon watershed in east-central Illinois was selected as the case study site, where the multi-fidelity Gaussian process model was used to estimate the hydraulic conductivity in the region of interest. Multi-source observation data were obtained from electrical resistivity and borehole pumping tests. The accuracy of the model prediction is dependent on the locations and the distribution of both high- and low-fidelity data. Furthermore, the multi-fidelity model was compared with the single-fidelity model. The uncertainties and confidence in the measurements and parameter estimates were quantified and used to design future cycles of data collection to further improve the confidence intervals.

Stage-by-Stage Hydraulic Fracture and Reservoir Characterization through Integration of Post-Fracture Pressure Decay Analysis and the Flowback Diagnostic Fracture Injection Test Method

Summary The post-fracture pressure decay (PFPD) technique is a low-cost method allowing for stage-by-stage hydraulic fracture characterization. The analysis of the PFPD data is complex, with data affected by both hydraulic fracture and reservoir properties. Available analysis methods in the literature are oversimplified; reservoir or fracture properties are often assumed to be constant along the horizontal well, and therefore changes in the trend of pressure decay data are attributed to hydraulic fracture or reservoir properties only. Moreover, methods analogous to those applied to the analysis of conventional diagnostic fracture injection tests (DFITs) are often used and ignore critical mechanisms involved in main-stage hydraulic fracture stimulation. A conceptual numerical simulation study was first conducted herein to understand the key mechanisms involved in main-stage hydraulic fracturing. An analytical model was then developed to account for the dynamic behavior of the hydraulic fracture, leakoff, proppant distribution, multiple fractures, and propped- and unpropped-closure events. The analytical model is cast in the form of a new straightline analysis (SLA) method that provides stage-by-stage estimates of the ratio of unpropped fracture surface area to total fracture surface area. The SLA method was validated against numerical simulation results. Moreover, to account for the variation of reservoir properties along the horizontal well, the PFPD model is integrated with DFIT-flowback (DFIT-FBA) tests, performed at some points along the lateral, to obtain a reliable stage-by-stage hydraulic fracture and reservoir characterization approach. The practical application of the proposed integrated approach was demonstrated using PFPD and DFIT-FBA data from a horizontal well completed in 22 stages in the Montney Formation. The numerical simulation study demonstrated that the use of proppant and injection into multiple clusters (creating multiple fractures) results in multiple closure events. The closure process may start early after the pump-in period at a pressure significantly higher than the minimum in-situ stress. Using DFIT-based analytical models, which ignore the presence of proppant, causes significant errors in hydraulic fracture and reservoir property estimation. The PFPD field data examined herein exhibited a similar pressure trend to the numerical simulation cases. The ratio of unpropped fracture surface area to total fracture surface area was determined stage by stage using the PFPD SLA method, constrained by DFIT-FBA data. Engineers can use this information to optimize the hydraulic fracture stimulation design in real time, optimize the well spacing, and forecast the production. The cost and time advantages of this diagnostic method make this approach very attractive.

Fault Zone Hydraulic Parameter Estimation by Passive Methods Using Natural Forces

AbstractHydrogeological conditions within fracture zones control subsurface fluid, solute, and heat flux and storage. While conventional groundwater methods using induced disturbances often require elaborate and expensive equipment, passive methods that use observed responses of groundwater levels to atmospheric pressure and Earth tides provide the opportunity to estimate hydrogeologic properties without having to conduct field testing. We present estimates of hydraulic properties of a fault‐damage zone embedded within crystalline rock using responses to natural perturbations, and then compare these to estimates obtained using conventional methods. We calculate the skin factor using the exhaustive algorithm to improve the consistency between the tidal and conventional methods and compare it with different barometric‐response methods in the frequency and time domains. For the tidal method, the hydraulic conductivity is 16% larger than the estimate obtained from a conventional aquifer test, the barometric‐response method in the frequency domain is 6% larger, and the inverse, Hvorslev's, CBP, and Valois's methods in the time domain are, respectively, 71%, 72%, and 97% smaller and 624% larger. Estimated fault‐damage zone properties yield a hydraulic diffusivity of D ≈ 3 m2 s−1 and a permeability of k ≈ 4 × 10−13 m2 (0.4 Darcy), which confirms the presence of a highly damaged zone. The combined tidal‐ and barometric‐response methods provide a new and robust approach for understanding and characterizing hydrogeological properties of fault‐damage zones.

Analysis of Multiple Flow/Buildup Tests Including a 5-Year Buildup: Case Study of an Australian Shale Gas Well

Summary Long-term (multiyear) buildup tests conducted for multifractured horizontal wells (MFHWs) completed in shale reservoirs offer the unique opportunity to study and analyze flow-regimes sequences that are not commonly observed with typical buildup test periods. In this study, two buildup periods (including a rarely observed, nearly 5-year buildup), and the preceding extended flow tests, were analyzed for an MFHW completed in an Australian shale gas reservoir within the Beetaloo Basin. The objectives of the analyses were to (a) identify the sequence of flow regimes observed for each test (flow/buildup, F/BU) period; (b) extract estimates of reservoir permeability and hydraulic fracture properties; and (c) study the evolution of these properties with each subsequent test. An MFHW, the Amungee NW-1H, completed in the Velkerri B shale in Australia, was analyzed. Due to a casing deformation and inability to mill out plugs beyond this, most of the flow contribution was from the heel stages of the well. The first F/BU period was conducted from 2016 to 2021 (a nearly 5-year buildup), while the second F/BU was initiated in 2021 (buildup is currently continuing). The extended (>1 month) production tests (EPTs) preceding the buildups were analyzed using rate-transient analysis (RTA) methods [flow-regime identification/straightline /type curve analysis (TCA)] modified for shale gas properties (e.g., desorption), while the buildups were analyzed using classic pressure-transient analysis (PTA) methods. The first (~5-year) buildup period (BU 1) revealed a sequence of bilinear-linear-elliptical-pseudoradial flow followed by a second linear flow period. The first two flow regimes are interpreted to be associated with interfracture flow, while the latter is assumed to correspond to linear flow to the well. Elliptical/radial flow around fractures is rationalized to occur due to interpreted relatively short fracture half-lengths (corresponding to the high-conductivity portion of the fractures). Permeability estimates are in good agreement with diagnostic fracture injection test (DFIT) analysis. Flow-regime interpretations for the other test periods (EPTs 1 and 2, BU 2) are largely consistent, although EPT 1 flow-regime interpretation was challenged by noisy data. Permeability values derived from EPTs 1 and 2 are smaller than from buildup tests, suggesting stress sensitivity caused by drawdown. Properties derived from the analysis of BU 1 and 2 are in good agreement, suggesting that any effects caused by stress sensitivity of reservoir parameters are largely reversible. Permeability derived from all tests are much larger than those obtained from laboratory data, leading to the interpretation that natural fractures are elevating system permeability. Fracture half-lengths are also much shorter than those typically reported for MFHWs. The mostly “textbook” quality well test data obtained for this field example, combined with the length of the test periods, resulted in one of the most complete flow-regime sequences observed for an MFHW completed in a shale gas reservoir. The existence of a radial flow period observed for all test periods (interpreted to be interfracture radial flow) allows for confident estimates of reservoir permeability/skin and their evolution with each subsequent test, which is rarely reported. The radial-flow-derived permeability, combined with early linear flow analysis, also allowed fracture half-length to be estimated for all tests. This case study adds significantly to our understanding of shale gas reservoir characteristics and flow-regime sequences associated with MFHWs.

In situ estimation of soil hydraulic and hydrodispersive properties by inversion of electromagnetic induction measurements and soil hydrological modeling

Abstract. Soil hydraulic and hydrodispersive properties are necessary for modeling water and solute fluxes in agricultural and environmental systems. Despite the major efforts in developing methods (e.g., laboratory-based, pedotransfer functions), their characterization at applicative scales remains an imperative requirement. Accordingly, this paper proposes a noninvasive in situ method integrating electromagnetic induction (EMI) and hydrological modeling to estimate soil hydraulic and transport properties at the plot scale. To this end, we carried out two sequential water infiltration and solute transport experiments and conducted time-lapse EMI surveys using a CMD Mini-Explorer to examine how well this methodology can be used to (i) monitor water content dynamic after irrigation and to estimate the soil hydraulic van Genuchten–Mualem parameters from the water infiltration experiment as well as (ii) to monitor solute concentration and to estimate solute dispersivity from the solute transport experiment. We then compared the results with those estimated by direct time domain reflectometry (TDR) and tensiometer probe measurements. The EMI significantly underestimated the water content distribution observed by TDR, but the water content evolved similarly over time. This introduced two main effects on soil hydraulic properties obtained by the two methods: (i) similar water retention curve shapes, but underestimated saturated water content from the EMI method, resulting in a scaled water retention curve when compared with the TDR method; the EMI-based water retention curve can be scaled by measuring the actual saturated water content at the end of the experiment with TDR probes or by weighing soil samples; (ii) almost overlapping hydraulic conductivity curves, as expected when considering that the shape of the hydraulic conductivity curve primarily reflects changes in water content over time. Nevertheless, EMI-based estimations of soil hydraulic properties and transport properties were found to be fairly accurate in comparison with those obtained from direct TDR measurements and tensiometer probe measurements.

An approximate solution to one-dimensional upward infiltration in soils for a rapid estimation of soil hydraulic properties

• A concise soil water content profile expression was obtained by an analytical method. • An approximate solution was derived for one-dimensional upward infiltration. • A method with a standard ring was proposed to determine BC model parameters. Soil hydraulic properties quantify soil pore structure and are essential input parameters for simulating soil hydrological processes in the vadose zone. Although methods have been proposed to estimate soil hydraulic properties, efficient and applicable ones are still scarce. In this study, we derived an approximate solution for a one-dimensional upward infiltration process with initially uniform soil water content distribution. Founded on our solution, a nonlinearly constrained optimization method was developed to simultaneously estimate the parameters K s and n , h d of the Brooks-Corey model by measuring the upward infiltration process in a 5-cm high soil column. Numerical experiments simulated with Hydrus-1D were performed on six theoretical soils to evaluate the accuracy of the new method. The results indicate that the approximate solution can accurately simulate the upward infiltration process at the low initial soil water content range, with a relative error ( Re ) of 2.85% to 5.47% for soil water content distribution in space and time. For the cumulative infiltration curve, the Re ranges from 0.2% to 1.01%. The estimated parameters K s and n , h d of the Brooks-Corey model are close to the actual parameter values, with a Re of 0.59% to 4.68% for n , 0.00% to 7.91% for h d , and 0.50% to 8.83% for K s , respectively. It is concluded that the new method provides a simple and valuable tool for the accurate estimation of soil hydraulic properties.

Probabilistic Contaminant Source Assessment-Getting the Most Out of Field Measurements.

This paper describes a methodology for undertaking probabilistic investigations into the locations at which contaminants have leaked into a groundwater system. The methodology is built with highly parameterized, stochastic history-matching in mind. It is able to reduce uncertainties associated with estimates of subsurface hydraulic properties at the same time as it reduces uncertainties associated with inferences of contaminant sources. Particles are used to simulate contaminant movement. This reduces simulator execution time while increasing simulator stability. Borehole measurements of groundwater chemistry are endowed with a binary classification that indicates the presence, or otherwise, of a contaminant plume. This classification is transferred to passing particles as a detect or nondetect status awarded to their trajectories. Because this status is continuous with respect to model parameters, the latter can be adjusted in order to ensure that the same trajectory cannot possess both a detect status and a nondetect status. Particle trajectory statuses can be assigned to model cells from which they are released. By calculating cell statistics using a large number of history-match-constrained, stochastic parameter fields, probability maps can be drawn. We illustrate two of these. The first maps the probability that a contaminant sourced at a particular location will go undetected by the current observation network. The second maps the probability that a contaminant source cannot exist at a particular location. The method is extended to examine the worth of supplementing an existing observation network with new wells.

Delineation of the aquifer structure and estimation of hydraulic properties on the flanks of Mount Meru, Northern Tanzania

Understanding of the aquifer structure and its hydraulic properties provides comprehensive knowledge for proper groundwater utilisation and management. This study delineated the aquifer structure using litho-hydrostratigraphical cross-sections, and estimated the hydraulic parameters using single well pumping tests for various locations on and around Mount Meru. Results show that, the aquifer system on the flanks of Mount Meru is a sloping aquifer with sloping beds. On the far east of the eastern flank, the aquifer is composed of debris avalanche deposits, while on the north-eastern and west flanks the aquifer is composed of weathered fractured lava, whereas on the south-western flank, the aquifer is composed of different layers: pyroclastics on the top, weathered fractured lava, weathered pyroclastics, and weathered fractured lava at the bottom. The aquifer is semi-confined on the north-eastern and western flanks; on the north-eastern flank, the overlying debris avalanche deposits acting as an aquitard, while on the western flank, the overlying layers: pyroclastics and unweathered lava acting as an aquitard and aquiclude, respectively. The aquifer is unconfined on the far east of the eastern flank and south-western flank. The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth, while variable, both at the shallow depth of hand-dug wells and the larger depth of boreholes, on the south-western flank; indicating aquifer heterogeneity. On the north-eastern flank, the topmost part of the aquifer, exploited by hand-dug wells, has a low transmissivity (T = 1.3 m2/d) and potential for smaller withdrawals for local water supply with limited consumption, while the upper part of the aquifer, captured by boreholes, has an intermediate transmissivity (T = 35 m2/d) and potential for local water supply, whereas the deeper part of the aquifer has a high transmissivity (T = 788 m2/d) with potential of somewhat regional importance. On the western flank, the aquifer has a very low transmissivity (T = 0.4 m2/d) and potential for local water supply with limited consumption. On the south-western flank, on average, the topmost part of the aquifer, exploited by hand-dug wells, has very low to intermediate transmissivity (range of T: 0.3–21 m2/d), leading to variable potential for smaller withdrawals for local water supply (private consumption), whereas the deeper part of the aquifer, captured by boreholes, has low to intermediate transmissivity (range of T: 9–43 m2/d) and potential for local water supply.

A new application of the upward infiltration method to quantify preferential flow hydraulic conductivity on undisturbed soil cores

Soil water preferential flow, PF, is the phenomenon where water moves along certain pathways, while bypassing a fraction of the porous matrix. This work presents a laboratory procedure to estimate the hydraulic conductivity of the soil water preferential flow, KPF. Using an upward infiltration curve followed by an over-pressure step, KPF is calculated as the difference between the total hydraulic conductivity, KT, measured with the constant head method, and the soil matrix hydraulic conductivity, Ks, calculated from the inverse analysis of the transient upward infiltration curve. Previous to this analysis, a new approach to detect and remove the effect of possible overpressures due to the soil core placement on the sorptivimeter on the hydraulic properties estimate was presented. This consisted on searching the best fitting between the experimental infiltration curve after removing successive early time steps and the corresponding simulated function. The method to estimate KPF was validated on four different 5-cm height soil columns packed with 2-mm sieved clay loam and loam soils traversed longitudinally by a closed/opened pipe of 1.5 mm and 2.5 mm internal diameter, respectively. This same experiment was also repeated on the same soils without artificial preferential channel. Next, the method was applied on 20 undisturbed soil cores collected from two fields with different grazing intensity and soil tillage management (conventional, CT, reduced, RT and no-tillage, NT, practices). Results showed that correction made to remove the infiltration curve jump due to an overpressure step allowed more accurate and realistic estimates of the soil matrix hydraulic properties. On the other hand, both KT and Ks, which could be satisfactorily calculated from a single upward infiltration curve followed by an overpressure step, where satisfactorily employed to quantify KPF. While no significant effect of grazing intensity on KPF was observed, the CT KPF was significantly larger than those obtained in RT and NT.

Functional Evaluation of Digital Soil Hydraulic Property Maps through Comparison of Simulated and Remotely Sensed Maize Canopy Cover

Soil maps can usefully serve in data scarce regions, for example for yield (gap) assessments using a crop simulation model. The soil property estimates’ contribution to inaccuracy and uncertainty can be functionally evaluated by comparing model results using the estimates as input against independent observations. We conducted a functional evaluation of digital maps of soil hydraulic properties of the Zambezi River Basin using a crop growth model AquaCrop. AquaCrop was run, alimented with local meteorological data, and with soil hydraulic properties derived from the digital maps of digital soil mapping (DSM) techniques, as opposed to estimations from the widely used Saxton and Rawls pedotransfer functions. The two simulated time series of canopy cover (CC) (AquaCrop-CC-DSM and AquaCrop-CC-Saxton), which were compared against canopy cover data derived from the remotely sensed Leaf Area Index (LAI) from the MODIS archive (MODIS-CC). A pairwise comparison of the time series resulted in a root mean squared error (RMSE) of 0.07 and a co-efficient of determination (R2) of 0.93 for AquaCrop-CC-DSM versus MODIS-CC, and an RMSE of 0.08 and R2 of 0.88 for AquaCrop-CC-Saxton versus MODIS-CC. In dry years, the AquaCrop-CC-DSM deviated less from the MODIS-CC than the AquaCrop-CC-Saxton (p < 0.001), although this difference was not significant in wet years. The functional evaluation showed that soil hydraulic property estimates based on digital soil mapping outperformed those based on Saxton and Rawls when used for simulating crop growth in dry years in the Zambezi River Basin. This study also shows the value of conducting a functional evaluation of estimated (static) soil hydraulic properties in terms of dynamic model output.

Balancing exploitation and exploration: A novel hybrid global-local optimization strategy for hydrological model calibration

Optimization problems in hydrological modeling are frequently solved using local or global search strategies, which either maximize exploitation or exploration. Thus, the elevated performance of one strategy for one class of problems is often offset by poor performance for another class. To overcome this issue, we propose a hybrid strategy, G-CLPSO, that combines the global search characteristics of the Comprehensive Learning Particle Swarm Optimization (CLPSO) with the exploitation capability of the Marquardt-Levenberg (ML) method and implement it into the hydrological model, HYDRUS. Benchmarks involving optimizing non-separable unimodal and multimodal functions demonstrate that G-CLPSO outperforms CLPSO in terms of accuracy and convergence. Synthetic modeling scenarios involving the inverse estimation of soil hydraulic properties are used to compare the G-CLPSO against the original HYDRUS ML solver, the gradient-based algorithm PEST, and the stochastic SCE-UA strategy. Results demonstrate the superior performance of the G-CLPSO, suggesting a potential use in other environmental problems.

Estimation of Hydraulic Properties in Permeable Pavement Subjected to Clogging Simulation

Permeable pavements are often affected by pore clogging, which leads to their functional failure and reduced service life. However, the clogging mechanism and its impact on the permeability and complex pore microstructures in pervious pavement remain unclear. The aim of current study is to quantify the clogging behavior in pervious pavement materials and carry out investigations on the development of pore characteristics and permeability. Novel polyurethane-bound pervious mixture (PUPM) was adopted for comparative study in present research with conventional Porous Asphalt (PA). The Aachen Polishing Machine (APM) was selected to perfectly serve as a simulator for clogging process of pavement in the actual service condition. The permeability and pore microstructure of the pervious pavement material were then characterized by using the self-developed permeameter and X-ray Computed Tomography (CT) scanning, respectively. The development of pore characteristics in terms of clogging was experimentally illustrated. Based on the pore characteristics, the flow behavior of PUPM subjected to different clogging periods was predicted based on the developed non-Darcy flow model. The developed experiments and analysis can further strengthen the understanding of the clogging mechanism within the porous pavement material. The results can also serve for the optimization of the pervious pavement design in the engineering application.

Estimation of Unsaturated Hydraulic Properties of a Crusted Layer Using the Evaporation Method

Estimation of Unsaturated Hydraulic Properties of a Crusted Layer Using the Evaporation Method

Prediction of soil hydraulic properties using VIS-NIR spectral data in semi- arid region of Northern Karnataka Plateau

Field capacity (FC) and permanent wilting point (PWP) are the important soil hydraulic properties which determine the availability of water for plant growth. Conventional estimation of soil hydraulic properties is tedious and expensive which are normally derived from pedo-transfer functions. Visible and near-infrared (Vis-NIR) spectroscopy is a low-cost, non-destructive alternative method for the rapid estimation of soil properties. The present study was carried out to predict soil hydraulic properties using Vis-NIR spectral data in the semi-arid region of the Northern Karnataka plateau. Spectral data of 558 soil samples were acquired using Field Spec ASD Spectroradiometer and three models (support vector machine, random forest and partial least square regression) were evaluated for prediction of FC and PWP. The models were calibrated using 2/3rd of total observations and validated using 1/3rd of observations. The validation results showed that RF and SVM provided slightly higher performance compared to PLSR model. Permanent wilting point was predicted well (R2 = 0.70–0.74, RMSE = 5.44–5.74%) compared to field capacity (R2 = 0.66–0.69 and RMSE = 7.25–7.51%). Among the soil orders, FC and PWP of Vertisols were poorly predicted by Vis-NIR spectra (R2 = 0.34&0.42) and moderately predicted for Alfisols (0.44&0.52) and Inceptisols (0.55&0.65) while excellent prediction was recorded for Entisols (0.83&0.76). The present results showed that Vis-NIR spectroscopy is helpful for fast estimation of hydraulic properties in semi-arid regions of the country with high accuracy.

Estimation of Stagnosol Hydraulic Properties and Water Flow Using Uni- and Bimodal Porosity Models in Erosion-Affected Hillslope Vineyard Soils

Erosion has been reported as one of the top degradation processes that negatively affect agricultural soils. The study objective was to identify hydropedological factors controlling soil water dynamics in erosion-affected hillslope vineyard soils. The hydropedological study was conducted at identically-managed Jastrebarsko (location I), and Jazbina (II) and (III) sites with Stagnosol soils. Soil Hydraulic Properties (SHP) were estimated on intact soil cores using Evaporation and WP4C methods; soil hydraulic functions were fitted using HYPROP-FIT software. For Apg and Bg/Btg horizons, uni- and bimodal soil hydraulic models could be well fitted to data; although, the bimodal model performed better in particular cases where data indicated non-uniform pore size distribution. With these SHP estimations, a one-year (2020) water flow scenario was simulated using HYDRUS-1D to compare water balance results obtained with uni- and bimodal hydraulic functions. Simulation results revealed relatively similar flux distribution at each hillslope position between the water balance components infiltration, surface runoff, and drainage. However, at the bottom profile at Jastrebarsko, bimodality of the hydraulic functions led to increased drainage. Soil water storage was reduced, and the vertical movement increased due to modified soil water retention curve shapes. Adequate parameterization of SHP is required to capture the hydropedological response of heterogenous erosion-affected soil systems.

Estimation of soil hydraulic and solute transport properties from field infiltration experiments

To model water flow and solute transport in soils, hydrodynamic and hydrodispersive parameters are required as input data in the mathematical models. This work aims to estimate the soil hydraulic and solute transport properties using a ponded axisymmetric infiltration experiment using a single-ring infiltrometer along with a conservative tracer (Cl-) in the field. Single ring infiltration experiments were accomplished on an Oxisol in Areia in the state of Paraíba, Brazil (6o 58' S, 35o 41' W, and 645 m), in a 50 x 50 m grid (16 points). The unsaturated hydraulic conductivity (K) and the sorptivity (S) were estimated for short or long time analysis of cumulative three-dimensional infiltration. The single tracer technique was used to calculate mobile water fraction (Ф) by measuring the solute concentration underneath the ring infiltrometer at the end of the infiltration. Two solute transfer numerical models based on the mobile-immobile water concept were used. The mobile water fraction (Ф), the dispersion coefficient (D), and the mass transfer coefficient (a) between mobile and immobile were estimated from both the measured infiltration depth and the Cl- concentration profile underneath the infiltrometer. The classical convection-dispersion (CD) and the mobile-immobile (MIM) models showed a good agreement between calculated and experimental values. However, the lowest standard errors to the fitted parameters were obtained by the CD model.

Assessing specific-capacity data and short-term aquifer testing to estimate hydraulic properties in alluvial aquifers of the Rocky Mountains, Colorado, USA

Study RegionRocky Mountains, United States Study FocusGroundwater-flow modeling requires estimates of hydraulic properties, namely hydraulic conductivity. Hydraulic conductivity values commonly vary over orders of magnitudes however and estimation may require extensive field campaigns applying slug or pumping tests. As an alternative, specific-capacity tests can be used to estimate hydraulic properties for large areas when benchmarked with slug or pumping tests. This study combined aquifer testing with specific capacity data to estimate hydraulic properties in a large alluvial aquifer. New hydrological insights for regionIn the Wet Mountain Valley, Colorado, both slug tests and pumping tests were conducted, resulting in a likely range of hydraulic-conductivity values. Aquifer-testing results were related to specific-capacity data, a more spatially distributed dataset, to expand the area of aquifer characterization beyond the distribution of wells included in aquifer testing. Specific-capacity data were used in two ways: (1) a regression was built between specific-capacity values and transmissivity derived from aquifer testing; and (2) an iterative method was utilized to estimate transmissivity from specific capacity at all sites (including sites lacking aquifer tests). Study results indicate that there is a statistically significant difference between hydraulic-conductivity values estimated using the two approaches and that the regression method yields systematically greater values. These results indicate that careful consideration of methods that use specific capacity for extrapolating aquifer properties is warranted as bias could be introduced depending on the applied methodology.

A basin-scale aquifer characterization using an inverse analysis based on groundwater level fluctuation in response to precipitation: Practical application to a watershed in Jeju Island, South Korea

Study RegionGujwa Watershed, Jeju Island, South Korea Study FocusIn this study, we investigated whether basin-scale hydraulic properties can be inversely estimated using groundwater level fluctuation data. A geostatistical principal component adaptation evolution strategy was proposed as the inverse analysis method. It was applied to the Gujwa basin in Jeju Island. For the hypothetical case, the inverse simulation results accurately estimated the distribution and spatial structure of the hydraulic conductivity values. The quality of prior information insignificantly affected the proposed method; thus, it could be used as a critical reference method for groundwater management over a basin-scale area. New Hydrological Insight for the RegionThe hydraulic characteristics of an actual aquifer can be characterized over an entire small watershed on the basis of the time-series data of the groundwater level fluctuation due to precipitation. The hydraulic properties estimated for this area correspond well to the geological features of the area that were not incorporated into the inverse analysis. Watershed-scale aquifer characterization is the most critical step in managing groundwater under the concept of watershed management. Owing to the reliability of the analysis, the estimates of aquifer hydraulic properties obtained from the proposed method can be used for various practical purposes, including establishing water resource management plans such as quantitative water resource management and groundwater pollution prevention.

Estimation of hydraulic properties of evaporitic rocks in southern Saskatchewan, Canada

Estimation of hydraulic properties of evaporitic rocks in southern Saskatchewan, Canada