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  • 201.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    A general memory function for modeling mass transfer in groundwater transport2012In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, p. W04528-Article in journal (Refereed)
    Abstract [en]

    A power-law extension of the gamma distribution is proposed as a general memory function for capturing rate limitations of retention in groundwater transport. Using moments, we show how the new memory function can be reduced to most other forms available in the literature, exactly or approximately. The proposed formulation is suitable for field scale or laboratory scale transport modeling. Rate limitation effects are illustrated for solute transport by considering the fractional mass release over a given transport scale. The equilibrium and no-retention cases set bounds for contaminant attenuation, between which the impact of rate limitations is clearly exposed.

  • 202.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Diffusion-controlled tracer retention in crystalline rock on the field scale2010In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, p. L13401-Article in journal (Refereed)
    Abstract [en]

    Tracer retention is a key process for the barrier function of crystalline rock to any contaminant. Here we investigate the nature of retention mechanisms and their field-scale parametrization using results of a comprehensive tracer transport experiment in crystalline rock on the field scale (Aspo Hard Rock Laboratory, Sweden). A method for identifying dominant retention mechanisms and inferring key parameters on the site scale is presented. Taking advantage of multiple tracer tests with a wide range of sorption affinities, retention is shown to be diffusion-controlled. For the considered site, robust features of tracer migration can be reasonably well predicted within a rock volume on at least 200 m scale, by combining independent information with a simple model.

  • 203.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Significance of fracture rim zone heterogeneity for tracer transport in crystalline rock2010In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, no 3, p. W03504-Article in journal (Refereed)
    Abstract [en]

    Conducting fractures of crystalline rock are typically altered over long periods of time. The fracture rim zone, a result of these alterations, will as a rule have different physical and chemical properties from the unaltered ("fresh'') rock, depending on various microscopic and macroscopic factors of the alterations. In this paper, we study the impact of rim zone heterogeneity, exemplified by a decreasing porosity trend as inferred from the Aspo Hard Rock Laboratory site (Sweden), on short- and long-term tracer transport. Our main finding is that this particular rim zone structure will have a dominant effect on transport of moderately to strongly sorbing tracers on experimental time scales and a notable effect on application time scales. The findings of this work lend further support to the interpretation of the relatively strong retention reported by Cvetkovic et al. The fracture rim zone porosity structure may provide an additional safety margin for sorbing radionuclides in crystalline rock at sites where fracture alteration is prevalent.

  • 204.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    The tempered one-sided stable density: a universal model for hydrological transport?2011In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 6, no 3, p. 034008-Article in journal (Refereed)
    Abstract [en]

    A generalized distribution for the water residence time in hydrological transport is proposed in the form of the tempered one-sided stable (TOSS) density. It is shown that limiting cases of the TOSS distribution recover virtually all distributions that have been considered in the literature for hydrological transport, from plug flow to flow reactor, the advection-dispersion model, and the gamma and Levy densities. The stable property of TOSS is particularly important, enabling a seamless transition between a time-domain random walk, and the Lagrangian (trajectory) approach along hydrological transport pathways.

  • 205.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Tracer attenuation in groundwater2011In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 47, no 12, p. W12541-Article in journal (Refereed)
    Abstract [en]

    The self-purifying capacity of aquifers strongly depends on the attenuation of waterborne contaminants, i.e.,irreversible loss of contaminant mass on a given scale as a result of coupled transport and transformation processes. A general formulation of tracer attenuation in groundwater is presented. Basic sensitivities of attenuation to macrodispersion and retention are illustrated for a few typical retention mechanisms. Tracer recovery is suggested as an experimental proxy for attenuation. Unique experimental data of tracer recovery in crystalline rock compare favorably with the theoretical model that is based on diffusion-controlled retention. Non-Fickian hydrodynamic transport has potentially a large impact on field-scale attenuation of dissolved contaminants.

  • 206.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Carstens, Christoffer
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Selroos, Jan-Olof
    Destouni, Georgia
    Water and solute transport along hydrological pathways2012In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, no 6, p. W06537-Article in journal (Refereed)
    Abstract [en]

    A Lagrangian framework for material transport along hydrological pathways is presented and consequences of statistically stationary space-time flow velocity variations on advective transport are investigated. The two specific questions addressed in this work are: How do temporal fluctuations affect forward and backward water travel time distributions when combined with spatial variability? and Can mass transfer processes be quantified using conditional probabilities in spatially and temporally variable flow? Space-time trajectories are studied for generic conditions of flow, with fully ergodic or only spatially ergodic velocity. It is shown that forward and backward distributions of advective water travel time coincide for statistically stationary space-time variations. Temporal variability alters the statistical structure of the Lagrangian velocity fluctuations. Once this is accounted for, integration of the memory function with the travel time distribution is applicable for quantifying retention. Further work is needed to better understand the statistical structure of space-time velocity variability in hydrological transport, as well as its impact on tracer retention and attenuation.

  • 207.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Cheng, H.
    Byegard, J.
    Winberg, A.
    Tullborg, E. -L
    Widestrand, H.
    Transport and retention from single to multiple fractures in crystalline rock at Aspo (Sweden): 1. Evaluation of tracer test results and sensitivity analysis2010In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 46, p. W05505-Article in journal (Refereed)
    Abstract [en]

    We evaluate the breakthrough curves obtained within a comprehensive experimental program for investigating the retention properties of crystalline rock, referred to as Tracer Retention Understanding Experiments (TRUE). The tracer tests were conducted at the Aspo Hard Rock Laboratory (Sweden) in two phases jointly referred to as TRUE Block Scale (TBS); the TBS tests comprise a total of 17 breakthrough curves with nonsorbing and a range of sorbing tracers. The Euclidian length scales are between 10 and 30 m, compared to 5 m for the earlier tests TRUE-1. The unlimited diffusion model is consistent with measured breakthrough curves and is adopted here for evaluation. The model has four independent parameters, two of which are related to advection and dispersion, one which is related to diffusion-sorption, and one which is related to surface sorption; the individual retention parameters or properties cannot be inferred from breakthrough curves alone and require additional constraints. The mean water residence times for the TBS tests are in the range 15-250 h, whereas the coefficient of variation of the water residence times is in the range 0.4-0.6. A consistent trend is found in the calibrated retention parameters with the sorption affinities of the tracers involved. Using Bode sensitivity functions, it is shown that sensitivity increases for the retention parameter with increasing sorption affinity; for nonsorbing tracers, diffusion and hydrodynamic dispersion are shown to "compete," exhibiting similar effects; hence, their estimates are uncertain. The analysis presented here exposes a few fundamental limitations and sensitivities when evaluating diffusion-controlled retention in the subsurface; it is general and applicable to any site with comparable tracer test data. In part 2, it will be shown how discrete fracture network simulations based on the hydrostructural information available can be used for further constraining individual retention parameters, in particular, the active specific surface area (s(f)) and the rock matrix porosity (theta).

  • 208.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Cheng, Hua
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Evaluation of single-well injection-withdrawal tests in Swedish crystalline rock using the Lagrangian travel time approach2011In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 47, p. W02527-Article in journal (Refereed)
    Abstract [en]

    A series of 10 single-well injection-withdrawal (SWIW) tests are evaluated with two tracers each: uranine and cesium (Cs). An evaluation tool for SWIW tests in crystalline rock is presented on the basis of the Lagrangian travel time approach, whereby probabilities of tracer particle residence times are computed for key stages of the test cycle. Calibration results for three transport parameters and each breakthrough curve are presented. We show that estimates of the controlling retention parameter group psi [1/root T] are robust for Cs but highly uncertain for uranine. The estimated retention for Cs is larger for the Laxemar-Simpevarp site compared to the Forsmark site. Deviations from the -3/2 asymptotic breakthrough curve slope observed in a few of the tests at Forsmark are possibly due to a thin fracture coating that has been identified in mineralogical studies at some locations of the site.

  • 209.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Cheng, Hua
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Sorbing tracer experiments in a crystalline rock fracture at Aspo (Sweden): 3. Effect of microscale heterogeneity2008In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, no 12Article in journal (Refereed)
    Abstract [en]

    We study the impact of microscale (10(-3) -10(-2) m) heterogeneity in material and structural properties on sorbing tracer transport in a single crystalline fracture of the TRUE-1 tests (mesoscale, 5 m) at Aspo (Sweden). The analysis is based on the microscale characterization results as presented in part 1 of this series. Our main objective in this last part of the series is to provide an independent interpretation (or "prediction'') of the effective parameters as estimated from calibration in part 2 by combining the data presented in part 1 with analytical and numerical transport modeling. We show here that the independent information from microscopic characterization can be used for "predicting'' the effective diffusion time t(d) reasonably well; a discrepancy is to be expected given the uncertainties of microscale retention properties, in particular of the sorption coefficient.

  • 210.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Cheng, Hua
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Widestrand, H.
    Byegard, J.
    Winberg, A.
    Andersson, P.
    Sorbing tracer experiments in a crystalline rock fracture at Aspo (Sweden): 2. Transport model and effective parameter estimation2007In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 43, no 11Article in journal (Refereed)
    Abstract [en]

    [1] Transport and retention of sorbing tracers in a single, altered crystalline rock fracture on a 5 m scale is investigated. We evaluate the results of a comprehensive field study ( referred to as Tracer Retention Understanding Experiments, first phase ( TRUE- 1)), at a 400 m depth of the Aspo Hard Rock Laboratory ( Sweden). A total of 16 breakthrough curves are analyzed, from three test configurations using six radioactive tracers with a broad range of sorption properties. A transport- retention model is proposed, and its applicability is assessed based on available data. We find that the conventional model with an asymptotic power law slope of - 3/ 2 ( one- dimensional diffusion into an unlimited rock matrix) is a reasonable approximation for the conditions of the TRUE- 1 tests. Retention in the altered rock of the rim zone appears to be significantly stronger than implied by retention properties inferred from generic ( unaltered) rock samples. The effective physical parameters which control retention ( matrix porosity and retention aperture) are comparable for all three test configurations. The most plausible in situ ( rim zone) porosity is in the range 1% - 2%, which constrains the effective retention aperture to the range 0.2 - 0.7 mm. For all sorbing tracers the estimated in situ sorption coefficient appears to be larger by at least a factor of 10, compared to the value inferred from through- diffusion tests using unaltered rock samples.

  • 211.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Frampton, Andrew
    Solute transport and retention in three-dimensional fracture networks2012In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, p. W02509-Article in journal (Refereed)
    Abstract [en]

    Resolving the hydrodynamic control of retention is an important step in predictive modeling of transport of sorbing tracers in fractured rock. The statistics of the transport resistance parameter beta [T/L] and the related effective active specific surface area s(f) [1/L] are studied in a crystalline rock volume on a 100 m scale. Groundwater flow and advective transport are based on generic boundary conditions and realistic discrete fracture networks inferred from the Laxemar site, southeast Sweden. The overall statistics of beta are consistent with statistics of the water residence time tau; the moments of beta vary linearly with distance, at least up to 100 m. The correlation between log tau and log beta is predominantly linear, however, there is significant dispersion; the parameter s(f) strongly depends on the assumed hydraulic law (theoretical cubic or empirical quadratic). Fast and slow trajectories/segments in the network determine the shape of the beta distribution that cannot be reproduced by infinitely divisible model over the entire range; the low value range and median can be reproduced reasonably well with the tempered one-sided stable density using the exponent in the range 0.35-0.7. The low percentiles of the beta distribution seems to converge to a Fickian type of behavior from a 50 to 100 m scale.

  • 212.
    Cvetkovic, Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Frampton, Andrew
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Transport and retention from single to multiple fractures in crystalline rock at Äspö (Sweden): 2. Fracture network simulations and generic retention model.2010In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973Article in journal (Refereed)
    Abstract [en]

    Hydrogeologic characterization of crystalline rock formations on the field scale is important for many applications but still presents a multitude of challenges [Neuman, 2005]. In this work we use comprehensive hydro-structural information and present a detailed simulation study of flow and advective transport in a discrete fracture network (DFN) that replicates the TRUE Block Scale rock volume at the Äspö Hard Rock Laboratory (Sweden). Simulated water residence time τ and hydrodynamic retention parameter β are used as independent constraints for estimating material retention properties as presented in part 1 of this series [Cvetkovic et al., 2009] whereas simulated mean water residence times are compared with observed values. We find that the DFN simulations reproduce water residence times reasonably well, indicating that the characterization data are sufficient and that the DFN model does capture dominant features of the flow paths analyzed. The empirical quadratic law that relates aperture and transmissivity seems to better reproduce calibrated mean water residence times than the theoretical cubic law, for the five flow paths. The active specific surface area (β/τ) [1/L] as inferred from simulations, is used for defining a generic retention model for the dominant rock type (”Äspö diorite”) that matches fairly well the entire range of calibrated retention parameters of the TRUE tests. The combination of Part 1 and this work provide a general, comprehensive methodology for evaluating tracer test results in crystalline rock where a comparable amount of information is available; critical to this methodology is that tracer tests are carried out using tracers with sufficiently different sorption affinities (of factor 10 to 100).

  • 213. Dagan, G.
    et al.
    Fiori, A.
    Jankovic, I.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Tailing of the breakthrough curve in aquifer contaminant transport: The impact of permeability spatial variability2008Conference paper (Refereed)
    Abstract [en]

    A contaminant plume of mass Mo is inserted at time t = 0 at an injection plane at × = 0 in an aquifer of spatially variable conductivity K. The log-conductivity Y = InK is modelled as stationary and isotropic, of univariate distribution f(Y), and of finite integral scale I. The flow of water is uniform in the mean (natural gradient) and the plume is of large transverse extent relative to the integral scale. Advective transport and longitudinal spread are quantified by the solute mass arrival ("breakthrough curve", BTC) M(t,x) at a control plane at × > I. For a large plume (ergodic conditions) the relative mass flux μ(t,x) = (l/Mo)M/t is approximately equal to the probability density function of travel times of solute particles f(τx) and the latter is used to analyse transport. f(τx) is derived by adopting a structural model of the aquifer that contains spherical or cubic inclusions of uniform size and of independent Y that fill the space. Such a structure can represent any formation of given f(Y) and I. The flow and transport solutions are obtained by a simple semianalytical model and by accurate numerical simulations. The travel time distribution at few control planes is determined for a log-normal f(K) first. Under the assumption of weak heterogeneity, i.e. for small variance σy 2 and for x»I, the travel time distribution is symmetrical and Gaussian. Subsequently, by using the semi-analytical model and numerical simulations we derive f(τx) for a highly heterogeneous formation of σ y 2 = 2. The main finding is f(τx) is highly skewed due to the presence of a thin, but long tail, for large travel times. The tail is of significance to applications that deal with aquifer pollution and remediation. The tail is related to the large residence time of solute particles in blocks of low conductivity. A simple relationship is established between the tail of f(Y) for low K and that f(τx) for large τ. To further examine the impact of the log-conductivity distribution on BTC tailing, a non-Gaussian model, the subordinate model, is adopted for f(Y). This distribution depends on an additional parameter Is; travel time distribution tends to normal for Is→0, whereas the tails of the two distributions are different for Is > 0. This choice reflects the difficulty of identification of the tail of f(Y) based on field data. The relevance of results to applications is examined in terms of impact of conductivity spatial distribution, as well as influence of plume size (non-ergodic behaviour) and diffusion.

  • 214.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Experimental study and 3D numerical simulations for a free-overflow spillway2006In: Journal of Hydraulic Engineering, ISSN 0733-9429, E-ISSN 1943-7900, Vol. 132, no 9, p. 899-907Article in journal (Refereed)
    Abstract [en]

    The main objectives of the present work were to investigate the flow field over a spillway and to simulate the flow by means of a three-dimensional (3D) numerical model. Depending on the wall curvature, the boundary layer parameters decreased or increased with increasing distance along the spillway. The growth of the boundary layer along the spillway is better described as a function of Reynolds number than the normalized streamwise length. A simplified form of the 3D momentum equation can be used to obtain a rough estimate of the skin friction. The velocity profile in the boundary layer along the spillway is described by a velocity-defect relationship. Numerical models provide a cost-effective means of simulating spillway flows. In this study, the water surface profiles and the discharge coefficients for a laboratory spillway were predicted within an accuracy range of 1.5-2.9%. The simulations were sensitive to the choice of the wall function, grid spacing, and Reynolds number. A nonequilibrium wall function with a grid spacing equal to a distance of 30 wall units gave good results.

  • 215.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Flow characteristics of bottom outlets with moving gates2010In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 48, no 4, p. 476-482Article in journal (Refereed)
    Abstract [en]

    This study investigates the discharge characteristics of a bottom outlet with a moving gate by Flow3D. Experimental results for a scale model outlet of the Aswan Dam, Egypt, were used. Two different flow features were found. Pressurized flow established if the flume was filled and then the gate was slowly opened. However, a free surface flow occurred if the gate was fully opened and the entire flume was slowly flooded with water. The numerical simulations successfully captured the two flow patterns as well as the discharges and water surface profiles. The discharges were predicted with sufficient accuracy using the first-order momentum advection scheme. In comparison with the k-epsilon turbulence model, the Re-Normalization Group model yields the best agreement with the experiments. The model performed with similar accuracy for both model and prototype cases.

  • 216.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Mitigation of sedimentation problems in the lower reach of the River Klaralven2008In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 46, no 2, p. 224-236Article in journal (Refereed)
    Abstract [en]

    The study focuses on the sedimentation problems found in the lower reach of the River Klaralven, where the river bifurcates into a west and an east channels at the city of Karlstad. During a period of thirty years, the sediment transport capacity of the west-channel has gradually diminished. This has caused a growing concern about the risk of flooding in the city. The study has aimed to find relevant methods for both increasing the hydraulic capacity of the west river channel, and mitigation of sedimentation problems. The main approach was numerical flow and sediment transport modelling. A two-dimensional depth-averaged model was used to study the influence of various river training measures. The model was found effective to address the sedimentation problem and the reduced hydraulic capacity in the river. To mitigate these problems, two effective engineering methods were controlling the water levels by partial gates and the use of groynes or vanes. The results suggested that a carefully calibrated and verified 2-D depth-averaged model can be used in supporting river restoration works and flood alleviation schemes.

  • 217.
    Dargahi, Bijan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Hydraulic Engineering (moved 20130630).
    Reservoir sedimentation2012In: Encyclopedia of Earth Sciences Series, Springer Netherlands, 2012, p. 628-649Chapter in book (Refereed)
  • 218.
    Dargahi, Bijan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Hydrodynamic and Transport Properties of Saltsjo Bay in the Inner Stockholm Archipelago2011In: Journal of Coastal Research, ISSN 0749-0208, E-ISSN 1551-5036, Vol. 27, no 3, p. 572-584Article in journal (Refereed)
    Abstract [en]

    DARGAHI, B. and CVETKOVIC, V., 2011. Hydrodynamic and transport properties of Saltsjo Bay in the inner Stockholm archipelago, Sweden. Journal of Coastal Research, 27(3), 572-584. West Palm Beach (Florida), ISSN 0749-0208. A three-dimensional hydrodynamic model was successfully calibrated and validated for Saltsjo Bay, located in the inner Stockholm archipelago. The work aims to obtain a scientific understanding of specific hydrodynamic characteristics of the bay. The focus is on the influence of the freshwater inflow on the hydrodynamic characteristics of the bay, which shares common features with other relatively small bays and estuaries. The model was used for investigating the flow structure, stratification, exchange process, flushing time, and oxygen content. The predicted water levels, temperature, salinity, and dissolved oxygen (DO) profiles were in good agreement with the measurements. The flow structure in the bay is characterised by the existence of large secondary flow regions and multilayer flows. The principal cause of the large secondary flow regions is the interaction of prevailing two-layer flows that have opposite directions. The stratification can be characterised by two long winter and summer stratification periods and two short overturn periods. In the absence of the freshwater, the two-layer flow changed to a three-layer flow but the flow stratification remained unaltered. The flushing time in Saltsjo Bay (2-29 days) is similar to that found in smaller water bodies. The flushing time increased to 40 days when the freshwater inflows were removed from the model boundaries. The period from 1 September to 1 November is characterised by bottom oxygen deficiency when the DO concentrations fall below 5 mg/L. At the open boundary, 3% to 25% of the total volume of the bay is exchanged daily. The work should be of interest and relevant to other bays of comparable size that have similar hydrodynamic characteristics and are subject to freshwater inflows.

  • 219.
    Dargahi, Bijan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Setegn, Shimelis Gebriye
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Combined 3D Hydrodynamic and Watershed Modelling of Lake Tana, Ethiopia2011In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 398, no 1-2, p. 44-64Article in journal (Refereed)
    Abstract [en]

     The growing high demand for lake Tana water portends a disturbing future. The main objective of this paper is to make a contribution to the development of a sustainable use of the water of Lake Tana. A fully three-dimensional hydrodynamic model was combined with a watershed model and together, these models were successfully validated for the year 2006. The flow structure is characterized by large recirculation and secondary flow regions. Secondary flows are induced by hydrodynamic instabilities occurring at the interfaces of layers with a velocity gradient and the interaction with the irregularities of the bed. The weak stratification process in Lake Tana is characterized by a classic summer profile, which is more pronounced during January-February. Mixing processes in the lake are controlled by wind, the mixing energy induced by both river inflows and the lake outlet, and convective mixing due to the negative buoyancy. An alarming fall of the water levels in Lake Tana was found in response to the planned water withdrawal. The long flushing time (19 months) will not allow a fast decay of contaminated materials released into the lake. The flow structure will not be significantly modified by the planned water withdrawal but the flushing time will decrease. The hydrodynamics of Lake Tana resemble a closed system similar to a shallow reservoir with an overflow type outlet. The implication is that the lake is vulnerable to changes in external conditions and sustainable use of the water resource of the lake will require awareness of this vulnerability. The combined watershed and hydrodynamic models would be effective tools to achieve this awareness. It is also necessary to address the impact of climate change on the fate of the lake. These are all difficult challenges that need to be addressed to safeguard the sensitive eco-system of the area.

  • 220.
    Darracq, Amélie
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Greffe, Fanny
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Hannerz, Fredrik
    Destouni, G.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water Resources Engineering.
    Nutrient transport scenarios in a changing Stockholm and Mälaren valley region, Sweden2005In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 51, no 3-4, p. 31-38Article in journal (Refereed)
    Abstract [en]

    Norrstrom catchment, west of Stockholm, covers most of the Malaren valley. Provision of drinking water from Lake Malaren is an absolute precondition for continued growth in the region. Stockholm County's population is expected to increase by 600,000 people before 2030. Current climate change predictions anticipate significant temperature and precipitation increases. We implement the PolFlow model embedded in PCRaster for quantifying water and substances fluxes on the catchment scale over a 30-year time horizon. We formulate scenarios for changes in water quality and quantity due to climate change and population development. Results indicate a mild impact from climate change on surface flow rates but substantial effects on sub-surface residence times. Population development slightly affects nutrients loads. Using source apportionment and sensitivity analysis, we identify a number of critical parameters/processes to be further studied, in order for future results to be more reliable and usable in a water resources management context.

  • 221.
    Darracq, Amélie
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Lindgren, Georg
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Destouni, Georgia
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Effects of neglecting travel time variability on modeled nitrogen attenuation rates in streamsManuscript (Other academic)
  • 222. David, E.
    et al.
    Zimmerman, Robert W.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Engineering Geology and Geophysics.
    Sliding crack model for the uniaxial compression of rock2007In: Proceedings of the 1st Canada-US Rock Mechanics Symposium - Rock Mechanics Meeting Society's Challenges and Demands, Taylor & Francis, 2007, p. 575-580Conference paper (Refereed)
    Abstract [en]

    Uniaxial compression tests on rocks, if conducted at stresses below failure, typically show non-linearity in the stress-strain curve, and hysteresis. Walsh (J. Geophys. Res., 1965) explained this behavior in terms of frictional sliding along the faces of closed cracks. Although well known and widely cited, Walsh's model has not previously been developed in sufficient detail to be used for quantitative predictions. We revisit and extend his model, by including the effect of the stress required to close an initially open crack, and we examine the unloading process in detail. Our analysis leads to closed-form expressions for the loading and unloading portions of the stress-strain curve, as functions of elastic modulus of the uncracked rock, the crack density, the characteristic aspect ratio, and the crack friction coefficient. The model provides a good fit to the loading and unloading portions of the stress-strain curves, for experimental data on sandstones taken from the literature.

  • 223.
    Demsar, Urska
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Skeppström, Kirlna
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Use of GIS and 3D visualisation to investigate radon problem in groundwater2005In: 10th Scandinavian Research Conference on Geographical Information Science, Scangis, Stockholm, Sweden, June 13-15 / [ed] H. Hauska and H. Tveite, 2005, p. 39-51Conference paper (Refereed)
    Abstract [en]

    Radon is radioactive and its origin in groundwater is principally linked to the content of its parent element, uranium or radium in bedrocks. However, an on-going research at the Department of Land andWater Resources Engineering shows that a number of factors other than bedrock may potentially influence the radon concentration in groundwater.These factors include: steepness of the terrain, soil type, distribution of uranium and the effect of fracture zone. This article presents an application of GIS and 3D visualisation to explore the radon problem in groundwater. After a GIS pre-processing, 3D visualisations of the thematic data were produced in order to see if the visual approach would be useful to preliminary identify possible relationships between the high concentration of radon and other parameters.

  • 224.
    Dessirier, Benoît
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Soltani, Safeyeh
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Dynamics of internal nutrient sources in the Baltic Sea - A comparative modelling study of the Gulf of Finland.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For decades the Baltic Sea has been subject to eutrophication due to heavy anthropogenic nutrient loads on the aquatic ecosystem. Quantitative projections of its effects require an understanding of its driving mechanisms, i.e., the hydrodynamics that are responsible for the physical transport and mixing and the biogeochemical nutrients pathways within the algal ecosystem and between the particulate and dissolved phases in the water and in the sediments.

    A simple basin-scale hydrodynamic framework is set for the Gulf of Finland to test different descriptions of the biogeochemical transformations and determine the most robust modelling strategy. A recently developed criterion to determine the occurrence of anoxic events, based on the amount of fresh carbon detritus in the sediments is implemented in comparison with the classical criterion based on the oxygen concentration in the bottom water.

    Time-averaging of the hydrodynamics over larger than daily intervals is proved to hinder the capture of rapid mixing events jeopardizing irremediably the water quality simulation. The new carbon based criterion for anoxia shows a better dynamic response and is less sensitive to the model’s internal parameters. An internal source in the sediments correlated to the amount of fresh detritus, to represent the release of iron-bound phosphorus is confirmed as a versatile modelling assumption.

  • 225.
    Destouni, Georgia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Hannerz, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Management and Assessment.
    Jarsjö, Jerker
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Prieto, Carmen
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Shibuo, Y.
    Resolving the diverse pathways of freshwater and pollutant inputs to coastal waters2005Article in journal (Other academic)
  • 226.
    Destouni, Georgia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Prieto, Carmen
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Quantifying hydrological and tidal influences on groundwater discharges into coastal waters2005In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 41, no 12, p. W12427-Article in journal (Refereed)
    Abstract [en]

    [1] In coastal aquifers the dynamic mixing zone between intruding seawater and fresh groundwater constitutes a zone of salinity transition that may supply brackish groundwater along with chemical tracers and nutrients to coastal waters. Tidal influence has been proposed as a possible mechanism for enhancement of recirculated seawater, total submarine groundwater discharge (SGD), and associated tracer loading through salinity transition zones into coastal waters. We show that tidal oscillation may, for relatively low SGD cases, considerably increase the average recirculated seawater component of total SGD relative to nontidal conditions. High SGD cases, however, are dominated by and require large fresh groundwater flow components also under tidal conditions; this result is obtained from a wide range of different groundwater simulation scenarios and is supported by direct comparison with field data from different reported high-SGD sites in the world. For cases with hydrologically limited fresh groundwater flow directly into the sea we propose that observed excessive coastal loading of groundwater-derived tracers may be the result of large groundwater flow and transport into unmonitored coastal stream reaches, in addition to SGD.

  • 227.
    Diawuo, Felix
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Management.
    Water Supply of Accra, with Emphasis on Sachet Water.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This project seeks to assess the impact of the sachet water industry on the health, socio-economic and the environmental situation of the inhabitants of Accra, the capital city of Ghana.

    In addressing the situation, the driving forces which have fuelled the shift of consum-er taste from the normal tap water and the traditional hand-tied-ice water products to the plastic sachet water (commonly known in as "Pure Water") are identified. Lack of access to continuous flow of improved water and the perceived poor quality of the urban water supply system as results of poor management structure are identified as some of the factors for the shift in consumers’ taste for plastic sachet and bottled drinking water.

    The quality of the plastic sachet is also assessed through the review of previous research results. These are confirmed by laboratory analysis of about six brands of plastic sachet water and two brands bottled drinking water. The laboratory analysis carried out assessed the microbial, physical and chemical quality of the various samples. To assess the health impacts of the products, the results from the analysis are compared with WHO guideline values and other international guideline values.

    Questionnaires are also administered to ascertain the socio-economic impacts of the products on the life of the young men and women as well sachet water manufacturers.

    From this, some measures are suggested as to how to mitigate the activities of the sachet water business to reduce its negative effects on the health, the environment and the socio-economic status of the inhabitants of the city.

  • 228.
    Dlugolecka, Maja
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Pharmaceutical compounds; a new challenge for wastewater treatment plants2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Analytical analyses conducted at the Himmerfjärden WWTP (285.000 PE connected) identified 70 pharmaceutical compounds belonging to different therapeutic classes. Such organic micropollutants at low detected concentration range of µg - ng l-1 did not affect the treatment processes at WWTP. Results from analytical studies indicated continuous discharge of organic micropollutants to the surface water with a calculated load amounting to 1.51 kg day-1. Metoprolol, carbamazepine and naproxen were chosen for testing different removal methods. Oxygen Uptake Rate (OUR) tests were conducted to assess the bacterial activity of an activated sludge taken from a full scale aeration plant with the presence of selected target compounds.

    A semi-technical scale membrane bioreactor ZeeWeed10™, treating final effluent from the Himmerfjärden WWTP (Sweden) was seeded with activated sludge from full scale biological stage. The membrane bioreactor (MBR) system placed after the final treatment appeared to be an insufficient technology for removal of residual amounts of organic micropollutants from WWTP effluents. Batch test studies with activated sludge taken from the membrane bioreactor and with application of granular activated carbon (GAC) filtration resulted in giving an overall assessment of removal efficiency. Metoprolol and carbamazepine tend to be resistant to the biodegradation process and in the dosed high concentration lead to bacterial cell decomposition in the activated sludge. Apparently, removal efficiency for naproxen exceeded the value of 46% with the spiked initial amount of 3.3 mg NAP g-1 MLSS. Application of the GAC filtration proved to be an efficient technique for removal of pharmaceutical compounds from treated wastewater.

    Application of the statistical programme Modde7 was a time saving tool in studies of fouling occurrence. The effect of fouling phenomenon, which is a highly limiting factor for MBR performance, was minimised by adjusting the operational parameters as predicted by the Modde7 programme.

  • 229.
    Dlugolecka, Maja
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Dahlberg, Alf-Göran
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Low concentrations of high prority: pharmaceutical and personal care products (PPCPs); occurrence and high removal at wastewater treatment plant2006In: Vatten, ISSN 0042-2886, Vol. 62, no 2, p. 139-148Article in journal (Other academic)
    Abstract [en]

    Development of advanced analytical tools and analysis of wastewater samples confirmed the presence of residualamount of pharmaceuticals in environment and WWTP effluent in many European countries. Significantamount of compounds (30–90 % of administrated dose of antibiotics) is transported as active substance viaurine. Only some part of taken drug dose is metabolized by organisms and the rest is excreted in changed orunchanged form. Many non-target organisms, that could share some receptors with humans, could be exposedon pharmaceutical activity. Another important issue discussed is the combination of additive, synergistic andantagonistic effect that might reveal in the mixture of pharmaceutically active compounds introduced to theenvironment. The objective of this paper is to give the overview of recent published data concerning PPCPs. Inorder to find the efficient technology for removal of residual amount of pharmaceuticals the studied methodsand solutions are presented. The most interesting removal system is based on membrane technology. Separationof micropollutants onto membrane surface gives satisfactory results in experiments. A polishing step seems tobe also a very attractive technology for treatment of biologically active substances that pass all the precedingsteps in conventional WWTP s.

  • 230.
    Dlugolecka, Maja
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Dahlberg, Alf-Göran
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Two years of experience with semitechnical scale membrane bioreactor (MBR)2007In: Vatten, ISSN 0042-2886, Vol. 63, no 1, p. 69-78Article in journal (Refereed)
    Abstract [en]

    In wastewater treatment applications the MBR technology combines biological treatment and a membrane systemto provide organic and suspended solids removal. Installation of low-pressure membranes within a biological reactor system replaces sedimentation, screening and media filtration as means of separating mixed liquorsuspended solids (MLSS) from treated wastewater. This study is focused on experiments with ZeeWeed10™MBR (Zenon GmbH) installed at the outlet of the main process line at Himmerfjärden WWTP, situated inGrödinge (south of Stockholm, Sweden). Results obtained for the MBR tests showed effluent water qualityimprovement in comparison with the full-scale plant performance with efficiency from 12 % removal efficiencyfor total nitrogen to 100 % for MLSS. Additionally, Design of Experiments methodology (Modde 7), wasappliedfor evaluation of fouling phenomenon in order to optimize the ZeeWeed10™ operation. 35 l m–2 h–1of flux and 7 minutes filtration with 40s of backwash were found as the optimal effective permeation conditionsfor the MBR process. The permeation fouling rate (PFR) was chosen as the major criterion that illustrates themembrane fouling occurrence and shows the necessity for membrane cleaning procedure. Furthermore, thecomparative studies of two membrane units (ZW500 and ZWNEW) were completed with an emphasis on fouling occurrence and indicated the ZWNEW as more fouling-resistant.

  • 231.
    Dlugolecka, Maja
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Hultman, Bengt
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Behaviour of carbamazepine, metoprolol and naproxen in membrane bioreactor (MBR) activated sludge culture and after granular activated carbon (GAC) filtration2007In: Enviromental Science and TechnologyArticle in journal (Other academic)
  • 232. Dlugolecka, Maja
    et al.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Dahlberg, Alf Göran
    Hultman, Bengt
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Application of Oxygen Uptake Rate (OUR) tests for study of Metoprolol inhibitory effects on activated sludge2006In: 5th IWA World Water Congress & Exhibition Proceedings, 2006Conference paper (Refereed)
  • 233.
    Dlugolecka, Maja
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Dahlberg, Alf-Göran
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Hultman, Bengt
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Application Oxygen Uptake Rate (OUR) tests for study of Metoprolo inhibitory effects on activated sludge.2006In: IWA World Water Congress & Exhibition, Beijing, 2006Conference paper (Refereed)
  • 234. Duarte, M.T.
    et al.
    Fernlund, Joanne
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Analysis of meso textures of geomaterials through haralick parameters2005In: PATTERN RECOGNITION AND IMAGE ANALYSIS, PT 2, PROCEEDINGS / [ed] Marques, JS; PerezdelaBlanca, N; Pina, P, 2005, Vol. 3523, p. 713-719Conference paper (Refereed)
    Abstract [en]

    The geomaterials used in this study are granites from Finland with very similar mineral composition. Visual evaluation of the rock texture is done to determine the most significant features of the patterns for the analysis of heterogeneity of meso textures are grain size and grain size spatial distribution. These are compared to results of parameters calculated using image structure analyser. Images are capture with a scanner of the polished slabs that are 9*9 cm in size. The geo textures are expressed by four main parameters: textural entropy, homogeneity, contrast and textural correlation. Reducing the number of parameters to entropy and textural correlation significantly reduce the calculation time. These two parameters are considered to be the most significant. The other two, homogeneity and contrast, can be estimated. The parameter textural correlation yields better results than does textural entropy. Comparison of the analysis of textures visually and using image analysis shows that textural parameters have to be further worked in order to have a better performance.

  • 235.
    Dubois, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    A contractarian jusification of social insurance with income maintenanceManuscript (preprint) (Other academic)
  • 236. Durdu, Oe F.
    et al.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Water Resources Engineering.
    Modeling water and nutrients fluxes in the Buyuk Menderes drainage basin, Turkey2009In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 59, no 3, p. 531-541Article in journal (Refereed)
    Abstract [en]

    Buyuk Menderes catchment, located in the southwestern part of Turkey, is one of the most populated river basins in Turkey with 2.5 millions inhabitants. Due to increasing activities in agriculture and industrial sectors, water resources management in the basin is one of the biggest matters for the future. During the past decade, it has been observed a basinwide shift to larger monocultural, intensively operated farm units. Therefore, there is land use conversion from native lands to agriculture. The threat of nutrients pollution, nitrogen and phosphorus, has become a preoccupation since many lands and rivers undergo a eutrophication process. The discharge of nutrients from Buyuk Menderes basin to the Aegean Sea through Buyuk Menderes river also needs to be reduced in order to bring the eutrophication problems under lasting control. In this paper, the PolFlow model embedded in PCraster is applied to the catchment for quantifying water and substances fluxes for the five-year period, 1999-2004. The implementation of the model in the catchment allows describing the water balance and thus nutrient transport on the landscape surface but also through the soil and aquifer's layers. Modeling process is complicated by the transfer of nutrients from diffuse and point-source emissions, managed by retention and periodic release from storages within the catchment. Modeling diffuse and point-source nutrient emissions contribution to river loads can be improved by better knowledge about spatial and temporal distribution of this retention and release in the basin.

  • 237.
    Earon, Robert
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Impact on Soil and Groundwater from Road Maintenance and Traffic: Initial Study of the E18 Highway.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The investigation of environmental impacts of 16 different contaminants originating from the E18 Highway (17 000 AADT) were carried out over the first six months of the highway‘s operational life. Investigative methods used include electrical resistivity surveying, water chemistry analyses, soil analyses, distribution modelling and transportation modelling.

    The investigation shows conclusively a year round infiltration due to melting of the snowpack from road salt, and a strong preferential anthropogenic pathway due to in-creased hydraulic conductivities of the road building materials relative to the natural soils. The resistivity surveys show values well below the expected values for the highway materials, indicating increased ionic content of the unsaturated zone. Time lapse resistivity modelling shows a clear downwards spreading of contamination from the roadway to subsurface distances greater than 5 m.

    Elevated concentrations of nearly every contaminant relative to baseline values were observed, with many concentrations of metals in the snow pack averaging values in excess of Swedish EPA groundwater limitations. Distribution modelling demonstrated a potential offset of peak values from the road surface due to ploughing and splash transport processes, but otherwise conformed to established distribution patterns. One dimensional transport modelling demonstrated the importance of adsorption and other retentive factors to the migration of contaminants to the water table, and provided an estimate for potential long term contaminant concentrations.

  • 238.
    Earon, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Olofsson, Bo
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Initial Effects of a New Highway Section on Soil and Groundwater2012In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 223, no 8, p. 5413-5432Article in journal (Refereed)
    Abstract [en]

    The environmental impacts of 16 different contaminants originating from the E18 Highway (17,510 annual average daily traffic) were studied over the initial months of the highway's operational life. Investigative methods used included electrical resistivity surveying, water chemistry analyses, soil analyses, distribution modeling, and transportation modeling of contaminants. The study conclusively showed a year-round infiltration due to melting of the snowpack from road salt, and a strong preferential, anthropogenic pathway due to increased hydraulic conductivities of road construction materials relative to in situ soils. The resistivity surveys produced values well below the expected values for the highway materials, indicating increased ionic content within the unsaturated zone. Time lapse resistivity modeling showed a clear downwards spreading of contamination from the roadway to subsurface distances greater than 5 m. Elevated concentrations of nearly every studied contaminant relative to baseline values were observed, with many metal concentrations within the snow pack averaging values in excess of the Swedish Environmental Protection Agency's groundwater limitations. Distribution modeling demonstrated a potential offset of peak values from the road surface due to plowing and splash transport processes, and indicated different distribution behavior during winter months than during summer months. One-dimensional transport modeling demonstrated the importance of adsorption and other retentive factors to the migration of contaminants to groundwater and provided an estimate for potential long-term contaminant concentrations.

  • 239.
    Edvardsson, Sara
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    The potential use of S-HYPE in the work of predicting landslides2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Landslides are expensive for the community as it causes changes to for example infrastructure, changes in land used for cultivation and can also result in loss of life. Climate change will in the future introduce higher amounts of precipitation in Sweden, which increases the risks of landslides, as groundwater levels will increase.

    Investigations, which are made, to determine the slope stability, become more expensive when more details are needed. Models for instability of slope have disadvantages of giving too low values, being too broad and not including long-term changes in groundwater and pore pressure. One modelling tool which might be useful is S-HYPE which produces, from normalised groundwater levels, a filling degree (% of groundwater aquifers). This study therefore investigates the potential use of S-HYPE in the work of predicting landslides.

    Programmes which have been used are S-HYPE, ArcGIS 10.5, Excel and SPSS (Statistical Package for Social Sciences). ArcGIS 10.5 have been used to connect the 57 landslides which have an exact date to the subcatchments found in S-HYPE, where after filling degree could be extracted. Soil type and slope of the ground have also been handled in ArcGIS 10.5. All data have been handled and gathered in histograms, graphs and tables by using Excel. SPSS was used to perform a PCA (Principle Component Analysis) and a one-way ANOVA (Analysis of Variance).

    The results show that for the small reservoir model almost half of the landslide had a filling degree of 70-100%, whereas for the large reservoir model almost half had a filling degree of 35-70%. These results show that for almost half of all landslides, for the model of the small reservoir, the groundwater might have played an important role. The trend of the filling degree is better shown for the large reservoir model. Not many landslides had occurred at a slope angle greater than 20 degrees. The only soil group happening at steeper slopes was the soil group till. The three components extracted from the PCA are indicators of climate, geology and slope of the ground. More parameters would be out of interest to include, such as closeness to streams and human activity in the area, to further investigate the use of S-HYPE. The comparison between six different landslides showed that for all except two, which had another type of geology, the landslides had occurred during high groundwater levels and rising filling degree for both reservoir models.

    The results indicate that S-HYPE could be used when looking at the risk of a landslide happening, when one knows the conditions on the site. However, less so as a tool that predicts that a landslide is going to happen. The use of S-HYPE as an assessment tool for the risks of a landslide requires, therefore, that other parameters are known, such as the sensitivity of the soil to changes in groundwater conditions. However, further studies are needed to further prove the use of S-HYPE.

  • 240.
    Ekneligoda, Thushan C.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Zimmerman, Robert W.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Boundary perturbation solution for nearly circular holes and rigid inclusions in an infinite elastic medium2008In: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 75, no 1, p. 011015-Article in journal (Refereed)
    Abstract [en]

    The boundary perturbation method is used to solve the problem of a nearly circular rigid inclusion in a two-dimensional elastic medium subjected to hydrostatic stress at infinity. The solution is taken to the fourth order in the small parameter epsilon that quantifies the magnitude of the variation of the radius of the inclusion. This result is then used to find the effective bulk modulus of a body that contains a dilute concentration of such inclusions. The corresponding results for a cavity are obtained by setting the Muskhelishvili coefficient K equal to -1, as specified by the Dundurs correspondence principle. The results for nearly circular pores can be expressed in terms of the pore compressibility. The pore compressibilities given by the perturbation solution are tested against numerical values obtained using the boundary element method, and are shown to have good accuracy over a substantial range of roughness values.

  • 241.
    Ekneligoda, Thushan C.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Zimmerman, Robert W.
    Shear compliance of two-dimensional pores possessing N-fold axis of rotational symmetry2008In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 464, no 2091, p. 759-775Article in journal (Refereed)
    Abstract [en]

    We use the complex variable method and conformal mapping to derive a closed-form expression for the shear compliance parameters of some two-dimensional pores in an elastic material. The pores have an N-fold axis of rotational symmetry and can be represented by at most three terms in the mapping function that conformally maps the exterior of the pore into the interior of the unit circle. We validate our results against the solutions of some special cases available in the literature, and against boundary-element calculations. By extrapolation of the results for pores obtained from two and three terms of the Schwarz-Christoffel mapping function for regular polygons, we find the shear compliance of a triangle, square, pentagon and hexagon. We explicitly verify the fact that the shear compliance of a symmetric pore is independent of the orientation of the pore relative to the applied shear, for all cases except pores of fourfold symmetry. We also show that pores having fourfold symmetry, or no symmetry, will have shear compliances that vary with cos 4 theta. An approximate scaling law for the shear compliance parameter, in terms of the ratio of perimeter squared to area, is proposed and tested.

  • 242.
    Ekneligoda, Thushan Chandrasiri
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Estimation of the Elastic Moduli of Porous Materials using Analytical Methods, Numerical Methods, and Image Analysis2007Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    The effective bulk modulus and effective shear modulus of porous materials having various types of pore shapes are investigated, using both analytical and numerical methods. These solutions, and the scaling laws that are derived with the aid of these solutions, are then used to make predictions of the effective elastic moduli of some sandstones and ceramics, based on two-dimensional images of the pore space.

    The complex variable method is used to find the hydrostatic and shear compliances of a large family of pores that have N-fold rotational symmetry, and which have at most four terms in their conformal mapping function. This solution is validated using boundary element (BEM) calculations, and is also used to test two scaling laws that estimate the compliances based on the area and perimeter of the pore.

    The boundary perturbation method is used to study the effect of small-scale roughness on the compressibility and shear compliance of a nominally circular pore. The solution is carried out to fourth order in the roughness parameter for the case of hydrostatic loading, and to second order for shear loading. These solutions allow one to judge the scale of roughness that can safely be ignored when obtaining images of the pores.

    Predictions are then made of the elastic moduli of some porous materials – two sandstones and a ceramic. Starting with scanning electron micrographs, image analysis software is used to isolate and extract each pore from the host material. The bulk and shear compliances are estimated using both BEM and the two scaling laws. Areally-weighted mean values of these compliances are calculated for each material, and the differential effective medium scheme is used to obtain expressions for the moduli as functions of porosity. These predictions agree well with the experimental values found in the literature.

  • 243.
    Ekneligoda, Thushan Chandrasiri
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Henkel, Herbert
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Interactive spatial analysis of lineaments2010In: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 36, no 8, p. 1081-1090Article in journal (Refereed)
    Abstract [en]

    An interactive software tool, here called Spatial Analysis of Lineaments (SAL), has been developed for calculating the spatial properties azimuth, length, spacing, and unidirectional frequency of lineaments which are defined by their start and end coordinates. In a series of steps the user is guided by displays of relevant statistical distributions, which can be user designed. Statistical outliers can be excluded and the total sample of lineaments can be subdivided into azimuth sets and, if required, into spatial clusters. Special attention is given to the removal of spatial outliers in an interactive way. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the program defines a window whose size depends on the mode value of the length distribution of the lineaments in the study area. The software can accept a large amount of lineaments and can analyze the spatial properties of each azimuth set avoiding the repetitive calling of the original database. A simple rule was developed to derive the unidirectional lineament frequency. The spatial properties are presented as histograms for each azimuth set together with the mode, mean, standard deviation, and number of involved lineaments. (C) 2010 Elsevier Ltd. All rights reserved.

  • 244.
    Ekneligoda, Thushan Chandrasiri
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Henkel, Herbert
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    The spacing calculator software - A Visual Basic program to calculate spatial properties of lineaments2006In: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 32, no 4, p. 542-553Article in journal (Refereed)
    Abstract [en]

    A software tool is presented which calculates the spatial properties azimuth, length, spacing, and frequency of lineaments that are defined by their starting and ending co-ordinates in a two-dimensional (2-D) planar co-ordinate system. A simple graphical interface with five display windows creates a user-friendly interactive environment. All lineaments are considered in the calculations, and no secondary sampling grid is needed for the elaboration of the spatial properties. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the programme defines a window that depends on the mode value of the length distribution of the lineaments in a study area. This makes the results more consistent, compared to the manual method of spacing calculation. Histograms are provided to illustrate and elaborate the distribution of the azimuth, length and spacing. The core of the tool is the spacing calculation between neighbouring parallel lineaments, which gives direct information about the variation of block sizes in a given category of structures. The 2-D lineament frequency is calculated for the actual area that is occupied by the lineaments.

  • 245.
    Ekneligoda, Thushan Chandrasiri
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Zimmerman, Robert W.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Compressibility of two-dimensional pores having n-fold axes of symmetry2006In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 462, no 2071, p. 1933-1947Article in journal (Refereed)
    Abstract [en]

    The complex variable method and conformal mapping are used to derive a closed-form expression for the compressibility of an isolated pore in an infinite two-dimensional, isotropic elastic body. The pore is assumed to have an n-fold axis of symmetry, and be represented by at most four terms in the mapping function that conformally maps the exterior of the pore into the interior of the unit circle. The results are validated against some special cases available in the literature, and against boundary-element calculations. By extrapolation of the results for pores obtained from three and four terms of the Schwarz-Christoffel mapping function for regular polygons, the compressibilities of a triangle, square, pentagon and hexagon are found (to at least three digits). Specific results for some other pore shapes, more general than the quasi-polygons obtained from the Schwarz-Christoffel mapping, are also presented. An approximate scaling law for the compressibility, in terms of the ratio of perimeter-squared to area, is also tested. This' expression gives a reasonable approximation to the pore compressibility, but may overestimate it by as much as 20%.

  • 246.
    Ekwall, Jakob
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering. KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water Resources Engineering.
    Kvalitetskontroll av Vattenförbrukningsdata: Ursprung till Fel och Osäkerheter i mätdata från Göteborgs kommun2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 247. Elberling, Bo
    et al.
    Søndergaard, Jens
    Jensen, Louise A.
    Schmidt, Lea B.
    Hansen, Birger U.
    Asmund, Gert
    Balic-Zunic, Tonci
    Hollesen, J. Orgen
    Hanson, Susanne
    Jansson, Per-Erik
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Friborg, Thomas
    Arctic vegetation damage by winter-generated coal mining pollution released upon thawing2007In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 41, no 7, p. 2407-2413Article in journal (Refereed)
    Abstract [en]

    Acid mine drainage (known as AMD) is a well-known environmental problem resulting from the oxidation of sulfidic mine waste. In cold regions, AMD is often considered limited by low temperatures most of the year and observed environmental impact is related to pollution generated during the warm summer period. Here we show that heat generation within an oxidizing, sulfidic, coal-mining waste-rock pile in Svalbard (78 degrees N) is high enough to keep the pile warm (roughly 5 degrees C throughout the year) despite mean annual air temperatures below -5 degrees C. Consequently, weathering processes continue year-round within the waste-rock pile. During the winter, weathering products accumulate within the pile because of a frozen outer layer on the pile and are released as a flush within 2 weeks of soil thawing in the spring. Consequently, spring runoff water contains elevated concentrations of metals. Several of these metals are taken up and accumulated in plants where they reach phytotoxic levels, including aluminum and manganese. Laboratory experiments document that uptake of Al and Mn in native plant species is highly correlated with dissolved concentrations. Therefore, future remedial actions to control the adverse environmental impacts of cold region coal-mining need to pay more attention to winter processes including AMD generation and accumulation of weathering products.

  • 248.
    Embertsén, Maria
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Sustainable Stormwater Handling and Water System Urban Design.: A literature review and a case study in Nacka, Sweden.2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Climate change presents us with greater and greater challenges and stormwater is an important part of our future water problems. In some parts of the world the increase and intensification in precipitation causes strain on existing infrastructure while, in others, draughts are becoming more and more severe. Handling stormwater sustainably does not only gain the environment by controlling pollutant spreading, helping with flooding control and water reuse but can also have added values in urban areas if included in urban planning. Implementing green infrastructure and sustainable stormwater solutions creates jobs and are in many countries seen as the future way of handling stormwater. There are many different techniques and ways of adopting sustainable stormwater handling depending on the local problem and physical as well as economic conditions. Together they all have in common of creating added values when implemented. Increased biodiversity, improved air quality, reduced noise, improved growing conditions for urban trees and aesthetical values that have a positive effect on human health are just some of the positive added values of sustainable stormwater handling.

    The case study in this report concerns a new development on a peninsula in the municipality on Nacka, Stockholm. The recommendation is to adopt the approach of many small solutions that combines to a sustainable way of handling stormwater that not only solves the problem but creates added values in the living and working area. Stormwater is a resource that should be used as one in order to have sustainable urban planning.

  • 249. Englund, David
    et al.
    Brunberg, Anna
    Jacks, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    A CASE STUDY OF A FRESHWATER PEARL MUSSEL (MARGARITIFERA MARGARITIFERA) POPULATION IN CENTRAL SWEDEN2008In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 90A, no 4, p. 251-258Article in journal (Refereed)
    Abstract [en]

    Most of the Margaritifera margaritifera populations in Sweden are not reproducing. Land use such as forestry, eutrophication and water regulation for hydropower are commonly reported causes for the absence of reproduction. A brook with a very dense population of pearl mussels has been investigated with regard to the age distribution of the population and their habitat, in order to discover the reason for the absence of reproduction. The population consisted almost entirely of old mussels with very few young ones. The water flow and chemistry of the water are very stable and well buffered, due to a large glacifluvial deposit in the catchment area. The substrate in the stream is favourable and well aerated to a depth of at least 15 cm. Forestry has been practised with care for at least the last 15 years to avoid siltation of the stream sediments. The most likely reason for the lack of reproduction seems to be the water regulation of the main stream introduced 60 years ago, which has left the main stream dry seasonally. This is likely to have affected the population of brown trout which is the host for the first life-stage of the mussels, the glochidia.

  • 250. Engqvist, A.
    et al.
    Stenström, Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Pierce, Kena
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Modelling the effects of a pumping program for increasing water circulation in a semi-enclosed bay in the Stockholm archipelago2006In: Proceedings of the International Conference on Estuarine and Coastal Modeling, 2006, p. 253-269Conference paper (Refereed)
    Abstract [en]

    Brunnsviken in the inner Stockholm archipelago, close to the City of Stockholm and popular for recreational activities, is a semi-enclosed bay with a very narrow passage to the adjacent archipelago and consequently has a limited water exchange. Various attempts have been made over the past three decades to improve the water quality in the bay. Since 1986, the drinking water authorities of Stockholm withdraw bottom water by pumping it from one of the deep basins of the bay through a pipe to be eventually discharged into the nearest embayment of the archipelago. There are, however, some questions regarding the cost-benefit aspect of this strategy. In particular, it is unclear if the location and the rate of pumping are well chosen in order to increase the ventilation of the bay at large. In addition, it should be possible to eventually optimize the pumping schedule, so that these energy-demanding and thus costly efforts are concentrated to times when they act in concert with natural forcing to increase water exchange. To help improve the pumping program, a modelling project was started in spring 2004. First, a one-dimensional (1-D) layer model that resolves the bay into one basin with multiple-layer stratification was attempted. Second, a three-dimensional (3-D) model with the capacity to be run under non-hydrostatic assumptions was set up at high resolution to study a number of scenarios. Both models were forced by wind, river discharge, surface temperature and the exchange driven by density fluctuations across the boundary to the adjacent archipelago. In the 3-D model, the pumping is included as a virtual divergence of the flow at the location of the pipe. The main results are that the 1-D model performs considerably better than the 3-D model in simulating the measured salinity profiles, even though it does not resolve the basin in the horizontal direction. The poor performance of the 3-D model with regard to salinity is however mainly due to boundary problems: too little inflow of saline water through the narrow and shallow entrance channel, and underestimation of the freshwater supply. The dynamics of the thermocline is better captured by the 3-D model but can certainly also be improved.

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