Successfully modeling one system response (e.g. hydrograph or solute transport) sometimes gives the false sense of well-characterizing the modeled system. This is partly because of the well-known equifinality issue; during the calibration process multiple parameter combinations can produce similarly good results. One step forward towards a better-defined system is using measured (at relevant scale) values for the model parameters, as well as using multiple conditions to constrain the model. But when not enough, or relevant, field measurements are available, virtual experiments (VE’s) can be used as a supplementary method to model calibration. The advantage of VE’s over model calibration is that they can also be used to explore assumptions both on the system hydrological processes, and on the model structure. One goal of this study was to utilize both field measurements and models for better characterization of the S-transect hillslope, located in Västrabäcken catchment, Northern Sweden. This included (a) characteristics in space: system vertical boundaries, hydraulic parameters, pore water velocity distribution, spatial correlation of flowpaths, soil water retention properties; (b) characteristic of system’s dynamic behavior: storage – discharge relationship, transit time distribution, turnover time; and (c) outputs’ sensitivity to external forcing, and to small scale structure assumptions. The second goal was to comment on the value of field measurements and virtual experiments for extracting information about the studied system. An intensely monitored study hillslope was chosen for this work. Although the hillslope has already been the subject of multiple field and modelling studies, there are still open questions regarding the characteristics listed above. The models used were the Vertical Equilibrium Model (VEM), and the Multiple Interacting Pathways (MIPs) model. It was found that the hillslope was well connected; from the near-stream areas up to the water divide the storage – discharge relationship could be described as an exponential function. Also, the dynamic storage (which controls the hydrograph dynamics) was much smaller comparing to the total hillslope storage. The unsaturated soil storage was found to be more sensitive to water table positions than vertical flux magnitude. The dynamic condition of external forcing (precipitation and evapotranspiration) affected the transit time distribution (TTD) shape. And, opposite to expectations, TTD was not sensitive to micro-scale structural assumptions tested here.

In this study, GIS methods were used in order to evaluate different wetness indicators — topographic indices and airborne gamma radiation measurements — from their ability to distinguish wet areas from other areas. As a surrogate measure of extreme wetness, the occurrence of mires from land use maps were used. The evaluation of each wetness indicator was made in two ways. First, mire and non mire values for each measure was tested for similarity. Then, predicted mire maps were produced by defining mire area class limits (threshold values), which gave the same fraction of mire area in the catchments as in the land use maps. The predicted mire maps were then compared to the map showing mires from land use surveys. The best predictions were made by the drainage efficiency index (46.8% correct mires of all mire cells), which was proposed as an alternative to the ln(α/tanβ) index (the TOPMODEL index) and slope. This index quantified the downslope drainage ability for any point in the catchment, which is likely to be important for the wetness status. Mire predictions from K-40 gamma radiation were correlated to the different geological regions in the area and did not reproduce an accurate overall mire pattern. The TOPMODEL index class limits were strongly correlated to the fraction of mire area, which prevented it from being a good indicator of mires. It did not reproduce accurate amounts of area in the subbasins from a global threshold value. However, the general pattern of the predicted mires agreed relatively well with the pattern of actual mires from the land use map. / I en studie undersöktes förmågan hos olika mått på markfuktighet — topografiska index samt flyguppmätt naturlig gammastrålning från K-40 att särskilja våta områden från övrig mark. Som ett mått på extremt fuktig mark användes förekomsten av myrar från Gröna Kartan. Utvärderingen av de olika fuktighetsmåtten gjordes först genom att jämföra frekvenskurvorna för myrmark respektive övrig mark och kvantifiera skillnaden mellan dessa fördelningar för varje fuktighetsmått. Därefter uppskattades ett tröskelvärde för varje fuktighetsmått, vilket delade frekvensfördelningen i två klasser. Tröskelvärdet valdes så att förhållandet mellan arean i våt respektive torr klass blev densamma som mellan myrmark och övrig mark ur Gröna Kartan. Med utgångspunkt från dessa tröskelvärden framtogs kartor med simulerade myrar för varje fuktighetsmått, vilka jämfördes med myrarna i Gröna Kartan. De simulerade myrarna från ett topografiskt index som kvantifierade dräneringsförhållanden nedströms i terrängen gav bäst överensstämmelse med de verkliga myrarna (46.8% rätt klassade myrceller av det totala antalet myrceller). Simuleringen av myrar från K-40 gammastrålning var starkt beroende av berggrundstypen i området, och det övergripande mönstret gav ingen god överensstämmelse med Gröna Kartans myrar. Tröskelvärdena för ett av de topografiska index som granskades, ln(α/tanβ) index (TOPMODEL index), visade ett mycket tydligt beroende av andelen myr i området som simulerades, vilket gjorde att det svart att sätta ett gemensamt tröskelvärde for alla delområden i studien. Trots detta överensstämde myrmönstret från detta index i huvudsak med myrområdena från Gröna Kartan. / <p>Delar av examensarbetet publicerades senare som ”Water Resources Research technical note”: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004WR003130</p>

Flow in fractured rocks has been intensively studied in the last decades, in part due to plans in manycountries to site repositories for high level nuclear waster in deep geologic formations. All investigated crystalline rocks have been found to be fractured and the majority of water flows through these fractures andfracture zones. Therefore, it is of interest to be able to understand and model flow rates, flow pathwaysand discharge through realistic rough-surfaced fractures. Conventional experiments using rock samples havedifficulty controlling and observing fracture properties, in particular the highly variable fracture aperturevoid space. Therefore, taking advantage of 3D printing technologies, two samples were created representinga constant and varying aperture fracture. This allows the properties of the fracture to be controlled andidentical geometries for both experiment and simulation to be prepared. Development of a laboratory experiment allowed for flow tests over different hydraulic gradients to be conducted through the printed samples.Discharge was numerically simulated through 9 single fracture cases, 5 of which have a constant aperture,assuming the Navier Stokes equations and using a computational fluid dynamics solver (OpenFOAM). Theresult of the simulation based on the Navier Stokes equations was within 5% of the experimental result forhydraulic gradients of 0.01 and 0.05, this suggests that the results from the experiment and simulation arereliable. In order to observe the transition from Darcy to non Darcy flow through a single fracture the hydraulic gradient was systematically increased. The results from both the experiment and the simulation werecompared to the simplified cubic law assumption using various estimates of aperture. Inertial forces influencethe discharge and have more importance on varying aperture geometry, therefore the transition to non Darcyflow in smooth apertures occurs at a higher hydraulic gradient. Calculation of the cubic law using the meanaperture value including zeros can reduce the difference between simulated discharge. A two-fracture systemwith one intersection was also simulated to investigate the influence of intersection geometry on discharge,which seems to be dependent on flow velocities, with low and high flows producing less variable discharge.Uncertainties between numerical simulation and laboratory experiments can be reduced by using 3D printedfracture networks, hence they can be a beneficial for understanding complex interactions that can happenwithin networks.

Avrinningens förändring i tid och rum beror av såväl klimat och årstid som av avrinningsområdets fysikaliska egenskaper. Kunskap om förändringar i avrinningsdynamiken är av stor vikt vid konstruktion av hydrologiska modeller. Avrinningsområdena i denna studie ligger inom NOPEX-projektets försöksregion. Regionen är ungefär 50 x 100 km2 och ligger till största delen nordväst om Uppsala. Områdena varierade i storlek från 0,45 till 11,5 km2. Tre av områdena var rena skogsavrinningsområden. De övriga två områdena var avsevärt större och utgjordes till största delen av skogs- respektive jordbruksmark. Den studerade perioden sträcker sig från juli 1994 till juli 1995. Avrinningsdynamiken studerades genom jämförelser av hydrogram, vattenbalanser, fördröjning snösmältning – avrinning, förändringen av avrinningens andel av det till området tillförda vattnet och analys av recessionskurvor. Dynamiska vattenmagasin har uppskattats genom integration av recessionsekvationer och magasinskoefficienter har uppskattats. Skillnaderna i avrinningsdynamik mellan områdena var i vissa fall avsevärda trots likartade fysikaliska egenskaper. Det minsta skogdominerade avrinningsområdet uppvisade en mycket avvikande avrinningsdynamik med stora avrinningstoppar under tidig höst, en vattenbalans med mycket hög avrinning, liten fördröjning snösmältning – avrinning och snabb recession. De övriga tre skogsdominerade områdena hade inte lika accentuerade skillnader i avrinningsdynamiken. Det av jordbruksmark dominerade området intog även det en särställning med litet och långsamt gensvar på nederbörd och en recessionskurva vars form inte liknade något annat område. Analysresultaten i detta arbete gav fingervisningar om vilka processer och förlopp som är av stor vikt vid beskrivning av avrinningsdynamiken i hydrologiska avrinningsmodeller. Den ibland mycket stora rumsliga variationen i avrinningsdynamik tydliggör de representativitetsproblem som är förknippade med användandet av regionala modellparametrar. / Changes of runoff in time and space are dependent on climate and season as well as on the physical properties of the catchment. Knowledge of changes in runoff dynamics in time and space is of great importance in the construction of hydrological models. The five catchments in this study were located in the NOPEX region. The region is approximately 50 x 100 km2 and it is located northwest of Uppsala. The studied catchments varied in size from 0.45 to 11.5 km2. Three small catchments were forested. The other catchments were larger and were dominated by woodlands and farmlands. The studied period extended from July 1994 to July 1995. The runoff dynamics were studied through comparisons of hydrographs, water balances, delays between snowmelt and runoff, variations in the runoff fraction of the water input to the area and analysis of recession curves. The dynamic groundwater storage was estimated by integrating the recession equations. The storage coefficient was also estimated. The differences in runoff dynamics between the catchments were considerable in some cases despite physical similarities. The smallest wooded catchment showed very different runoff dynamics with large runoff peakflows during early fall, a very large runoff in the waterbalance, a short delay between snowmelt and runoff and a quick recession rate. The differences in runoff dynamics between the remaining three wooded catchments were not as accentuated. The catchment dominated by farmland held a unique position with a slow runoff response to precipitation and a recession curve with a different shape. The results of this study gave pointers to the processes that are of great importance in describing the runoff dynamics in hydrologic runoff models. The sometimes large variation in runoff dynamics in space elucidates the problems with representativity associated with the use of regional model parameters.

I denna uppsats har den laterala och den longitudinella dispersionen studerats i en grusås, (Finnerödjaåsen) med hjälp av spårämnesmärkning. Spårämnet, NaI injicerades i ett grundvattenrör. Jodidkoncentrationen i grundvattnet mättes i injiceringsröret, i sju grundvattenrör placerade tvärs över åsen och i ett rör 50 meter nedströms injiceringsröret. För att bestämma den laterala och den longitudinella dispersionskoefficienten användes en förenklad modell som förutsätter laminärt flöde i ett homogent medium. Modellen visade god överensstämmelse med försöksresultaten från Finnerödjaåsen. Den laterala dispersionen beräknades till 2.4 m2/dygn. Den longitudinella dispersionen visade sig vara mycket större i åsens kärna, ända upp till 260 m2/dygn än någon meter från kärnan ut mot åskanten där dispersionen i genomsnitt var 16 m2/dygn. Hastigheten hos grundvattnet i åsens kärna var ungefär dubbelt så stor som i övriga åsen och troligtvis transporteras största delen av flödet i en liten del av åsens mitt. / The lateral and longitudinal dispersion of groundwater was studied in a gravel ridge, (Finnerödjaåsen) in the central part of southern Sweden. NaI was injected into a groundwater tube. The iodine concentration in the groundwater was then measured in the injection tube, in seven groundwater tubes placed in a transverse row 1,5-4 m apart 20 m downstream the injection tube and in one tube 50 m downstream the injection tube. The coefficients of lateral and longitudinal dispersion were determined by using a model assuming laminate flow in a homogeneous medium. For the gravel ridge examined, there was a good fit between the experimental data and this model. The lateral dispersion was found to be 2,4 m2/day. The longitudinal dispersion was much larger in the narrow passage in the middle of the ridge, 260 m2/day, than in the marginal zones of the ridge, 16 m2/day. The flow velocity of the groundwater in the middle of the ridge was about twice as large as the flow velocity in the rest of the ridge, i.e. the bulk flow of groundwater occured in the middle of the ridge.

Övergödning är ett av Sveriges mest allvarliga miljöproblem. Genom utsläpp till följd av antropogen verksamhet läcker näringsämnen ut i vattnet. Den senaste undersökningen av Stockholms stads grundvatten har kartlagt halterna av kväve och fosfor. Eftersom grundvatten är en del utav det hydrologiska kretsloppet, och efter en viss omsättningstid övergår till ytvatten, påverkar kvalitén hos grundvattnet recipienten samt det ekosystem som denna ingår i. Rapporten ämnar undersöka halterna av kväve och fosfor i grundvattnet utifrån befintliga bedömningsgrunder samt kartlägga huruvida grundvattnet bidrar till övergödning av Stockholms kommuns ytvattenförekomster. Detta är av vikt för kommunens vattenförvaltning i linje med EU:s vattendirektiv och mål om god status för vattenförekomster, men även för att verka mot landets miljökvalitetsmål. Miljöförvaltningens undersökning av grundvattenkvaliteten visar på höga halter av fosfor samt ammoniumkväve. Halterna av nitrat samt nitrit är enbart höga i vissa av provpunkterna. Halterna av främst fosfor och ammoniumkväve kan enligt bedömningsgrunder ha övergödande effekt på ytvattendrag. En översiktlig undersökning baserad på grundvattnets strömningsriktning visar att kommunens vattenförekomster får ett tillskott av vatten via grundvattnet inom kommunen. Detta finns representerat i kvalitetsundersökningen av grundvattnet varpå slutsatsen dras att ytvattenförekomsterna inom kommunen påverkas negativt av grundvattnet. / Eutrophication is one of Sweden’s most severe environmental issues. Due to emissions through anthropogenic activity nutrients are added to aquatic systems. The latest analysis of the Stockholm municipality groundwater has examined the levels of nitrogen and phosphorus. Due to the fact that the groundwater is part of the hydrological cycle and will eventually reach the surface water, the condition of the groundwater will affect the recipient and correlating ecosystem. This report aims to analyze the levels of nitrogen and phosphorus in the groundwater of Stockholm based on current national quality standards, and to identify whether the groundwater is contributing to the eutrophication of the surface water bodies in the municipality of Stockholm. This is of significance regarding the water management in Stockholm municipality, based on the EU water framework directive, and the target of achieving good status for all water bodies. It is also of great importance regarding the Swedish environmental quality objectives. The groundwater quality analysis indicates high levels of phosphorus and ammonium. The nitrate and nitrite levels are only excessive in certain cases. Primarily, the levels of phosphorus and ammonium may, according to national quality standards, have eutrophic effect on surface water bodies. A cursory examination based on the flow directions of the groundwater, indicates that the municipality’s surface waters are supplied with water from the municipality’s groundwater. This correlation is represented in the analysis of groundwater quality and it is therefore concluded that the groundwater has a negative impact on the surface water bodies within the municipality.

Time-lapse reflection seismic methods have proven effective fordetecting and monitoring the injection and spreading of geologicallystored CO2. These methods are based on interpreting changes in themedia’s elastic properties that result from replacing the native salinewater by the injected CO2, which in turn affects the seismic velocitiesof the media. Since applications of these methods in the field areexpensive, and the interpretation process is time consuming, pre-studyinvestigations should be done in order to determine whether or notreflection seismic surveys can successfully be applied to monitor theCO2 plume in the case of interest.In the present study, CO2 injection and migration in a deep salineaquifer based on a structure situated below the south-western part ofthe Baltic Sea was modeled. To determine the CO2 saturationdistributions at different times, the injection was numericallysimulated using TOUGH2/ECO2N. A radial-symmetric model withhomogeneous and isotropic properties was assumed and two differentinjection rates were studied, with the results analyzed at differenttimes after the start of the injection.The saturation and density values resulting from the TOUGH2simulation were converted to seismic velocities using the Biot-Gassmann model. A synthetic velocity model was built based on bothTOUGH2 and Biot-Gassmann models and synthetic seismic responsefields before and after injection were generated. The results show thatthe amplitude changes in the seismic response are detectable even forsmall amounts of injected CO2, while noticeable signs of velocitypushdown, as a signature of the CO2 substitution, could only beobserved if the injection rate is high enough.

The understanding of where the streams begin is an important factor in both hydrology and geomorphology, as well as for land use activities. Despite this, only a few research projects have been done in a snowmelt-dominated boreal landscape. The main objective in this study is to see if one could predict where a stream initiates by knowing possible controlling factors. Data points from stream initiation points in the boreal landscape of Krycklan, situated 50 km Northwest of Umeå, were analyzed. Krycklan is a well-known research area and a lot of research projects have been done here. The landscape is diverse and most of the streams have been modified by human impact. The data points were collected with help of a Global Positioning System (GPS) during three different sampling campaigns; May 2012, May 2013 and August 2013. Maps were made from a Digital Elevation Model (DEM) showing slope, elevation and contributing areas for the stream heads. No clear relationship between the contributing area and slope could be found in this area, although it has been demonstrated in more semi-arid climates. The results show that other factors than the contributing area, elevation and slope seem to have a greater impact for the initiation of streams in a boreal landscape. The results were expected because of the modifications done for the streams.

An isotope analysis using stable water isotope ratios, δ18O and δ2H, paired together with PFAS monitoring has been conducted to achieve a comprehensive understanding of the groundwater origin, transport processes and PFAS contamination dynamics for a portion of the Uppsala Esker affected by artificial infiltration. This information is valuable in developing strategies to meet the water demand that is expected to increase with the growing population, manage and reduce the PFAS contamination and protect the drinking water supply in Uppsala. The foundation of this project is a large set of δ18O and δ2H isotope data stretching back to 2014 until today, provided by Uppsala Vatten, as well as water samples taken between September and November 2023 at six groundwater sampling points in the area around Tunåsen, Uppsala. These six sampling points consisted of four groundwater observation wells, Galgbacken’s wellfield and Tunåsen’s infiltration chamber where water from Fyrisån passes through before being infiltrated in the aquifer.     By determining the travel time of the water through the esker from the infiltration point to the wellfield using the stable isotopes δ18O and δ2H the travel time was found to be on average 225 days and the average speed of water at this site was found to be 1·10-4 m s-1. By calculating the percentage of infiltrated surface water from the Tunåsen infiltration chamber in Galgbacken wellfield, a blending ratio could be assessed. This blending ratio was found to be on average 89 % surface water from river Fyris and 11 % virgin groundwater originating from north of the study area. When investigating the PFAS concentration at the six sampling points between Tunåsen and Galgbacken sampling point D showed high concentrations of PFAS indicating that there might be a point source near that sampling point. The PFAS composition did not change drastically along the travel path and not all PFAS comes from infiltration.  The isotope analysis can be used as a tool to estimate when a high total PFAS concentration found at Tunåsen is likely to reach Galgbacken, however it cannot be used to draw conclusions about the transport of individual PFAS substances or composition profiles.

No description available.