The hydrological regime in Arctic catchments is being altered as an effect of climate change. To be able to project future changes in Arctic hydrology and hydrogeology, the mechanisms and drivers affecting runoff generation needs to be understood. This thesis aims to investigate and compare rainfall-runoff processes in three hillslope subcatchments, one glacierized and one non-glacierized catchment, in the Arctic. By estimating catchment response parameters and using recession analysis it was found that soil layer extent, rather than catchment size, explained differences in catchment response. The character of the rainfall events was a dominant factor affecting catchment response in both the glacierized and non-glacierized catchment. Saturation excess overland flow was a runoff-generating process in all catchments. Furthermore, permafrost and glacier presence, as well as meltwater contribution to the streams, were suggested to result in a larger variability in catchment response and storage contribution along the hillslopes and the glacierized catchment. Meanwhile, the wetness of the non-glacierized catchment was suggested to influence the storage-discharge dynamics in the non-linearized catchment. Water height recession analysis was not considered reliable to characterize aquifer properties in the catchments. However, it was able to describe the changes in storage-discharge relations over time in Arctic catchments.

Vatten är en livsviktig resurs därför behöver kvalitén övervakas. Slamhalt i vatten är viktigt eftersom det kan föra med sig gifter och näringsämnen, men även grumlar vattnet vilket kan påverka livsmiljön för vattenlevande organismer. Slamhalt varierar över tid på grund av olika processer som transporterar material till vattendrag. För att mäta slamhalten har man historiskt tagit vattenprover i fält. Det är tidsödande och görs sällan vilket leder till att man lätt missar toppar och dalar i flödet.  Turbiditet är möjligt att mäta in situ och innebär att vattnets ljusgenomsläpplighet mäts. Det kan mätas med täta intervall vilket ger detaljerad information om förändringar i vattendragen. Korrelationen mellan turbiditet och slamhalt har undersökts flera gånger men eftersom mätningar reagerar på partiklars storlek och form behöver man utvärdera sambandet för varje enskilt vattendrag.  2017 gjordes en studie för Sveriges lantbruksuniversitet där Hoang (2017) använde multivariabel statistik för att undersöka turbiditet korrelerat med fosfor samt jordarters och markanvändnings påverkan på relationen i svenska vatten.  Sedan dess har markdata uppdaterats vilket gör det aktuellt att undersöka korrelationen mellan slamhalt och turbiditet. Genom linjär regression visades ett tydligt samband mellan turbiditet och slamhalt för många avrinningsområden. De högsta korrelationerna syntes för områden med hög fördelning av åkermark och lerhalt. / Water is a vital resource for life, that is why water quality is monitored. Suspended solids in water are important because it transports pollutants and nutrients, it also dims the water which can affect the environment for water living organisms. Suspended solids change over time due to different processes that transport materials to waterbodies. Historically, suspended solids have been measured by taking samples in the field. That takes a lot of time and fluctuations are lost because of dispersed measuring periods.  Turbidity can be measured in-situ and quantifies the light attenuation of the water. It can be measured with tight intervals which results in detailed information about changes in the waterbody. The correlation between suspended solids and turbidity has been studied several times, however, a turbidity sensor reacts to particle size and form which means that the correlation needs to be investigated for every individual waterbody.  2017 a study at the Swedish university of agriculture was done where Hoang (2017) used multivariate statistics to study turbidity correlated with phosphorus, as well as soil classes and land use factors influence on the relationship in Swedish waters. Since then, new data for soil and land use have been updated which makes it relevant to evaluate the correlation between suspended solids and turbidity. Through linear regression a clear correlation was shown for many catchments. The highest correlations were found in areas with high rates of agriculture and clay rich soils.

Dikesrensning är en etablerad åtgärd inom skogproduktion i Sverige för att bevara dikenas förmåga att leda vatten, och den sänkta grundvattennivån som ökat trädens tillväxt. I denna studie skapades och testades ett verktyg för att prognostisera förändringen av grundvattennivån vid simulerad dikesrensning för att förstå dikesrensningens påverkan på trädens tillväxt och negativa miljöeffekter. Verktyget applicerar Depth-to-Water (DTW) metoden för att skatta grundvattendjupet som lägsta summerade höjdskillnad till härlett ytvattensystem, med topografin från en digital markmodell. För att skatta grundvattennivån efter dikesrensning, så applicerades DTW på en markmodell med simulerad dikesrensning. Den simulerade dikesrensningen redigerade höjdvärdet längs dikesbotten i markmodellen till att representera dikesdjupet bättre men inte tillräckligt för att efterlikna en dikesrensning. DTW-metoden testades med olika hydrologiska bearbetningsmetoder av markmodellen för härledning av ytvattensystem och med höjdskillnaden beräknad från markmodellen respektive den hydrologiskt bearbetade markmodellen. Hydrologiska bearbetningsmetoden med samtliga funktioner, fylla och gräva kopplingar mellan sänkor, och utjämna markytan, härledde det mest realistiska ytvattensystemet och skattade grundvattennivån med generellt lägst medelavvikelsejämfört med fältmätningar och andra hydrologiska bearbetningsmetoder. När höjdskillnaden beräknades från den hydrologiskt bearbetade markmodellen skattades grundvattennivån markant bättre. Verktygets metod för skattade grundvattennivå med lägst medelavvikelse var på 0,28 m och bias på 0,10 m, vilket inte är tillräckligt för att använda verktyget för beslutsunderlag. Fortsatta studier skulle behövas för en bättre skattad grundvattennivå och med utvecklad metod för att kunna använda verktyget som beslutsunderlag vid dikesrensning. / Ditch network maintenance (DNM) is an established forestry practice in Sweden to keep ditches ability to convey water, which lower the water table to increase tree growth. In this study, a tool was created and tested to forecast the change in groundwater table during DNM to understand the impact from DNM on tree growth and negative environmental effects. The tool applied the Depth-to-Water (DTW) method to estimate groundwater table depth as the lowest summed elevation difference to surface flow channels, with respect to the topography in a digital terrain model (DTM). To estimate the groundwater table after DNM, DTW was applied to a DTM with simulated DNM. Compared to field measures the DTM with simulated DNM had an improved representation of ditch depth than the DTM without, but not sufficiently to mimic a DNM. The DTW method was tested with different hydrological processing on the DTM for derivation of surface flow channels and with the elevation difference calculated from the DTM versus hydrologically processed DTM. The hydrological preprocessing method with all functions, filling and breaching sinks, and smoothing the ground surface, derived the most realistic surface flow channels and estimated the groundwater table with generally the lowest root mean standard deviation (RMSE) compared to field measurements and other hydrological processing methods. When the elevation difference is calculated from the hydrologically processed DTM it improved the estimated groundwater table. The tool's estimated groundwater table had the lowest RMSE of 0.28 m and a bias of 0.10 m, which is not enough to use the tool for decision support. Further studies would be needed for better estimated groundwater table and developed methods to be able to use the tool as decision support for DNM.

On the northeast coast of Gotland in Slite lies one of Heidelberg Materials' limestone quarries. Today, the factory has permission to extract limestone until 2027, and an application for extended quarrying operations for the next 30 years is in process. The new quarrying activity will involve removing a part of a catchment area. This catchment area supplies water to several Natura 2000 areas south of the quarry. With the removal of land, there will be water losses, and as a protective measure, the factory intends to infiltrate water back into surface and groundwater. The water to be used for this purpose is drainage water from the quarry. Due to nitrogen-based explosives, this water has higher nitrogen levels than the natural levels in the area. The purpose of this study was to investigate how nitrogen levels in the area are affected by the protective measure using INCA-N, a software for simulating nutrient transport in rivers. According to the model, the future infiltration will not affect the water balance as the volumes added are relatively small. However, the infiltration will affect nitrate levels in the area where it is infiltrated. Downstream along the river, nitrogen levels will not be affected by the infiltration. INCA-N is a surface water model, and the groundwater situation in the limestone bedrock of Gotland is complex. Therefore, this model comes with many uncertainties regarding the interaction between surface and groundwater at the site.

Dagvatten är det vatten som faller som nederbörd och sedan rinner över vägar och bebyggelse ned i brunnar eller direkt till recipienten. Dagvatten innehåller många olika föroreningar som kan vara direkt skadliga för vattenmiljön. I examensarbetet undersöks Gottsunda dagvattenpark som syftar till att rena dagvattnet innan det når recipienten Hågaån. Målet är att alla ytvattenförekomster i Sverige ska uppnå god ekologisk och kemisk ytvattenstatus, då Hågaån inte uppnår detta i dagsläget är det viktigt att kvantifiera hur väl den befintliga reningen av dagvatten fungerar. Syftet med examensarbetet är att undersöka om kontinuerlig turbiditets- och flödesmätning kan vara en fungerande metod för att kvantifiera transport och avskiljning av dagvattenföroreningarna suspenderat material, fosfor, kadmium, krom, nickel, koppar, bly och zink. Kontinuerliga sensormätningar kan i högre grad fånga in den snabba variationen i dagvatten än konventionella mätmetoder. Bland annat kan turbiditet mätas kontinuerligt med sensorer, en parameter som ofta visar hög korrelation med bland annat suspenderat material. Denna studie visade att signifikanta linjära samband finns mellan turbiditet med suspenderat material, fosfor och metaller för Gottsunda dagvattenparks in- och utlopp. En viss osäkerhet förekommer för sambanden i inloppet till följd av extremvärden med hög influens där ett behov finns av fler stickprover. Den beräknade avskiljningen i denna studie är något lägre än vad som förväntas, en möjlig förklaring är den stora fraktionen lerjordar i avrinningsområdet samt att dammen är förhållandevis nyetablerad. En ytterligare förklaring kan vara att det inte är exakt samma vattenpaket som undersökts i in- och utlopp, vilket antas gett upphov till en underskattning av avskiljningen. Vid viktning av mängderna utifrån en korrekt vattenbalans uppnås en högre avskiljning. Avskiljningsförmågan i Gottsunda dagvattenpark har i stort ökat med tiden men med sämre avskiljning under vintermånaderna. Kontinuerliga sensormätningar fungerar bra för att uppskatta medelkoncentrationer och belastningar av föroreningar och har potentialen att revolutionera dagvattenövervakningen. Dock behövs mer forskning där bland annat partikelsammansättningens påverkan behöver undersökas. / Stormwater is the precipitation that falls over cities and proceeds to flow on our streets, collecting pollutants on its way to the recipient. Stormwater contains a lot of different pollutants that can cause harm to our water bodies. In the study, Gottsunda stormwater pond is examined, whose purpose is to purify the stormwater before it reaches the recipient Hågaån. The goal is that all waters in Sweden should achieve good ecological and chemical surface water status. Since this isn’t achieved by Hågaån it is important to quantify if the current stormwater purification works as intended. The purpose of this study is to examine the potential to use high frequency sensors, measuring turbidity and discharge, to quantify transport and removal of the stormwater pollutants suspended solids, phosphorus, cadmium, chromium, nickel, copper, lead, and zinc. Measuring turbidity and discharge continuously using high frequency sensors can capture the fast variation in stormwater to a higher extent than conventional methods. Turbidity is a parameter which often shows high correlation with e.g. suspended solids. The study showed significant linear relationships between turbidity with suspended solids, phosphorus, and metals for incoming and outgoing water of Gottsunda stormwater pond. Uncertainty is present in the relationships for the incoming water due to extreme values with high influence, thus more grab samples are required. The calculated removal of pollutants is below the expected level, a possible explanation for this is the high fraction of clay soils in the catchment and the young age of the pond. Another explanation could be that the water volumes differ between in- and outlet. Considering the same volumes a higher removal is retrieved. The ability to remove pollutants has increased over time since the pond was established, with exception for the winter months. High frequency sensor measurements work well for estimating mean concentrations and loads of pollutants and has the potential of revolutionizing surveillance of stormwater. Although, more research is required where the effect of particle composition needs to be examined more closely.

This PhD study focusses on the use of MEdium Resolution Imaging Spectrometer (MERIS) data for reliable and quantitative water-quality assessment of optically-complex waters (lake, brackish and coastal waters). The thesis is divided into two parts: A. intercalibration of reflectance measurements in different optically-complex water bodies (Paper I), and validation of various satellite processing algorithms for the coastal zone (Paper II). B. Applications: the use of MERIS data in integrated coastal zone management mostly using Himmerfjärden bay as an example. Himmerfjärden bay is one of the most frequently monitored coastal areas in the world and it is also the recipient of a large urban sewage treatment plant, where a number of full-scale nutrient management experiments have been conducted to evaluate the ecological changes due to changes in nutrient schemes in the sewage plant. Paper I describes the development and assessment of a new hyperspectral handheld radiometer for in situ sampling and validation of remote sensing reflectance.  The instrument is assessed in comparison with readily available radiometers that are commonly used in validation. Paper II has a focus on the validation of level 2 reflectance and water products derived from MERIS data. It highlights the importance of calibration and validation activities, and the current accuracy and limitations of satellite products in the coastal zone.  Bio-optical in situ data is highlighted as one of the key components for assessing the reliability of current and future satellite missions. Besides suspended particulate matter (SPM), the standard MERIS products have shown to be insufficient to assure data quality retrieval for Baltic Sea waters. Alternative processors and methods such as those assessed and developed in this thesis therefore will have to be put in place in order to secure the success of future operational missions, such as Sentinel-3. The two presented manuscripts in the applied part B of the thesis (paper III and IV), showed examples on the combined use of in situ measurements with optical remote sensing to support water quality monitoring programs by using turbidity and suspended particulate matter as coastal indicators (manuscript III). The article also provides  a new turbidity algorithm for the Baltic Sea and a robust and cost-efficient method for research and management.  A novel approach to improve the quality of the satellite-derived products in the coastal zone was demonstrated in manuscript IV. The analysis included, the correction for adjacency effects from land and an improved pixel quality screening.  The thesis provides the first detailed spatio-temporal description of the evolution of phytoplankton blooms in Himmerfjärden bay  using quality-assured MERIS data, thus forwarding our understanding of ecological processes in in Swedish coastal waters. It must be noted that monitoring from space is not a trivial matter in these optically-complex waters dominated by the absorption of coloured dissolved organic matter (CDOM). These types of coastal waters are especially challenging for quantitative assessment from space due to their low reflectance.  Papers III and IV thus also provide tools for a more versatile use in other coastal waters that are not as optically-complex as the highly absorbing Baltic Sea waters. The benefits of the increased spatial-temporal data coverage by optical remote sensing were presented, and also compared to in situ sampling methods (using chlorophyll-a as indicator). / <p>Research funders:</p><p>European Space Agency (ESA, contract no.21524/08/I-OL)</p><p>NordForsk funding: Nord AquaRemS Ref. no. 80106</p><p>NordForsk funding:  NordBaltRemS Ref.no. 42041</p><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

All life on Earth is based on and is constantly dependent on flows of water through every plant, every animal and every human body. This makes water Earth's most important natural resource. Lack of water can cause enormous suffering to faculty of agriculture, industry and local ecosystem. Although models, research and pure common sense shows the rational and positive in cooperating on shared water resources, it takes time to build up a stable cooperation between the different political states. Although a generalization is not possible, it is possible to find patterns that despite prevailing political situation, there is a willingness and desire to override political differences and seek a sustainable development in the region. Today there is a consensus among scientists that shared water combined with water shortages, often causes political conflicts. These disputes rather get the parties to realize that they are dependent on each other to get the water they need, and that they find ways to cooperate.

Geological Carbon Storage (GCS) is considered as one of the key techniques to reduce the rate of atmospheric emissions of CO2 and thereby to contribute to controlling the global warming. A successful application of a GCS project requires the capability of the formation to trap CO2 for a long term. In this context, processes related to CO2 trapping and also possible leakage of CO2 to the near surface environment need to be understood. The overall aim of this thesis is to understand the flow and transport of CO2 through porous media in the context of geological storage of CO2. The entire range of scales, including the pore scale, the laboratory scale, the field experiment scale and the industrial scale of CO2 injection operation are addressed, and some of the key processes investigated by means of experiments and modeling.  First, a numerical model and laboratory experimental setup were developed to investigate the CO2 gas flow, mimicking the system in the near-surface conditions in case a leak from the storage formation should occur. The system specifically addressed the coupled flow and mass transport of gaseous CO2 both in the porous domain as well as the free flow domain above it. The comparison of experiments and modelling results showed a very good agreement indicating that the model developed can be applied to evaluate monitoring and surface detection of potential CO2 leakage. Second, the field scale CO2 injection test carried out in a shallow aquifer in Maguelone, France was analyzed and modeled. The results showed that Monte Carlo simulations accounting for the heterogeneity effects of the permeability field did capture the key observations of the monitoring data, while a homogeneous model could not represent them. Third, a numerical model based on phase-field method was developed and model simulations carried out addressing the effect of wettability on CO2-brine displacement at the pore-scale. The results show that strongly water-wet reservoirs provide a better potential for the dissolution trapping, due to the increase of interface between CO2 and brine with very low contact angles. The results further showed that strong water-wet conditions also imply a strong capillary effect, which is important for residual trapping of CO2. Finally, numerical model development and model simulations were carried out to address the large scale geological storage of CO2 in the presence of impurity gases in the CO2 rich phase. The results showed that impurity gases N2 and CH4 affected the spatial distribution of the gas (the supercritical CO2 rich phase), and a larger volume of reservoir is needed in comparison to the pure CO2 injection scenario. In addition, the solubility trapping significantly increased in the presence of N2 and CH4.

Sub-Saharan Africa is today facing a big challenge regarding food deficiency and water scarcity due to climate change. One of these countries is Rwanda, a small landlocked country in the middle of Africa. Rwanda strongly depend on agriculture, both in the aspect of reducing poverty and hunger but also because their economy security depend on it. Because of increasingly fluctuating rainfalls their agriculture becomes more dependent on irrigation and the availability to water resources. To investigate how the climate change will affect the amount of water resources in the coming decades, this study is focusing on the watershed and marshland of Muvumba P8 in Nyagatare, Rwanda. A hydrological model was created, in a software called Soil and Water Assessment Tool (SWAT), with soil, land use and slope maps for the watershed. Calibrating the model was done with help of Climate Forecast System Reanalysis (CFSR) data and run for nine different climate model datasets. An uncertainty had to be taken into account regarding both the measured local data and the downloaded data. To be able to compare the amount of water resources and the irrigation requirements for the rice crop the farmers were growing on the marshland, the crop water requirements for rice was estimated with FAO’s program called CROPWAT. The irrigation system on the marshland allows a double cropping of rice every year and consist of a system depending on elevation differences to create natural fall. There was three reservoirs along the marshland but to limit the project, only the first reservoir was taken into account. This was complemented with existing data and field survey. Six out of nine climate models showed a decrease in median discharge over the coming 30 years compared to the CFSR historical median discharge. This means that less water in general will reach the outlet of the watershed in the years to come. At the same time all climate models indicate an increase in irrigation requirements for the rice crops. The seasons are probably going to change, a longer and drier season between June and August and a rainier season between September and November are projected.

En endimensionell SVAT-modell (Soil-Vegetation-Atmosphere) användes för att simulera avdunstning och uppskatta den kritiska vattenpotentialen där reduktionen av vattenupptaget börjar. Detta gjordes i en blandad tall- och granskog i norra Uppland för perioden 1 maj - 31 oktober 1994. Denna period var ovanligt varm och torr och gav därför en unik chans att studera vattenupptag och upptorkning. Som indata till modellen användes markfysikaliska egenskaper och dagliga meteorologiska data. Modellen kalibrerades med TBR-, tensiometer- och grundvattenståndsmätningar för samma period. Den kritiska vattenpotentialen uppskattades till -100 hPa och visade sig vara en känslig parameter i modellen. Reduktionen av vattenupptaget började i slutet av juni. Ytresistansen beräknades med hjälp av Lohammarekvationen och bladyteindex. De markfysikaliska egenskaperna hade stor betydelse för simuleringsresultaten. Dessa egenskaper var mycket osäkert bestämda på grund av svårigheterna att mäta i inhomogen moränmark. Modellsimuleringarnas överenstämmelse med markvattenmätningarna varierade mellan olika djup i marken. / A one-dimensional SVAT-model (Soil-Vegetation-Atmosphere) was used to simulate evaporation and estimate the critical soil water potential where the reduction of the water uptake begins. This was done in a mixed pine and spruce forest in the north of Uppland, Sweden for the period 1 May to 31 October 1994. This period was unusually warm and dry and gave a unique chance to study the water uptake and the drought. Driving variables to the model were daily meteorological data and soil physical properties. The model was calibrated with TDR- (Time-Domain Reflectometry), tensiometer and ground water level measurements from the site for the same period. The critical water potential was estimated to -100 hPa and appeared to be a sensitive parameter in the model. The reduction of the water uptake began at the end of June. The surface resistance was calculated from the leaf area index and the Lohammar equation. The soil physical properties were shown to be significantly affecting the results of the simulation. The determination of these properties was uncertain because of the problems to measure in an inhomogenous till soil. The model simulations agreed generally well with the soil moisture measurements in some layers but a good agreement for all layers was not possible to obtain.