In 2022, a significant fish die-off happened in the Odra River due to a bloomof the toxic gold algae species Prymnesium parvum, which occurs in saline andwarm waters. This event is seen as a major ecological disaster in recent Europeanriver incident history. Understanding the hydro-climatic factors and basin characteristicsthat led to this disaster is crucial to prevent similar occurrences inthe future. Multiple national and international research groups have been activelystudying this event, reconstructing its chronology and analyzing the toxicalgal bloom. However, the specific relationship between the algal occurrence andhydro-climatic conditions, as well as the potential for recurrence, remains largelyunexplored. This project utilizes the semi-distributed hydrological model Soiland Water Assessment Tool (SWAT) on a daily time scale to investigate runoffbehavior during the disaster year. The main goal is to assess SWATs capability tosimulate runoff in a large-scale watershed. The obtained results are then analyzedin relation to water quality parameters and climatic conditions. The focus is onunderstanding the relationship between runoff and salinity, which is further examinedthrough a climate change scenario analysis to evaluate the potential riskof increased river salinity due to a change in the flow regime in the future. Byimplementing two Shared Socioeconomic Pathway (SSP) scenarios in the calibratedand validated SWAT model, a relative trend of runoff behavior and salinityin the Odra River is examined. The findings indicate that SWAT effectively simulatesrunoff in a large-scale catchment, despite limited information and computationalresources. The analysis reveals a significant relationship between salinityand runoff. The climate change scenario analysis predicts a decrease in runoffunder the pessimistic scenario, while the optimistic scenario suggests a more balancedrunoff trend. Additionally, the estimation of future river salinity suggestsan increase under reduced runoff conditions, and a subsequent recovery in salinitylevels for high discharge conditions. This thesis provides insights into the2022 disaster event in the Odra River and highlights the interplay between hydroclimaticfactors, catchment conditions, and toxic algae blooms. The findings contributeto a better understanding of potential risks and can give information foreffective water management strategies to protect the river ecosystem.

No description available.

In marine ecosystems around the world, iron (Fe) is a well-studied and important trace element which has been found to stimulate phytoplankton and cyanobacteria growth, as well as limit nitrogen fixation and being essential for Legionella pneumophila which is known as the main cause of Legionnaires’ disease. Fe also contributes to the brownification of freshwater and has recently been documented to increase in concentration in rivers in Sweden. The aim of this study was to investigate the link between Fe and humic substances (HS) in rivers and a coastal area in the northern Baltic Sea. In late winter, surface samples from rivers and the coast were analyzed for Fe, HS, dissolved organic carbon (DOC), pH, salinity, and temperature. Overall, the results showed a positive correlation between Fe and HS, indicating a terrestrial input of Fe. Other variables affecting Fe and HS including pH, salinity, and temperature were analyzed using principal component analysis (PCA), which showed spatial variations between river and coastal samples. Fe is known to be transported in water as two main carrier phases, Fe-OM complexes and Fe-oxyhydroxides. Which carrier phase is the most contributing depends on multiple factors, including catchment characteristics, seasonal variations, and water chemistry. Understanding the link between Fe and HS in land-sea transitional areas is important since terrestrial Fe is identified as a source of bioavailable Fe in marine waters such as the Baltic Sea.

River restoration is something that is often used to help restore watercourses that were historically used for timber floating. In these restorations, instream wood (IW) plays a big role in increasing biodiversity and habitat heterogeneity in watercourses. Uncrewed Aerial Vehicles (UAVs) have proven to be useful when monitoring changes following river restoration but there is a need for less time-consuming methods to detect IW. This study’s objective was to investigate IW following a river restoration in an alluvial reach in Vargån, Northern Sweden and how well UAVs can be used to do this. Manual digitizing of IW was done in GIS from orthomosaics of three different flight occasions: pre-restoration, directly after and one year after restoration. An object- and color-based automated image thresholding was done to investigate if it could be used to automatically detect IW. The results showed that there were differences in number of IW, volume, width, and length between the different flight occasions. There was also indication that there had been movement of IW as well as changes in cluster composition, with more clusters with a higher number of wood pieces in the latest flight occasion. The automated image thresholding was able to accurately detect IW with an accuracy of 47,4 %, but it had limitations due to natural conditions. However, it showed the possibility of using automated methods to detect IW and with improvements it could become a faster and more accessible way of detecting IW in river monitoring.

No description available.

No description available.

Groundwater abstraction for irrigation use has steadily increased over the past decades, resulting in additional evaporation to the atmosphere, and increased precipitation. The precipitation stemming from groundwater irrigation (or Groundwater-dependent precipitation) has received little attention during recent years and is solely researched by the Eulerian model. This study aims to provide a supplement and improvement of the global fate of groundwater-dependent precipitation with the Lagrangian model outcome. The analysis combines the UTrack model output between 2008 to 2017, a global groundwater irrigation area map, groundwater abstraction from PCR-GLOBWB version 1, and groundwater irrigation efficiency to generate the global groundwater-dependent precipitation trajectory from 2001 to 2010. The primary assumption is that atmospheric factors do not change significantly in all pressure levels during 2001 – 2010 and 2008 – 2017. The simulation result shows that groundwater-dependent precipitation is generally more substantial in Asia than in other continents. Bhutan, Bangladesh, Nepal, India, Yemen, and Afghanistan are the top six countries receiving high groundwater-dependent precipitation contributions monthly and yearly. Moreover, groundwater-dependent precipitation in the continent and country shows a significant seasonal change in the monthly average. A country or continent with a high groundwater abstraction does not necessarily receive a massive amount of groundwater-dependent precipitation regardless of monthly and yearly scale. For instance, China has a yearly average groundwater abstraction of 100 km3 year-1 but receives less than 1% groundwater-dependent precipitation contribution per year. Approximately 75% of groundwater-dependent precipitation falls into the land, and 25% ends in the ocean from 2001 to 2010. The groundwater-dependent precipitation does not significantly contribute to land and ocean, with 0.16% and 0.015%, respectively. Consequently, the study suggests groundwater-dependent precipitation does not have a greater effect on downwind area precipitation on a yearly scale but a larger effect during a specific month. The highest monthly average groundwater-dependent contribution is 18% in January, whereas the highest yearly groundwater-dependent contribution is 2.5% in 2006. Major regions with high groundwater-dependent precipitation contributions are found along the Himalayas Range from January to April and moving eastward to Arabic Peninsula in July.

No Abstract Provided / Thesis / Candidate in Philosophy

The Sub artic regions are becoming increasingly important due to the effects of climate change. In northern Sweden, thawing of permafrost has led to significant increases in annual minimum flows in several catchments. This has led to studies of groundwater flow, responses to precipitation and runoff, and subsurface connectivity of springs on slopes. However, there remains a limited understanding of the interplay between surface flow and subsurface flow in the hillslopes of subarctic region. There is a need to better understand the flow pathways and connectivity of groundwater flows within the slopes. This study aims to analyze the interactions between surface flow and subsurface flow on an Sub artic mountainside. Utilizing tracer experiments and a hydrological model, the complex dynamics governing water movement within this intricate system have been studied.  Tracer experiments affirmed the hydraulic connection between hillslope and spring. The spring's response to tracer injection hinted at dominant preferential flow paths within the regolith layer's base. Nonetheless, only 40% mass recovery raised queries about factors affecting the flow in the hillslope. Thus, in this project, a model was developed using Advanced Terrestrial Simulator (ATS) to examine the dominant flow processes and evaluate the influence of various hydrogeology parameters and fluid flow properties on tracer movement. The results highlight the dominance of subsurface flows occurring close to the surface. The parameter sensitivity analysis conducted in the study showed that roughness coefficient and permeability significantly influenced specific pathways and directions that water, and tracers took as they moved through the hillslope's subsurface layers and regolith.  However, the model has limitations, such as neglecting the lateral variations of the subsurface material, seasonal freeze-thaw processes and the simplified representation of the slope and catchment. The results of this study show the need for utilizing more field-based methodologies and further refinement of the modeling approach to improve our understanding of hydrologic processes in high latitude areas.

This study aims at increasing the amount of data available on recent past Swedish glacier front variations, at improving the knowledge on the present behavior of these glaciers, and at contributing to the defnition of the guideline for future of glacier front observations in Sweden. To do so, the study proposes Sentinel-2 based yearly front variation measurements for 22 Swedish glaciers between 2015 and 2022, calculated based on the multicentreline approach of the MaQiT tool. It also assesses the uncertainty of Sentinel-2 based mapping by comparing it to 0.48 m spatial resolution aerial imagery based mapping and to field based mapping conducted on four northern Sweden glaciers during the end of the summer 2022: Kaskasatj SE, Kebnepakteglaciären, Mårmaglaciären, and Storglaciären. The fieldwork included handheld GNSS, UAV photogrammetry, and total station survey in order to compare the three methods in the mapping of glacier fronts. This study also compares the measured glaciers front variations to climatic factors and glaciers boundary conditions. The resulting glacier front variations in Sweden between 2015 and 2022, averaged over all glaciers studied, is −10.28 m yr−1. Small glaciers retreated on average 0.51 % of their length per year, while large glaciers retreated on average 0.35 % per year. This study highlights the importance of recording yearly front positions of a large amount of glaciers, and therefore encourages for the future the use of satellite imagery to observe all Swedish glaciers fronts on a yearly basis. It also supports the conduction of regular UAV photogrammetry surveys to provide high resolution mapping of a sample of glacier fronts chosen for their vicinity with the Tarfala Research Station, the Swedish field centre for glaciological and alpine research.