Integrated hydrologic flow characterization of the Krycklan catchment (Sweden).

Sammanfattning: Currently there are urgent water related problems, such as use of groundwater and surface water resources, which need a more integrated view on the hydraulic cycle and how the different processes interact with each other. This has led to new ways of thinking in management of watersheds, which sparked the creation of new integrated tools for flow characterization. Characterization of a watersheds flow is an important step in future research regarding water quality and climate change issues. The Krycklan catchment, located in the northern part of Sweden, has been under research for many years. With a great deal of measurements regarding stream water chemistry as well as climate measurements (evaporation, transpiration and temperature), the catchment has great potential regarding solute transportation and climate change investigation. This thesis was made to aid in future research by characterization of the catchments groundwater and surface flow, by the use of an integrated model software tool, MIKE-SHE. The model have been calibrated and validated with the help of real time observed measurements at Krycklan combined with model data from SMHI:s HYPE-model. Throughout the calibration it was discovered that the hydraulic conductivities were important for the surface and groundwater interaction, regulating base flow as well as peak flows. The shape and timing of the spring flood was also affected by the snow melt while the summer peaks for the upstream rivers, probably due to the relatively large difference in topography elevation, were more affected by the representation of the topography created by the grid size. A smaller grid-size resulted in a finer representation of the topography, which resulted in a quicker runoff to the upstream rivers without an increase of base flow. This gave better fitted hydrographs of the flows in the upstream rivers compared to observed measurements. The final model created was able to capture the discharge-hydrograph and groundwater fluctuations with small error and high correlation coefficients compared to observed data and model data from SMHI. The results as well as the calibration process helped with a deeper understanding of the modeling tool itself as well. Future improvements that can be considered are to introduce new calibration data and the use of an even smaller grid size. This can improve the understanding of the catchment as well as the representation of the flow in the upstream rivers. However, the effects of a smaller grid size must be reflected upon. The model will most likely become more unstable and the run time of the model will greatly increase. One suggestion to solve this issue is to look into a sub-catchment to reduce these complications.