Hydrological and chloride transport processes in a small catchment of the Norrström Basin : a MIKE SHE modelling approach

Abstract: Water is ubiquitous on our planet and constitutes a vital part of ecosystems. It supports the life of all beings on the earth while simultaneously evokes water-related issues such as water shortage, water contamination. As UN advocates, a globally shared blueprint for available clean water is depicted in Sustainable Development Goals (SDGs). However, there still exists a gap between current water management situations and our sustainable goals Modelling based on Hydro-Meteorological Data provides a way to understand regional hydrological processes and monitor environmental chemistry changes, especially for anthropogenic pollution. Furthermore, hydrological models make it possible to predict changes in water quantity and quality, under the context of climate change. The study area of this project is located in the Kringlan catchment, Norrström basins, occupying an area of 54.5 km2. The local discharges merge into Rastälven river and flow to the east, eventually discharging into the Baltic Sea. This project builds up a water balance model based on the meteorological data in the time frame from 2011 to 2012. The water balance model is calibrated to accurately simulate realistic hydrological components interactions, during each process, various parameters have been tested and adjusted to improve model robustness. Meanwhile, the project tries to strike a balance between the complexity of the model and amount of time it takes to run the model. The calibrated model is also validated to ensure model performance using statistical analysis. Additionally, a particle tracking model for the saturated zone is developed on the basis of the water balance model. Chloride is chosen as the trace element due to its feature of unreactive in ecological systems. The model results could also provide a value to groundwater age estimation. Suggested by previous researches targeting the area, leakage from vegetation and forest soil in this catchment have contributed to imbalances in local Cl- budgets. An internal source of chloride from soil leaching is specified in the model at the same time with an external source from stream discharge. The coupled modelling through the application of MIKE SHE software and calibration process help us to understand dynamic processes of hydrological modelling and chloride particle transport in the Kringlan catchment. A future improvement to consider is extending the current model boundary to a larger area and introducing more reference data. It is also possible to establish a fully integrated solute transport model to investigate Chloride transport in the catchment.