Title: Analysis of land use effects on the discharge of the river Fnjóská

The study was conducted to analyse the impact of land use on a river discharge and to explore the sensitivity of a hydrological model by testing the effects of different land use data and soil characteristics of a specific watershed. The study area was the watershed of the River Fnjóská, which is located in the Fnjóská valley in the north of Iceland. The WaSiM model applied in this study was initially calibrated with the discharge at the water gauge, and the outcome of the model simulation reflected the discharge well. After the initial calibration of the River Fnjóská watershed, five fictional land cover scenarios were imported into the calibrated WaSiM model to analyse the effects and sensitivity of different land covers on the river flow. ArcGIS spatial analyst tools were applied to process the watershed delineation and establish the five fictional different land use scenarios. The alternate land covers included in the watershed were: grassland, wetland, barren land, moss and heath land, forest and shrubs. The simulated discharge with different land covers was compared with the outcome of the calibrated model. The simulated discharges for grassland, moss and heath land, and observed discharges revealed a similar behaviour of distribution. However, the runoff from the barren land cover was quite distinctively different, often returning the highest discharge. The outcome of the model reflects well that the condition and type of land use contribute significantly to the runoff and are accompanied by predicted scenarios of land cover and soil type changes. This work on the overall results determined that simulated land cover change had a significant impact on the discharge distribution of the River Fnjóská through barren land covers. Subsequent research in the Fnjóská watershed should investigate land use and climate change effects on sediment transportation.