Development of spatially distributed hydrological WetSpa modules for snowmelt, soil erosion, and sediment transport

Hossein Zeinivand

Research output: ThesisPhD Thesis

Abstract

Hydrological modelling is very important for prediction of runoff and soil erosion, and is a major tool for research hydrologists and water resources engineers for planning and management of water resources. Distributed hydrological models are based on our understanding of the physics of the hydrological processes which control catchment response and use physically based equations to describe these processes. A spatially distributed hydrologic model, WetSpa, has been developed at the Department of Hydrology and Hydraulic Engineering of VUB. The hydrologic processes considered in this model are precipitation, interception, depression, surface runoff, infiltration, evapotranspiration, percolation, interflow, groundwater flow, and water balance in the root zone and the saturated zone. The basic model inputs are a digital elevation model (DEM), land use and soil maps of the study area in GIS raster format, and hydrometeorological data. The model combines these data within GIS, and predicts flood hydrographs and the spatial distribution of hydrologic characteristics in the watershed. The purpose of this research is to develop and test new WetSpa modules for (a) snow accumulation and melt, and (b) soil erosion and sediment transport. Snow is important in cold regions and in these areas snowmelt is of importance to many aspects of hydrology including water supply, erosion, and flood control. A snow module was provided in the original WetSpa model based on a conceptual temperature index or degree-day method, which three snowmelt parameters which should be calibrated. The new snowmelt module is developed based on an energy balance approach which is fully physically based, and hence, does not need any calibration. This approach only needs physical data that can be easily obtained, as air temperature and windspeed. Three study catchments with distinct basin characteristics are selected to investigate the applicability and adaptability of the module: The first one is the Hornad river basin (4262 km2) up to Zdana station in Slovakia, for which the model was applied and calibrated with 8 years of daily data. The model (Nash-Sutcliffe) efficiency turns out to be 79%. The second is the Hornad river up to Margecany station (1133 km2), a mountainous watershed situated in the upstream part of the Hornad river in Slovakia. The model was applied, calibrated, and verified with 10 years of daily data. The first 5 years were chosen for model calibration and the second 5 years for model validation. The model efficiency is good, i.e. 74% and 79%, respectively for the calibration and verification period. The third catchment is the Latyan dam watershed (435 km2) in Iran. The model is applied and calibrated with 3 years of daily data. The results of the degree day method and the energy balance approach are compared for this catchment. The model efficiency is more than 80% for both models, but for the energy balance approach this is obtained without calibration of snowmelt parameters. Hence, this study shows that the new model for snow accumulation and melt has great potentiality to predict the impact of snow accumulation and melt on the hydrological behaviour of a river basin. Also a physically based, spatially distributed model is developed to simulate erosion, sediment transport and deposition, within the framework of the hydrological WetSpa model. Soil detachment by raindrop impact is calculated based on relationships between soil detachment and the kinetic energy of rainfall. Soil particle detachment by overland flow is calculated based on actual and critical shear stresses. Water and sediment are routed over the land surface along t
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
Supervisors/Advisors
  • De Smedt, Florimond, Supervisor
Place of PublicationBrussels
Publication statusPublished - 2009

Keywords

  • WetSpa

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