Diagnosis of the hydrology of a small Arctic permafrost catchment using HBV conceptual rainfall-runoff model Marzena Osuch, Tomasz Wawrzyniak and Adam Nawrot ABSTRACT Changes in active layer thickness (ALT) over Arctic and permafrost regions have an important impact on rainfall-runoff transformation. General warming is observed across Svalbard Archipelago and corresponds to increases in ground temperatures. Permafrost thaw and changes in ALT due to climate warming alter how water is routed and stored in catchments, and thus impact both surface and subsurface processes. The overall aim of the present study is to examine the relationships between temporal changes of active layer depth and hydrological model parameters, together with variation in the catchment response. The analysis was carried out for the small unglaciated catchment Fuglebekken, located in the vicinity of the Polish Polar Station Hornsund on Spitsbergen. For hydrological modelling, the conceptual rainfall-runoff HBV (Hydrologiska Byråns Vattenbalansavdelning) model was used. The model was calibrated and validated on runoff within subperiods. A moving window approach (3 weeks long) was applied to derive temporal variation of parameters. Model calibration, together with an estimation of parametric uncertainty, was carried out using the Shufed Complex Evolution Metropolis algorithm. This allowed the dependence of HBV model parameters on ALT to be analysed. Also, we tested the inuence of model simplication, correction of precipitation, and initial conditions on the modelling results. Marzena Osuch (corresponding author) Department of Hydrology and Hydrodynamics, Institute of Geophysics Polish Academy of Sciences, Ksie ˛ cia Janusza 64, Warsaw, 01-452, Poland E-mail: marz@igf.edu.pl Tomasz Wawrzyniak Adam Nawrot Department of Polar and Marine Research, Institute of Geophysics Polish Academy of Sciences, Ksie ˛ cia Janusza 64, Warsaw, 01-452, Poland Key words | active layer thickness, HBV, parametric non-stationarity, runoff modelling, Svalbard INTRODUCTION Hydrological modelling in areas with the occurrence of per- ennially frozen ground together with seasonally changing active layer thickness (ALT) requires a better understanding of the inuence of soil processes on water balance. Ground- water movement in permafrost terrain is limited because the frozen soil is practically impermeable and so inltration and groundwater recharge are possible only within the active layer that thaws in summer or in taliks (Woo ). The impact of climate change on the ground thermal regime may affect active groundwater and hydrogeological pro- cesses directly and indirectly (Streletskiy et al. ; Walvoord & Kurylyk ). Dramatic environmental changes including higher air temperature, changes of pre- cipitation patterns, permafrost degradation, and longer melting seasons have all been occurring recently in cold environment catchments (Callaghan et al. ; Bindoff et al. ; Bring & Destouni ; Walvoord & Kurylyk ; Osuch & Wawrzyniak , ). The hydrological cycle in the Arctic is currently undergoing alterations due to different impacts (Vihma et al. ) and affects the global climate system (Bindoff et al. ). Despite widely documented evidence, remote catchments are still charac- terised by the poor availability of hydro-climatological data from in situ measurements, so a modelling approach is especially required for checking consistency in datasets, vali- dation of assumptions, description, and parametrisation of processes which, by all means, improve our understanding of natural processes. 459 © IWA Publishing 2019 Hydrology Research | 50.2 | 2019 doi: 10.2166/nh.2019.031 Downloaded from http://iwaponline.com/hr/article-pdf/50/2/459/548920/nh0500459.pdf by guest on 09 September 2022