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What can we learn from the projections of changes of flow patterns? Results from Polish case studies

Piniewski M., Meresa H. K., Romanowicz R., Osuch M, Szcześniak M., Kardel I., Okruszko T., Mezghani A., Kundzewicz Z. W.

Acta Geophysica

2017

Vol. 65, no. 4

809--827

River flow projections for two future time horizons and RCP 8.5 scenario, generated by two projects (CHASE-PL and CHIHE) in the Polish-Norwegian Research Programme, were compared. The projects employed different hydrological models over different spatial domains. The semi-distributed, process-based, SWAT model was used in the CHASE-PL project for the entire Vistula and Odra basins area, whilst the lumped, conceptual, HBV model was used in the CHIHE project for eight Polish catchments, for which the comparison study was made. Climate projections in both studies originated from the common EURO-CORDEX dataset, but they were different, e.g. due to different bias correction approaches. Increases in mean annual and seasonal flows were projected in both studies, yet the magnitudes of changes were largely different, in particular for the lowland catchments in the far future. The HBV-based increases were significantly higher in the latter case than the SWAT-based increases in all seasons except winter. Uncertainty in projections is high and creates a problem for practitioners.

Understanding changes and trends in projected hydroclimatic indices in selected Norwegian and Polish catchments

Meresa H. K., Romanowicz R., Napiórkowski J.

Acta Geophysica

2017

Vol. 65, no. 4

829--848

The aim of the study is to investigate trends in selected hydroclimatic indices using novel and conventional tools, for future climate projections in the twenty-first century. Selected quasi-natural Norwegian and Polish catchments are used as a case study. The projected flows are provided by GR4J rainfall-runoff conceptual model, coupled with an ensemble of climate model projections from EURO-CORDEX initiative. The trends are analysed using conventional Mann–Kendall and modified Mann–Kendall statistical approaches, a time–frequency approach based on discrete wavelet transform (DWT) and the dynamic harmonic regression (DHR) method. Of all methods applied the DHR gives the most conservative trend estimates. Trends depend on the specific hydroclimatic character and flow regime of the catchment. The results confirmed that in catchments with a rainfall-driven flood regime, an increase in the amount of precipitation is followed by increased flows, with strong seasonal changes, whereas, in catchments with a snow-driven flood regime, despite an increase of mean annual flow, decrease in annual maximum flow is observed. Generally, positive trend is the most dominant in all catchments studied and the methods were consistent in detection of trend except in seasonal trend test.

Climate Change Impact on Hydrological Extremes: Preliminary Results from the Polish-Norwegian Project

Romanowicz R. J., Bogdanowicz E., Debele S. E., Doroszkiewicz J., Hisdal H., Lawrence D., Meresa H. K., Napiórkowski J. J., Osuch M., Strupczewski W. G., Wilson D., Wong W. K.

Acta Geophysica

2016

Vol. 64, no. 2

477--509

This paper presents the background, objectives, and preliminary outcomes from the first year of activities of the Polish–Norwegian project CHIHE (Climate Change Impact on Hydrological Extremes). The project aims to estimate the influence of climate changes on extreme river flows (low and high) and to evaluate the impact on the frequency of occurrence of hydrological extremes. Eight “twinned” catchments in Poland and Norway serve as case studies. We present the procedures of the catchment selection applied in Norway and Poland and a database consisting of near-natural ten Polish and eight Norwegian catchments constructed for the purpose of climate impact assessment. Climate projections for selected catchments are described and compared with observations of temperature and precipitation available for the reference period. Future changes based on those projections are analysed and assessed for two periods, the near future (2021-2050) and the far-future (2071-2100). The results indicate increases in precipitation and temperature in the periods and regions studied both in Poland and Norway.