Abdelkader Mezghani

Changes in low and high flows in the Vistula and the Odra basins: model projections in the European-scale context

A number of extensive droughts and destructive floods have occurred in Poland in the last 25 years, hence projections of low and high river flows are of considerable interest and importance. In the first part of this paper, projections of low and high flows in the rivers of the Vistula and the Odra basins (VOB region), for two future time horizons, are presented. Projections are based on the SWAT hydrological model simulations driven by results of the EURO-CORDEX experiment under Representative Concentration Pathways 4.5 and 8.5. The VOB region covers most of Poland and parts of five neighboring countries, giving this study an international relevance. In the second part of the paper a review of projections of low and high flows in rivers in Central and Eastern Europe is presented. Despite a substantial spread of flow projections, the main message of the modelling part is that increases of both low and high flows are dominating. The magnitude of increase of low flow is considerably higher than that of high flow. In other words, future streamflow droughts are projected to be less severe, while, in contrast, river floods are projected to increase, which is a challenge for flood risk reduction, water management and climate change adaptation. There is an overall agreement of our findings for the VOB region with projections of hydrological extremes from large-scale models forced by EURO-CORDEX results in the European-scale studies.

CHASE-PL Climate Projection dataset over Poland – bias adjustment of EURO-CORDEX simulations

The paper provides an update of climate projections over Poland by adopting the new generation of concentration pathways and recent developments in climate modelling.It provides a dataset of scenarios of temperature and precipitation developed for nine individual RCM simulations and the ensamble one. For each RCM the bias is firstly assessed and than the scenario is adjusted. The scenarios are prepared on annual and seasonal resolution.

Performance of CMIP3 and CMIP5 GCMs to Simulate Observed Rainfall Characteristics over the Western Himalayan Region

AbstractThe Western Himalayan Region (WHR) was subject to a significant negative trend in the annual and monsoon rainfall during 1902-2005. Annual and seasonal rainfall change over WHR of India was estimated using 22 rain gauge station rainfall data from the India Meteorological Department. The performance of 13 global climate models (GCMs) from the coupled model intercomparison project phase 3 (CMIP3) and 42 GCMs from CMIP5 was evaluated through multiple analysis: the evaluation of the mean annual cycle, annual cycles of interannual variability, spatial patterns, trends and signal-to-noise ratio. In general, CMIP5 GCMs were more skillful in terms of simulating the annual cycle of interannual variability compared to CMIP3 GCMs. The CMIP3 GCMs failed to reproduce the observed trend whereas ~50% of the CMIP5 GCMs reproduced the statistical distribution of short-term (30-years) trend-estimates than for the longer term (99-years). GCMs from both CMIP3 and CMIP5 were able to simulate the spatial distribution o...

Changes of snow cover in Poland

The present paper examines variability of characteristics of snow cover (snow cover depth, number of days with snow cover and dates of beginning and end of snow cover) in Poland. The study makes use of a set of 43 long time series of observation records from the stations in Poland, from 1952 to 2013. To describe temporal changes in snow cover characteristics, the intervals of 1952–1990 and of 1991–2013 are compared and trends in analysed data are sought (e.g., using the Mann–Kendall test). Observed behaviour of time series of snow-related variables is complex and not easy to interpret, for instance because of the location of the research area in the zone of transitional moderate climate, where strong variability of climate events is one of the main attributes. A statistical link between the North Atlantic Oscillation (NAO) index and the snow cover depth, as well as the number of snow cover days is found.

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

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.

Hydroclimatic Projections for the Upper Vistula Basin

In this study, we apply a previously calibrated SWAT model of the Vistula and Odra basins in order to assess hydrological impacts of climate change in the Upper Vistula Basin. Raw projections from an ensemble of nine EUR-11 CORDEX climate model runs (precipitation and minimum and maximum temperatures) assuming an intermediate greenhouse gas emission scenario of 4.5 W/m2 were adjusted using a quantile-mapping correction approach. We analysed changes between two future horizons 2024–2050 (near future) and 2074–2100 (far future) and a reference period (1974–2000). We found that, for the near future, all climate models agree well about ubiquitous warming on both seasonal and annual scales, while eight models agree about an increase in projected mean annual precipitation and total runoff. For the far future, an increase in temperature, in mean annual precipitation, as well as in the total runoff, is projected using all climate models. Results also highlighted a higher temperature increase in winter than in other seasons and a higher increase in minimum temperature than in maximum temperature. The highest runoff increase is projected in winter, consistently, by all climate models. In addition, we assessed projected changes in high streamflow indicator based on the 90th monthly flow percentile (Q90). Based on the median of climate model simulations, we found that the mean basin-wide increase in monthly Q90 is 6.4 and 15 % for the near future and the far future, respectively. Nevertheless, the range of projected changes in precipitation, runoff and high flows calculated across the whole ensemble remains relatively high and spatial patterns are not fully consistent across different climate models.