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Studies on the effect of climate change on water resources in the 21st century indicate an increase in intense rainfall, an increase in the duration of the dry season, and a decrease in snowfall and, accordingly, snow cover. Based on data from the EURO-CORDEX project, the average multi-year monthly runoff amounts (Copernicus Climate Change Service, Climate Data Store, 2021) for each 30-year period and for the reference period for a rectangular area covering the territory of Bulgaria have been calculated. Climatic ...

This article presents a reproducible workflow for deriving gridded total runoff threshold layers for Bulgaria and the adjacent regional domain. ERA5-Land hourly runoff for 1981-2025 was first converted from accumulated fields to hourly increments following the ERA5-Land accumulation convention [4][7]. Annual maxima were then derived for 1 h, 3 h, 6 h and 24 h totals, and fixed annual exceedance probability (AEP) return levels were estimated for 1% and 5%. The fine resolution product uses D(Q) downscaling: return l...

Manual measurement of flow velocity and streamflow discharge during high waters is often impossible because of different factors: night events, harsh meteorological conditions, very high dangerous river velocities and levels or infrastructure destruction. The purpose of this study is to determine maximums of river flow velocity and streamflow discharge with hydraulic engineering methods, as well to determine the modulus of runoff at some stations in the East Aegean River Basin in South Bulgaria for the period betw...

The article is about three hydrological river routing models (RRM) implemented in Bulgaria, coupled to a land surface model (LSM), mainly for flood forecasting purpose. For the evaluation of the three RRMs the authors use a river basin of Mediterranean climate - the Varbitsa River with catchment area of 1200 km2. The river is prone to dangerous flash floods because of their fast propagation. LSM SURFEX (Surface Externalisee) but formally the integrated part ISBA (Interface Soil Biosphere Atmosphere) is used to com...

In this study SURFEX land surface model is used coupled to RAPID river routing model in order to investigate the influence of alternative ground and rooting depth, soil texture and land cover maps on the ability of the coupled system to adequately simulate the river flow in Upper Arda River basin in Bulgaria. This was done by comparing the statistical scores of computed from the model data series against measured streamflow discharge series: that is scores of simulations using former soil texture maps from Harmoni...

Measurements of high water in rivers are an important element of all collected stream discharge information. It is necessary to have such information in real time during floods because of the danger caused by inundations. Another aspect is the relatively large discharge volume of high water compared to medium and low flow periods. On the other hand, measuring the river discharge during high water with the traditional methods with propeller or floats is often constrained by the manpower availability for that precis...