Search

This paper presents a scheme describing low flow formation processes in areas with different environmental conditions, including the impact of the selection and explanatory power of predictors for a probabilistic model based on the Logit model. The research was carried out using 29 daily streamflow gauges located in the Lublin region of southeastern Poland for the hydrological period 1976–2018. Analysis resulted in two distinct low flow schemes. In the lowland rivers, low flows occur during the warm season and are related to evaporation exceeding precipitation. In the upland rivers, hydrogeological factors related to water levels in the local Cretaceous aquifers determine the occurrence of low flows. This differentiation affects the quality of the predictive models. For lowland rivers, models based on the climatic water balance with a monthly shift have a better fit, while these models used for upland rivers are characterized by an approximately 10% decrease in accuracy. For upland rivers, the combined CtHt models without shifts produce the best model fit. The generalized precision of the Logit models is around 80%–90%. [ABSTRACT FROM AUTHOR]

The objective of this study is to quantify the seasonal and multi-annual variability and trends of low-flow river conditions in southeastern Poland. The study was performed using daily values of river discharge at 29 gauging stations for hydrological years 1976–2014. The results show regionally specific patterns, such that seasonality is high for the lowland rivers (low flows occur during the warm season), while in the upland rivers a 10- to 15-year cycle is observed. Increasing trends in warm-season temperature and a decrease in humidity were observed; however, no direct correlation with low flows was found. These results suggest that the initiation and maintenance of low-flow events over some regions are more sensitive to local surface water and groundwater circulation conditions than to atmospheric drivers, especially when the recurrence interval of events is low, and that the primary mechanisms driving and maintaining low-flow conditions can change over relatively small spatial scales. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides a meteorological overview of the 2015 mega‐heatwave (MHW) over Poland and compares the event with other MHWs in the region since World War II (up until 2015). A mega‐heatwave is defined as an event with at least 6 consecutive days with a maximum air temperature in excess of 30°C. These events are analysed here using observational meteorological data from ten major cities in Poland and neighbouring countries, along with 0.25° × 0.25° analysis fields from the Global Forecast System (GFS). Although the various events had different regional characteristics, in general they were caused by the inflow of a hot tropical air mass from the south, and were perpetuated by a high‐pressure system to the east of Poland and in some cases a low‐pressure system to the west. The 2015 MHW was the most extreme of the studied events, lasting from 9 days in Bialystok to 14 days in Warsaw and Poznan. [ABSTRACT FROM AUTHOR]