The paper identifies relationships between lake water levels and indices of macroscale atmospheric circulations: Arctic Oscillation (AO), North Atlantic Oscillation (NAO), East Atlantic (EA), and Scandinavian pattern (SCAND). Correlation coefficients between synchronous and asynchronous series of monthly water levels and 4 circulation indices were calculated. Based on Ward hierarchical grouping considering 156 correlation coefficients, the groups of lakes were designated due to the strength and term of relation of circulation indices with lake water levels. It was found that these links are not strong but noticeable. The strength of relationships varies in space and time, and the designated groups of lakes refer not only to the climatic diversity of the studied area, but also to some extent to the types of water levels regime. The observed relationships are the most important in the case of AO and NAO (particularly in winter period), and slightly weaker for EA and SCAND. The analysis used mean monthly water levels of 15 lakes in northern Poland from 1976–2015.

In this study, on the basis of the maximum and mean annual values of flows, dependencies between flows recorded in seven water gauges located in the upper part of the Indus River Basin (IRB) in Pakistan were analyzed. First, the non-parametric Mann–Kendall (M–K) test was used to detect trends in the flows. Next, the Pearson’s correlation coefficient was applied. Then, the selected copulas were used to find joint distributions of the studied time series. In the next stage, the degrees of synchronous and asynchronous occurrence of, respectively, the annual maximum (AMAXF) and mean annual flows (MAF) were calculated. The study revealed that correlations between the flows in selected gauge stations were very strong and statistically significant. These results were confirmed by the synchronicity analysis carried out with the help of the copula functions. The highest relationship was detected in the case of gauges Besham Qila and Kachura on the Indus mainstream, while the lowest was detected in gauges Besham Qila and Naltar on the Naltar River. These findings can be of high practical value in the field of sustainable water resource management, including for flood protection, agricultural water supply, reservoir water storage, and hydropower generation in the IRB.

Floods are natural phenomena, inextricably related to river regimes, which can threaten human health and life, the environment, cultural heritage, economic activity and infrastructure. The aim of the research is to assess the connection between rainfall and river flood risk. The proposed methodology is presented on the example of the upper Nysa Kłodzka River (NKR) catchment and Kłodzko town located on NKR, which are two of the most flood-prone areas in the Odra River basin. The methodology is based on the well-established methods of potential flood losses (PFL) estimation and the copula-based model, allowing an assessment of connections between rainfall and flood losses in a probabilistic way. The results are presented using the ‘synchronicity’ measure. Seventeen significant summer (rainfall-driven) flood waves were selected, for which PFL were estimated and cumulative rainfall was calculated for 24, 48, 72, 96 and 120 h preceding the flood peak. It was found that the synchronicity of PFL and the 24 h rainfall was the lowest among the analyzed variants, while for the 48 to 120 h rainfall the highest synchronicity was identified at precipitation gauge Podzamek.

The hydrology of coastal lakes differs significantly from that of inland water bodies due to the influence of the neighboring sea. Observed climatic changes are expected to enhance the effect of the sea on coastal lake ecosystems, which makes research on sea–lake interactions even more significant. In this study, on the basis of maximum annual and monthly values of water level, dependencies among the water levels of six lakes located along the southern coast of the Baltic Sea in Poland, and the Baltic Sea water levels were analyzed. First, the Spearman rank correlation and the linear regression method were applied. Then, selected copulas were used to find joint distributions of the studied time series. In the next stage, the degrees of synchronous and asynchronous occurrences of maximum water levels in lakes and the sea were calculated. The study revealed that correlations between the maximum annual water levels in coastal lakes and in the Baltic Sea in the selected gauge stations were very strong and statistically significant. These results were confirmed by a synchronicity analysis carried out with the help of a copula function. The highest relationship was detected in the case of Lake Resko Przymorskie (correlation coefficient 0.86, synchronicity 75.18%), while the lowest were observed in Lakes Jamno (0.62 and 58.20%, respectively) and Bukowo (0.60 and 56.82%, respectively). The relation strength between maximum water levels of the sea and coastal lakes may increase in the future due to sea level rises caused by climate warming.

Based on daily flows recorded in the period 1971–2010, the synchronous occurrence of the annual (AMAXq), winter (WMAXq), and summer (SMAXq) maximum specific runoffs in 39 sub-catchments of the Warta River catchment (WRC) in Poland was analyzed. First, trends in the flows were detected using the non-parametric Mann–Kendall (M-K) test. Then, the degree of the synchronous and asynchronous occurrences of the maximum specific runoffs (MAXq) in respective sub-catchments in relation to the Gorzów Wielkopolski gauge closing the WRC was calculated. Finally, the reasons for the detected spatial and temporal differences were discussed. The study revealed a noticeable variability of the analyzed parameters. The highest synchronicity of AMAXq and WMAXq in relation to the closing Gorzów Wielkopolski gauge was revealed in the man-made Kościański and Mosiński canals and in the sub-catchments of the Noteć, Wełna, and lower Prosna rivers. While compared to AMAXq and WMAXq, the summer maxima showed relatively lower degrees of synchronicity, an increase in the synchronous occurrence of SMAXq in the southern part of WRC, and a decrease in its central part were identified. It was concluded that the stronger synchronicity of WMAXq resulted from the nival regime of the investigated rivers. Consequently, the annual maxima were most often associated with the winter half-year. The detected differences of synchronicity of the annual and seasonal runoffs are conditioned by climate, more specifically by the course of winter and resulting from it snow cover thickness, and also the amount and intensity of rainfall in summer.

This paper seeks to identify the features of the flow regime of the rivers in Kłodzka Valley in terms of the runoff, the structure and the spatiotemporal variabilities. The analysis was carried out on the basis of data provided by the Institute of Meteorology and Water Management from the period of 1971–2015 and obtained from 8 gauging stations located in 5 rivers. The research embraced the Nysa Kłodzka river and its main tributaries to the gauging station in Kłodzko. The runoff conditions in the analysed sub-basins are different. As a result, the rivers in Kłodzka Valley have different regime features. Due to the regularities in their flow variability, they can be classified into 2 types of hydrological regime: nival and nival-pluvial. There are significant differences in the total runoff, from 375 mm in Kłodzko to above 700 mm in the Wilczka river. The differences also occur in terms of the groundwater runoff and its contribution to the total runoff which ranges between 31% and 53%. All of the analysed basins have contributions to groundwater runoff below the mean value for the entire country (55%). In terms of viabilities of discharges, in general there are differences between the upper Nysa Kłodzka and its eastern tributaries and the western part of the basin.