A headwater basin in the Sumava Mountains (Czech Republic), the upper Vydra basin, has undergone forest disturbance as a result of repeated windstorms, a bark beetle outbreak, and forest management. This study analyzed the long-term hydro-climatic changes by using a combination of statistical analyses, including Mann-Kendall tests, CUSUM analysis, Buishand's and Petitt's homogeneity tests, and Kriging. Although the runoff balance over the study period experienced no apparent changes due to climate warming and forest disturbance, significant changes were detected in the share of direct runoff and baseflow, intra-annual variability of the runoff regime, seasonal runoff patterns, and the distribution of peak and low flow events. The seasonal runoff substantially shifted from summers (decreased from 40% to 28%) to springs (increased by 10%). The occurrence of peak flow events has doubled since the 1980s, with a seasonal shift from late spring towards the early spring, while the occurrence of low-flow days decreased by two-thirds. By 1990, these changes were followed by a seasonal shift in runoff from autumn to mid-winter. The changes in hydrological regime in the mid-mountain basin indicate the sensitivity of its hydrological system and the complexity of its feedback with the changing environment. OPEN ACCESSWater 2015, 7 3321

This paper explores the potential of the joint application of unmanned aerial vehicle (UAV)-based photogrammetry and an automated sensor network for building a hydrodynamic flood model of a montane stream. UAV-based imagery was used for three-dimensional (3D) photogrammetric reconstruction of the stream channel, achieving a resolution of 1.5 cm/pixel. Automated ultrasonic water level gauges, operating with a 10 min interval, were used as a source of hydrological data for the model calibration, and the MIKE 21 hydrodynamic model was used for building the flood model. Three different horizontal schematizations of the channel-an orthogonal grid, curvilinear grid, and flexible mesh-were used to evaluate the effect of spatial discretization on the results. The research was performed on Javori Brook, a montane stream in the Sumava (Bohemian Forest) Mountains, Czech Republic, Central Europe, featuring a fast runoff response to precipitation events and that is located in a core zone of frequent flooding. The studied catchments have been, since 2007, equipped with automated water level gauges and, since 2013, under repeated UAV monitoring. The study revealed the high potential of these data sources for applications in hydrodynamic modeling. In addition to the ultra-high levels of spatial and temporal resolution, the major contribution is in the method's high operability, enabling the building of highly detailed flood models even in remote areas lacking conventional monitoring. The testing of the data sources and model setup indicated the limitations of the UAV reconstruction of the stream bathymetry, which was completed by the geodetic-grade global navigation satellite system (GNSS) measurements. The testing of the different model domain schematizations did not indicate the substantial differences that are typical for conventional low-resolution data, proving the high reliability of the tested modeling workflow.

There is public concern that large-scale disturbances to forest cover caused by insects and storm winds in the Bohemian Forest could intensify high water flows and enhance the expected flooding risks predicted in current regional climate change scenarios. We analysed stream discharge in Upper Vydra and Große Ohe, neighbouring catchments in the Bohemian Forest, the largest contiguous forested area in Central Europe. Upper Vydra, in the Šumava National Park, and Große Ohe (including the Upper Große Ohe headwater catchment in the Bavarian Forest National Park) are similar in size, but differ in land use cover and the extent of disturbed Norway spruce stands. Publicly available runoff and meteorological data were examined using non-parametric trend and breakpoint analysis. Together with mapped vegetation cover changes, the results were used to address the following questions: 1) are there significant changes in the hydrological cycle and, if so, do these changes relate to 2) the extent and expansion of disturbance in forests stands and/or 3) altered precipitation dynamics and thermal conditions?We found no marked overall change in annual runoff or in annual or seasonal precipitation, but a significant increase in high flows in March. This overall trend related to the marked warming in late winter and early spring (+~4 K in April, p < 0.01), irrespective of altitude and slope position. It significantly shifted the end of the snow cover period by more than three weeks to the beginning/middle of April depending on altitude, and intensified snow melt.In the Upper Große Ohe catchment, a significant decrease in catchment balance, the difference between the long term precipitation and runoff (-72 mm, 11%) was found when the loss of tree cover reached 30% of catchment area. Diminished evapotranspiration losses from severely disturbed stands increased groundwater recharge during summer and caused a significant rise in low flows in autumn.However, observed increases in late winter high flows were due to warming only. They could be further intensified by the increasing winter precipitation predicted under present climate change scenarios, and would therefore increase the risk of flooding at lower elevations.

This study analyzed the long-term alterations in runoff regime, seasonality and variability in headwater montane basins in Central Europe in response to the manifestations of climate change. We tested the common hypotheses on climate change effects on surface runoff dynamics in the Central Europe region, assuming that (i) recent climate warming will result in shifts in the seasonality of runoff, (ii) the runoff balance will remain without significant changes and (iii) that higher variability in runoff can be expected. The analyses were done on eight montane catchments in four mid-latitude mountain ranges in Central Europe, based on the uninterrupted time series of daily discharge observations from 1952 to 2018. We used 33 indicators of hydrologic alteration (IHA), 34 indicators of environmental flow components, the baseflow index, the calculation of surplus and deficit volumes and the frequency of peak and low flows. Homogeneity testing using Buishand, Pettitt and SNHT tests was applied to test the response of the hydrological alteration indicators to climate warming. We have proved the significant shifts in runoff seasonality, coinciding with the timing of the air temperature rise, marked by earlier snowmelt, followed by a decline in spring flows and a prolonged period of low flows. There was detected a rise in the baseflow index across the mountain ranges. Unlike the common hypotheses, the expected rise of runoff variability and frequency of peak flows was not demonstrated. However, we have identified a significant change of the flood hydrographs, tending to steeper shape with shorter recessing limbs as a sign of rising inner dynamics of flood events in montane catchments.

&lt;p&gt;The study analyzed long-term changes of runoff variability of headwater montane basins in Central Europe as a response to the effects of climate change and modifications to the environment.&lt;/p&gt;&lt;p&gt;The aim was to compare the patterns of variability of the indicators of hydrologic alteration, derived from long-term time series of daily discharge observations in montane basins with the recent premises of climate change effects on surface runoff dynamics in the Central Europe region. In particular, there were tested the following assumptions: (i) recent climate warming will result in the shifts of the runoff seasonality and distribution and in (ii) higher variability of runoff, displayed by a higher frequency of floods and droughts, while (iii) the indicators of runoff balance will remain without significant changes.&lt;/p&gt;&lt;p&gt;These hypotheses were tested in a set of 8 unregulated montane catchments, spreading over the border mountain ranges of the Czech Republic - the &amp;#352;umava Mountains (Bohemian Forest), Kru&amp;#353;n&amp;#233; hory (Ore Mountains), Jizera Mountains, Krkono&amp;#353;e (Giant Mountains), Orlick&amp;#233; Mountains and Beskydy Mountains. All basins are of comparable size (30-90 km2), and without significant hydrological regulations. Their west-east geographical distribution allows for tracking the potential effects of the gradient of climate continentality in the Central European region. The uninterrupted time series of daily discharge observations from 1953 to 2018 were used for the analyses at the gauging stations.&amp;#160;&lt;/p&gt;&lt;p&gt;We focused on indicators that reflect the aspects of the runoff regime, that are likely to be affected by the assumed effects of the changing climate. Variety of time series analysis and statistical techniques was applied, including the set of 33 Indicators of hydrologic alteration (IHA), 34 Indicators of Environmental flow components, frequency and distribution of the peak an low flows, statistical testing of significance of changes using Mann-Kendall test, breakpoint analysis, analysis of deficit and surplus volumes and homogeneity testing using Buishand, Petitt and SNHT tests.&lt;/p&gt;&lt;p&gt;The study has identified the significant shifts in the hydrological response of montane basins that are apparent in seasonality, balance, and variability of discharge. The analyses proved (i) changes in runoff response reflecting the timing of the observed changes in air temperatures, (ii) the shift of spring snowmelts towards earlier spring and a corresponding decline of may flows, occurring in all of the investigated regions, (iii) diverging trends of high flows across the basins, (iv) changing dynamics of rainfall-runoff response (v) better sensitivity of indicators, reflecting low magnitude events and (vi) decline of low flow indicators across the basins.&lt;/p&gt;

The Thaya river basin is one of the key river basins in the southern part of the Czech Republic. Due to extensive river regulations and partial drainage of the basin area, it belongs to river basins sensitive to climate change impacts. This is supported by significant negative runoff trends over the past 40 years. The main aim of this contribution is to analyze impacts of the hypothetical land use changes on the hydrological processes of the upper Thaya basin. In this study, we used a hydrological Mike SHE model. The physically based and spatially distributed model Mike SHE was calibrated and validated using measured river discharge data in the three hydrological profiles for the period 1991&#8211;2020. Selected hypothetical adaptation land use scenarios including the vegetation cover changes were compared to the reference scenario (represents the current land use of the basin) to analyze the impacts of the simulated land use changes on the hydrological processes in the basin. Except the field management changes, the land use scenarios encompassed extreme vegetation changes, where the entire basin in the model was changed to (1) grassland, (2) mixed deciduous-coniferous forest, (3) deciduous forest, or (4) cropland. These extreme land use scenarios were analyzed for several CMIP6 downscaled climate models and different RCP emissions scenarios up to the end of the first half of the 21st century. The results showed that the evapotranspiration is the dominant water loss component for all simulated land use scenarios in the basin. The highest evapotranspiration was modeled for the mixed deciduous-coniferous forest, while the lowest was for the grassland and cropland scenarios. The Mike SHE model also simulated that the total runoff was lowest for both forest scenarios. Results of the study showed the sensitivity of the river basin on the climate change impacts, where a slight increase of the evapotranspiration value in the basin has a significant effect on the total runoff from the basin. This study was conducted within the evaluating and designing nature-based adaptation measures to climate change in the Thaya river basin.

&lt;p&gt;The Svratka river basin represents an important water resource in the South Moravian Region of the Czech Republic. Due to its relatively low aridity index (the ratio of precipitation to potential evapotranspiration), it belongs to river basins sensitive to climate change. This is also supported by significant negative runoff trends over the past 40 years. The aim of this study is to evaluate the impacts of a hypothetical land use change on the hydrological processes of the Svratka river basin. We used a physically based and spatially distributed hydrological model Mike SHE. The Mike SHE model was calibrated and validated using measured river discharge data in the three hydrological profiles in the Svratka basin for the period 1981&amp;#8211;2020. Several land use scenarios were tested against the reference scenario (i.e. current land use) to analyze the impacts of land use change. The land use scenarios encompassed the following hypothetical extreme changes where the entire basin in the model was changed to (i) grassland, (ii) mixed deciduous-coniferous forest, (iii) deciduous forest, or (iv) cropland. These extreme land use scenarios were tested for the baseline period 1981&amp;#8211;2020 and also for several CMIP6 downscaled climate models and different socioeconomic pathways (emissions scenarios) up to the end of the 21&lt;sup&gt;st&lt;/sup&gt; century. The results showed that the evapotranspiration was the highest for mixed deciduous-coniferous forest while the lowest was the grassland scenario and cropland . The lowest total runoff from the river basin was simulated for both forest scenarios (mixed forest and deciduous forest). The results also demonstrated that the dominant loss component for all scenarios of the water balance in the Svratka river basin is evapotranspiration. The sensitivity of the hydrological balance in the Czech landscape was also demonstrated, where a slight increase in the evapotranspiration value in the basin has a significant effect on the total runoff from the Svratka basin. The climate change scenarios additionally suggest further exacerbating the water balance and runoff decline in the region. The results of this study are a first step towards evaluating and designing nature-based adaptation measures to climate change in the Svratka river basin.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Acknowledgment:&lt;/strong&gt; &lt;br /&gt;The research infrastructure and CzechGlobe team was financially supported by the SustES - Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/0000797). The study was also supported by the Internal Grant Agency of the AgriSciences faculty at Mendel University in Brno (AF-IGA2023-IP-031).&lt;/p&gt;

&lt;p&gt;This study tends to attribute the spatial patterns of hydrologic alteration in mid-latitude montane basins to the key driving forces being the climate and land use change. Physically-based distributed modeling system MIKE SHE was used for the analysis of changing spatiotemporal patterns of extreme runoff processes in montane catchments by using time series of hydrometeorological&amp;#160; observations, and spatially distributed MODIS data for evapotranspiration (ET) and leaf area index (LAI) as key resources for the model setup.&lt;/p&gt;&lt;p&gt;Czech Republic is surrounded by mountain ranges from all sides but the southeastern border, which is drained towards the Danube. Due to this concentric orientation of topography each mountain range has different aspect and exposition due to atmospheric processes. Does the basin hydrological reaction on changing the environment depend on the aspect or is there an overall trend present in all basins? In order to answer such a question, it is necessary to understand the main drivers of changes and to quantify the effect of each separately.&amp;#160;&lt;/p&gt;&lt;p&gt;8 headwater basins were analyzed of average size of 73 km2 where significant trends of hydrologic processes were detected from long-termed time series (1952 to 2018). Some of the trends are common for all basins such as seasonal shift of snowmelt period but other trends are rather site specific such as frequency of peak flows. Previous studies show that the hydrologic reaction on climate signal is the most dominant driver of the hydrologic alterations however there are other drivers such as forest disturbances that can mislead the interpretation of trend behavior.&amp;#160;&lt;/p&gt;&lt;p&gt;The aim of the study was to separate the effects of those main drivers by a detailed distributed physically-based modeling system MIKE SHE. Input data originated from official and publicly available sources in order to design a methodology that could be reproduced in other basins of comparable properties. Models are bent together thus results of similar spatial-temporal quality were obtained for further analysis. Stational data but also remote sensed data in the grid format were gathered in a comprehensive database.&amp;#160;&lt;/p&gt;&lt;p&gt;Two groups of scenarios were applied. First group was focused on climate signals (namely trends in precipitation, mean daily temperature and potential evapotranspiration) and the second group included land use changes such as bark beetle outbreak. Effect of both groups was quantified and compared with baseline simulation across all basins.&lt;/p&gt;&lt;p&gt;The model proved the long-term shifts in runoff seasonality, driven by the air temperature rise, and apparent across the mountain ranges. The seasonal runoff changes are marked by the shift of spring snowmelt toward an earlier season and a decline in spring flows. The second aspect of the changing seasonality is an earlier and prolonged period of summer low flows.&lt;/p&gt;&lt;p&gt;The results proved the dominancy of climate change as a main factor of runoff alteration, acting in large scale patterns, despite the local variations in physiography and land use.&lt;/p&gt;