Historical trends and the long-term changes of the hydrological cycle components in a Mediterranean river basin

2018 ◽  
Vol 636 ◽  
pp. 558-568 ◽  
Author(s):  
A. Mentzafou ◽  
S. Wagner ◽  
E. Dimitriou
2020 ◽  
Vol 24 (4) ◽  
pp. 1721-1740 ◽  
Author(s):  
Erwin Rottler ◽  
Till Francke ◽  
Gerd Bürger ◽  
Axel Bronstert

Abstract. Recent climatic changes have the potential to severely alter river runoff, particularly in snow-dominated river basins. Effects of changing snow covers superimpose with changes in precipitation and anthropogenic modifications of the watershed and river network. In the attempt to identify and disentangle long-term effects of different mechanisms, we employ a set of analytical tools to extract long-term changes in river runoff at high resolution. We combine quantile sampling with moving average trend statistics and empirical mode decomposition and apply these tools to discharge data recorded along rivers with nival, pluvial and mixed flow regimes as well as temperature and precipitation data covering the time frame 1869–2016. With a focus on central Europe, we analyse the long-term impact of snow cover and precipitation changes along with their interaction with reservoir constructions. Our results show that runoff seasonality of snow-dominated rivers decreases. Runoff increases in winter and spring, while discharge decreases in summer and at the beginning of autumn. We attribute this redistribution of annual flow mainly to reservoir constructions in the Alpine ridge. During the course of the last century, large fractions of the Alpine rivers were dammed to produce hydropower. In recent decades, runoff changes induced by reservoir constructions seem to overlap with changes in snow cover. We suggest that Alpine signals propagate downstream and affect runoff far outside the Alpine area in river segments with mixed flow regimes. Furthermore, our results hint at more (intense) rainfall in recent decades. Detected increases in high discharge can be traced back to corresponding changes in precipitation.


2018 ◽  
Vol 11 (1) ◽  
pp. 241-257 ◽  
Author(s):  
Sicheng Wan ◽  
Jianyun Zhang ◽  
Guoqing Wang ◽  
Lu Zhang ◽  
Lei Cheng ◽  
...  

Abstract Investigating long-term streamflow changes pattern and its response to climate and human factors is of crucial significance to understand the hydrological cycle under a changing environment. Caijiazhuang catchment located within Haihe River basin, north China was selected as the study area. To detect the trend and changes in streamflow, Mann–Kendall test was used. Elasticity and hydrological simulation methods were applied to assess the relative contribution of climate change and human activities on streamflow variability under three periods (baseline (1958–1977), impact I (1978–1997), and impact II (1998–2012)). The long-term hydro-climatic variables experienced substantial changes during the whole study period, and 1977 was the breaking year of streamflow change. Attribution analysis using the two methods showed consistent results: for impact I, climate change impacts explained 65% and 68% of streamflow reduction; however for impact II, it only represented 49% and 56% of streamflow reduction. This result indicated that human activities were intensifying over time. Various types of human activities presented significant effects on streamflow regimes including volumes and hydrographs. The findings of this paper could provide better insights of hydrological evolution and would thus assist water managers in sustainably managing and providing water use strategies under a changing environment.


2019 ◽  
Vol 489 (3) ◽  
pp. 307-312
Author(s):  
V. M. Kotlyakov ◽  
L. P. Chernova ◽  
A. Y. Muraviev ◽  
T. Y. Khromova

The results of measurements of the area of surging glaciers in 1974 and 2018 are compared to the data on their areas in 1913. A large decadal (middle-term) variability in the area of basin glaciation is revealed, and it is comparable to the respective secular (long-term) changes. It is shown that in, the southern meridional circulation epoch, despite high summer temperatures, the surging glaciers in the Sugran River basin grew in area due to increased precipitation, supporting the idea about their flood-runoff nature.


Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1400
Author(s):  
Isaac Kwesi Nooni ◽  
Guojie Wang ◽  
Daniel Fiifi T. Hagan ◽  
Jiao Lu ◽  
Waheed Ullah ◽  
...  

Actual evapotranspiration (ET) and its individual components’ contributions to the water–energy nexus provide insights into our hydrological cycle in a changing climate. Based on long-term satellite ET data assimilated by the Global Land Evaporation Amsterdam Model (GLEAM), we analyzed changes in ET and its components over the Nile River Basin from 1980 to 2014. The results show a multi-year mean ET of 518 mm·year–1. The long-term ET trend showed a decline at a rate of 18.8 mm·year–10. ET and its components showed strong seasonality and the ET components’ contribution to total ET varied in space and time. ET and its components decreased in humid regions, which was related to precipitation deficits. ET increases in arid-semiarid regions were due to water availability from crop irrigation fields in the Nile Plain. Precipitation was the dominant limiting driver of ET in the region. Vegetation transpiration (an average of 78.1% of total ET) dominated the basin’s water fluxes, suggesting biological fluxes play a role in the regional water cycle’s response to climate change. This analysis furthers our understanding of the water dynamics in the region and may significantly improve our knowledge of future hydrological modelling.


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