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Abstract: Evapotranspiration is an important flux term in the water cycle that integrates atmospheric demands and surface conditions. Thus, analysis of the temporal variation of reference evapotranspiration (ET0) will help us to understand climate change and its effect on hydrology. In this paper, we present an analysis of the monthly ET0 at 15 stations during 1961–2005 in the Taoer River basin in China, calculated by the FAO Penman–Monteith method. We derived the growing season and annual total ET0 time series and using the Mann–Kendall method, moving t test and Morlet wavelet conducted comprehensive time series analysis to characterize significance test, abrupt change and period in the ET0 data sets. The results present that: (i) in terms of the seasonal cycle, monthly ET0 reaches its peak in May and growing season ET0 accounts for 60.7% of annual total. Long term growing season ET0 fluctuates in accordance with annual ET0, both having turning points in 1982 and 1993; (ii) with respect to the long term persistence, the trends for growing season and annual ET0 show the same spatial patterns: high positive values in the west study area in the upper reach and negative values in the Southeast study area in the lower reach. The spatial distribution of annual tendencies suggests an influence from the altitude and latitude; (iii) for individual station, abrupt changes in annual ET0 are more pronounced than those in growing season ET0. The timings for the abrupt changes in ET0 series at individual stations are consistent with those in regional ET0. Abrupt changes detected in the early 1980s are all increasing changes, while those in earlier 1990 are all decreasing changes; and (iv) based on the Morlet wavelet analysis, there exist significant periods of 1, 3 and 7.3 years in annual ET0 series and significant 1 year period and 7.3 years period in growing season ET0 series. Maximum air temperature, mean air temperature, relative humidity and bright sunshine hours are main climate variables responsible for the periodicity in ET0. [Copyright &y& Elsevier]

Abstract: This paper addresses the emergent issues by the case study of Haihe River Basin in North China. The advantage of the water international study and the background for the cause of these problems from natural change and in particular human activity are analyzed. The key points are addressed as four aspects: (a) the study of the water cycle process impacted by climate change and high intensity human activity; (b) water utilization related to new economic partner change, such as saving water model; (c) study on eco-hydrology, and the interaction of water and ecology impacted by climate change and human activity; and (d) reasonable water allocation that includs water diversion from south to north and saving water issue in the local areas. Several suggestions are proposed both on the study on the water cycle, which is a very important base of water security in north China, and on the application study of water resources and eco-environmental rehabilitation. These key issues will benefit both the advantage of water science and the sustainable development in China. [Copyright &y& Elsevier]

Evapotranspiration is an important component and key link of river basin water cycles and plant hydrological processes, and is a core issue in global climate change research. It is not only an important way to understand the energy and water consumption of permafrost regions, but also is an important channel to master the water cycle and energy balance in cold regions. In this paper, multiple linear regression analysis method and weighted comprehensive analysis of major factors method were used to investigate the variation characteristics and impact factors of evapotranspiration in the Genhe River Basin. The results showed the following: (1) The monthly average evapotranspiration in the Genhe River Basin during the freezing-thawing periods in 1980–2017 was 28.29 mm. Compared with the freezing-thawing periods, the total evapotranspiration in the growing seasons was much higher than that in the freezing-thawing periods, with monthly average evapotranspiration of 67.71 mm; (2) The main factors affecting evapotranspiration in the Genhe River Basin were precipitation and temperature. During the freezing-thawing periods, the variation in evapotranspiration in May was mainly determined by temperature. In the growing season, precipitation was the main factors affecting evapotranspiration in June. This will lay a foundation for clarifying the relationship between permafrost–climate change–hydrologic cycle in the permafrost active layer during the land surface process, so as to provide some basic data and important scientific basis for the comprehensive study of the hydrologic process and its impact on climate, ecology, water resources and environment in the permafrost area. • Evapotranspiration variability in permafrost zone have been analyzed in growing season and freezing and thawing period. • The influencing factors of evapotranspiration in a long term have been explored. • This study enriches the data of eco-hydrology research in data-deficient areas. [ABSTRACT FROM AUTHOR]