Climatic Characteristics of Reference Evapotranspiration in the Hai River Basin and Their Attribution

Lingling Zhao,Leszek Sobkowiak,Jun Xia,Zongli Li

doi:10.3390/w6061482

Abstract

Based on the meteorological data from 46 stations in the Hai River Basin (HRB) from 1961–2010, the annual and seasonal variation of reference evapotranspiration was analyzed. The sensitivity coefficients combined with the detrend method were used to discuss the dominant factor affecting the reference evapotranspiration (ETo). The obtained results indicate that the annual reference evapotranspiration is dominated by the decreasing trends at the confidence level of 95% in the southern and eastern parts of the HRB. The sensitivity order of climatic variables to ETo from strong to weak is: relativity humidity, temperature, shortwave radiation and wind speed, respectively. However, comprehensively considering the sensitivity and its variation strength, the detrend analysis indicates that the decreasing trends of ETo in eastern and southern HRB may be caused mainly by the decreasing wind speed and shortwave radiation. As for the relationship between human activity and the trend of ETo, we found that ETo decreased more significantly on the plains than in the mountains. By contrast, the population density increased more considerably from 2000 to 2010 on the plains than in the mountains. Therefore, in this paper, the correlation of the spatial variation pattern between ETo and population was further analyzed. The spatial correlation coefficient between population and the trend of ETo is −0.132, while the spatial correlation coefficient between the trend of ETo and elevation, temperature, shortwave radiation and wind speed is 0.667, 0.668, 0.749 and 0.416, respectively. This suggests that human activity has a certain influence on the spatial variation of ETo, while natural factors play a decisive role in the spatial variation of reference evapotranspiration in this area.

Highlights

Hydrologists have found that climate change has resulted in some changes in the water cycle [1,2,3]
One major challenge of recent hydrological modeling activities is the assessment of the effects of climate change on the terrestrial water cycle [4]
Hydrological models are usually based on the calculation of reference evapotranspiration and reducing it to the actual evapotranspiration by considering the soil moisture status [5] or the number of days since the last rainfall event [6]

Summary

Introduction

Hydrologists have found that climate change has resulted in some changes in the water cycle [1,2,3]. One major challenge of recent hydrological modeling activities is the assessment of the effects of climate change on the terrestrial water cycle [4]. Analyzing how climate change affects reference evapotranspiration (ETo) is critical for understanding the impact of climate change on the hydrological cycle. The middle and lower reaches of the basin are important wheat production regions in China. This region has a semi-humid and semi-arid climate and has been strongly influenced by human activities. Several eco-environmental problems in that area have come to the fore under the combined impacts of climate change and intensified human activities. Due to the very limited available water resources in the basin, water has been diverted from other basins to supply it for agriculture and to maintain essential ecosystem functions [8]

Objectives

Methods

Results

Conclusion