2.1 Data
In this work, Daily precipitation and temperature data were downloaded
from 698 evenly distributed weather stations nationwide from the China
Meteorological Data Network from 1961 to 2016
(https://data.cma.cn/), which covers
a wide range of climate, ecological regions and landscapes throughout
China. The temperature data was used to estimate the potential
evaporation. Then abnormal data was excluded, and the research parameter
changes and relationships in the
middle and lower reaches of the Yangtze River were focused on. The 30
meter digital elevation model (DEM) was downloaded from the geospatial
data cloud
(http://www.gscloud.cn/) by using
ArcGIS, and the corresponding watershed area of the hydrological station
was extracted. According to the Hydrological Annual Report of the
People’s Republic of China, daily runoff data was collected from 224
stations with records from 1970 to 1990 and from 2007 to 2016 for at
least 20 years. Daily precipitation and temperature data were chosen
from 267 weather stations in and near Yangtze river basin (YZRB). The
observed precipitation and estimated potential evaporation were
interpolated into the whole YZRB using the Thiessen polygon method
(Meena et al., 2013). Then the interpolated precipitation and potential
evaporation of the basin area corresponding to 224 hydrological stations
were averaged to obtain the daily precipitation and potential
evaporation data of each hydrological station.