  Miyun Reservoir has produced huge benefits in flood control, agricultural
irrigation, power generation, aquaculture, tourism, and urban water supply.
Accurately water mapping is of great significance to the ecological environment
monitoring of the Miyun Reservoir and the management of the South-to-North
Water Diversion Project. On the 60th anniversary of the completion of the Miyun
Reservoir, we took the Miyun Reservoir as the study area and collected all the
Landsat-5 and Landsat-8 remote sensing images from 1984 to 2020 for water
mapping. Based on the spectral, topographical and temporal-spatial
characteristics of water, we proposed an automated method for long-term
researvoir mapping, which can solve the problems caused by cloud, shadow, ice
and snow pixels. Moreover, it can also deal with 'the same objects with
different spectra' and spectral mixed problems. The overall accuracy is as high
as 98.2% for the case with no cloud or snow/ice cover. The landscape division
index is introduced to analyze the morphological changes of Miyun Reservoir.
Based on the mapping results, we analyzed the changes of Miyun Reservoir from
1984 to 2020 and the driving factors of them.
