Extracting Miyun reservoir’s water area and monitoring its change based on a revised normalized different water index
CAO Rong-long①②, LI Cun-jun②, LIU Liang-yun②, WANG Ji-hua②, YAN Guang-jian①(①Research Center for Remote Sensing and GIS, School of Geography, Beijing Normal University, State key Laboratory of Remote Sensing Science, Beijing Key Laboratory for Remote Sensing of Environment and Digital Cities, Beijing 100875, China; ②National Engineering Research Center for Information Technology in Agriculture, Beijing 100097, China)
Miyun reservoir is the sole surface water supply of Beijing City, and detecting the change of the reservoir water is helpful for government management and decision-making. Based on analyzing the spectrum characteristics of water, vegetation and soil etc., a revised normalized different water index (RNDWI) is constructed to extract reservoir area with red band (TM3) and shortwave infrared band (TM5) of Landsat TM. To some extend, RNDWI can eliminate negative influence of mixed pixel and shade in mountainous area, and distinguish water from land area precisely, especially narrow water stri Pcan be identified. By comparing the precision of extracting reservoir area with RNDWI, modified normalized different water index (MNDWI) and single band methods, it is found that the precision of single band method is the lowest, MNDWI is higher and RNDWI is the highest. Then based on RNDWI, the dynamic change of Miyun reservoir’s water area is monitored by multi-temporal Landsat TM images from 1984 to 2005. The Miyun reservoir’s water area was largest (152.306km2) in 1996, since then the water area has gradually reduced year by year. Until 2004, it has become the least (56.632 km2), almost one third of 1996’s.