Abstract
Abstract. Urban lakes are important natural, scenic and pattern attractions of the city, and they are potential development resources as well. However, lots of urban lakes in China have been shrunk significantly or disappeared due to rapid urbanization. In this study, four Landsat images were used to perform a case study for lake change detection in downtown Wuhan, China, which were acquired on 1991, 2002, 2011 and 2017, respectively. Modified NDWI (MNDWI) was adopted to extract water bodies of urban areas from all these images, and OTSU was used to optimize the threshold selection. Furthermore, the variation of lake shrinkage was analysed in detail according to SVM classification and post-classification comparison, and the coverage of urban lakes in central area of Wuhan has decreased by 47.37 km2 between 1991 and 2017. The experimental results revealed that there were significant changes in the surface area of urban lakes over the 27 years, and it also indicated that rapid urbanization has a strong impact on the losses of urban water resources.
Highlights
Urban lakes are important freshwater resources available for ecosystems, they provide precious water to residents, fish and waterfowls, as well as regulate the urban environment, i.e., humidity, temperature, flood storage (J. Zhu, Zhang, and Tong 2015; Snehal and Unnati 2012; W. Zhu, Jia, and Lv 2014; Taravat et al 2016)
Since the Landsat archive was open to public by the U.S Geological Survey (USGS) in 2008 (Woodcock 2008), Many studies have focused on water change detection, lake monitoring and lakefront land use classification using multi-temporal Landsat images
The results show that the coverage of urban lakes continues to decrease over these years, and the proportion of urban lake areas in the downtown has dropped by 4.93% from 1991 to 2017
Summary
Urban lakes are important freshwater resources available for ecosystems, they provide precious water to residents, fish and waterfowls, as well as regulate the urban environment, i.e., humidity, temperature, flood storage (J. Zhu, Zhang, and Tong 2015; Snehal and Unnati 2012; W. Zhu, Jia, and Lv 2014; Taravat et al 2016). Since the Landsat archive was open to public by the U.S Geological Survey (USGS) in 2008 (Woodcock 2008), Many studies have focused on water change detection, lake monitoring and lakefront land use classification using multi-temporal Landsat images Michishita et al (2012) examined the two decades of urbanization in the Poyang Lake area in China, using a timeseries Landsat-5 TM dataset, and performed a quantification and visualization of the changes in time-series urban land cover fractions through spectral unmixing. Zhu et al (2015) quantitatively analysed the impacts of lakefront land use changes on lake area in Wuhan, based on two Landsat TM/ETM+ images taken in 1991 and 2005 Song et al (2013) estimated the water storage changes in the lakes of the Tibetan Palteau by combining time-series water level and area data derived from optical satellite images over a long time scale, and analysed the changes therein. Zhu et al (2014) monitored the fluctuation of Qinghai Lake by estimating the variations of water volume based on MODIS (Moderate Resolution Imaging Spectroradiometer) and Landsat TM/ETM+ images from 1999 to 2009. Zhu et al (2015) quantitatively analysed the impacts of lakefront land use changes on lake area in Wuhan, based on two Landsat TM/ETM+ images taken in 1991 and 2005
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