Journal of Geo-information Science ›› 2019, Vol. 21 ›› Issue (5): 781-788.doi: 10.12082/dqxxkx.2019.180643.

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Spatiotemporal Change Analysis of Sri Lanka Inland Water based on Landsat Imagery

Jianfeng LI1,2,3(), Huping YE2,3,5,*(), Zongke ZHANG2,3, Jinling KONG1, Xianhu WEI2,3, Deepakrishna SOMASUNDARAM2,3,4, Fali WANG2,3,4   

  1. 1. School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
    2. Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China
    3. China-Sri Lanka Joint Research and Demonstration Center for Water Technology, Chinese Academy of Sciences, Beijing 100085, China
    4. University of Chinese Academy of Sciences, Beijing 100049, China
    5. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
  • Received:2018-12-06 Revised:2019-02-21 Online:2019-05-25 Published:2019-05-25
  • Contact: Huping YE E-mail:ljf_chd@163.com;yehp@radi.ac.cn
  • Supported by:
    China-Sri Lanka Joint Research and Demonstration Center for Water Technology, China-Sri Lanka Joint Center for Education and Research, Chinese Academy of Sciencese;The Strategic Priority Research Program of the Chinese Academy of Sciences, No.Xda2003030202;State Development And Reform Commission's Special Financial Projects, No.2017ST000602.

Abstract:

Sri Lanka is an important node on the Maritime Silk Road, where rainfall is abundant in quantity but uneven in terms of spatiotemporal distribution. There is obvious seasonal water shortage. Monitoring the changes of water cover area in inland lakes and reservoirs is important for guiding the development and utilization of water resources. To understand the spatial distribution characteristics and temporal variations of lakes and reservoirs in Sri Lanka, this paper, based on Landsat series imagery, analyzed and compared the precision of different water extraction models on the images, following which the optimal algorithm was determined. A typical reservoir was chosen to analyze the interannual and monthly variations of the water cover sizes. The optimal water extraction algorithm was applied to the inland lakes and reservoirs in 1995, 2005, and 2015. Lakes and reservoirs were divided into four grades by area. The number and area of lakes and reservoirs of different grades in each year were counted, and their spatiotemporal variation characteristics were examined. Conclusions can be made according to the results as the following statements: (1) The water body extraction model based on the Normalized Difference Water Index (NDWI) with threshold value from the Otsu method (OTSU) had the best accuracy and was suitable for the water body extraction in Sri Lanka. The overall classification accuracy is above 97% and it has the lowest mis-extraction rate and the missing rate. (2) The water cover area of typical reservoir showed a fluctuatingly increase trend in Augusts from 1988 to 2018. The smallest water cover area occurred in 1992, and the largest was in 2013. The water cover area of reservoir was also of large intra-annual fluctuations. In 2017, the biggest water cover area appeared in February, while the smallest appeared in September, with a discrepancy of 2.24 times between the cover area in February and September, exactly the ends of local rainy season and dry season, respectively. (3) From 1995 to 2015, the number and area of lakes and reservoirs of different grades increased to some extent, and the trend of lake and reservoir water resources was increasing. Findings of the research will provide necessary data support for the management and planning of soil and water resources in Sri Lanka.

Key words: Sri Lanka, lakes and reservoirs, Maritime Silk Road, water body extraction, spatiotemporal change, OTSU