Reservoir surface water area variations change research using Sentinel 2 MSI data. A case study in Dak Lak province, Central Highlands (Vietnam)

Agriculture is one of the most important economic sectors in Vietnam, however, in recent times, agricultural production has been negatively affected by drought, reducing crop productivity and quality. Due to the effects of climate change, drought occurs in most regions of the country with varying degrees and duration, seriously affecting water resources and agricultural production. Particularly for the Central Highlands region, drought is a natural disaster with the most negative impacts on life and production. This paper presents the results of monitoring the changes in water surface area of some reservoirs in Dak Lak province in the dry season in early 2020 from Sentinel 2 data. The MNDWI index calculated from green and NIR band of Sentinel 2 images is used to extract surface water, and thereby evaluating the change in surface water area of the reservoirs. The obtained results show a very strong decrease in water surface area of reservoirs in Dak Lak due to the influence of drought. The water surface area of Ea Sup Thuong Lake decreased about 6 times at the end of the dry season (May 2020) compared to the period of January 2020. The water surface area of Ea Uy Lake decreased about 4 times, while with the Krong Buk Ha Lake, the decrease in water surface area was lower, reaching about 28% compared to the beginning of the dry season. The results obtained in the study provide timely information to help managers effectively respond to the effects of drought on water resources.