The impact of the decline in area of the storage areas on water level at downstream of the Sai Gon – Dong Nai river system

Abstract

ABSTRACT The purpose of this research is to evaluate the impact of climate change, area decline of storage areas due to land levelling and dyke building activities on the water level at downstream of the Sai Gon – Dong Nai river system. The research methods were used include trend analysis and relation analysis between water levels and area of storage areas. The annual statistical data of typical water levels were collected at five monitoring stations from 1980–2018. The area was determined by satellite image classification. Thirty-two images of Landsat 5 and Landsat 8 in 1980–2018 period were used. The results indicated, due to the impact of climate change, the highest and lowest water level of station on the sea (Vung Tau) rose about 0.35 and 0.31 cm/year, respectively. At stations on the river, due to the simultaneous impact of sea-level rise and storage area decline, the water levels changed quite differently from Vung Tau. At stations near the storage areas such as Nha Be and Phu An, the highest water level rose about 1.1–1.2 cm/year, meanwhile, the lowest water level fell or rose insignificantly. There was a tight correlation between typical water levels and the area of storage areas over time, especially at stations near the storage areas. The study results have contributed to clarifying the cause of the extraordinary increase in the highest water level at downstream of the research area.