Surface Water Evolution (2001–2017) at the Cambodia/Vietnam Border in the Upper Mekong Delta Using Satellite MODIS Observations

Abstract

Studying the spatial and temporal distribution of surface water resources is critical, especially in highly populated areas and in regions under climate change pressure. There is an increasing number of satellite Earth observations that can provide information to monitor surface water at global scale. However, mapping surface waters at local and regional scales is still a challenge for numerous reasons (insufficient spatial resolution, vegetation or cloud opacity, limited time-frequency or time-record, information content of the instrument, lack in global retrieval method, interpretability of results, etc.). In this paper, we use 17 years of the MODIS (MODerate-resolution Imaging Spectro-radiometer) observations at a 8-day resolution. This satellite dataset is combined with ground expertise to analyse the evolution of surface waters at the Cambodia/Vietnam border in the Upper Mekong Delta. The trends and evolution of surface waters are very significant and contrasted, illustrating the impact of agriculture practices and dykes construction. In most of the study area in Cambodia. surface water areas show a decreasing trend but with a strong inter-annual variability. In specific areas, an increase of the wet surfaces is even observed. Ground expertise and historical knowledge of the development of the territory enable to link the decrease to ongoing excavation of drainage canals and the increase of deforestation and land reclamation, exposing flooded surfaces previously hidden by vegetation cover. By contrast, in Vietnam, the decreasing trend in wet surfaces is very clear and can be explained by the development of dykes dating back to the 1990s with an acceleration in the late 2000s as part of a national strategy of agriculture intensification. This study shows that coupling satellite data with ground-expertise allows to monitor surface waters at mesoscale (<100 × 100 km2), demonstrating the potential of interdisciplinary approaches for water ressource management and planning.

Upskilling Low‐Fidelity Hydrodynamic Models of Flood Inundation Through Spatial Analysis and Gaussian Process Learning

“…An alternative way of reducing dimensionality of spatial‐temporal data is to extract key features in the form of patterns or trends (feature extraction methods). A common feature extraction method is Empirical Orthogonal Function (EOF) analysis, which has been used in areas of remote sensing, climate science and oceanography (e.g., Aires et al., 2014, 2020; Alvarez & Pan, 2016; Chang et al., 2020; Ghosh et al., 2021; Golestani & Sørensen, 2013; Jolliffe & Cadima, 2016; Marques et al., 2009). EOF analysis reduces the spatial‐temporal data into pairs (modes) of spatial patterns (EOF) and temporal variability functions, termed expansion coefficients (EC) (Jolliffe & Cadima, 2016; Zhang & Moore, 2015).…”

What Is the Future of the Lower Mekong Basin Struggling against Human Activities? A Review

“…The MD is very dynamic and is the first area for agriculture and aquaculture production in South East Asia [37]. During the wet season, large areas of the lower basin are naturally flooded due to the rain and regulated for agriculture optimization [38]. These floods are making the lower basin highly fertile and create numerous ecosystems rich in biodiversity [39].…”

“…The MD has the capacity to produce three rice crops per year, and even to supply the whole region. This important production is possible because of the implementation of irrigation, drainage channels and flood protection infrastructures [38,78,79]. However, these infrastructures also change flows and sediment transports.…”

The multi-channel system of the Vietnamese Mekong Delta: impacts on the flow dynamics under relative sea level rise scenarios

“…Recently, researchers have paid more attention to the whole domain by extensive monitoring networks (Dang et al, 2016 andGugliotta et al, 2017), satellite observations (Balica et al, 2014;Yamazaki et al, 2014) and by applying 1D (Hoa et al, 2008;Duong et al, 2018b andDang et al, 2018a), semi/quasi 2D (Triet et al, 2017) or 1D -2D coupled flow simulation models (Le et al, 2007;Eslami et al, 2019a). Other studies concentrated on the impacts of dyke systems on the hydrodynamics (Fujihara et al, 2016;and Aires et al, 2020). Even so, only few research works have assessed comprehensively the flow dynamics at a large scale.…”