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Integrated water resources management requires consistent and accurate data on available water storage in reservoirs as well as water stress level. Vietnam is enduring a significant deficit in collecting necessary information to manage its water resources in that manner. While reservoirs are abundant, the majority of them were constructed a long ago and often lack of regular and adequate measurement on storage volume. Furthermore, the condition of water stress is often missing or remains bias leading to certain risks in reservoir operation, e.g. during water scarcity period. This paper presents how remote sensing data can be used to acquire needed information that is fundamental to understand water resources conditions. The results indicated that Sentinel-1 and Moderate Resolution Imaging Spectroradiometer (MODIS) can be applied to determine water surface area and water stress, through vegetation health index (VHI). This information is deemed necessary to improve water resources monitoring and management and hence, ensure long-term drought resilience and water and food security.

Improving irrigation monitoring and efficiency is a current priority of the Government of Vietnam, focusing primarily on the agricultural sector which consumes most of the available surface and groundwater. This paper presents how remote sensing can be used in an integrated manner to achieve better understanding of key eco-hydrological processes including precipitation, evapotran-spiration, irrigation and crop growth. The results indicated that Normalized Difference Vegetation Index derived from Moderate Resolution Imaging Spectroradiometer (MODIS) can be applied to determine irrigated pixels on a spatial and temporal basis. The validation using measured water level showed a Pearson correlation of 0.7 proving the high accuracy of this method. The inclusion of these technologies is deemed necessary to improve water resources monitoring and management and hence, ensure long-term drought resilience and water and food security. Ca River Basin in the central Vietnam was selected as a case study to test this approach.