Index Terms: 1622: Earth system modeling; 1630: Land/atmosphere interactions; 1800: Hydrology; 1836 Hydrological cycles and budgets; 1840 Hydrometeorology; 1855: Remote sensing; 1996 Web Services; 4305: Space weather; 6334: Regional Planning This work addresses a key objective of SERVIR-Mekong Project related to integrating geospatial information in government decision-making, planning, and communication for societal good. The SERVIR-Mekong is a partnership between the U.S. Agency for International Development (USAID) and the U.S. National Aeronautics and Space Agency (NASA) formed to help regional organizations in the Lower Mekong Region to use information provided by Earth observing satellites and geospatial technologies in managing climate risks. Our work integrated multiple satellite-based earth observation systems, in-situ station data and spatial data with the Soil & Water Assessment Tool (SWAT) hydrologic model employed in the Mekong River Basin region to develop a Lower Mekong River Basin region’s hydrological decision support system. Simulated hydrological fluxes of streamflow, soil moisture, and evapotranspiration at the Lower Mekong River Basin were presented utilizing our developed hydrological decision support system. Our work results have been presented via multiple Tethys platforms, Tethys is an easily customizable platform that hosts web applications, that facilitate accessing NASA satellite-based earth observation systems as well as the Lower Mekong River Basin region’s hydrological decision support system. Earth observations data has provided solutions to assist people in the Lower Mekong River Basin to overcome various obstacles experienced in enhancing hydrological decisions that are related to difficult access and incompleteness, inconsistency, scarcity, as well as poor spatial representation of in situ data products.

The Lower Mekong is facing an increasing impact of droughts and at the regional level, the Mekong River Commission (MRC) is mandated to work with government agencies on creating and distributing flood, drought, water resource governance and use to improve policy and practice. The MRC is striving to provide regional, locally calibrated and downscaled information on drought forecasts and real-time monitoring through a portal. The Regional Drought and Crop Yield Information System (RDCYIS) is built on regionally and locally calibrated Regional Hydrologic Extreme Assessment System (RHEAS) framework that integrates the Variable Infiltration Capacity (VIC) and Decision Support System for Agro-technology Transfer (DSSAT) models, allowing both nowcast and forecast of drought. This model is co-developed by NASA Jet Propulsion Laboratory (JPL) and the SERVIR-Mekong teams. In this work, we outline how the MRC Drought Team’s requirements were met via RHEAS. Driven with earth observation data, the main aim of this service is to improve present regional and national drought monitoring and forecasting services to Lower Mekong countries for their water allocation and drought mitigation information needs. We provide an overview of the model calibration and validation methodology, and we find reasonable reliability of the soil moisture model results with the satellite based observations from the SMAP and SMOS retrievals. Through this support to MRC in integrating new drought assessment, monitoring and warning methodologies using RHEAS, more data and analyses will be available to support them to develop improved advice on drought early warning to the National Mekong Committees across the Mekong countries. MRC’s assistance is envisaged to enable comprehensive, accurate and useful warnings for the decision-makers at local and provincial level to take effective action. Ultimately this service is expected to assist farmers to make preemptive decisions about their water use, cropping and planting patterns and market decisions which should reduce crop loss and support livelihoods from farming, including from appropriate compensation to farmers from the governments, wherever this is in effect.