Abstract
Numerous large river basins of the world have few and irregular observations of the components of the terrestrial hydrological cycle with the exception of stream gauges at a few locations and at the outlet along with sparsely distributed rain gauges. Using observations from satellite sensors and output from global land surface models, it is possible to study these under-observed river basins. With populations greater than a billion people, some of these rivers (e.g., the Ganga-Brahmaputra, the Yangtze, the Nile and the Mekong) are the economic engines of the countries they transect, yet thorough assessment of their flow dynamics and variability in regard to water resource management is still lacking. In this paper, we use soil moisture (0–2 m) and surface runoff from the NASA Global Land Data Assimilation System (GLDAS), evapotranspiration, and Normalized Difference Vegetation Index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and rainfall from the Tropical Rainfall Measuring Mission (TRMM) and total water storage anomaly from the Gravity Recovery and Climate Experiment (GRACE) to examine variability of individual water balance components. To this end, understanding the inter-annual and intra-seasonal variability and the spatial variability of the water balance components in the major river basins of the world will help to plan for improved management of water resources for the future.
Highlights
The water availability per capita in many locations of the world is constantly decreasing
Five variables are derived from three different sources: precipitation from Tropical Rainfall Measuring Mission (TRMM), total water from Gravity Recovery and Climate Experiment (GRACE), evapotranspiration, and Normalized Difference Vegetation Index (NDVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) and runoff and soil moisture from
We have examined the water balance components for eleven global river basins using publicly available monthly satellite data and model output products for a period of 15 years between
Summary
The water availability per capita in many locations of the world is constantly decreasing. Obtaining data from river basins in countries other than United States is at times very difficult since many countries may not freely distribute or share data Given these reasons, satellite remote sensing observations and hydrological model outputs are an attractive solution that can overcome spatial heterogeneity and temporal consistency issues. The lack of in-situ water data from most of the large river basins of the world implies that we can only use the readily available satellite data sets and global land model outputs. The U.S./German Gravity Recovery and Climate Experiment (GRACE) satellite mission was launched in 2002 to provide estimates of changes in total terrestrial water storage (represented as the sum of groundwater, soil moisture, snow, and surface waters) at large spatial scales and on a monthly basis (Tapley et al, 2004). We use the root zone soil moisture (0-2m) and runoff from the improved GLDAS version 2 product in this study
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