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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #331007
Title: Resolving inter-annual terrestrial water storage variations using microwave-based surface soil moisture retrievals

Author
item Crow, Wade
item HAN.E - Columbia University
item RYU, E. - Melbourne University
item HAIN, C. - University Of Maryland
item Anderson, Martha

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2017
Publication Date: 4/1/2017
Citation: Crow, W.T., Han.E, Ryu, E., Hain, C., Anderson, M.C. 2017. Resolving inter-annual terrestrial water storage variations using microwave-based surface soil moisture retrievals. Water Resources Research. 21:1849–1862.

Interpretive Summary: Terrestrial water storage is defined as the total volume of water existing in the land surface - regardless of its location within the hydrologic cycle (e.g. lakes, reservoirs, soil water, snow and groundwater). As such, it provides a holistic view of the water cycle that is valuable for agricultural water resource management and drought monitoring. Currently, variations in terrestrial water storage can only be measured at extremely coarse spatial resolutions (> 200^2 km^2) using gravity-based remote sensing. Here we demonstrate, for the first time, that higher-resolution surface soil moisture retrievals obtained from microwave remote sensing can also be used to track these variations. This advance allows for annual closure of the terrestrial water balance at higher spatial resolutions and improved tracking of agricultural drought within medium-scale (~50^2 km^2) agricultural watersheds. The techniques introduced in this paper will eventually be used by hydrologists and water resource managers to better understand, track and predict variations in water resource availability for crop and rangeland production.

Technical Abstract: Due to their shallow vertical support, remotely-sensed surface soil moisture retrievals are commonly regarded as being of limited value for water budget applications requiring the characterization of temporal variations in total terrestrial water storage (S). However, advances in our ability to estimate evapotranspiration remotely now allow for the direct evaluation of approaches for quantifying annual variations in S via water budget closure considerations. By applying an annual water budget analysis within a series of both medium- (10^3-10^4 km^2) and large-scale (10^5-10^6 km^2) basins within the United States, we demonstrate that, despite their clear theoretical limitations, surface soil moisture retrievals derived from passive microwave remote sensing contain useful information concerning relative inter-annual variations in S. This suggests the possibility of using (relatively) higher-resolution microwave remote sensing to enhance the spatial resolution of S estimates acquired from gravity remote sensing. However, challenging calibration issues regarding the relationship between S and surface soil moisture must be resolved before the approach can be used for absolute water budget closure.