title: Monitoring groundwater variation by satellite and implications for in-situ gravity measurements.
abstract: In order to establish a new technique for monitoring groundwater variations in urban areas, the applicability of precise in-situ gravity measurements and extremely high precision satellite gravity data via GRACE (Gravity Recovery and Climate Experiment) was tested. Using the GRACE data, regional scale water mass variations in four major river basins of the Indochina Peninsula were estimated. The estimated variations were compared with Soil-Vegetation-Atmosphere Transfer Scheme (SVATS) models with a river flow model of 1) globally uniform river velocity, 2) river velocity tuned by each river basin, 3) globally uniform river velocity considering groundwater storage, and 4) river velocity tuned by each river basin considering groundwater storage. Model 3) attained the best fit to the GRACE data, and the model 4) yielded almost the same values. This implies that the groundwater plays an important role in estimating the variation of total terrestrial storage. It also indicates that tuning river velocity, which is based on the in-situ measurements, needs further investigations in combination with the GRACE data. The relationships among GRACE data, SVATS models, and in-situ measurements were also discussed briefly.
authors.affiliation: Department of Geophysics, Graduate School of Science, Kyoto University, Kitashirakawaoiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan. fukuda@kugi.kyoto-u.ac.jp
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Fukuda
authors.forename: Keiko
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nakaegawa
authors.forename: Jun
authors.initials: J
authors.lastname: Nishijima
authors.forename: Makoto
authors.initials: M
authors.lastname: Taniguchi
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D006112:Gravitation; D007564:Japan; D008962:Models, Theoretical; D045483:Rivers; D018531:Spacecraft / Q000295:instrumentation*; D014877:Water Pollution, Chemical / Q000032:analysis*; D014881:Water Supply