The scarcity of water encourages scientists to develop new analytical tools to enhance water resource management. Water accounting and distributed hydrological models are examples of such tools. Water accounting needs accurate input data for adequate descriptions of water distribution and water depletion in river basins. 5 Ground-based observatories are decreasing, and remote sensing data is a suitable alternative to measure the required input variables. This paper reviews the reliability of

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... ote sensing algorithms to accurately determine the spatial distribution of actual evapotranspiration, rainfall and land use. For our validation we used only those papers that covered study periods of one season to annual cycles because the accumulated 10 water balance is the primary concern. Review papers covering shorter periods only (days, weeks) were not included in our review. Our review shows that by using remote sensing, the spatial distribution of evapotranspiration can be mapped with an overall accuracy of 95 % (STD 5 %) and rainfall with an overall accuracy of 82 % (STD 15 %). Land use can be identified with an overall accuracy of 85 % (STD 7 %). Hence, more 15 scientific work is needed to improve spatial mapping of rainfall using multiple spaceborne sensors. Actual evapotranspiration maps can be used with confidence in water accounting and hydrological modeling.