The Watershed Allied Telemetry Experimental Research (WATER) is an airborne, satellite- and ground-based integrated remote sensing experiment aiming to improve the observing ability of remote sensing technique, and understanding and predictability of hydrological and related ecological processes on catchment scale. Under the auspices of the Chinese Academy of Sciences (CAS), it was started as a CAS’s West Action Plan project, and later was jointly supported by the State Key Basic Research Project “Theory and method for a synthetic retrieval of terrestrial ecological variables from both active and passive remote sensing approaches” under the auspices of the Chinese Ministry of Science and Technology of China (MOST).
Due to its unique natural environment, the inland river basins in northwestern China can serve as an ideal laboratory for the study of hydrological processes at catchment scale in cold and arid regions. In these river basins, cold and arid regions coexist, and mountain cryosphere and the world’s most dry land stand sharply in contrast. From the headwater to downstream, the landscape pattern is controlled by the quantity and distribution of the water resources. In the high mountain area, glacier and permafrost exist. In middle mountain area, alpine meadow and forest dominate. The middle and lower reaches are characterized by a desert-oasis-river landscape pattern, with agriculture well developed in middle stream and riparian ecosystem distributed along the river downstream. It should be noted that the airborne remote sensing has a higher resolution. It is able to bridge the gap between ground observation and satellite remote sensing and therefore play very important role in WATER.
WATER is composed of three hydrological experiments, one crosscutting experiment, and an integrated study. i.e., (1) cold region hydrology experiment, (2) forest hydrology experiment, (3) arid region hydrology experiment, (4) hydrometeorology experiment, (5) development of the WATER information system and a catchment-scale land/hydrological data assimilation system. In total, four periods were determined as necessary for the implementation of WATER, the experiment planning period, the pre-observation period (POP), which was carried out in the summer (July-October) of 2007 in the forest and arid region experimental areas and in winter (October-December) in the cold region experimental area, the intensive observation period (IOP), during which the airborne missions and intensive filed campaigns were carried out in winter (March-April) 2008 in the cold region experimental area and in summer (May-July) 2008 in the forest and arid region experimental areas, and the persistent observation period, during which two years (Jan. 1, 2008-Dec. 31, 2009) of continuous data collection was planned based on the established ground hydrometeorological network. The experiment design, the comprehensive experiment summary, and the tentative summaries for the the cold region experiment in the upper reaches and the middle reaches are introduced in (Li Xin et al, 2008), (Li Xin et al, 2009), (Wang Jian et al, 2009), (Ma Mingguo et al, 2009), respectively.