This paper introduces the background, scientific objectives, experiment components and implementation plan of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER). The overall objective of HiWATER is to improve the observability of hydrological and ecological processes, to build a worldclass river basin observing system, and to increase the applicability of remote sensing and other new generation observation techniques in ecohydrological studies and water resource management at basin scale. HiWATER encompasses fundamental experiments, thematic experiments, application experiments, remote sensing methods development and products generation, and an integrated information system.
(1) Fundamental experiments: ① Microwave radiometer, imaging spectrometer, thermal imaging camera, Light Detection and Ranging (LiDAR) and other sensors will be used in the airborne missions to observe key eco-hydrological parameters and at the meantime to develop and improve the remote sensing models and methods for the retrieval of those variables. ② To establish a comprehensive hydrometeorological observation network that will cover the entire Heihe River Basin, in order to provide more representative model parameters and forcing data, and more accurate ground truths. ③ An eco-hydrological Wireless Sensor Network (WSN) will be established to capture the spatial-temporal dynamics and variations of key forcing data, eco-hydrological parameters, and model state variables over heterogeneous land surfaces. ④ Airborne sensors calibration and ground-based remote sensing experiments will be conducted. Remote sensing products will be validated rest upon the WSN, in association with simultaneous in situ measurements and other intensive observations.
(2) Thematic experiments: A multiscale observation experiment on evapotranspiration will be performed over heterogeneous land surfaces. Eddy Covariance (EC) systems, Large Aperture Scintillometer (LAS), and Automatic Weather Stations (AWSs) will be intensively deployed to constitute an observing matrix to reveal the spatial heterogeneities of ET, to identify the scale effects and achieve scale transformation of ET over heterogeneous landscapes, and to provide elementary data sets for the development and validation of ET estimation models.
(3) Application experiments: Purposeful observation experiments will be performed in the upstream, middle stream, and downstream of the Hiehe River Basin, aiming at snow and frozen soil hydrology, water balance in irrigation management, and quantifying plant water consumption. Observed data sets and remote sensing products will be used in distributed hydrological model, coupled surface water-groundwater-crop growth model, and ecological water consumption model towards the areas of upstream, middle stream, and downstream. It is anticipated the applicability of remote sensing in integrated ecohydrological studies and water resource management can be enhanced by means of these empirical researches.
The intensive observations and field campaigns will be orderly undertaken in the middle stream, upstream, and downstream of the Heihe River Basin from May, 2012 to 2015. Dependent on various experiments, remote sensing products at basin scale for the key eco-hydrological variables will be created, scale transformation approaches will be explored, and a multi-source remote sensing data assimilation system will be eventually built.