- Related Research Areas
- Water & Energy Cycles
Water resources management is a critical issue in semiarid regions. Irrigated agriculture is the primary consumer of freshwater resources and consumed ~ 90% of global freshwater resources during the past century. Increasing water availability will require optimizing irrigation applications. Development of actual ET maps at ¡Ü250 m spatial resolution and daily temporal resolution would greatly enhance our ability to optimize irrigation applications and reduce water consumption for irrigated agriculture. The primary science question addressed by this study is How can satellite data be used to monitor ET at spatial and temporal scales appropriate for irrigation scheduling? The main objective of this study is to evaluate whether MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data can be used to reliably monitor ET at appropriate space and time scales for water resources management. This objective will be accomplished by detailed monitoring of ET on the ground at point scales (weighing lysimetry) and up to 2 km spatial scales (large aperture scintillometry, LAS) and using high resolution airborne remote sensing to estimate ET and to downscale MODIS derived ET estimates. Point lysimeters (4) will be used to calibrate the LAS systems, at rainfed and irrigated agricultural sites. ET will be estimated from airborne data and from MODIS satellite data using Energy Budget models such as the METRIC and the Two Source Model, TSM. MODIS temperature data (1000 m resolution) will be downscaled using visible, NIR and SWIR bands from MODIS (250 m resolution), and aircraft mounted sensors (1 m resolution) to improve spatial resolution of thermal images and resultant ET maps. In addition ET maps from MODIS will be compared with ET estimates from large aperture scintillometers installed at km spacing). The following tasks will be conducted to accomplish the objective: (1) conduct groundbased monitoring of ET using lysimeters and large aperture scintillometers, (2) acquire airborne data for ET estimation, (3) estimate ET using Energy Budget models using data from airborne and satellite (MODIS) remote sensing), (4) scale ET estimates by downscaling temperature data form MODIS using MODIS and airborne data and by comparing MODIS ET with ET estimates from widely spaced LAS instruments (1 ¨C 2 km). The study will be conducted in the Texas High Plains, which is part of one of the largest agricultural areas in the US and 90% of irrigation water is derived from the Ogallala aquifer. The advantages of this study area include its representativeness of water resource problems in semiarid regions, intense monitoring (4 lysimeters, 5 soil moisture stations, 30 potential ET monitoring stations, ~ 300 irrigation well pumpage, and 3 large aperture scintillometers. The expected benefits include development of a regional actual ET map at ¡Ü 250 m spatial resolution and daily temporal resolution, development of methodologies to downscale satellite ET estimates from MODIS, and assessment of potential water savings using the proposed ET mapping relative to traditional PET data. This proposal is directly relevant to the topic of the NASA Terrestrial Hydrology Program (THP) that relates specifically to ¡°use of remote sensing ¡-. to further the scientific basis of water resources management¡±. This study addresses the discrepancy in scale between in situ and satellite remote sensing observations and will link the data from these different scales by providing measurements at a range of intermediate spatial scales from point ground based measurements (lysimetry) to large scale ground based measurements (LAS), to airborne, and ultimately to satellite based (MODIS) measurements.
Project PI: Bridget Scanlon/University of Texas at Austin
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