Remote sensing and in situbased estimates of evap

Authors: Nathan C Healey Ayse Irmak Timothy J Arkebauer David P Billesbach John D Lenters Kenneth G Hubbard Richard G Allen Jeppe Kjaersgaard

Publish Date: 2011/12/24

Volume: 25, Issue: 3, Pages: 151-178

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Abstract

Water consumed through evapotranspiration ET impacts local and regional hydrologic regimes on various spatial and temporal scales Estimating ET in the Great Plains is a prerequisite for effective regional water resource management of the Ogallala High Plains Aquifer which supplies vital water resources in the form of irrigation for extensive agricultural production The Sand Hills region of Nebraska is one of the largest grassstabilized eolian windblown sand dune formations in the world with an area of roughly 50000–60000 km2 that supports a system of five major land cover types 1 lakes 2 wetlands with lakes ~5 3 subirrigated meadows water table is within ~1 m of surface ~10 4 dry valleys water table is 1–10 m below surface ~20 and 5 upland dunes water table is more than 10 m below surface ~65 Fully understanding the hydrologic regime of these different ecosystems is a fundamental challenge in regional water resource assessment The surface energy and water balances were analyzed using Bowen Ratio Energy Balance Systems BREBS at three locations 1 a meadow 2 a valley and 3 an upland dune Measurement of the energy budget by BREBS in concert with Landsat remote sensing image processing for 2004 reveals strong spatial gradients between sites in latent heat flux that are associated with undulating topographic relief We find that daily estimates of ET from BREBS measurements and remote sensing agree well with an uncertainty within 1 mm which is encouraging when applying remote sensing results across such a broad spatial scale and undulating topography

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