Annual Wide-Area Estimates of Consumptive Use of Water by Irrigation and Area Actually Irrigated
Abstract
Irrigated agriculture is estimated to account for 70% of global total water withdrawals and over 85% of total consumptive water use. Over 55% of the World's irrigated cropland is in regions with high or extremely high water stress and it is expected that water scarcity issues will become more prevalent in the future with or without changes in climate. However, the information basis for irrigated agriculture, the dominant human use of fresh water globally, is inadequate. The goal of this research is to develop and demonstrate globally scalable algorithms to derive annual estimates of evapotranspiration of applied water (ETAW) due to irrigation and area actually irrigated (AAI). We estimate ETAW as the annually integrated difference between satellite observed ET (MODIS/ALEXI) and modeled evapotranspiration (GLDAS2.1) after sharpening GLDAS2.1 using fractional in and out of season land cover type, and filtering differences to exclude out of season or non-cultivated land cover types. Irrigation amplifies ET during the growing season relative to rainfed vegetation. Satellite derived ET reflects this amplified signal whereas modeled ET does not (since irrigation is not represented in the GLDAS2.1). We adapt an area-frame sampling methodology originally developed to assess extent of cultivated lands in China to estimate AAI. Comparison of results to reference data for the California Central Valley for 2003-2013 result in R2≈0.9 for both ETAW and AAI, though our estimates are biased high by about 20%. We have also adapted the algorithm to work over a much larger region encompassing all of Italy, Egypt, and Pakistan. The ability to estimate ETAW using remote sensing is unique and we demonstrate that high quality annual estimates of ETAW and AAI can be cost-effectively produced over large geographic regions. This work enables research into causal mechanisms for interannual variability of irrigation practices. Approved for public release, 18-759.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC41F1517B
- Keywords:
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- 1640 Remote sensing;
- GLOBAL CHANGEDE: 1803 Anthropogenic effects;
- HYDROLOGYDE: 1926 Geospatial;
- INFORMATICSDE: 4323 Human impact;
- NATURAL HAZARDS