Investigation on Water Productivity of Winter Wheat Based on MODIS and SEBAL in the Huang-Huai-Hai Plain, China

Understanding how the productivity of water can be increased is widely accepted to be a high priority
where water resources are currently scarce and/or over-exploited in China. As the primary data source, MODIS
remote sensing, statistics, meteorological data, crop growth period data and ground truth-data from Jan. 2011 to
Dec. 2012 were used in actual evapotranspiration estimation, yields rasterizing, and water productivity calculation
for winter wheat in the Huang-Huai-Hai Plain (3H Plain). The statistical data were synthesized to calculate
district-state-level land productivity, which is then further extrapolated to pixel-level values using a MODIS NDVI
image, based on a crop dominance map. Spatial variation of crop water productivity was investigated in order to
reveal the key factors of crop water productivity. In addition, the relationship between water productivity and actual
evapotranspiration and in subsequence yield for winter wheat was discussed in 3H Plain. The main results indicated
that the SEBAL is suitable for estimating evapotranspiration in winter wheat based on the comparation between
evapotranspiration measured by Yucheng (in Shandong province). The regional average value of water productivity
for winter wheat was detected to be 1.21kg·m-3, with the higher value in Beijing, Tianjin, north part of Shandong
province and south part of Hebei province. The pronounced relationship of spatial correlation of the yield and water
productivity for winter wheat indicated that the increasing yield governed the increment of water productivity for
winter wheat in the coastal land-farming-fishing area (zone1), low plain-hydropenia irrigable land and dry land
zone (zone2) and basin- irrigable land and dry land (zone5). The increasing water productivity for winter wheat was
recognized to be controlled by rather the increment of yield than the reduction of actual evapotranspiration for
winter wheat in the piedmont plain-irrigable land (zone2). Whereas, the pronounced relationship of negative
correlation of water productivity and actual evapotranspiration for winter wheat described that only the reduction of
actual evapotranspiration was responsible for the increment of water productivity for winter wheat in hill-wet hot
paddy-paddy field (zone6). The results is expected to provide a basis information for agricultural water
management, improvement of crop water productivity and choice of adaptive mechanism under climate change in
Huang-Huai-Hai plain.