Increasing competition for water in China, due to industrialisation of its
economy and urbanisation of its population, has led to the introduction of
water-saving agricultural practices in an attempt to increase agricultural
water use efficiency (Ag WUE). This study was conducted to assess whether
changes in management practices have increased regional Ag WUE for a focus
area covering 20% of the 300 000 km2 North China
Plain (NCP). An ‘input–output’ definition of regional Ag WUE
was used, where ‘input’ is the water available over the crop
growing season and ‘output’ is grain yield. Regional databases of
precipitation, irrigation, and yield from 1984 to 1996 were established in a
Geographic Information System (GIS) to calculate winter wheat and summer corn
Ag WUE on a county basis. For wheat, the average Ag WUE was 7.0 kg/ha.mm
in 1984, whereas in 1996 it was 14.3 kg/ha.mm. For corn, Ag WUE increased
from 9.0 kg/ha.mm in 1984 to 10.1 kg/ha.mm in 1996, although values
>11.5 kg/ha.mm were obtained for both 1991 and 1992. Time series plots
of the resulting Ag WUE, and its components, were generated to reveal spatial
and temporal variability. Counties with a relatively high mean Ag WUE in
combination with low year-to-year consistency have been identified as those
with the highest potential for improving Ag WUE management. Total county water
resources (WR) were also calculated for the time series, and county-basis
normalisation of Ag WUE and WR also showed that there have been recent
improvements in Ag WUE. For some counties in wet years, there may be an
opportunity to plant larger areas of crop to increase county level Ag WUE. For
the focus study site (and for the time series data available), it is most
likely that recently introduced water-saving agricultural practices in the NCP
are associated with improvements to Ag WUE.