Abstract
Accurate quantification of irrigation water is necessary in order to
examine the realistic effect of agricultural water use on the
hydrological cycle and the climate. However, due to a lack of
survey-based statistics, the amount of irrigation water is often
estimated by irrigation demand derived from hydrologic models without a
proper ground validation. This study attempts to construct the first
State-level time series of irrigation water volume over India based
solely on survey statistics, with the aim of estimating historical
irrigation conditions. By assuming that the ratio of irrigated area
between States remained constant throughout the period, the annual
statistics of the State-level irrigated area were extended from the
period of 1990–2014 to the period of 1950–2014. The annual State-level
irrigation water volumes were then estimated as a function of the above
irrigated area data over 1950¬¬–2014 and calibrated using an
independent subset of State-level irrigation water quantity statistics.
The irrigation water volume data produced in the current study is
compared with a widely used irrigation water demand data. The comparison
suggests that the previous data might be significantly overestimated (up
to 80 Billion Cubic Metre) over most States with a few States with
underestimated values (up to 10 Billion Cubic Metre). The irrigation
area and volume data of this study is the first State-level estimate
that better represents the historical irrigation condition in India.