Forecasting daily net irrigation requirement maps of India using an ArcGIS toolbar A

摘要

Considering the vital importance of reference evapotranspiration (ETo) and net irrigation requirement (NIR) forecasts, a toolbar named Arc DSSET was developed to extend the capabilities of ESRI ArcGIS. The toolbar is capable of reading the five day forecasted meteorological data from India Meteorological Department (IMD) website for 75 stations all over India. An existing DSSET model was linked to the toolbar for estimation of ETo and thereby calculation of NIR for each station depending on the agro-ecological region (AER) in which it is situated. The toolbar was used to read data from IMD website from 4th November 2008 to 28th February 2009. These data were then used to estimate point ETo and NIR values and to prepare five days' forecasted maps of ETo and NIR by kriging. Four stations, namely, Ambala, Gadag, Jalpaiguri, and Pune, were selected to test the accuracy of forecasts. Most of the stations showed similar accuracy trends with higher accuracy for shorter lead time. It was also observed that the forecasts were slightly under predicted, but can be used up to five days as the error in forecasts were within acceptable range. Forecasted ETo, NIR, and rainfall were compared with the current day estimates and measurements in terms of Mean Absolute Error (MAE) for all five lead times for all the stations. Average MAE over AERs showed that error in ETo forecasts were also within acceptable range. Forecast accuracy of rainfall and NIR were found satisfactory except for mountaneous and coastal AERs 8, 15, 17, and 19 where frequent occurance of high variability rainfall was noticed.