Irrigation requirement of crops under changing climatic scenarios in a semi-arid region of Northern Karnataka.

Abstract

The groundwater status of Vijayapura district is under semi-critical to over-exploited category and optimal application of irrigation water is needed for the sustainable water management in this region. In the present study, the rainfall, temperature, evapotranspiration variability and irrigation requirement of major crops was analyzed for three future scenarios, namely, 2020’s (2010 to 2039), 2050’s (2040 to 2069) and 2080’s (2070 to 2099) with respect to the baseline period (1976-2005). The ENSEMBLE data corresponding to four different emission scenarios was used. Rainfall and temperature are important factors governing the irrigation requirement and the rainfall is predicted to increase from 590 mm during baseline period to 611, 646 and 677 mm under RCP 4.5 (medium emission scenario) and 617, 674 and 742 mm under high emission scenario (RCP 8.5). The maximum temperature is predicted to increase by 0.8, 1.6, 2.00C under RCP 4.5 and 0.9, 2.0, 3.60C under RCP 8.5. The minimum Temperature is predicted to increase by 1.0, 1.8, 2.30C under RCP 4.5 and 1.1, 2.5, 4.20C under RCP 8.5 respectively. Correspondingly, the evapotranspiration values (ET0) are estimated to increase from 1851 to 1877, 1900 and 1916 mm under RCP 4.5 and 1876, 1912 and 1958 mm under RCP 8.5. The irrigation requirement of rabi sorghum is predicted to increase from 434 to 440, 447 and 449 mm under RCP 4.5 and 438, 445 and 453 mm under RCP 8.5. Similarly, the irrigation requirement of rabi maize is predicted to increase from 667 to 678, 688 and 694 mm under RCP 4.5 and 679, 694 and 712 mm under RCP 8.5, respectively. No considerable increase in the irrigation requirement for kharif crops was predicted in Vijayapura. In order to ensure long-term and sustainable groundwater utilization in the region, proper estimation of crop water requirement and its application are needed.