Investigating Spatiotemporal Variation of Evapotranspiration Trends using Non Parametric Statistical Techniques across North Eastern Dry Zone of Karnataka, India

Abstract

This paper examines the temporal variation of ETo over the 10 main subdistricts of the North Eastern Dry Zone of Karnataka, India, during the period 1982-2022 using non-parametric statistical analysis. The findings show that ETo variability also exhibits diverse spatial and temporal characteristics in the study area. February month shows the highest decrease in the values (ZMK -2.33 to -1.72, p<0.05). Winter and summer shows highly significant decreasing trends, Manvi showing the maximum decreasing trend in winter (ZMK = -2.57, p < 0.01) and Raichur in summer (ZMK = -2.89, p < 0.01). Sen’s slope estimates show average decrease of -0.18 to -0.15 mm/month in winter and an average value of -0.246 mm/month in summer. For monsoon and post monsoon, the trends are weaker and not significant ranging from -0.05 to 0.03 mm/month. Yearly changes reveal slightly negative values (-0.12 to -0.04 mm/month). Spatial interpolation of the ETo changes is done using ArcGIS’s inverse distance weighting (IDW) method to show the regional differences. An increase in air temperature results in the rise in the trends in some months while, a decline in wind speed may be reason in other region. These findings are useful in understanding the ETo dynamics in the region and its relation to water and agriculture. More studies are required to understand why there was a reduction in wind speed as well as to develop individual water management strategies that will adapt to these changes.