Trends in temperature over Godavari River basin in Southern Peninsular India

There is little dispute that global surface air temperature has increased and the anthropogenic-induced global warming is likely to play an important role in the management of water resources of a river basin. Therefore, this study was undertaken for Godavari River basin, a large southern peninsular river basin in India. After removing the effect of significant lag-1 serial correlation by pre-whitening procedure, the Mann-Kendall (MK) test was employed to investigate trends in maximum temperature (T_max), minimum temperature (T_min) and mean temperature (T_mean) at 35 stations in the basin. At seasonal (monthly) time scales, a majority of the stations exhibited no trends in T_mean, T_max and T_min in any of the four seasons (12 months) with the exception of post-monsoon (December) for T_max and monsoon (July and September) for T_min. About 60% (45%) of the stations exhibited increasing trends in T_max (T_min) in different durations: the month of December and post-monsoon season (the months of July and September and monsoon season) indicating the presence of an element of seasonal cycle in temperature over the Godavari basin. Results of tests of spatial and temporal homogeneity of trends by the Van Belle and Hughes method showed that trends in temperature over the Godavari basin were not homogeneous for different months or at different stations. In spite of the warmer climate in the basin, the evaporation (Epan) has been found to decrease significantly over the Godavari basin. Strong decreases in wind speed and increases in relative humidity may have actually caused the Epan decreases over the southern peninsular region of India.