Abstract:
In this study, ETo was calculated using FAO-56 Penman Monteith method. Lag-1 autocorrelation coefficient
was performed to detect the presence of serially correlation in data series. Mann-Kendall (MK) or Modified Mann
Kendall (MMK) and Spearman’s rho test were applied to detect the trend in annual and monthly ETo at 8 districts over
49 years (1960–2008) in the Soenath river basin, Chhattisgarh (India). The slopes of trend lines were computed using the
Theil–Sen’s slope estimator. The increasing trends in ETo were more pronounced than the decreasing trends. Annual
analysis of the ETo series indicated a increasing trend in almost all the districts except Bilaspur district. The percentage
change in annual ETo was maximum for Raipur (1.72%) and minimum for Bilaspur (-1.41%). On the monthly time scale
increasing trends were identified in ETo data in most of the months. The significant positive trend magnitude was found
for the months of September, October and November with Theil–Sen’s slope equal to 1.08, 1.15 and 1.30 mm/year. The
Coefficient of Variability (CV) revealed that inter-annual variability was high in the whole river basin, with highest
variability noticed for Durg district (104.31%).
