Pan Evaporative Changes in Trans-boundary Godavari River basin, India

Pan evaporative changes are one of the key components of water resources management of a basin under changing climate and anthropogenic-induced warming. This study was undertaken for trans-boundary Godavari River (India) to identify trends through the Mann-Kendall (MK) test after removing the effect of significant lag-1 serial correlation from the climatic time-series by pre-whitening in pan evaporation (Epan) and in the probable causative meteorological parameters responsible for evaporative climatic changes in a large basin. Further, the Pettitt’s test was applied on Epan time series for estimating the change point year of Epan to find out the effective year when the change in pattern started reflecting in the time-series. At seasonal (monthly) time scales, statistically significant decreasing trends in Epan were witnessed in pre-monsoon season (in the months of March, April and May) over all the seven sites of the Godavari basin. Four sites witnessed statistically significant increasing trends in Tmin (Tmax) in July (December) and in monsoon (post monsoon) season in the basin. Statistically significant decreasing (increasing) trends in wind speed (relative humidity) in pre-monsoon and in month of March at these seven sites support the observed decline in the evaporative demand in the basin leading to possible enhancement in the total yield of the basin. Results of stepwise regression analysis showed that wind speed followed by relative humidity was found to be two main causative parameters of the observed decline in the Epan under the warmer environments in the basin. Pettitt’s test shows year 1991–1992 to be the probable year of change in the Epan in the Godavari river basin.

Detection of Changes in Hydrological Time Series During Recent Decades

An analysis of a hydrological time-series data offers the possibility of detecting changes that have arisen due to climate change or change in land use. This paper deals with the detection of changes in the hydrological time data series. The trend analysis was applied at 58 stage-discharge gauging stations that are located throughout Slovakia, with the measurement period from 1962 to 2017. The Mann-Kendall test show a declining trends in the summer and a few rising trends in the winter in discharges. In the town of Banská Bystrica at a station on the Hron River, decades of discharges, air temperatures, and precipitation totals were analyzed. The five decades from the 1960s to the 2000s were used. The hydrological time data series were also analyzed by the Pettitt’s test, which is used to detect change points. The decadal analysis at the Banská Bystrica station shows an increase in the air temperature but insignificant changes in discharges and precipitation. Pettitt’s test identified many change points in the 1990s in the air temperature.