Spatio-Temporal Changes in the Streamflow Regimes Across Mahanadi River Basin

The current study analyses the changes in streamflow regimes using daily observed streamflow data at sixteen stream gauging stations in the Mahanadi River basin. In this study, non-parametric Pettit's test is used for detection of abrupt change, while Spearman's Rho and modified Mann–Kendall tests are used for trend assessment in annual total (QTOT) and maximum (Qx1day) streamflow series at a 5% significance level. Further, flow duration curves (FDCs) are derived at decadal time scales from daily streamflow data at each station to analyze the changes in streamflow regimes. The percentage change in the FDC quantiles representing low, moderate, high and peak flow conditions for the current period with respect to the baseline period are evaluated. The results indicate the presence of a significant change point in QTOT and Qx1day for the Bamnidhi and Kesinga stations. A contrasting pattern in the streamflow trends is evident between the northern (decreasing trend) and southern (increasing trend) parts of the Mahanadi basin, particularly upstream of the Hirakud reservoir. The changes in the decadal FDCs are classified into two broad categories based on the changes in magnitude and timing of streamflows; wherein seven stations have shown a notable transition from perennial to intermittent behavior. In contrast, no changes in the perennial nature of the stream were noticed at eight stations. The changes in the streamflow quantiles indicate an increase (decrease) in peak and high flow (dry and low flow) conditions in the region upstream of the Hirakud dam. Such contrasting changes in the streamflow characteristics would need careful consideration by the local authorities to resolve water management issues in the basin.