Four decades of water and sediment discharge records in Subarnarekha and Burhabalang basins: an approach towards trend analysis and abrupt change detection

The outcomes of trend analyses, abrupt change detection of discharge, sediment load data of Subarnarekha River for the last four decades are presented in this paper and possible causes of these changes are discussed. Bivariate linear regression, Mann–Kendall non-parametric test, Pettitt test have been implemented on the daily discharge and sediment concentration data provided by Water Resources Information System of India (India-WRIS). A statistically significant decreasing trend of discharge is found in the Subarnarekha upstream, whereas other stations in downstream show an insignificant increasing trend during the past four decades. Sediment load shows a decreasing trend in the entire study area where the change is significant in downstream regions since last four decades. An abrupt downward shift on the discharge is found only in case of Muri station from the year 2000, located in the upstream of Subarnarekha main river. Abrupt changes on the sediment load were found in the downstream after the period of construction of dams on Subarnarekha River. More precisely, sediment load had started declining progressively from 1998 in the Subarnarekha River and since 2010 in its adjacent river, Burhabalang.