Investigation of changes in seasonal streamflow and sediment load in the Subarnarekha-Burhabalang basins using Mann-Kendall and Pettitt tests

Abstract

In the present research, the trends and abrupt changes in the seasonal streamflow and sediment load of the Subarnarekha and Burhabalang basins over the past 40 years (1972–2013) were analysed utilizing Mann-Kendall and Pettitt tests. Daily time series data was utilized to measure the seasonal discharge and sediment load. The results indicated a statistically significant decrease in water discharge in upstream (Muri) during all seasons. During pre-monsoon, a significant increase in discharge was observed in the downstream over the past 40 years. Ghatshila, as the terminal gauging-station of the Subarnarekha catchment, indicated a significant increase in streamflow at a rate of 23 MCM (million cubic meters) per year during the post-monsoon. The recent seasonal changes in discharge might be associated with climate change (changes in precipitation behaviour). A significant negative trend in sediment load during pre-monsoon was recorded in Adityapur (rate = 0.07 × 103 tons year-1) and Govindpur (rate = 1.11 × 103 tons year-1). Jamshedpur showed a significant increase (rate = 0.12 × 103 tons year-1) in sediment load during pre-monsoon. All stations exhibited a significant declining trend in sediment load during monsoon; and the maximum rate (100 × 103 tons year-1) was observed in Govindpur. The Pettitt test demonstrated an upward shift in water discharge during pre-monsoon at Jamshedpur and Ghatshila during 1994–1996. A downward shift of sediment load in almost all stations in the Subarnarekha was recorded during 1995–1997. The significant decline in the sediment load is probably being influenced by increasing anthropogenic activities irrespective of any specific seasons. The findings of this study are highly important as the data presented in this paper might help with water resources, ecological management, and planning within the catchments.