Author(s): Mehendra B. Baniya; Takashi Asaeda; Takeshi Fujino; Rocky Talchabhadel; Shiv Aram K. C. ; Guligena Muhetaer
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Keywords: Suspended sediment; Himalayas; Kali Gandaki River basin; Mann- Kendall trend test
Abstract: The complex process of weathering, land sliding, glacial and fluvial erosion yields the sediment from a catchment which depends on the catchment area, topography, slope of catchment, amount of rainfall, temperature and soil characteristics. Stream flow with suspended sediment (SS) transport rate variation is one of the most remarkable effects of rainfall changing patterns in Himalayas, Nepal. This study analyzed relationship between specific discharge and rainfall together with SS transport from Kali Gandaki (KG) River basin area of 7060 km2 at hydropower reservoir. Mann-Kendall trend (MKT) test along with Sen’s slope for 20 homogenized meteorological stations situated between the elevations ranges 700 to 2744 m MSL were used to evaluate monthly, seasonal and annual time series rainfall data over the period 1957-2017. Among 20 homogenized stations, MKT statistics showed that the rainfall in 9 stations exhibited increasing and remaining 11 stations showed decreasing trends. Statistically, four stations showed decreasing trend during winter (December-February), three stations showed increasing trend during pre-monsoon (March-May), one station showed decreasing and one station showed increasing trend during monsoon (June-September) and only one station showed significantly decreasing trend in 95% confidence interval during post monsoon (October- November). The increasing trend of rainfall during monsoon increased the discharge of KG River which transported an average of 40.90±12.45 Megatons (Mt) of suspended sediment annually in to hill-side reservoir dam.
Year: 2020