Effect of land use change on runoff and sediment yield in Da River Basin of Hoa Binh province, Northwest Vietnam

The objective of this study was to assess runoff discharge and sediment yield from Da River Basin in the Northwest of Vietnam using Soil and Water Assessment Tools (SWAT) model. The SWAT model was calibrated and validated using the observed monthly stream flows and sediment yield at selected gauging stations. The results indicated that SWAT generally performs well in simulating runoff and sediment yield according to Nash-Sutcliffe efficiency (NSE), Observation's standard deviation ratio (RSR), and percent bias (PBIAS) values. For runoff, the values of NSE, RSR, and PBIAS were 0.98, 0.02, and 3.69 during calibration period and 0.99, 0.01, and 1.56 during validation period, respectively. For sediment yield, the efficiency was lower than the value of NSE, RSR, and PBIAS during calibration period were 0.81, 0.19, and -4.14 and 0.84, 0.16, and -2.56 during validation period, respectively. The results of the study indicated that the vegetation status has a significant impact on runoff and sediment yield. Changes in land use type between 1995 and 2005 from forest to field crop and urban strongly contributed to increasing the average annual runoff from 182.5 to 342.7 mm and sediment yield from 101.3 to 148.1 ton(-1) ha. Between 2005 and 2010, a decrease of both runoff (from 342.7 to 167.6 mm) and sediment yield (from 148.1 to 74.0 ton(-1) ha) was due to the expansion of forested area and application of soil conservation practices. The results of this study are important for developing soil and water conservation programs, extending future SWAT modelling studies and disseminating these results to other regions in Vietnam.