Estimation of Sediment Yield Change in a Loess Plateau Basin, China

Abstract

Soil erosion is one of the most serious land degradation problems and the primary environmental issue in the Loess Plateau region of China. To identify the critical sub-basins and assess the impacts of land use change and climatic variability change on soil loss, this study tested the feasibility of the Soil and Water Assessment Tool (SWAT) model on sediment load simulation in the upper Sang-kan (USK) River basin. Based on a land use map of 1986, the SWAT model (Scenario 0) was calibrated at a monthly step using climate data from 1979 to 1985; then it was validated using climate data from 1986 to 1990. The monthly sediment simulation results indicated that the model did not work as well as streamflow simulation, indicating lower NS (Nash-Sutcliffe Efficiency) and r 2 values of 0.68, 0.69 and 0.61, 0.59 for the calibration period and validation period, respectively. This model could perform well under relatively low rainfall events, but it underestimated or overestimated the sediment load under high rainfall events. Comparing the results of scenarios with different land use maps (year of 1986 vs. 2012) and climate periods (1979-1990 vs. 2001-2012), it can be concluded that: (i) extreme and severe erosion almost always happened in FRST (forest land) and RNGE (grassland) in the hilly area; (ii) long-term traditional farming weakens the soil anti-erosion capability of land, leading to higher soil erosion, while forest can improve the soil structure, enhance the soil anti-erosion capability, and reduce soil erosion; (iii) both land use change and climatic change have led to the sediment yield decrease in the USK basin. Acting as the major influencing factor, land use change contributed to about 64.9% of the sediment yield reduction in the USK river basin.

Process based modelling of future variations in river flows and fluvial sediment supply to coasts due to climate change and human activities : data poor regions

“…G-Gauge precipitation, I-Interpolated gauge precipitation, P-PERSIANN-CDR, and C-CHIRPS. Corresponding parameter changes in sub-basins for each stations: Hkamti -1, 17,18,19 and 20,3,4,5,6,9,10 and 11,13,14 and 22,23,24,25,26,27,28,[29][30][31]32. 4.4 Results and discussion: Kalu River Basin…”

“…Maharjan et al (2014) showed that the sediment yield in the Nam Ou Basin (26,180 km 2 ) in Mekong River Basin, was less than 20 t/ha/yr for their base period of 1980 to 2000. The soil erosion rate in the Loess Plateau, China was shown to range between 0 and 80 t/ha/yr (at sub-basin levels) during 1980 to 1990 (Zhang et al, 2017). Betrie et al (2011) found that most areas of the Blue Nile Basin have soil erosion rates ranging between 1 to 20 t/ha/yr, while the erosion rate in cultivated lands therein exceeds 150 t/ha/yr.…”

“…Figure[6][7][8][9][10] and (b) sediment load at Pyay with bias-corrected GCM data(CSIRO Mk3.6, for the base period(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) in the Irrawaddy River Basin. The observed streamflow and sediment loads are presented in thick pink color line.…”