Background This work aims to ascertain the contribution of sediment retention by check-dams to sediment discharge reduction, and to further reveal the attribution of the water and sediment changes in the Yellow River and provide the decision-making basis of check-dam construction on the Loess Plateau.

Methods The typical tributaries of Yanhe River in the loess hilly-gully region and Huangfuchuan River in the weathered sandstone hilly-gully (pisha) region were selected. On the basis of the safety survey database of check-dams in 2009, the operation period of check-dams, dams-controlled area, erosion-sediment yield modulus of dams-controlled watershed and sediment delivery ratio, the estimation method of the sediment retention were determined, and the contribution of sediment retention by check-dams to sediment discharge reduction in the typical tributaries on the Loess Plateau was analyzed.

Results The average annual retained sediment amount by check-dams in different decades during 1960-2015 in the Yanhe watershed ranged from 0.92 million t/a to 8.54 million t/a, in which the maximum appeared in the 1980s, followed by the 1970s (7.89 million t/a), the minimum occurred in 2000-2009. While in the Huangfuchuan watershed, the average annual retained sediment amount in different decades varied from 0.36 million t/a to 11.39 million t/a, the maximum in 2010-2015, then 1990s (7.41 million t/a) and the minimum in 1960s. In addition, the results showed that the significant reduction of the annual sediment discharge in the Yanhe and Huangfuchuan watersheds (P < 0.01) according to the Mann-Kendall trend test. On the basis of the Pettitt's abrupt test, the first transition year of the annual sediment discharge from 1955 to 2014 in the Yanhe and Huangfuchuan watersheds appeared in 1996 and 1984 (P < 0.05), while the second transition year of the annual sediment discharge were in 2005 and 2003 (P < 0.05), respectively. Meanwhile, the sediment discharge reduction after the abrupt change ranged from 18.25 million t/a to 42.20 million t/a in the Yanhe watershed and from 27.49 million t/a to 50.37 million t/a in the Huangfuchuan watershed, respectively. The influence of precipitation on sediment discharge reduction was weakened after abrupt change, while the effect of human activities was enhanced gradually. In addition, the contribution of sediment retention amount by check-dams to human activities in the Yanhe and Huangfuchuan tributaries were 29.1% and 28.5% after the first transition year, 8.4% and 18.2% after the second transition year, respectively. After 2000, the decreased sediment discharge was more than 85% in the Yanhe and Huangfuchuan tributaries, while the contribution of retained sediment amount by check-dams was less than 10% and 20%, respectively.

Conclusions It showed that the effect of sediment retention by check-dams was not the main factor of sediment discharge reduction. Due to the different soil erosion environment, especially the differences in the vegetation restoration effect and proportion of dam-controlled area to watershed area, the contribution of check-dams on sediment discharge reduction in the Huangfuchuan tributary was greater than that in the Yanhe tributary.