Double radionuclide tracers of 137Cs and 210Pb were used to investigate sediment sources in the Wujia Gully, a small catchment in the Hilly Sichuam Basin in 2002. Aver-age 137Cs and 210Pb concentrations in the source soils of the steep forest slopes, gentle cultivated terraces and bare slopes were 7.15±0.40 and 162.01±3.86 Bqkg-1, 4.01±0.31 and 70.96±2.65 Bq·kg-1, and 0 and 15.12±1.22 Bq·kg-1, re-spectively, while those concentrations in the recently depos-ited sediments in the reservoir were 3.06±0.23 and 72.66±1.61 Bq·kg-1, respectively. By using the mixing model, the relative sediment contributions from steep forest slopes, gen-tle cultivated terraces and bare slopes (including channel banks) were estimated to be 18%, 46% and 36%, respec-tively. Cultivated terraces and bare slopes (including channel banks) were the first and the second important sediment sources in catchment. Specific sediment yield in the catch-ment was 642 t·km-2·a-1 from the deposited sediment volume in the reservoir since 1956. Soil erosion rates for the forest slopes and cultivated terraces, which accounted for 2/3 and 1/3 of the drainage area in the catchment, were esti-mated to be 173 and 886 t·km-2·a-1, respectively. Double radionuclide traces of 137Cs and 210Pb were used to investigate sediment sources in the Wujia Gully, a small catchment in the Hilly Sichuam Basin in 2002. Aver-age 137Cs and 210Pb concentrations in the source soils of the steep forest slopes, gentle cultivated terraces and bare slopes were 7.15 ± 0.40 and 162.01 ± 3.86 Bqkg-1, 4.01 ± 0.31 and 70.96 ± 2.65 Bq · kg-1, and 0 and 15.12 ± 1.22 Bq · kg-1, respectively, re-spectively, while those concentrations in the recently depos -disited sediments in the reservoir were 3.06 ± 0.23 and 72.66 ± 1.61 Bq · kg -1, respectively. By using the mixing model, the relative sediment contributions from steep forest slopes, gen-tle cultivated terraces and bare slopes (including channel banks) were estimated to be 18%, 46% and 36% respec- tively. Cultivated terraces and bare slopes (including channel banks) were the first and the second important sediment sources in catchment. Specific sediment yield in the catch-ment was 642 t · Km-2 · a-1 from the deposited sediment volume in the reservoir since 1956. Soil erosion rates for the forest slopes and cultivated terraces, which accounted for 2/3 and 1/3 of the drainage area in the catchment, were esti- mated to be 173 and 886 t · km-2 · a-1, respectively.