Temporal variations of sediment source from a reservoir catchment in the black soil region, Northeast China

• Deposited sediment is used to disclose its source with a simple model.
• Cultivated lands are the main sediment source.
• Increasing yearly rainfall decreases sediment contribution from cultivated lands.
• Increasing yearly rainfall increases sediment contribution from gullies/channels.
• Yearly rainfall controls temporal variations of sediment source.

An understanding of long term temporal variations in sediment sources from a catchment is necessary to identify the major sources of sediment for effectively implementing soil conservation measures. For this purpose, a sediment column from Qixin reservoir and 410 samples from the three potential sediment sources were collected and radionuclides, soil organic carbon (SOC) and soil texture were analyzed. The relative contributions from different sources were determined using a simple mixing model with 137Cs and 210Pbex. The mean contribution of sediment from cultivated lands to the sediment deposit was 50.87%, varying from 12.22% to 80.84%. Uncultivated lands contributed a mean of 5.22% ranging from 0.01% to 21.49% and gully/channel banks contributed 43.91% ranging from 15.15% to 86.91%. The relative contributions from the cultivated and uncultivated sediment sources to the reservoir deposit were significantly (P = 0.01) correlated with radioactivities, SOC and D50. The temporal variations of sediment source were determined by yearly rainfall amount and rainfall erosivity. The results indicate that conservation practices should be prioritized in the cultivated lands and gullies/channels and temporal preparation strategies for heavy rainstorms should be considered using physical soil erosion models combined with field investigation.