Stream Sediment Sources in Midwest Agricultural Basins with Land Retirement along Channel

Area of Science:

• Environmental Science
• Hydrology
• Soil Science

Background:

• Agricultural land retirement is crucial for improving water quality and aquatic habitats.
• Quantifying sediment sources from conservation easements, often discontinuous in agricultural regions, is challenging.

Purpose of the Study:

• To determine if isotopic and elemental concentrations can identify sediment sources (cropland, retired land, stream banks, roads).
• To assess how land retirement distribution affects sediment source contributions in West Fork Beaver Creek, Minnesota.

Main Methods:

• Collected channel-bed and suspended sediment samples from nine locations.
• Utilized linear discriminant analysis and a four-source mixing model with seven tracers (In, P, total C, Be, Tl, Th, Ti).
• Compared sediment samples with local source samples.

Main Results:

• Significant differences in sediment source proportions between suspended and channel-bed sediment.
• Retired land contributed to channel-bed sediment but not suspended sediment.
• Stream banks were a major source of suspended sediment, but continuous retired land reduced stream-bank contributions to channel beds.
• Higher cropland sediment contributions correlated with higher phosphorus (P) concentrations.
• Retired land reduced cropland material in suspended sediment.

Conclusions:

• Land retirement effectively reduces cropland-derived sediment and nutrient movement to streams.
• Continuous riparian land retirement is more effective in mitigating stream-bank erosion and sediment contributions.
• Isotopic and elemental analysis are valuable tools for source apportionment of stream sediment.