Socio-economic aspects and impact of land use change on sediment production dynamics in the northeastern region of India

摘要

The northeastern region of India, with an area of 255 090 km2, is predominantly hilly. Major socio-economic factors affecting sediment production in the region are; shifting cultivation, land tenure system, fast growing population, small land-holdings, deforestation and free range grazing. A multi-disciplinary long-term study showed that 92.9 to 99.1% of rainwater can be retained in-situ, compared to 66.3% in shifting cultivation. Mean annual soil loss varied from 11.2 to 97.2 t km-2 in new land use systems as against 3621.3 t km-2 in shifting cultivation. The sediment load per litre of runoff from watersheds varied from 1250-20,300 mg suspended sediment, 5.4 to 23.6 mg NO₃ - N, 2.3 to 6.5 mg P-PO₄, 17.2 to 35.8 mg K₂O, 0.4 to 1.8 mg Zn, 0.9 to 2.7 mg Mn, 6.5 to 12.0 mg Mg, 7.1 to 18.4 mg Fe and 4.0 to 7.2 mg SO₄. The sediment transport from the catchments showed spatial and temporal variations.