Prof. Tamme S Steenhuis
Cornell University, USA
Abstract: The increasing world pollution requires a greater food supply. To meet this demand, agriculture has intensified on existing agricultural land, and new lands are being developed. These interventions often negatively affect the environment and its services. An example of intensifying agriculture is the double cropping in the North China Plain that caused groundwater to decline. New land development in the Ethiopian Highlands increased sediment concentrations and filled reservoirs. To counter these negative effects, best management practices have been introduced, which seem promising initially but, in practice, do not often live up to their envisioned potential. In North China Plain, many irrigation management practices reduced the amount of water pumped from the groundwater but stopping the groundwater decline remained elusive. In the Ethiopian highlands, best management practices were implemented in the uplands by increasing the infiltration. Sediment concentrations in the runoff were reduced as a result for some period. These positive effects, however, were negated by gullies downstream that increased sediment concentrations to the transport limit. The gullies were formed after deforestation disturbed the equilibrium in the watershed water balance due to decreased evaporation.
Management practices that are successful address the main factor that disturbed the equilibrium, which in both cases was the change in evaporation. Practices in China that reduce the evaporation to less than the amount of rainfall will stop the groundwater decline. In contrast, in (sub) humid Ethiopian Highlands, practices that increase the evaporation during the dry phases will decrease saturation, delay the runoff and reduce active gully erosion while also drying up springs. Engineered solutions that at great expense could counter the environmental harm consist of importing water in the North China Plain and stabilizing gully banks in Ethiopia.
Host：Prof. Cheng Gu
Executive Editor
Nanjing University
Time：09:00pm August 18, 2022 (Beijing time)
Zoom ID: 816 9975 7155
Bilibili: 25002335
