Perennial energy crops like switchgrass that are used for biofuel production have the potential to generate various water quality benefits such as reduced nitrogen runoff. Yet the current expected returns to switchgrass are not profitable enough for these crops to be widely adopted by U.S. farmers due to relatively unstable yields, volatile revenues, and high costs of crop establishment. This study uses a dynamic economic model to investigate the uncertainties in the yields and costs of switchgrass production, in comparison with those of corn-soybeans in the Chesapeake Bay Watershed in Pennsylvania. Results indicate that farmers would be willing to convert corn-soybeans to switchgrass land use with the provision of payments for ecosystem services (PES). A targeted PES policy based on the environmental effectiveness of the crop land is found to be slightly more effective in providing nitrogen reductions than a uniform PES policy with cost savings of 8–19%. Moreover, switchgrass has the potential of providing energy supply while reducing greenhouse gases emissions.

A limnological study was performed out, over 8 years from 1979 to 1986, in a shallow recently created sand-pit lake,Lake Créteil (Paris suburb, France). The lake is mainly supplied by phreatic waters. Typical of shallow waters, thermal stratification which occurred from May to October was intermittently broken by wind, leading to high seasonal fluctuations and allowing a reoxygenation of the total water column. The interannual development of the lake was characterized by a regular increase in transparency (from 1 m in 1979 to 2.7 m in 1985) which was partly due to not only stabilization of the bottom sediment and the banks, but also to a reduction of the biological component. A decrease in chlorophyll a concentrations resulted from nutrient diversion of domestic inputs collected through the rainwater pipe cominginto the lake. The rapid restoration of water quality shows that this small artificial lake is very sensitive to human interventions.