This report evaluates the flood control dams, designed and constructed under federal laws PL 544 and PL 566, to determine which structures can be modified to serve as watersupply reservoirs, i.e. conversion of ag dams to water supply dams.
Plant communities along the banks of rivers dammed for hydroelectric power contain significantly fewer species than those along neighboring free-flowing rivers. Riverbanks provide a variety of environments for plant life. The inflow of nutrients and sediments; changing water levels over the seasons; and waterborne dispersal of seeds all contribute to the biodiversity. There is considerable debate among ecologists about how well plant populations recover and reestablish themselves alongside new, regulated water courses. The team compared both the simple number of species and an index of "species richness," which compensates for differences of riverside areas. The team found about 1/3 fewer species around storage reservoirs of hydropower systems than at comparable undisturbed sites; the index of species richness was only about 1/2 for these sites. By studying the vegetation alongside regulation schemes between 1-70 years old, the team found that the number of species increases along the water's edge initially, but then the community development appears to halt and the communities look permanently different. These results are likely to fuel debate on the relicensing of hydropower systems to regulate water. Different options are briefly discussed.
American Rivers produced abstract
Six reservoirs located in the Western United States (F. D. Roosevelt, Dworshak, Wallula, Shasta, Oroville, and New Melones) were sampled in order to estimate their greenhouse gas (GHG) emissions. Two types of fluxes were assessed : 1) diffusive fluxes of methane (CH4) and carbon dioxide (CO2) at the air/water interface; 2) degassing fluxes of CH4 and CO2 from water passing through the turbine spillways. Diffusive flux measurements indicated that the surface of the reservoirs were a source of CH4 during the sampling period (from +3,2 to +9,5 mg CH4