Impact interaction potential: a basin-wide algorithm for assessing cumulative impacts from hydropower projects

Vol. 23( ) 341-360

The US Federal Energy Regulatory Commission (FERC) has proposed a "Cluster Impact Assessment Procedure" (CIAP) for analyzing cumulative impacts from hydropower projects on the resources of a river basin. While the CIAP is based on analyses of perceived magnitudes of impacts, it avoids any interpretation of the potential for basin-wide interaction among the projects leading to an accumulation of their effects in the resources. A measure of an "impact interaction potential" (IIP) is suggested here to describe the functional side of cumulative impacts. This tendency of a project cluster to cause cumulative impacts, or its "cumulativity", is examined through subbasin disaggregations of projects and resources. A dispersion of the project's impacts across subbasins I evaluated using linear algebra and principles of information theory. The formalized algorithm is programmed in BASIC and proposed as an IIP Assessment Loop in the CIAP. The IIP loop attaches to the Multiple Projects Assessment Phase as a causal interpretation of cumulative impacts, complementary to the effects analyzed via the CIAP's use of weighted summations. Use of the algorithm is demonstrated with a hypothetical project cluster in the Salmon River Basin (Idaho).


Emery, R.M.