ABSTRACT
Pollution of a river or lake, to the extent that it diminishes the satisfaction of some individuals, is viewed as damage while improved water quality is considered a benefit. The travel cost approach to estimation of demand effect of changes in water quality is based on observed behavior of a sample of users responding to changes in out-of-pocket and time costs of traveling to: a single recreation site before and after water quality is improved, or a cross section of recreation sites with varying water quality. The basic premise of the approach is that number of trips to use a recreation resource will decrease as out-of-pocket and time cost of travel increase, other things remaining equal. The contingent value approach was recently approved by the US Water Resources Council as suitable for the valuation of recreation and environmental change. The unit day approach is the third method recommended by the US Water Resources Council to value recreation and environmental change.
