When the water quality of the Daechung reservoir was getting worse, the Korean government has particularly improved the water quality by the legal control of business and activation in the Daechung reservoir area Ⅱ(Daechung-riverside). As a result, it did lead to the damage of residents in the Daechung reservoir area Ⅱ. In this paper it is to estimate their damage using the conception of the compensating surplus. In oder to hold a level of life like so many before the construction of the Daechung reservoir area Ⅱ, residents in the reservoir area Ⅱ have to increase their expenditure. This additional expenditure is just same with their damage in the reservoir area Ⅱ. In oder to prognose their damage in the reservoir area Ⅱ, we estimate the subjective appraised value of the damage of the reservoir area Ⅱ, O"chung-Gun using Tobit-Model, CVM. As a result of the estimation, it proves that the annual damage of riverside residents in O"chung-Gun gets to 13.7billion Won. This paper focused on the implication for protecting the deterioration of the water quality of the Daechung reservoir.