This paper reviews the theory and reffers the problems of renewable investment, furthermore through one empirical case study and analyzes the adaptability for that of agricultural irrigation assets in pond irrigation area to paddy field. At first, the durable years is evaluated by MAPI and New MAPI method as usual, however, it is too long as compare with technical sense. Secondly, as the alternative, Morris present valuation method is employed. The result is reasonable with some restricted interpretation. As reffered area is urbanized, the needs for multiple uses of pond water is increasing. Therefore, for water conservation, especially of pond, some public charge system are to be considered.
Agriculture and forestry yield many kinds of external economies. Land conservation and the preservation of traditional rural culture are typical ones of these. The present paper tries to evaluate these two of external services of public benefit in monetary terms for mountainous region in Wakayama Prefecture. Survey method is applied to find willingness to pay (WTP) per year for each external benefit by people in living neighboring urban areas. Questionnaire were sent to 3, 000 of inhabitants of three cities of Wakayama, Hashimoto and Tanabe in the prefecture. Using attribute data about the respondents, we estimate the bid equations for each benefit. At our econometric estimation, special effort is made by applying diagnostic tests stepwise to check pathological phenomena of models and to reflect properties of data on the models. The estimated bid equations show that personal attributes of respondents strongly and systematically influence magnitude of the WTP. The most important determinants are (1) respondent's image of the natural resources and the people in forestry and agricultural district; (2) respondent's interest and experience in participating in rural lives; (3) respondent's attitude to rural values; and (4) income of respondent households. Social benefits of land conservation and traditional rural culture are estimated at three cities' level in 1992 as 364 million yen and 329 million yen respectively.