This study analyzed and evaluated the effect of agricultural water reduction by introducing automated agricultural water management using alternative cost approach. The approach is possible to evaluate none market property as an asset. The saved agricultural water was evaluated as none market property. As the alternative goods, Seongju and Donghwa dam, typical irrigation dams in domestic, were employed. The economic benefit from water saving effect of an automated agricultural water management was calculated as depreciation expense and maintaining cost of construction agricultural dam per saved agriculture water. As a result, the saved agriculture water was 8.5 million ton per year, and the economic benefit of it was $1.3{sim}2.1$ million won.