Changes in forest overstory lead to changes in runoff. This report estimates what such changes in runoff are worth to society using two sources of information: economicvaluation studies and, most importantly, water market transactions. Evidence from over2,000 transactions that occurred in the western U.S. over the past 14 years (1990 through 003) was examined to learn who is selling to whom and for what purpose, how muchwater is involved, and how much it is selling for. Roughly half of the transactions were sales of water rights; the rest were water leases. The transactions show that the price ofwater is highly variable both within and between western states, reflecting the localized nature of the factors that affect water prices. Ideally, if water market prices or valuationstudies are to be used to help determine the marginal value of water from specific areas, such as national forests, information from local markets or local studies should be used.Lacking site-specific value information, only rough estimates are possible.