One of the more important ways in which water supplies can be maintained and, in some cases increased substantially, is through the proper management of watersheds or land areas producing water. Attention is being focused, in particular, on land areas supporting forest vegetation, and, specifically in Arizona, on the ponderosa pine type. Watershed studies have shown that these forested areas, which are normally limited to regions of high rain and snow fall, are best suited for intensive water yield management. Some forest management practices affect water yield.