Recent studies indicate that extremely dense vegetation is not the most satisfactory condition for development of maximum watershed values.

Greater yields of high-quality water have been obtained from some mountain-forest regions by thinning the natural tree stands with no resultant increase in soil erosion or flood danger.

A forest or shrub cover containing numerous small openings has been found to be more effective for production of water than a dense, continuous cover that intercepts much snow and rain and permits the moisture to be lost by evaporation. Highly important in watershed conservation is the preservation of wetlands, which function as filtration systems that stabilize water tables by holding rainfall and discharging the water slowly, and act as natural flood control reservoirs.