Castle Creek Watersheds

Results and Current Status

Results from the harvesting treatment in predominately ponderosa pine on Castle Creek, West Fork were:

• An annual average water yield increase of about 30%, or 0.5 inch, was attributed to reduced evapotranspiration and increased snow accumulations in the openings.
• Evapotranspiration was lowered by 4 inches (19 to 15 inches).
• Increased water yield remained stable for 21 yr (1967 to 1987), probably because new tree roots had not fully occupied the soil mantle, and the height differences between the residual trees surrounding the openings and the regeneration continued to provide aerodynamics that favored increased snow accumulations in the openings.
• Effects on wildlife were important. The mixture of forest and interspaced clearcut blocks provided excellent conditions for deer and elk.

Results of prescribed fire on Castle Creek, East Fork included:

• No increase in average annual water yields, which was understandable because the fire did not affect forest overstory conditions or consume much of the forest floor.
• Concentrations of NH4-N and NO3-N, PO4, and K increased during the first 2 post-fire snowmelt periods. The changes in nutrient concentrations, while statistically significant, were small and of little consequence in terms of site productivity and downstream water quality.

Current Status

Most of the watershed experiments were terminated between 1983 and 1986. However, the Apache-Sitgreaves National Forest continues to collect streamflow and precipitation measurements from the Castle, Willow, and Thomas Creek Watersheds as part of its hydrological monitoring program. The vegetation transects and points continue to be visited by USDA forest pathologists to determine changes in dwarf mistletoe infections over time. Additional inventories are being considered by scientists at the Rocky Mountain Research Station. Data from the watersheds have also been used by graduate students at the University of Arizona.