Whitespar Watersheds

Results

The channel treatment of trees and shrubs at Whitespar B (Phase 1) resulted in an increase in both amount and duration of streamflow. Although only 15% of the watershed was treated, it produced perennial flow in previously ephemeral stream channels which was considered beneficial to both wildlife and livestock (Hibbert et al. 1986). When the increases were prorated to the area treated, there was an annual increase in streamflow of 4.2 inches. The increase in streamflow was short-lived as vegetation recovered after treatment and below normal precipitation occurred.

Ridgetop treatment of trees and shrubs at Whitespar B (Phase 2) resulted in no additional streamflow increases (Hibbert et al. 1986). It was concluded that any water saved by reducing the shrub cover along the ridgelines was utilized by the untreated downslope shrubs before it reached the channels.

The mosaic treatment of brush on Whitespar A (Phase 3) resulted in:

• Increased annual streamflow of 1.5 to 5.0 inches over a seven?year posttreatment evaluation period (Davis 1993).
• A small but statistically significant increase in nitrate concentrations also occurred (Davis 1993). Nitrate nitrogen released from converted areas was diluted by streamflow from untreated areas, reducing nitrate concentrations in streamflow at the watershed outlet.

Evaluations on the Whitespar watersheds were discontinued in 1986.