Scale effects and variability of forest-water yield relationships on the Loess Plateau, China

Abstract

The relationship between forests and water yield on the Loess Plateau is a concern to forest hydrologists and local governments. Most research indicates that forests reduce runoff but the degree of reduction is different at different sites. Data on precipitation, runoff depth, evapotranspiration and forest cover were collected for 67 watersheds through synthesizing published literature. Results suggest that afforestation on sparsely vegetated catchments reduces runoff and that this effect decreased with increasing forest cover. Annual runoff coefficients fluctuate around 4.1%. Catchment scales influence the relationship between percent forest and runoff coefficient. We believe that afforestation-water yield relationships are variable. Large-scale watersheds may have a relatively high buffering capacity that masks forest cover effects on runoff because of a number of interacting factors. Results from this research will support the implementation of large-scale afforestation programs on the Loess Plateau.