Influence of pebble size and cover on rainfall interception by gravel mulch

Rainfall interception by surface rock fragments may be an important component of the water balance of the stone mulched fields. However, interception loss by rock fragment layer receive only slight attention and field studies under natural rainfall are still scarce. A field study was conducted to investigate the effects of pebble size and cover percentage on interception during naturally occurring rainfall events in the semiarid loess regions of northwest China. The results indicate that pebble size and cover percentage have a different effects on rainfall interception. Interception increased with pebble cover percentage but decreased with pebble size. Interception was 8.9% of the gross rainfall at the 25% cover, followed by 15.7, 21.8 and 29.8% at the 50, 75 and 100% cover, respectively. In the case of pebble size, interception accounted for 36.4% of the gross rainfall for the pebble diameter of 2.5 cm, which is about 1.2, 2.1 and 2.5 times higher than that for the pebble diameters of 5.0, 7.5 and 10.0 cm, respectively.