关键词: 降水, 沙丘水分, 水分下渗, 民勤

Abstract: A study on natural precipitation supplemented by artificial precipitation imitation showed that in Minqin sandy area the depth of rainfall permeation was related to the property of sand surface: rainfall permeation was affected by field capacity of the upper layer of surface soil, which was influenced by the content of silt and clay particles in the sand layer; the correlation between rainfall and its permeation was less significant. In fixed sand dunes when precipitation intensity was within 29.8 mm·d^-1 the maximum moistened soil depth by rainfall was 10~15 cm and the permeation rate was 15 cm·d^-1; in semi-fixed dunes when precipitation intensity was within 28.2 mm·d^-1 the maximum depth of soil moistened by rainfall was 30~35 cm and the permeation rate was 15~17.5 cm·d^-1; in shifting dunes while precipitation intensity was within 21.7 mm·d^-1 the maximum depth of soil moistened by rainfall was 130~135 cm and the permeation rate can reach 32.5~33.8 cm·d^-1. In fixed and shifting dunes the precipitation with intensity less than 8 mm·d^-1 would vapor soon, whereas in semi-fixed dunes it can stay longer. In contrast with fixed and semi-fixed dunes the moisture in the surface of shifting dunes would vapor most likely (i.e. under 8 mm precipitation) in a short time.

Key words: precipitation, moisture in dunes, rainfall permeation, Minqin in Gansu province