Abstract: Variational regularity of various components of water balance in forestbelt, grassland and bareland is explored from view point of water balance. The distribution proportions of various components of water balance in forestbelt, grassland and bareland are respectively: 1) All precipitation100%; 2) evapotranspiration96.4%, 95.7% and 89.5%; 3) slope runoff 3.6%, 4.3% and 10.5%. Since the forestbelt consists of canopy and forestland, their compositions of various components of water balance and variational regularity were analysed. The effect of forestbelt on river runoff is discussed.

Key words: Forestbelt, Water balance, Grass