南水北调华北受水区植被与降水的关系研究

华北地区年际归一化植被指数(NDⅥ)的变化与降水的年际变化有相当强的正相关,降水量增加会显著的改善植被覆盖.华北的NDⅥ变化显示了很强的季节变化特征,6月是华北农作物种植和生长的关键时期,但该月的需水量并不大,农作物生长旺季在7～8月.北京、邢台和潍坊的7月份农作物增长最快,月平均相对NDⅥ增长速度为0.4,8月的为0.2,因此,在7～8月农作物生长需水量最大,相当降水量接近180 mm,因此,在调配农业用水时应充分考虑这些因子.

The Relationship between the Vegetation Canopy and Rainfall over North China

There is a positive correlation between the variation of annual normal difference vegetation index(NDVI) and the annual rainfall,and increasing of rainfall will improve the vegetation canopy over north China.The variation of NDVI over north China is seasonal.June is the key phase of summer crops growing and the amount of needed water is not so much.During the summer,July is the fastest period of the crops growing over the fields of Beijing,Xingtai and Weifang.The mean relatively growing velocity of NDVI in July and August is 0.4 and 0.2,respectively.Therefore,the amount of needed water of crops growing in July and August is larger than other months,the equivalent rainfall is close to 180 mm. Discussion above should be considered during scheduling and distribution of water needed by crops growing.