Rainfall data were collected to systematic study rainfall patterns and pulse characteristics from 1967 to 2008 in desert regions of the Heihe River basin. The results showed that the annual rainfall averaged 113. 3 mm and the interannual variability accounted for 27. 93% of the annual rainfall that were described as a downward trend. The majority of rainfall events were characteristic by 5 mm, and the interannual variability were relative small large rainfall events ( ≥10mm) were infrequent but the interannua l variability was wide comparatively. Rainfall date of 5 mm d-1 were the most common, whereas the date of ≥10mm d-1 varied widely. Inter rainfall period of < 10 d accounted for them ost proportion and the variability were relative small ( CV = 18. 29% ), whereas the variability of > 10 d were relative large ( CV =27.21% ). Annual rainfal lwere significantly positively correlated with rainfall events, rainfall period, < 10 d interrainfall period and total interrainfall period. The variation coefficient of 5 mm were 24. 57% and approached to that of annual rainfall ( 27. 93% ), whereas > 10 mm were 76. 68%, which indicated that the interannual variability of large rainfall events werem ainly resulted in the difference of annual rainfall and rainfall pattern.

The relationship between total rainfall of <5mm and >10mm and annual rainfall

(Picture/Acta Ecologica Sinica)