Abstract. Differences between meteorological and hydrological
droughts could reflect the regional water consumption by both natural
elements and human water-use. The connections between these two drought
types were analyzed using the Standardized Precipitation Evapotranspiration
Index (SPEI) and Standardized Streamflow Index (SSI), respectively. In a
typical semi-arid basin of the middle Yellow River (Qingjianhe River basin),
annual precipitation and air temperature showed significantly downward and
upward trends, respectively, with the rates of −2.37 mm yr−1 and
0.03 ∘C yr−1 (1961–2007). Under their synthetic effects, water balance
variable (represented by SPEI) showed obviously downward (drying) trend at
both upstream and whole basin areas. For the spatial variability of
precipitation, air temperature and the calculated SPEI, both upstream and
downstream areas experienced very similar change characteristics. Results
also suggested that the Qingjianhe River basin experienced near normal
condition during the study period. As a whole, this semi-arid basin mainly
had the meteorological drought episodes in the mid-1960s, late-1990s and the
2000s depicted by 12-month SPEI. The drying trend could also be depicted by
the hydrological drought index (12-month SSI) at both upstream and
downstream stations (Zichang and Yanchuan), but the decreasing trends were
not significant. A correlation analysis showed that hydrological system
responds rapidly to the change of meteorological conditions in this
semi-arid region. This finding could be an useful implication to drought
research for those semi-arid basins with intensive human activities.
Spatio-Temporal Analysis of Droughts in Semi-Arid Regions by Using Meteorological Drought Indices
