Correlations between hydrological drought and climate indices with respect to the impact of a large reservoir

With the construction of numerous water conservation projects, an assessment of the correlation between the evolution of hydrological drought and climate indices under in the context of large reservoirs helps to elucidate the response of the global environment to variations in hydrological drought. This study is focused on the Jinjiang River basin in southeastern China, where the Shilong hydrological station is affected by a large reservoir, and the Anxi hydrological station is not. Based on monthly streamflow data from 1960 to 2010, the Standardized Streamflow Index (SSI) was used to identify hydrological droughts. Pearson correlation coefficients (PCC) and the cross-wavelet transform (XWT) method were used to reveal detailed correlations between the SSI and climate indices. The correlations detected for both stations were then compared. The results indicate the following: (1) the correlations between the SSI and both ENSO (EI Nino-Southern Oscillation) and PDO (Pacific Decadal Oscillation) are more obvious than those of the other two climate indices, NAO (North Atlantic Oscillation) and AMO (Multi-decadal Oscillation). Moreover, the effect of EI Nino was more notable than that of La Nino. (2) Apparent intra-annual (12-48 months) and inter-decadal (128-256 months) common oscillation cycles between the SSI and ENSO were detected. Furthermore, there is an unequal lag time (1.47-1.80 months) between the coherence cycles of the SSI with ENSO. (3) The regulation functions of the large reservoir with respect to streamflow changed the correlations between the SSI and climate indices. The correlations at Shilong were weaker (stronger) than those at Anxi in the dry (wet) season.