Abstract
The impact of the El Niño-Southern Oscillation (ENSO) phenomenon within the Huangfuchuan watershed, one of the major first-order sub-basins in the middle region of the Yellow River, has not clearly been established. Consequently, the co-varying relationships between rainfall and El Niño/La Niña spanning the period 1954 to 2010 are investigated. Trends and step changes in annual rainfall are investigated with the Mann-Kendall and the distribution free cumulative sum (CUSUM) tests. Wavelet transforms are employed to perform spectral analysis of temporal variations in rainfall rates within the watershed. Cross wavelet and wavelet coherence transforms are used to study localized co-varying relationships between rainfall and ENSO index. Results from statistical tests indicate that rainfall in the Huangfuchuan watershed is declining, although not significantly. In addition, wavelet coherency and cross wavelet analysis, and comparison of the extracted dominant annual rainfall and 2–7 year ENSO signals demonstrate that ENSO events impact Huangfuchuan rainfall with El Niño corresponding to rainfall decline and La Niña to rainfall increment with a semiannual to annual lag.
Highlights
The Yellow River, the second largest river in China and the sixth longest in the world is the most important freshwater resource for northern and north-western China, supporting about 107 million people [1,2,3]
We investigate the relationship between rainfall and El Niño-Southern Oscillation (ENSO) in the Huangfuchuan watershed, an important sub-catchment in the middle region of the Yellow River
The trend line indicates that rainfall intensity in the Huangfuchuan watershed decreased during the period of study
Summary
The Yellow River, the second largest river in China and the sixth longest in the world is the most important freshwater resource for northern and north-western China, supporting about 107 million people [1,2,3]. We investigate the relationship between rainfall and ENSO in the Huangfuchuan watershed, an important sub-catchment in the middle region of the Yellow River. (b) to examine the relationship and impact of ENSO events on rainfall variability in terms of timescales, on the Huangfuchuan, which is one of the major middle source sub-basins of the Yellow River in northern China over the period 1954 to 2010. To this end, the current study adopts exploratory data analysis (EDA) and wavelet transforms to investigate trends and variability in rainfall patterns over the Huangfuchuan basin.
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