Multi-Scale Analysis Based on Wavelet Transform of Reservoir and River Total Phosphorus Correlation and Determination of Monitoring Time Scales
2025
Zewen Liu | Jihong Xia | Mengshi Li | Roland Bol | Qiqi Wang | Yue Wang | Jiayi Zu | Qihua Wang | Shuyi Ji | Hongli Zhan
Total phosphorus (TP) dynamics between reservoirs and inflowing rivers critically affect eutrophication risks, but their multi-scale interactions remain insufficiently quantified. This study applied wavelet transform analysis to 8-year TP time series data from the Shanxi Reservoir and its inflowing rivers. Key findings include the following: (1) Morlet wavelet decomposition revealed dominant 8&ndash:16-month cycles for reservoir TP, contrasting with 4&ndash:8-month cycles in river TP: (2) wavelet coherence analysis identified a 90°: phase lag (2&ndash:4 months delay) between reservoir and river TP at the 8&ndash:16-month scale: and (3) the time&ndash:frequency localization capability quantified rapid responses&mdash:reservoir TP reacted within 2 months to abrupt river TP increases, showing stronger intensity. Multi-resolution analysis further distinguished the driving mechanisms: interannual cycles (>:12 months) governed reservoir TP variations, while seasonal cycles (<:8 months) controlled river TP fluctuations. The study demonstrated wavelet analysis&rsquo: dual strengths: resolving scale-specific interactions through multi-scale decomposition and quantifying transient responses via phase coherence metrics. The 90°: phase shift exposes hysteresis in TP transport, and the 2-month response threshold defines critical intervention timing. An adaptive monitoring framework is proposed as follows: &le:8-month sampling under stable conditions and 2-month intervals during TP surges, providing a time&ndash:frequency decision tool for precise reservoir water quality management.
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