March 3, 2026Journal of Hydrology0 citationsOpen Access

Spatiotemporal variation of net anthropogenic phosphorus input and its delayed effect on lake phosphorus in a plateau lake of southwestern China

HLHuanyao LiuHunan Agricultural University CMCen MengChinese Academy of Sciences SWShuaibing WangYuxi Normal University

Key Points

Lake total phosphorus concentrations exhibit a nonlinear upward trend that signals persistent eutrophication.
Net anthropogenic phosphorus input peaked at 6,984 kg km−2 yr−1, mainly from food/feed and ore mining sources.
Using convergent cross mapping revealed a significant four-year lagged causal relationship from anthropogenic input to lake phosphorus levels.
Threshold analysis identified critical phosphorus input levels that lead to dramatic increases in lake total phosphorus concentrations.

Abstract

• P from food/feed, fertilizer, and ore mining were important potential P sources. • Lake TP exhibited a nonlinear upward trend. • Changes in NAPI would be reflected in TP concentrations 4 years later. • Threshold effects of P sources revealed abrupt changes in lake P levels. Plateau lakes are highly sensitive to anthropogenic phosphorus (P) enrichment. Despite recent management strategies reducing watershed P inputs, lake eutrophication persists, indicating a delayed recovery of water P level in response to external P reduction. This study focuses on Xingyun Lake, a typical shallow plateau lake in central Yunnan Province (Yuxi City), China, and applies the net anthropogenic P input (NAPI) model to evaluate the influences of different P sources in the watershed of Xingyun Lake from 1989 to 2020. The convergent cross mapping (CCM) approach was utilized to detect nonlinear and time-lagged causal relationships between NAPI and total phosphorus (TP) dynamics. Segmented regression analysis was further used to identify thresholds of P inputs leading to abrupt changes in lake TP concentrations. NAPI ranged from 1,148 ± 304 to 6,984 ± 2,206 kg km −2 yr −1 during the study period and was primarily driven by food/feed net P input (P im ), ore mining P input (P ore ), and fertilizer P input (P fer ). From 2000 to 2020, P ore was the dominant contributor to NAPI changes in the northern and eastern region, particularly in Jiangcheng and Luju towns. CCM analysis identified a significant nonlinear and unidirectional causal link from NAPI to TP with a 4-year time lag. Threshold analysis demonstrated that lake TP concentrations exhibited a nonlinear upward trend when P fer and P ore exceeded 806 and 1,305 kg km −2 yr −1 , respectively. This study provides the first quantitative evidence for the time-lagged response of lake P dynamics to anthropogenic P inputs in plateau lake systems, offering theoretical support and technical guidance for setting watershed water quality improvement goals and optimizing policy intervention timing

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