Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China.
Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China.
Water Res. 2024 Aug 15;260:121951. doi: 10.1016/j.watres.2024.121951. Epub 2024 Jun 16.
Land use plays a critical role in managing water quality in a watershed, as it governs the import and distribution of nutrients. In addition to the land use, some rivers in Southwest China are encountering a new environmental stressor of damming, which is being driven by the national strategy of hydropower development. However, the coupling effect of land use and dams on nutrients remains poorly understood, challenging the effective management of riverine water quality. Therefore, this study examined the nutrients in the Nu, Yarlung Tsangpo (YT), and Lancang (LC) Rivers, which have no dam, 1 dam, and 11 dams, respectively, during different regulatory periods (spring and fall) to identify variations in nutrient control patterns influenced by land use and dams. The findings suggested that an increase in hydropower development contributed to a notable shift in nutrient patterns from land use regulation towards dam regulation and coupling effects. Land use dominated the nutrient variations of the Nu (27.4 %-32.8 %) and low hydropower development YT (25.2 %-30.9 %) Rivers during both seasons, but the primary contributors to the nutrient variations of the high hydropower development LC River were dams (17.9 %-41.6 %) and coupling effects (16.5 %-29.0 %). Dams transform nutrient levels and compositions through internal reservoir cycling, decoupling land use and nutrients. Partial least-squares structural equation model analysis further suggested that the coupling effects of the LC River were seasonal-specific, which was primarily attributed to hydrological variations that affected their interactions. During spring, the reservoir underwent a drainage mode characterized by high-level nutrients in the bottom water. Combined with the import of riverine nutrients, it exacerbated the increase of nutrients (synergistic effect). In contrast, the reservoir transitioned into a storage mode where it intercepted nutrients from the upstream and watershed during the fall, leading to a reduction in the previously observed increasing trend and an increase in nutrient variability (antagonism effect).
土地利用在流域水质管理中起着至关重要的作用，因为它控制着养分的输入和分布。除了土地利用之外，中国西南地区的一些河流还面临着新的环境胁迫因素，即大坝建设，这是国家水电开发战略的推动。然而，土地利用和大坝对养分的耦合效应仍知之甚少，这给河流水质的有效管理带来了挑战。因此，本研究调查了努、雅鲁藏布江（YT）和澜沧江（LC）三条河流的养分情况，它们分别没有大坝、有一个大坝和有 11 个大坝，分别在不同的调节期（春季和秋季），以确定受土地利用和大坝影响的养分控制模式的变化。研究结果表明，水电开发的增加导致了从土地利用调节向大坝调节和耦合效应的显著转变。在两个季节中，土地利用都主导着努（27.4%-32.8%）和低水电开发 YT（25.2%-30.9%）河流的养分变化，但高水电开发 LC 河流的养分变化的主要贡献者是大坝（17.9%-41.6%）和耦合效应（16.5%-29.0%）。大坝通过内部水库循环改变养分水平和组成，使土地利用和养分脱钩。偏最小二乘结构方程模型分析进一步表明，LC 河的耦合效应具有季节性特征，这主要归因于影响它们相互作用的水文变化。在春季，水库经历了一种以底层水高营养水平为特征的排水模式。结合河流养分的输入，它加剧了养分的增加（协同效应）。相比之下，水库在秋季过渡到一种储存模式，从上游和流域中截留养分，导致之前观察到的增加趋势减少，养分变异性增加（拮抗效应）。
