Spatiotemporal variations of water quality in Lake Baihua, Guiyang City in the past decade (2009-2018)

Abstract

百花湖是贵阳市重要的城市饮用水源地，并且近年来经常发生水质异常现象.本文利用2009-2018年百花湖长时间序列的监测数据，采用综合营养状态指数法和Pearson相关性分析，研究了百花湖10年间的水质变化特征和影响因素.结果表明：1）库区叶绿素a（Chl.a）、总磷（TP）、总氮（TN）、高锰酸盐指数（COD_Mn）和透明度（SD）的浓度范围分别是3.43~39.72 mg/m³、0.034~0.115 mg/L、1.200~2.759 mg/L、1.41~5.51 mg/L和0.75~2.07 m，且高氮磷比（12~63）表明百花湖是磷限制型.2）在空间上，TP、TN、氨氮、COD_Mn和Chl.a浓度沿水体流向逐渐降低，SD呈相反变化趋势.3）10年来，百花湖水质由Ⅳ类转变为Ⅲ类，综合营养状态由轻度富营养化状态转变为中营养状态，水质整体向好.4）入库支流是影响百花湖库区水质的主要因素，长期以来，东门桥河、南门河水质TP和TN等超标严重，给库区水质稳定达标带来威胁.5）百花湖Chl.a浓度与气温、水位、风速和TP等指标显著相关，是受水文、气象及营养盐因素的综合控制.未来在百花湖水环境保护治理过程中，应加大对东门桥河、南门河等重点支流的污染治理，加强对水动力学、气候变化等水文气象因素影响库区水质（藻类水华）的机制研究.;Lake Baihua is an important source of urban drinking water in Guiyang City, and water quality anomalies often occur for many years. The long-term water quality monitoring data (from 2009 to 2018), together with the comprehensive trophic level index(TLI) method and Pearson correlation analysis, are used to study the water quality change characteristics and influencing factors of Lake Baihua over the past ten years. The results show that:1) The concentrations of chlorophyll-a(Chl.a), total phosphorus(TP), total nitrogen(TN), permanganate(COD_Mn) and transparency(SD) ranged from 3.43 to 39.72 mg/m³, from 0.034 to 0.115 mg/L, from 1.200 to 2.759 mg/L, from 1.41 to 5.51 mg/L and from 0.75 to 2.07 m, respectively. The high N/P ratio (12-63) indicates that Lake Baihua is a phosphorus limited type. 2) In space, the concentrations of TP, TN, ammonia nitrogen, COD_Mn and Chl.a decreased gradually along the flow direction of the water body, and SD showed the opposite trend. 3) The water quality of Lake Baihua has gradually improved from class Ⅳ to class Ⅲ from 2009 to 2018, and TLI has changed from light-eutrophic state to mesotrophic state. 4) The inflow tributaries are the main factors affecting the water quality in the reservoir area. The water TP and TN in Dongmenqiao and Nanmen Rivers were seriously over standard, which threatens the stability of water quality in the reservoir area. 5) The concentration of Chl.a was significantly related to temperature, water level, wind speed, and total phosphorus, which is considered to be controlled by the combination of hydrological, meteorological and nutrient factors. In the future, the pollution control of Dongmenqiao, Nanmen Rivers needs to be strengthened. Meanwhile, the mechanism of water quality (algal bloom) influenced by hydrodynamics, climate change and other hydrometeorological factors also needs to be further studied.