城镇化过程中滇池流域不透水表面扩张特征及其水环境效应

Characteristics of Dianchi Lake watershed impervious surface expansion and its effect of water environment during urbanization

以云南省昆明市滇池流域为研究区,揭示了滇池流域近30 a来高速城镇化发展过程中不透水表面扩张特征,在此基础上利用距离衰减函数和重力学模型分析了不透水表面扩张背景下的水环境效应。研究结果表明,滇池流域不透水表面呈现出沿着滇池全面扩张的趋势,高强度城区由2001年的1个变为2017年的4个,自然地表面积向不透水表面面积转移了35%,高强度城区面积比例由0.06%增加到了12.05%;近30 a来流域不透水表面增长速率超过了21 km2/a,在2004至2017期间,其增长速率达到了38 km2/a;不透水表面空间影响力与湖泊水质呈现出显著的相关关系,溶解氧(dissolved oxygen,DO)、叶绿素a(chlorophyll a,Chl.a)、总磷(total phosphorus,TP)、高锰酸盐指数(permanganate index,PI)、酸碱度(potential of hydrogen,p H)、透明度(transparency,Trans)均通过了显著性检验;各水质参数呈现周期性变化,同时不透水表面扩张对水质参数的影响是显著的,表明滇池流域高速城镇化是导致滇池富营养化和蓝藻水华频繁爆发主要原因。

Since the 20th century,urbanization is the most significant process of human activities,which is directly shown as the impervious surface area(ISA)expansion.ISA has become the main urban landscape.Although ISA rate just occupy no-iced surface about 0.2%-2.7%,the impacts on human and nature are extremely significant.Intensive research demonstrated that the relationship between urbanization and water quality was nonlinear.The foreigner researchers revealed that the deterioration of water environment could not be reversed when the ISA rate exceeded 25%.But the threshold influenced by natural and human conditions of research area,different areas have different threshold.To date analyzing the changing characteristic and correlation between water quality parameters and ISA are lees carried out.In this paper,the Dianchi lake watershed of Kunming,Yunnan province was studied,and improved normalized difference build-up index(INDBI)and linear spectral mixture analysis(LSMA)algorithm were used to analyze the characteristics of Dianchi Lake watershed impervious surface expansion in the context of rapid urbanization in the past 30 years.Secondly,the distance decay function and gravity model was used to quantitatively analyze the impervious surface area impact on water quality.Thirdly,Morlet wavelet analysis method was used to reveal water parameters periodicity.Results showed that the impervious surface area of Dianchi Lake Watershed expanded fast around Dianchi Lake(α=0.001),nearly half of the land use/land cover has been changed.The natural surface area in 2017 was approximately 59%,the percent of high-intensity urban area was increased from 0.06%to 12.05%.Under the national strategy background of“One Road,One Belt”,“One lake,four core urban area”and“Build the Urban Area on the hill”,the number of main district(high-intensity urban areas)changes from 1 in 2001 to 4 in 2017(Kunming main district,Airport main district,Chenggong main district and Jinning main district),cities are surrounding the Dianchi Lake.35%of natural surface area was transferred into impervious surface.In the last 30 years,the growth rate of impervious surface area in the Dianchi watershed has been exceeded 21 km2 per year,and the growth rate reached 38 km2 per year from 2004 to 2017.There is a significant correlation between the spatial influence of impervious surfaces and water quality of lakes.The correlation coefficients between water quality parameters(dissolved oxygen(DO),chlorophyll a(Chla),total phosphorus(TP),permanganate index(PI),potential of hydrogen(pH)and transparency(Trans))and the spatial influence of impervious surfaces were all passed the significance test,which shows that the high speed urbanization is the main cause of frequent eutrophication and blue-green algae bloom in Dianchi Lake Watershed