海绵城市建设对流域海绵体生态水文过程的改善

Sponge city construction improves eco-hydrological process of spongy body in watershed

快速城市化驱动的不透水面比例增加是引起流域洪峰和径流总量增加的直接原因,海绵城市建设通过生态基础设施网络构建增加流域透水面比例,是重构流域生态水文过程的重要途径。但是海绵城市建设在流域海绵体生态水文过程中发挥的作用尚不清楚。以深圳市布吉河流域洪湖片区为例,通过雨季水文过程要素在线连续监测来确定海绵城市建设是否改善洪湖片区生态水文过程。结果表明,中观尺度上,雨季降雨量对洪湖片区地表径流总量无直接影响,降雨强度显著影响洪湖片区地表径流峰值流量(P<0.05),日降雨量对布吉河水质影响极显著(P<0.01)。洪湖片区通过28.3%(0.85 km^(2))海绵面积建设,透水面比例提升,以生物滞留设施和透水铺装等强化片区蒸散和下渗过程,减少雨季径流97.2%(248.72万m^(3)),削减典型降雨峰值流量98.2%以上,降低易涝点积水水位至7.8 cm以下,2.8%形成河川径流(布吉河),海绵面积(比例)和地表径流量削减无直接量化关系。洪湖片区污染物截留时空随保水能力得到提升,控制排放悬浮物月均浓度均低于15.60 mg/L,污染物通过径流裹挟进入布吉河的总量和速率降低,促使布吉河黑臭消除、水质提升至IV类。海绵城市建设对微观尺度生态水文过程的影响与中观尺度存在差异,降雨量等因素与典型项目生态水文过程量化关系不明显。学校、道路和社区公园利用绿色屋顶、透水铺装等强化下渗、蒸散,可削减雨季径流99.0%以上、削减峰值流量97.0%以上,控制悬浮物月均浓度低于17.10 mg/L。总之,以上研究结果强烈表明海绵城市中微观尺度源头减排设施和调蓄设施的耦合建设模式可以削减洪湖片区径流总量、峰值流量、积水水位和径流污染,是一种改善相似流域生态水文过程的有效途径。

The impervious surface increase driven by rapid urbanization directly causes flood peak and total runoff increasing in watershed.An important way to reconstruct eco-hydrological process of watershed is sponge city construction.Sponge city can enhance the pervious surface through ecological infrastructure network construction.However,the role of sponge city construction in eco-hydrological process of spongy body in watershed is still unclear.This paper takes Honghu Area of Buji River watershed in Shenzhen as an example to assess eco-hydrological process after sponge city construction.The assessment method was online continuous monitoring of hydrological process elements in rainy season.The results showed that rainfall volume in rainy season affected indirectly the total surface runoff in Honghu Area on mesoscale.The rainfall intensity significantly affected the peak runoff flow in Honghu Area(P<0.05).The daily rainfall volume had a very significant effect on the water quality of Buji River(P<0.01).Pervious surface in Honghu Area increased through sponge city construction of 28.0%(0.85 km^(2)).The construction of biological retention facilities and permeable pavement and others strengthened the evapotranspiration and infiltration process in Honghu Area.Sponge facilities promoted Honghu Area reduced the total surface runoff in rainy season by 97.2%(2.4872 million m^(3)).Peak flow was reduced by more than 98.2%under two typical rainfall.The water level of waterlogging points was reduced to less than 7.8 cm in rainy season.The rest 2.8%surface runoff formed river runoff of Buji River.The reduction of surface runoff had no directly quantitative relationship with sponge area(proportion).The pollutants intercepted time and space improved with the water retention capacity in Honghu Area.Adequate interception of pollutants promoted monthly average concentration of SS(suspended solids)discharge lower than 15.60 mg/L.The lower SS concentration indicated that the total amount of pollutants from runoff decreased and migrated slowly to Buji River.Effective interception of pollutants promoted black and odour in Buji River dissolved and water quality improved to Class IV.The influence of sponge city construction on eco-hydrological process on mesoscale was different with that on microscale.The quantitative relationship between rainfall and eco-hydrological process of typical projects was not obvious.School,road and community park used green roof and permeable paving and others to strengthen infiltration and evapotranspiration.The sponge facilities promoted the typical projects reduced runoff in rainy season by more than 99.0%,and reduced peak flow by more than 97.0%,and controlled monthly average concentration of SS below 17.10 mg/L.In conclusion,our research results strongly suggest that sponge city construction can reduce the total runoff,peak flow,ponding water level and runoff pollution in Honghu Area.Coupling construction of source emission reduction facilities and storage facilities on microscale and mesoscale is an effective way to improve the eco-hydrological processes of similar watershed.