基于ParFlow.CLM的居民小区屋顶雨水断接水文效应研究

Study on the Hydrological Effects of Roof Disconnection in a Residential Compound Based on ParFlow.CLM

城市不透水面的快速扩张极大地改变了自然的水文循环过程,是造成城市内涝、河湖生态退化等城市水问题的主要原因之一。海绵城市建设及低影响开发利用源头海绵设施或城市绿地断接城市不透水面,减少不透水面的水文效应,是缓解城市水问题的重要措施。探究不透水面断接的水文效应对我国海绵城市建设具有重要意义。基于全分布式物理水文模型ParFlow.CLM,充分考虑城市地下构筑物,探究了不同土壤质地情景下西宁市某典型居民小区建筑屋顶断接在连续的降雨、蒸发过程中的水文效应。模拟结果显示,利用该居民小区自然绿地断接建筑屋顶能取得较好的径流控制效果:当土壤饱和导水率(K_(s))大于0.01m/h时,屋顶径流的年削减率能达到72.9%以上。屋顶断接在建筑物雨落管附近形成了集中入渗,增加了根区土壤湿度,且这一效应随着土壤渗透性的增加而增强。根区土壤湿度的增加进一步促进了绿地的蒸散发:与屋顶断接前相比,不同土壤质地情景下居民小区年蒸散发总量增加了6.2%~7.8%。另一方面,集中入渗在局部也形成了更深的湿润锋,使得更多下渗水量能够脱离植被根区的蒸散发作用,从而促进根区水分的深层渗漏。模拟结果表明,尽管该居民小区地下停车场限制了大部分区域的深层渗漏,当土壤K_(s)大于0.01m/h时,屋顶断接情景下的年深层渗漏总量仍能超过城市化前的水平。

The rapid expansion of urban impervious surfaces has greatly altered the natural hydrological cycle process and is one of the main causes of urban water syndrome such as urban flooding and degradation of rivers and lakes.Sponge city construction and Low Impact Develop-ment are important measures to alleviate the urban syndrome.They use sponge facilities or urban green areas to disconnect the impervious surface to reduce its impact on hydrology.It is of great significance to explore the hydrological effect of imperviousness disconnection for sponge city construction in China.Based on the fully distributed physical hydrological model ParFlow.CLM,we explored the hydrological im-pacts of building roof disconnection in a representative residential compound in Xining City during continuous rainfall and evaporation under different soil texture scenarios.The urban underground structures were also fully considered in the simulation.The results show that roof dis-connection using the natural green space can have a good runoff control performance:when the saturated hydraulic conductivity(K_(s))of the soil is greater than 0.01 m/h,the annual reduction rate of roof runoff can reach more than 72.9%.The roof disconnection generated concen-trated infiltration near the roof downspout,which increased the soil moisture in the root zone,and this effect is more pronounced when the soil permeability is higher.The increase in soil moisture in root zone further promoted evapotranspiration from the green space:the annual to-tal evapotranspiration of the residential compound increased by 6.2%to 7.8%in different soil texture scenarios compared to the scenarios with no roof disconnection.On the other hand,the concentrated infiltration creates local deeper wetting front,which allows more infiltrated water to escape from the evapotranspiration of the root zone and promotes deep drainage.The simulation results show that although the under-ground parking lot in the residential compound limits deep drainage over most of the area,the annual total deep drainage under impervious-ness disconnection can still exceed pre-urbanization levels when soil K_(s) is greater than 0.01 m/h.