Self-adaptive Green-Ampt infiltration parameters obtained from measured moisture processes

The Green-Ampt(G-A) infiltration model(i.e., the G-A model) is often used to characterize the infiltration process in hydrology. The parameters of the G-A model are critical in applications for the prediction of infiltration and associated rainfall-runoff processes. Previous approaches to determining the G-A parameters have depended on pedotransfer functions(PTFs) or estimates from experimental results, usually without providing optimum values. In this study, rainfall simulators with soil moisture measurements were used to generate rainfall in various experimental plots. Observed runoff data and soil moisture dynamic data were jointly used to yield the infiltration processes, and an improved self-adaptive method was used to optimize the G-A parameters for various types of soil under different rainfall conditions. The two G-A parameters, i.e., the effective hydraulic conductivity and the effective capillary drive at the wetting front, were determined simultaneously to describe the relationships between rainfall, runoff, and infiltration processes. Through a designed experiment, the method for determining the GA parameters was proved to be reliable in reflecting the effects of pedologic background in G-A type infiltration cases and deriving the optimum G-A parameters. Unlike PTF methods, this approach estimates the G-A parameters directly from infiltration curves obtained from rainfall simulation experiments so that it can be used to determine site-specific parameters. This study provides a self-adaptive method of optimizing the G-A parameters through designed field experiments. The parameters derived from field-measured rainfall-infiltration processes are more reliable and applicable to hydrological models.     

城市地表径流胶体对重金属下渗迁移行为的影响

为了解城市地表径流胶体对重金属在下渗设施中迁移行为的影响,提取道路雨水径流中的胶体,采用下渗柱试验研究了存在径流胶体时Cu~(2+)、Pb~(2+)和Cd~(2+)的下渗迁移出流质量浓度变化,分析进水流速、pH值、Na~+浓度、重金属离子共存和胶体粒径对胶体携带重金属迁移行为的影响。结果表明:径流胶体能够促进重金属离子的下渗迁移;进水流速越高,径流胶体对重金属离子的携带迁移作用越明显;弱酸性条件更有利于径流胶体对重金属离子的携带迁移;雨水径流中存在Na~+或多种重金属离子共存时,胶体携带重金属离子的下渗迁移过程会受到抑制,且离子浓度越大,其受抑制作用越明显;胶体粒径会显著影响径流胶体对重金属离子的携带迁移能力,胶体粒径越小,越容易携带重金属离子下渗迁移。     

基于入渗产流分析的透水砖地面铺装结构试验

为了找出有利于降雨入渗、削减径流的透水地面铺装结构,通过人工降雨试验,研究不同铺装垫层结构透水地面的降雨入渗与产流特性。根据8种铺装结构在径流削减、入渗量增加、开始产流时间滞后等方面的效果比较,推荐透水砖地面自上而下的铺装结构为"透水砖面层+无砂混凝土+单级配碎石"形式。     

汶川震区滑坡堆积体降雨入渗产流特征人工模拟实验研究

5.12汶川地震引发了大量的滑坡堆积体,在雨水的冲刷下,不仅会造成山体崩塌,还会发生次生灾害。本文以汶川震区滑坡堆积体为研究对象,采用室内人工模拟降雨方法,探讨了不同降雨强度和土石比条件下滑坡堆积体坡面产流与入渗规律。结果表明:(1)除土石比1∶4的滑坡堆积体在所设计的降雨强度(1.0,1.5和2.0 mm/min)和土石比为1∶2滑坡堆积体在降雨强度为1.0 mm/min时没有出现产流,其他条件下的滑坡堆积体的产流时间随着降雨强度的增大而减小,而产流率随着降雨强度的增大而增大,且土石比为1∶1的平均产流率比土石比为1∶2的滑坡堆积体大。(2)根据3种入渗模型的对比分析,可知Horton模型为最适合震区堆积体的入渗模型。(3)在降雨强度为1.5 mm/min时,土石比1∶1的滑坡堆积体累积产流量比土石比为1∶2的堆积体大;在降雨强度为2.0 mm/min时,土石比1∶1和1∶2滑坡堆积体累积产流量的变化规律几乎相同。本研究可为汶川震区滑坡堆积体的灾后修复提供实验依据。     

城市不同下垫面条件的降雨径流模拟试验研究

城区降雨径流过程主要受降雨过程和下垫面变化的影响。开展城区降雨径流观测试验,对不同下垫面条件的降雨入渗—径流关系进行研究,引用分布式水文模型,对4种下垫面条件的降雨径流关系进行摸拟,取得了较好的模拟效果,提出了科学化生态化城市建设的建议。     

基于径流系数的城市降雨径流模型参数校准方法

为了解决我国城市降雨径流模型参数校准数据欠缺的问题,应用较易获得的径流系数作为校准目标,以峰现时间作为径流系数模拟值的计算依据,以合成单峰降雨作为校准降雨事件,在SWMM平台上进行模型参数校准.通过校准模型适用性和灵敏度分析,表明该法既可以满足模型参数预校准的要求,也可以在模型参数不确定性分析的基础上用于实践.因此,该法是改善城市降雨径流模型参数校准状况的有效途径.     

Improvement of rainwater infiltration and storage capacity by an enhanced seepage well: From laboratory investigation to HYDRUS-2D numerical analysis

Seepage well is an emerging Low Impact Development (LID) technology that can effectively control the storm runoff. However, its rainwater infiltration rate and storage capacity still require further enhancement. By setting a horizontal infiltration structure at the bottom of conventional rainwater seepage well (CSW), an enhanced seepage well (ESW) was proposed in this study, and its infiltration performances compared with the permeable pavement (PP) and the CSW were systemically investigated using static infiltration experiment and HYDRUS-2D simulation. The results showed that the infiltration efficiency of ESW was significantly higher than that of PP and CSW, and the process of water infiltrated through soil mainly controlled the macroscopic infiltration rate. The Nash-Sutcliff Efficient (NSE) index was used to evaluate the accuracy and reliability of the HYDRUS-2D model, and the results of NSE values greater than 0.75 (varied between 0.75 and 0.91) confirmed the applicability of HYDRUS-2D to describe correctly the hydraulic behavior of the ESW system. Simulation infiltration tests showed that the ESW performed a higher average infiltration rate and fewer total runoff volume than the CSW, indicating the effectively enhancement of the infiltration and water retention capacity of ESW, especially under heavy rainfall intensities. Additionally, the ESW system exhibited an excellent runoff-control and rainwater retention capacity in an actual rainfall scenario.     

海绵城市LID设施运行效能衰减机理及寿命分析研究综述

为了研究海绵城市LID设施长期受纳降雨径流后填料理化性质的演变规律,揭示设施运行效率的衰减过程及机理,探索设施合理的使用寿命,以海绵城市LID设施为研究对象,从设施填料理化性质与水分入渗和污染净化能力的关系、入渗性能改变及污染物吸附饱和、LID设施运行效能衰减及运行寿命几个方面,通过文献资料综合评述国内外研究的进展与不足。结果表明：现有研究大多围绕LID设施结构、效果与影响机制展开,对其填料理化性质的演变规律、入渗性能改变及污染物吸附饱和等缺乏系统研究,对设施运行效率的阶段性、动态化衰减过程研究鲜见报道,制约设施运行寿命的机理不明确,影响其合理使用。建议今后从以下3个方面开展进一步研究: (1)明确LID设施填料在运行期间理化性质的动态演变过程,发展基于LID设施水量调控和污染物净化效果的新方法;(2)揭示填料入渗性能和污染物吸附量随运行时间尺度的变化规律,从径流水质、材料两个方面探索海绵城市集中入渗条件下,LID设施不同填料发生堵塞和污染物吸附饱和的内在机理及驱动因子;(3)阐明LID设施运行效能衰减机制,建立LID设施运行效能衰减评价方法,进一步研究并确定LID设施合理的使用寿命。     

考虑径流补给的滑坡渗流三维有限元模拟

现有数值模拟方法在模拟边坡降雨入渗时通常不能考虑径流流量补给对滑体渗流的影响,当滑床和滑带的渗透性相对于滑体极低时,会出现低估降雨入渗量、高估滑坡稳定性的现象。以Richards方程、运动波方程和有限元法为基础,提出了一种降雨时滑坡渗流数值模拟方法。该方法忽略滑床和滑带的渗流而只考虑滑体渗流过程,从而减小计算规模,也避免了因滑体与滑床(滑带)渗透性差异过大引起的数值计算困难;依据地形和滑体降雨入渗边界饱和情况,修正降雨入渗边界类型和流量,实现了考虑径流流量补给的滑坡降雨入渗简化数值模拟。对简单土质边坡降雨入渗进行数值模拟,从水量平衡与边坡渗流场两个角度,对比了考虑和不考虑径流流量补给的区别;结果表明,考虑径流流量补给时才能保证计算结果水量平衡,正确反映降雨入渗对基质吸力大幅降低的作用。     

Comparison of infiltration models to describe infiltration characteristics of bioretention

Bioretention is one of low-impact development measures, which widely used not only because it can reduce stormwater runoff total volume, decrease peak flow rate and delay peak flow time, but also can remove the runoff pollutants. Infiltration is an important hydrological process for bioretention to evaluate its runoff total volume reduction and pollutants removal. So, it is important to find an optimal infiltration model that can well describe the infiltration performance of bioretention. The Horton, Philip and Kostiakov infiltration models were selected to compare their accuracy when using for describe the infiltration characteristics of bioretention, and the errors between the different models simulate results and experiment results were assessed via the maximum absolute error (MAE), bias and coefficient of determination (R²). The experimental results showed that Horton model is fitting well and flexible under different experiment conditions, especially when the hydraulic head was 10 cm, with MAE of 0.50–0.81 cm/h, bias of 0.1–0.23 cm/h and R² of 0.98–0.99. R² of the Philip and Kostiakov models were all over than 0.87 at the initial infiltration period, but the model fitting accuracy decreased significantly with infiltration time elapse. Furthermore, the total runoff volume capture ratio and emptying time were advanced used to evaluate the flexibility of Horton model, and the Nash-Sutcliffe efficiency coefficients of them were over than 0.61 and 0.58, respectively. Therefore, the Horton model can be optimal selected to describe the infiltration process of bioretention and for its hydrological evaluation.     

用人工降雨和数值模拟方法研究降雨入渗规律

进行四种雨强处理的人工降雨土壤入渗田间试验，并对入渗过程进行数值模拟，提出初始土壤含水率分布均匀时降雨～入渗～径流过程的简便计算方法.     

On-site infiltration of road runoff using pervious pavements with subjacent infiltration trenches as source control strategy

The focus in this work was on subsoil infiltration of stormwater from parking lots. With regard to operation, reduced infiltration performance due to clogging and pollutants in seepage, which may contribute to contaminate groundwater, are of interest. The experimental investigation covered a pervious pavement with a subjacent infiltration trench draining an impervious area of 2 ha. In order to consider seasonal effects on the infiltration performance, the hydraulic conductivity was measured tri-monthly during monitoring with a mobile sprinkling unit. To assess natural deposits jointing, road bed, gravel of infiltration trenches and subsoil were analysed prior to commencement of monitoring for heavy metals, polycyclic aromatic and mineral oil type hydrocarbons. Furthermore, from 22 storm events, water samples of rainfall, surface runoff, seepage and ground water were analysed with regard to the above mentioned pollutants. The study showed that the material used for the joints had a major impact on the initial as well as the final infiltration rates. Due to its poor hydraulic conductivity, limestone gravel should not be used as jointing. Furthermore, it is recommended that materials for the infiltration facilities are ensured free of any contaminants prior to construction. Polycyclic aromatic and mineral oil type hydrocarbons were, with the exception of surface runoff, below detection limits. Heavy metal concentrations of groundwater were with the exception of lead (because of high background concentrations), below the permissible limits.     

降雨条件下露天矿井坡面径流入渗综合系数探讨

弄清降雨条件下地下工程的坡面径流入渗综合系数,对于有针对性制定地下工程防洪排水对策具有重要意义。利用某矿井长期大量地下水实测数据,采用流量过程线法,探讨了降雨条件下该露天矿井坡面径流入渗综合系数变化规律,分析了其动态变化机制。研究表明,一次降雨过程径流入渗综合系数变化于0.65～0.96之间,平均值为0.81,最大降雨径流入渗综合系数基本上出现在降雨期的前2 d内。多峰雨型或连续雨型条件下,径流入渗综合系数(0.84)比单峰雨型条件下(0.76)大。应用流量过程线分割法测定矿井坡面径流入渗综合系数,理论严谨、方法可行、结果可靠,可为类似地下工程排水设计提供理论依据。     

基于暴雨洪水管理模型的低影响开发设施应用研究

海绵城市是针对解决我国水危机提出的新理念,而低影响开发(LID)设施是构建海绵城市的关键。为了分析不同降雨重现期、不同降雨历时、占地面积对单项LID设施径流控制能力的影响,以亦庄调节池一期工程为研究区域,利用暴雨洪水管理模型(SWMM)进行模拟计算,研究了不同占地面积下各LID设施对不同降雨过程的径流削减效果,分析了降雨重现期及降雨历时与占地面积影响作用的相关性。结果表明:随着降雨重现期由1年增加至10年,透水铺装径流削减率下降了13%～35%;随占地面积占比由25%增至100%时,其径流削减率增大了4. 8%～23%,且占地面积变化对低重现期降雨径流削减效果影响明显,生物滞留槽和植草沟呈相同规律。相反,下凹绿地占地面积变化对高重现期径流削减效果影响较大。绿色屋顶的径流削减率与土壤层厚度成正比,与降雨重现期成反比,且绿色屋顶厚度对低降雨重现期削减效率影响稍大; LID设施的径流削减率随降雨历时增加而增大(削减率增长区间为1. 7%～7. 7%),且占地面积越大,降雨历时变化对径流削减率的影响就越明显。各LID设施的性价比和适用情况对比计算表明,下凹绿地和透水铺装性价比较高,适于作为主控设施大面积应用,而植草沟、生物滞留池及绿色屋顶适于作为辅助设施部分应用。研究成果为选择效益最优的海绵城市建设模式提供科学参考。     

广州天河智慧城SWMM参数敏感性分析

为研究城市雨水模拟中参数对SWMM模拟结果的影响,构建了广州天河智慧城SWMM水文模型,开展降雨径流水量水质同步监测,对模型参数进行率定与验证,并使用Morris方法分析水文水力参数和水质参数的敏感性。结果表明:水文水力参数中最大下渗速率对总径流量敏感性最高,地表曼宁系数对峰值流量敏感性最高,下渗参数为影响水文水力模拟结果的主要参数;水质参数中冲刷指数对污染物模拟结果敏感性最高,前期干旱天数对污染物模拟结果敏感性比总径流量模拟的敏感性高。     

无资料城区管网排水过程概化模拟研究

许多城市地区都没有可用的排水管网数据,从而降低了城市雨洪模拟的准确性,因此需要一种新的方法来表征管网的排水能力。提出了雨水井等效排水法(RIA)和仅在道路上等效排水法(CIR)两种表征管网排水能力的方法,采用高效高分辨率的城市雨洪模型,以西咸新区为研究区域,模拟了城市内涝积水过程,并与实测数据进行了对比。通过实际降雨与设计降雨条件下的内涝结果发现,较原有的模拟方法,该方法可以精准的表征管网排水能力,提高模型的准确性。     

考虑倾角的土质边坡Green-Ampt改进入渗模型

针对传统Green-Ampt入渗模型忽略坡角和土体非饱和区对边坡降雨入渗的影响这一情况,利用倾角对土体入渗势能梯度进行修正,并将入渗时边坡土体按含水率划分为饱和层、过渡层和未湿润层,建立考虑倾角的土质边坡分层假定入渗模型,推导边坡降雨入渗深度与降雨历时的关系,并通过入渗实例将新模型与传统模型进行比较。研究结果表明:分层假定模型预测的坡面产流时间及湿润锋深度与降雨历时的关系较传统Green-Ampt入渗模型（简称为GA模型）更接近实测值;自由入渗阶段,分层假定模型的湿润锋扩展深度与GA模型一致,但入渗速率低于GA模型;积水入渗阶段,分层假定模型的湿润锋扩展深度及入渗速率均大于GA模型,湿润锋扩展深度的差值随着降雨历时的增大逐渐增大,而入渗速率差值的变化呈相反趋势。根据新模型,分析了倾角和雨强对边坡降雨入渗的影响,发现随着边坡倾角的增大或雨强的减小,雨水入渗到坡体内相同深度所需的降雨历时增加,这种现象在倾角大于60°或雨强小于20 mm/h时尤为明显。     

Performance comparison between infiltration and non-infiltration type of structural stormwater treatment systems

The study was constructed to monitor representative inflow and outflow from infiltration and non-infiltration type best management practice (BMP) sites developed at a university campus, allowing the determination of overall performance efficiency in terms of runoff reduction and pollutant removal. Based on the monitored storm events, the runoff and discharged volume and flow rates exhibited high positive correlations with total rainfall depth (p<0.001). Findings revealed that as the total rainfall increases, the amount of volume reduction and pollutant removal decreases for both types of BMP. Infiltration BMP showed a higher ability in treatment performance especially during small storm events than non-infiltration type; however, the differences were not significant. Pollutant removal rates of infiltration type were in the range of 70-90% while between 35 and 80% for the non-infiltration type for storm events with less than 10 mm rainfall depth. Average volume reductions were 71 ± 33% and 32 ± 32% for the infiltration and non-infiltration type, respectively. The ratio of the discharge volume was significantly greater than the ratio of discharge pollutant load indicating a high potential for water quality improvement. Design recommendations were provided considering sizing and cost for on-site application of similar BMP designs in the future.     

A long-term suspended solids runoff simulation in a highway drainage system.

A long-term monitoring investigation was carried out in a highway drainage system in Winterthur, Switzerland. Several runoff quality and quantity simulations were carried out using the distributed model 'InfoWorks-CS'. Serial rainfall monitoring data was used for investigation of SS runoff behavior from the highway. Under continuous rainfall conditions, the quantity simulation showed a good agreement with the measured hydrograph. However, in some cases where rainfall was not continuous, overestimation of the peak height was found at the later stage after the end of the rainfall. It was believed that the initial/depression loss on the road surface was recovered during the halting period of rainfall. The consideration of regenerated depression loss significantly improved runoff simulation results in the on-and-off type rainfall events. A single event quality simulation underestimated the SS load in light rainfall events. One of the reasons was possibly inadequate consideration of pipe sediment conditions. A long term simulation was carried out to establish the initial condition of surface and pipe sediment for the target event. The newly simulated pollutograph gave a good agreement with the measured one. It revealed that it was essential to consider appropriateness of the initial condition of pipe sediment as well as surface sediment.     

考虑多层非饱和土降雨入渗的边坡稳定性分析

降雨是诱发滑坡的最主要因素之一,降雨入渗将显著降低非饱和土的基质吸力,从而降低边坡土体抗滑力。本文提出了考虑降雨入渗的多层非饱和土边坡稳定性分析方法。首先改进Green-Ampt入渗模型,提出适合多层非饱和土边坡降雨入渗的计算方法;然后得到各层土体在入渗各阶段的强度参数值;最后,采用强度折减法计算整个边坡在入渗条件下的安全系数。将本方法应用于广州大夫山滑坡案例发现滑动面和实际情况接近,为短期强降雨诱发的浅层滑坡。分析了不同降雨强度和历时对滑坡稳定性的影响,结果表明:降雨入渗导致边坡潜在最危险滑面的位置主要在浸润锋处或土体与基岩交界处。低强度长历时的降雨过程中,雨水入渗深度较大,易发生深层滑动;在高强度短历时的降雨过程中,雨水入渗深度较小,更易发生浅层滑动;随着降雨强度和降雨时间的增加,入渗深度增加,进而降低边坡的稳定性。