变化环境下城市水文学的发展与挑战——I.城市水文效应

全球气候变化和快速城市化导致的城市水循环过程变化是当前城市水文学研究的热点问题。为综合理解城市水循环演变过程,结合城市水文学的发展历程,剖析水循环过程对快速城市化进程的响应机制。总结了国内外城市化水文效应的主要成果,包括城市化对水循环过程、洪涝灾害、水生态系统以及水资源的影响。系统归纳了城市化水文效应的评估方法和技术手段。针对现有研究中的不足,指出变化环境下城市化水文效应研究面临的主要挑战及关键技术难题,提出未来研究的重点方向,如城市化降水效应的机理、不透水面的分布及有效性评估、城市化与水生态系统的响应关系与综合城市水资源管理及需水预测等。     

快速城市化地区多尺度水文观测试验与暴雨洪水响应机理分析

城市下垫面改变引起水文循环过程发生变异, 导致目前已掌握的天然情况下的产汇流规律和机制难以解释城市化等新形势下的水文现象与过程, 而面临需重新再认识的挑战。本文以长三角地区为典型, 建立了不同城市化水平及空间规模的水文试验流域, 探讨了快速城市化地区暴雨洪水响应规律和机制。结果表明: ①不同量级降水事件下城镇用地土壤水响应程度(表层土壤水涨幅基本超过4%)总体高于其他土地利用类型, 城市化地区下垫面的改变通过影响土壤水动态响应模式直接影响了地表产流过程, 植被覆盖率较低的城镇用地和荒地土壤含水率呈现出陡涨陡落现象, 而植被作用下的土地利用类型则表现出缓慢上升和缓慢消退的土壤水响应过程。②流域洪峰滞时和洪峰流量整体表现为随流域面积增加而呈幂律函数关系形式的增加。③总降水量与主要洪水特征(如洪峰流量、单位面积洪峰流量和径流深)基本呈显著相关(相关系数分别达0.49、0.41和0.78以上)。城市下垫面通过改变土壤水动态响应等产汇流特征而直接影响了洪水过程, 未来长三角地区暴雨洪水在城市化和气候因素双重作用下呈现持续加剧的趋势。     

北京城市洪涝问题与成因分析

利用社会经济统计数据和水文气象资料,探讨城市化背景下北京城市洪涝特征、形成机制及影响因素。近50年来城市内涝逐渐成为北京洪涝灾害的主要类型,随着城市化迅猛发展,城市内涝积水点数量在时间上表现为显著增加趋势,在空间上呈现出由内环逐步向外环扩张趋势,与城市化发展空间格局关系密切。从水循环的角度分析城市洪涝形成机制,指出区域气候变化和城市化发展改变了城市降水格局,汛期降水量和极端降水事件呈现下降趋势,但城区短历时强降水事件呈现增加态势;城市化发展改变了区域下垫面条件、城市流域产汇流特性和城市排水格局,进而影响了区域水循环过程和水量分配,在一定程度上增加了城市洪涝灾害风险;同时城市基础设施建设水平不足、排水排涝标准偏低、应急管理能力不足等因素,导致城市洪涝发生风险增加,降低了城市洪涝综合应对能力。     

考虑有效不透水下垫面的城市雨洪模拟模型——Ⅰ.模型原理与模型构建

为满足新形势下雨洪管理实践的需求, 揭示有效不透水下垫面对城市水文过程的影响, 需研发考虑有效不透水下垫面的城市雨洪模拟模型。将不透水下垫面分为道路和屋顶, 综合运用地理信息系统、城市雨洪模型等技术手段, 基于不同分类属性分步确定有效不透水面积; 考虑模型复杂性、建模数据可用性和模型预测能力, 确定模型结构。区分有效不透水下垫面和非有效不透水下垫面产汇流过程, 将具有高度异质性的城市下垫面离散成具有均匀或准均匀特性的子汇水区, 考虑不同下垫面各子汇水区内部及子汇水区之间汇流路径, 采用不同的产汇流计算方法, 构建了精细模拟模型, 可为城市洪涝防治及海绵城市建设提供技术支撑。     

不透水面遥感提取及应用研究进展

不透水面信息的提取方法与应用是近年来城市规划、热岛效应分析、水环境监测和水资源管理等诸多领域的研究热点.遥感技术的发展使不透水面快速准确提取成为可能.从影像特征(光谱、空间几何、时间)选择、分类器(参数、非参数)选择和空间尺度(像元、亚像元尺度)选择3个方面归纳和总结了各种不透水面遥感提取方法原理、应用现状和存在问题,回顾了不透水面在城市化监测、人口估计、水环境监测、热岛效应分析、水文气候建模分析等领域的应用,指出了不透水面遥感提取和应用的发展方向.     

基于太湖流域模型的城市内涝过程高效模拟

城市内涝的高效模拟对于降低内涝灾害影响、制定防灾减灾措施具有极其重要的意义。本文提出了基于雨篦子耦合地表与管网的城市降雨-产汇流-内涝全过程高效模拟方法, 结合常州市双桥浜城市产汇流与内涝试验基地监测数据, 分别构建了基于高效模拟算法和二维水动力算法的城市内涝模型。根据监测数据对所构建的模型进行了率定与验证, 并分析对比了2种算法在不同降雨事件中的精度与可靠性。结果表明: 太湖流域模型中基于雨篦子的城市水文特征单元高效模拟方法能够较为真实地反映城市内涝的具体特征, 且在模型参数一致的前提下, 其计算效率约为二维水动力算法的780~1 275倍, 能够对城市内涝情况进行快速模拟。     

遥感技术在东江-韩江流域下垫面变化动态监测中的应用

遥感技术应用于下垫面各要素信息的提取,其具有动态、宏观、快速等特点.本文基于Landsat影像和ASTER GDEM数字高程数据,对2009年和2019年东江-韩江流域下垫面各要素包括坡度、坡向、土地利用分类、植被覆盖度、不透水面等信息进行了监测,并分析了下垫面各要素十年间的变化,为该地区水文地质调查提供基础数据.     

城市水文效应规划对策的探讨

造成洪涝灾害、水质污染等问题的原因是城市建设行为对水文循环过程的干扰,当超过水文循环自我调节能力的极限后,知识水文生态功能退化。从研究城市水文效应入手,分析城市建设对水文循环过程的扰动行为,主要包括隔断降雨入渗下垫面、打破水文地景格局、破坏水文系统自我调节能力等几个方面。对城市化水文循环扰动作用进行分析,在城市规划中引进水文循环健康这一概念,通过多学科进行交叉融合,形成城市化过程中规划水文效应的有效方法。研究过程中得出,以城市作为孤立点展开对策研究,不仅忽了水文效应的外部成本,而且割裂了河流的汇水边界。     

基于地图代数的数字地表流线模拟研究

降雨在地表上随地形流动自然形成沟谷线、汇流区、分水岭等流域形态,研究地表流水线的数字模拟对数字流域水文分析具有重要意义.提出数字地表流线模型的概念,只考虑地形因素,利用等高线图建立一个能获得区域内每滴雨水沿地表流动的轨迹模型.并运用地图代数的距离变换对等高线及所在空间进行全方位的距离度量,研究了数字地表流线模型的建立方法.实验表明,该模型利用距离变换信息而不是高程计算流向,可避免DEM高程误差对流向、流线的影响,且不需要在DEM上进行复杂的洼地、平地的识别与处理.该模型对原始数据要求不高,能有效应用于沟谷线的自动提取、汇流区自动分割和分水线网络的自动提取.     

水文下垫面分析与分类初探

提出了水文下垫面的定义,分析了组成水文下垫面各要素的基本性质及其在产、汇流方面的作用。以山西省为例,提出了水文下垫面的分类方法,并讨论了水文下垫面分类在水文分析计算、水文预报和水文地理学等方面的可能应用。     

Predicting future urban impervious surface distribution using cellular automata and regression analysis

Urban impervious surfaces are considered as key indicator of urbanization intensity and environmental quality. Due to their significant impact on surface runoff, flood frequency, and water quality, impervious surfaces have been identified as an important indicator for examining the hydrological impact of urbanization. The amount and distribution of impervious surfaces have been estimated using remote sensing and geographic information system (GIS) techniques. Little research, however, has been conducted to predict future impervious surface distributions. To address this problem, we developed an integrated residential/commercial growth and impervious surface distribution model to predict urban impervious surface distribution. Taking Milwaukee River Basin, Wisconsin as a case study, we simulated future residential and commercial developments using a CA model. Further, we developed a linear regression model to predict impervious surface distributions in residential and commercial land uses. Analysis of results suggests that the proposed model performs significantly better than the traditional approaches.     

Spatial evaluation of impacts of increase in impervious surface area on SCS-CN and runoff in Nagpur urban watersheds,India

The changing land use due to rapid urbanization has profound impact on the runoff in urban watersheds. The spatial analysis in urban watersheds is felt necessary for management of surface and subsurface water regimes. Significant increase in impervious zones was observed in Nagpur urban watersheds between 2000 and 2012 having impacts on runoff, and even flash floods were observed. This study presents spatial and temporal impacts of change in urban built-up area on curve number (CN) and runoff during the years 2000 and 2012. The study also analyzes effect of slope on CN values and shows that CN increases with slope. High-resolution satellite images were used to map impervious surface areas (ISAs) which show an increase of 0.9 to 34 % during 2000–2012. Spearman’s and Pearson’s coefficients have been generated to establish relationship between runoff, impervious surface areas, vegetation index, slope, and runoff coefficient. It has been hypothetically assumed that if 100, 50, and 25 % rooftop rainwater harvesting is considered, the estimated runoff reduces in 2012 as compared to the year 2000. The study suggests that increase in impervious areas within urban watersheds can be utilized for groundwater augmentation adopting rooftop rainwater-harvesting techniques and to prevent flash floods.     

西苕溪流域城镇化对径流的长期影响研究

城镇化的发展使流域下垫面产生了较大变化,从而使流域降雨径流条件发生变化,随着城市化水平的提高,土地利用性质发生了改变,不透水地面积的增加,对径流的形成过程产生很大影响。长期水文影响模型(Long-Term Hydrological Impact Analysis,L-THIA GIS)是一个基于GIS平台的城市水文模型,可用于评价城市化对径流的长期影响。本文选取太湖上游浙江省安吉县西苕溪流域作为研究区域,利用L-THIA GIS模型对流域31年的长期径流进行模拟,在验证模型有效应用的基础上,探讨了城镇化对径流的影响。     

Impact of city expansion on hydrological regime of Rispana Watershed,Dehradun, India

Rispana River flows through the heart of Dehradun, the capital city of Uttarakhand State, India. Uttarakhand had separated from Uttar Pradesh State in the year 2000; since then, Dehradun City has witnessed numerous changes. Both urban sprawl and densification were noticed, with around a 32% increase in population. The city had faced recurrent high runoff and urban flood situations in these last 2 decades. Therefore, the study was conducted to detect the change in land use/land cover (LULC), especially urbanization, through remote sensing data; and later to determine the impacts of such changes on the Rispana watershed hydrology. The LULC maps for the year 2003 and the 2017 were generated through supervised classification technique using the Landsat Series satellite datasets. The LULC change analysis depicted that mainly the urban settlement class increased with significant area among other classes from the year 2003–2017. It was noticed that majorly agriculture and fallow land (8.18 km², which is 13.52% of total watershed area) converted to urban, increasing the impervious area. Almost all the municipal wards, falling in the Rispana watershed, showed urbanization during the said period, with an increase of as high as 71%. The change in LULC or effect of urbanization on the hydrological response of the watershed was assessed using the most widely used Natural Resources Conservation Services Curve Number method. It was noticed that the area under moderated runoff potential (approx. 10.23 km²) steeply increased during the lean season, whereas, high runoff potential zones (5 km²) increased significantly under wet season. Therefore, it was concluded that an increase in impervious surface resulted in high runoff generation. Further, such LULC change along with climate might lead to high runoff within the watershed, which the present storm drainage network could not withstand. The situation generally led to urban floods and affected urban dwellers regularly. Therefore, it is critical to assess the hydrological impacts of LULC change for land use planning and water resource management. Furthermore, under the smart city project, the local government has various plans to improve present infrastructure; therefore, it becomes necessary to incorporate such observations in the policies.

     

构建考虑煤矿采空区特殊下垫面的水文模型并在山西省小流域应用

随着中国经济的快速发展,能源需求的增加,作为中国最主要的煤矿开采省份,山西省的煤矿开采量也一直在增加。但长期以来不合理和不科学的煤层开采,导致全省许多地区出现了煤矿采空区和伴生的地表裂隙。同时山西省内许多流域观测资料显示河道径流明显减少,水库存储量下降。认识煤矿开采,这一重要人类活动对水文过程影响,并在此基础上发展考虑煤矿采空区特殊下垫面的水文模型意义重大。收集山西省几个典型小流域的煤炭开采、遥感、水文资料,经过调查和分析发现煤炭采空区引起的裂隙和塌陷在山坡上会增加地表优先流,在河道上会导致明显渗漏现象。基于以上对煤炭开采对水文过程影响的认识,发展了考虑煤矿采空区特殊下垫面的水文模型,并在山西芦庄小流域进行了模型验证与应用研究。此研究方法对认识人类活动可能引起水文过程的变化有一定的借鉴意义,发展的模型也可以推广到具有类似水文过程的地区,对由于不合理的煤炭开采受到影响的流域进行水文分析和预报。     

雅鲁藏布江流域气候和下垫面变化对径流的影响研究

典型高原寒区雅鲁藏布江流域径流变化是反映该区域气候和下垫面变化的重要指标。在全球升温背景下,由于观测资料稀缺,导致缺乏针对整个流域的气候和下垫面变化对径流影响的研究。因此,本研究基于1986—2010年的气象数据和奴下水文站月尺度、动态土地利用数据等,利用改进的水文模型并结合不同的模拟策略厘清了流域1991—2010年不同时段间气候和下垫面变化对径流的影响。结果表明：在1991—2010年期间,不同时段间气候和下垫面变化对径流变化的贡献率差异较大,气候变化对径流变化的贡献率高于下垫面变化,且使径流量增加。从空间上看,气候变化对流域产流的贡献率在上游和中游都较大,在下游东北部的贡献率较小,而在该区域下垫面变化的贡献率较大。雪冰融水径流呈增加的趋势,对年径流的平均贡献率在21.1%~48.6%范围内,多年平均贡献率为33.6%;雪冰融水径流一般从4月开始增大,8月达到最大,10月达到消融末期。本研究的开展和发现既是雅鲁藏布江流域水文、水资源基础性研究的需要,具有重要的理论研究意义,同时也可为该流域的水资源保护、规划与管理提供科学理论和决策依据,具有重要的现实意义。     

Regional modelling of rainfall-induced runoff using hydrological model by incorporating plant cover effects: case study in Kelantan,Malaysia

The objective of this paper is to develop a spatial temporal runoff modelling of local rainfall patterns effect on the plant cover hilly lands in Kelantan River Basin. Rainfall interception loss based on leaf area index, loss/infiltration on the ground surface, and runoff calculation were considered as the main plant cover effects on the runoff volume. In this regard, a hydrological and geotechnical grid-based regional model (integrated model) was performed using Microsoft Excel^® and GIS framework system for deterministic modelling of rainfall-induced runoff by incorporating plant cover effects. The infiltration process of the current model was integrated with the precipitation distribution method and rainfall interception approach while the runoff analysis of integrated model was employed based on loss/infiltration water on the ground surface with consideration of water interception loss by canopy and the remaining surface water. In the following, the spatial temporal analysis of rainfall-induced runoff was performed using 10 days of hourly rainfall events at the end of December 2014 in Kelantan River Basin. The corresponding changes in pressure head and consequent rate of infiltration were calculated during rainfall events. Subsequently, flood volume is computed using local rainfall patterns, along with water interception loss and the remaining surface water in the study area. The results showed the land cover changes caused significant differences in hydrological response to surface water. The increase in runoff volume of the Kelantan River Basin is as a function of deforestation and urbanization, especially converting the forest area to agricultural land (i.e. rubber and mixed agriculture).     

变化环境下城市洪水演变驱动机理——以北京市温榆河为例

气候变化和人类活动被认为是城市洪水演变的主要驱动因素,不同区域气候变化和城市化对洪水演变的影响不尽相同,科学识别城市洪水演变的关键驱动要素、量化气候变化与城市化对城市流域洪水演变的影响是城市洪水管理的重要依据。本文以高度城市化的北京市温榆河流域为例,以季节降雨量、气温、流域前期湿度、不透水面积比及流域内地下水埋深作为潜在驱动要素,对温榆河夏季不同概率的洪水建立GAMLSS模型,分析探讨城市流域洪水演变的主要驱动机制。研究结果表明:温榆河流域夏季不同概率的洪水在研究期均呈现出非一致性特性;城市不透水面积的扩张和降水是温榆河流域夏季洪水变化的主要驱动要素,不同等级洪水的变化具有不同的驱动机制,高于概率70%的小洪水的变化主要受到流域下垫面变化的影响,而小于概率45%的低频洪水的变化主要受降水的影响。