Methodology for the Calculation of the Runoff Coefficient with the Arrangement Tirado

For this research work, an adequate methodology was sought for the calculation of the runoff coefficient with the Tirado arrangement. To achieve this, first, the variables that affect the runoff coefficient were identified, then the model was described with the Tirado arrangement, and as a third part for the calculation of the runoff coefficient, the Tirado model is proposed. From the theory for the calculation of the runoff coefficient, the equation of the weighted coefficients and the expression of Nadal were manipulated, resulting in the following relationship , considering this as the expression for the arrangement Tirado. The expression is tested with different intensities, the magnitudes correspond to 150, 200, 250 and 300 mm/hrs, resulting in runoff coefficient 0.82, 0.87, 0.89, 0.91 respectively. This means that, the higher the intensity, the runoff coefficient will be higher, logically the characteristics of the basin affect that this coefficient has variation in the space studied.

Estimating runoff coefficient for quantity assessment of roof rainwater harvesting system

In order to accurately estimate the runoff coefficient for the quantity assessment of the roof rainwater harvesting system RRHS great differences in the value of event runoff coefficient ψERC were observed by field monitoring under different roof types roof slope and material and diverse rainfall distributions rainfall depth and intensity in three years 2010 to 2012 in Handan Hebei China.The results indicate that the distribution of ψERC is more highly correlated with the event rainfall depth than other factors. The relationship between ψERC and the rainfall depth can be well represented by the piecewise linear function.Further based on the daily rainfall data over the period from 1960 to 2008 the value of the annual runoff coefficient ψARC is calculated. Although the total rainfall depth in each year is different ψARC in Handan can be considered as a constant 0.62 approximately. The results can be used for the quantity assessment and performance analysis of the RRHS.

Impacts of Climatic Factors on Runoff Coefficients in Source Regions of the Huanghe River

Runoff coefficients of the source regions of the Huanghe River in 1956-2000 were analyzed in this paper. In the 1990s runoff of Tangnaihai Hydrologic Station of the Huanghe River experienced a serious decrease, which had attracted considerable attention. Climate changes have important impact on the water resources availability. From the view of water cycling, runoff coefficients are important indexes of water resources in a particular catchment. Kalinin baseflow separation technique was improved based on the characteristics of precipitation and streamflow. After the separation of runoff coefficient （R/P）, baseflow coefficient （Br/P） and direct runoff coefficient （Dr/P） were estimated. Statistic analyses were applied to assessing the impact of precipitation and temperature on runoff coefficients （including Dr/P, Br/P and R/P）. The results show that in the source regions of the Huanghe River, mean annual baseflow coefficient was higher than mean annual direct runoff coefficient. Annual runoff coefficients were in direct proportion to annual precipitation and in inverse proportion to annual mean temperature. The decrease of runoff coefficients in the 1990s was closely related to the decrease in precipitation and increase in temperature in the same period. Over different sub-basins of the source regions of the Huanghe River, runoff coefficients responded differently to precipitation and temperature. In the area above Jimai Hydrologic Station where annual mean temperature is -3.9℃, temperature is the main factor influencing the runoff coefficients. Runoff coefficients were in inverse relation to temperature, and precipitation had nearly no impact on runoff coefficients. In subbasin between Jimai and Maqu Hydrologic Station Dr/P was mainly affected by precipitation while R/P and Br/P were both significantly influenced by precipitation and temperature. In the area between Maqu and Tangnaihai hydrologic stations all the three runoff coefficients increased with the rising of annual precipitation, while direct runoff coefficient was inversely proportional to temperature. In the source regions of the Huanghe River with the increase of average annual temperature, the impacts of temperature on runoff coefficients become insignificant.

Experimental Study of Runoff Coefficients for Different Hill Slope Soil Profiles

The estimation of peak discharge from a catchment due to intense rainfall is a difficult task that may occur in a return period. If cannot be estimated accurately, it may lead to serious problem in hydraulic structure design like bridge, culvert across a river and drainage system. The main parameter which affects the peak flow is runoff coefficient of the catchment which directly depends on the soil type, its slope and land use pattern with vegetation covers. For the purpose, this study was carried out to estimate maximum runoff coefficients for different land profiles and soil types in hill slope model developed in 10 degree with the horizontal to the rainfall simulator rig (Basic Hydrology system-S12) experimentally which can give more reliable value than the real field test method as it is easier than field test especially in hill slope. The soil slope preparation was made of sand, silt and clay separately and the experiments were carried out in a controlled system. The slope prepared represented a small catchment on a plot of 2.02 meter length, 1 meter wide and 0.15 m depth soil plots (at the slope of 10° to the horizontal plane). From the experiment in different soil plots, the rainfall runoff coefficients were observed as 0.428 - 0.53 for sand soil slope, 0.46 - 0.55 for silt soil slope and 0.42 - 0.51 for clay soil slope under uniform rainfall rate of 4 lpm to 13 lpm in each soil slope. Rainfall runoff correlation equation was found with the values of R above 90% in each soil slope. The value observed is within the range of rational value of 0.05 to 0.95 as standard which concluded that the performance of simulator was found good to deal with rational values. And the runoff coefficients for these soil types can be taken within the range obtained to estimate peak discharge in any small catchment area depending on the soil types.

Determination of Potential Runoff Coefficient Using GIS and Remote Sensing

Flash floods in arid environments are a major hazard feature to human and to the infrastructure. Shortage of accurate environmental data is main reason for inaccurate prediction of flash flooding characteristics. The curve number (CN) is a hydrologic number used to describe the storm water runoff potential for drainage area. This study introduces an approach to determine runoff coefficient in Jeddah, Saudi Arabia using remote sensing and GIS. Remote sensing and geographic information system techniques were used to obtain and prepare input data for hydrologic model. The land cover map was derived using maximum likelihood classification of a SPOT image. The soil properties (texture and permeability) were derived using the soil maps published my ministry of water and agriculture in Saudi Arabia. These soil parameters were used to classify the soil map into hydrological soil groups (HSG). Using the derived information within the hydrological modelling system, the runoff depth was predicted for an assumed severe storm scenario. The advantages of the proposed approach are simplicity, less input data, one software used for all steps, and its ability to be applied for any site. The results show that the runoff depth is directly proportional to runoff coefficient and the total volume of runoff is more than 136 million cubic meters for a rainfall of 103.6 mm.

牛栏江—滇池补水工程水源区不同时间尺度径流变化特征

为做好补水工程水资源调度、配置、流域水安全治理和区域防汛抗旱工作,充分发挥工程效益,基于牛栏江—滇池补水工程水源区代表站长系列水文资料,采用集中度、不均匀系数、Hurst系数、M-K趋势检验、滑动T检验等多种方法分析了牛栏江—滇池补水工程水源区不同时间尺度径流变化特征。结果表明,水源区不同时间尺度径流年际变化大、丰-平-枯周期明显;年内分配向均匀性和坦化趋势演变;最小1、7 d径流显著上升,其他7个径流趋势变化不显著,均发生突变;年、丰水期、极端最大等5个径流指标突变后径流量减少明显,枯水期和极端最小等4个径流指标突变后为增长趋势;年径流突变后8~10月来水量减少明显;预计补水工程水源区未来一段时间不易发生极端枯水事件,但总来水量可能会进一步衰减。

土壤磷素地表径流提取系数研究进展

土壤磷素地表径流提取系数(phosphorus extraction coefficient,ECp)是模拟表层土壤可溶性磷随地表径流迁移,估算农业磷非点源污染负荷模型中的一个重要参数。当前ECp的相关研究存在内涵模糊,确定方法各异,变异范围和影响机制也不够清晰等问题。本文梳理了国内外相关研究中ECp的提取方法、影响因素,为提高农业磷非点源污染评估的精度提供理论依据。ECp定义为地表径流溶解态磷(dissolved phosphorus,DP)浓度与表层土壤可溶性磷含量的比率。该系数通常基于降雨试验,通过建立地表径流DP和表层土壤磷含量的线性回归方程,用回归线的斜率表示ECp,因此其概念本质主要体现在统计学意义上。ECp受降雨、土壤、植被覆盖和农田管理措施等多种因素影响,变异范围较大。ECp通常与土壤黏粒含量、吸附性、植被覆盖度等因素呈反比,而与土壤初始含水量呈正比。非石灰性土壤ECp值一般大于石灰性土壤。为简化计算,ECp在NPS污染模型中通常被设为一个定值。例如,在化学物质、径流和土壤侵蚀(chemicals,runoff,and erosion from agriculture management,CREAMS)及农业非点源(agricultural nonpoint source,AGNPS)模型中,ECp值设为7.5,而在土壤侵蚀和作物生产力评价(erosion/productivity impact calculator,EPIC)和水土评估工具(soil and water assessment tools,SWAT)模型中,ECp值则设为5.7。因此,未来研究仍需重视ECp的物理内涵,精准测算多次降雨平均和动态ECp,阐明土壤磷素地表径流提取的动力机制;加强地表径流和表层土壤中可溶性磷素含量间的非线性关系的研究,提高ECp值确定方法的适用性;深入分析不同区域ECp的变异特征和影响因素,针对施肥频繁且易发生复杂强烈水力侵蚀的坡耕地,尤其需要提出ECp的校正值;用核定后或者监测获得的ECp统计值代替现有NPS污染模型中的常数,以提高土壤磷素流失负荷模拟精度。

绿色屋顶降雨径流特性及其结构参数优选试验研究

为研究北方半湿润区绿色屋顶降雨径流特性,探究结构参数变化对其雨水蓄滞效应的影响,为海绵城市绿色新基建提供数据支撑及引导。建立绿色屋顶(坡度0°)、普通屋顶(坡度0°)、坡面屋顶(坡度5°)3种类型屋顶的对照试验,以及基于基质层厚度、基质层、排水层和排水方式结构参数调整的五组绿色屋顶试验,基于实测降雨径流开展监测。研究表明:监测期内,绿色屋顶、普通屋顶、坡面屋顶综合降雨量的平均径流系数分别为0.27、0.50、0.77,绿色屋顶降雨径流削减效应明显。随着降雨强度增大,绿色屋顶产流概率呈逐渐增大趋势,径流总量控制率呈逐渐较小趋势,绿色屋顶对小雨~大雨级别场次降雨蓄滞效应显著。监测期内降雨事件中,绿色屋顶降雨径流系数与降雨总量显著正相关,与前期降雨间隔天数和前期降雨量为弱负相关;绿色屋顶降雨径流控制效率显著降低对应降雨强度临界值为30 mm。绿色屋顶雨水蓄滞效应影响因素显著程度由大到小依次为基质层(超轻量基质层)、排水方式(距底部5 cm排水)、基质层厚度(20 cm)、排水层(陶粒层)。绿色屋顶降雨径流特性及雨水蓄滞效应受到内、外因多因素影响,后续应基于长序列降雨监测期,进一步研究不同结构、不同尺度的绿色屋顶的海绵城市生态效应。

长期植被覆盖对紫色土坡面减流减沙能力的影响

[目的]研究长期林草植被覆盖小区减流减沙能力的变化速率,为西南土石山区水土保持植被恢复提供科学依据。[方法]2018—2021年在贵州省赤水市天台镇径流场观测了15°裸地、15°草地、15°林地、30°林地与30°草地5个径流小区的产流产沙、植被覆盖、土壤表层含水量数据,用径流系数和含沙量的变化反映各小区减流减沙能力的变化。[结果]5个小区减流减沙效益排序为30°草地>15°林地>30°林地>15°草地>裸地。其中,30°草地小区植被覆盖度最高,为92.8%,其径流量和土壤侵蚀模数分别为2.43 mm和6.51 t/(km^(2)·a)。裸地小区径流量最高,为153.49 mm,土壤侵蚀模数最高,为1214.5 t/(km^(2)·a);15°草地小区径流系数降低速率最快,为-0.292%/a,其含沙量降低速率也最快,为-14.6 g/(L·a)。植被覆盖度与径流量之间负相关关系极显著,与含沙量负相关关系显著,与土壤表层含水量呈极显著正相关关系。[结论]高植被覆盖度有利于植被恢复、水源涵养和控制水土流失。对于水土流失相对严重的15°草地坡面,其长期植被覆盖的水土保持效益更为明显。

河南省主要河川径流变化归因

为相对全面客观地分析气候变化和人类活动对河南省主要河川径流变化的影响,基于河南省内卫河、伊洛河、洪汝河和唐河流域1961—2022年径流和降水资料,以及国家气候中心根据Penman-Monteith公式计算的年潜在蒸散发资料,比较4个蒸发对比站年潜在蒸散发和蒸发皿年蒸发值,运用Mann-Kendall突变检验法和累积双曲线法分析4个研究流域控制水文站年径流序列的变化趋势和突变年份,以及4个流域年降水和潜在蒸散发的变化趋势。采用基于Budyko假设的弹性系数法对径流变化开展归因分析。结果表明:4个蒸发对比站年潜在蒸散发与蒸发皿年蒸发变化趋势基本一致,4个水文站年径流深及4个流域年降水和年潜在蒸散发均呈下降趋势。4个水文站年径流深分别在1977年、1985年、2008年和2010年发生了突变。气候变化对径流减少的贡献率在卫河和伊洛河流域为7%以下,在洪汝河和唐河流域约为12%~18%,降水减少不显著和潜在蒸散发呈下降趋势是贡献率小的原因,可见人类活动是影响4个流域径流变化的主要驱动因素。

径流曲线数模型在湖南省山区小流域的优化与应用

径流曲线数模型(Soil Conservation Service Curve Number Model,简称SCS-CN模型)可以利用降雨资料估算径流,对水资源合理配置和山洪灾害预警具有重要意义,因为其方便计算、参数简单,而被广泛应用。目前标准SCS-CN模型在山区小流域的适用性欠佳,因此需要对模型参数进行优化以提高预测精度。本文以湖南省螺岭桥流域为例,根据实测降雨径流资料优化径流曲线数CN(Curve Number)查算表,并利用步长优化参数算法研究初损率对模型精度的影响,将优化模型的方法应用于湖南省凤凰小流域,验证该优化方法的可靠性。结果分析表明:与标准SCS-CN模型相比,优化后的SCS-CN模型效率系数NSE从0.576提升至0.813,决定系数R^(2)为0.858。将模型优化方法验证于气候地形条件相似的凤凰流域,模型NSE值提高117%。通过预测径流深与实测径流深比较,优化模型模拟精度较为理想,对湖南省山区小流域场次降雨产流预报有一定的参考意义。

北方岩溶区降水入渗补给系数及补给机制:以羊庄岩溶水系统为例

为建立北方岩溶区水文地质参数系列,提高岩溶地下水可采资源计算精度,笔者团队于20世纪80年代开始,在山东羊庄封闭式泉排型岩溶水系统开展了岩溶水均衡试验研究,积累了40余年的监测试验数据。根据长期野外水均衡要素观测资料,推导出裸露型、半覆盖型和覆盖型岩溶区降水入渗补给系数计算公式,建立了岩溶区降水入渗补给系数α与降水量P和地下水位埋深D的相关方程,以及可调控的最大降水入渗补给系数系列,揭示了降水入渗补给过程与α变化机制。结果表明:α随水位埋深D的改变而改变,每个降水量P段分别对应一个最大降水入渗补给系数α_(max)和最大降水入渗补给量即补给极限G_(max),相应的水位埋深便是最佳水位埋深D_(critical)。D>D_(critical)时,包气带截留量随着水位埋深的增大而增大,α<α_(max);D<D_(critical)时,地表径流量随着地下水位埋深的减小而增大,α<α_(max)。不同的降水量段对应不同的D_(critical),降水量增大时,对应的α_(max)及D_(critical)也增大。在任意水位埋深时,G_(max)为蓄满产流临界降水量与包气带最大截流量之差。本研究解决了岩溶区降水入渗补给的关键科学问题,即揭示降水入渗补给机制、建立降水入渗补给系数与降水量和水位埋深的定量关系,提升了我国北方岩溶水资源基础性研究水平。

动态径流系数法和基于城市功能区的SWMM参数率定方法研究

城市雨洪模型是研究城市内涝形成规律及演进过程的重要手段,但在我国城市化进程加速、雨水内涝监测能力不足的背景下,模型参数率定和应用面临挑战。为解决缺乏实测雨洪数据条件下城市雨洪模型参数校准的难题,本文提出了根据地理和气候特征计算雨水径流量的动态径流系数法和基于城市功能区的Storm Water Management Model(SWMM)参数率定方法。在福建省三明市的应用表明:动态径流系数法与规范和经验公式结果一致,与传统方法相比则能反映降雨产流随雨强、下渗等因素变化的规律,更符合城市降雨产流的实际过程。基于城市功能区的参数率定方法结果与研究区城市化水平和下垫面特征相符。率定后雨水径流过程NSE值达到0.80,雨水总径流量误差处于6%以内,洪峰时间误差小于3分钟。本文提出的方法可为缺乏实测雨洪数据地区的城市雨洪模拟提供参考。

基于SWAT模型的荆州市不同土地利用类型对雨水入渗量和径流系数的影响

以荆州市为研究对象,结合试验观测、模型模拟与理论分析,研究不同尺度、区域和降雨条件下土地利用变化对雨水入渗量和径流系数的影响。结果表明,2010—2022年荆州市土地利用类型经历了明显转变,耕地面积缩减,建设用地扩张,林地与草地面积稳定,水域略增,其他用地略减,这些变化导致雨水入渗量呈上升趋势,而径流系数呈下降趋势。不同土地利用类型对雨水入渗量和径流系数的影响各异,林地和建设用地对雨水入渗量产生正面影响,对径流系数则是负面;耕地对雨水入渗量有负面影响,对径流系数则正面;草地、水域及其他用地的影响较为有限。土地利用变化对雨水入渗量和径流系数的影响随尺度、区域和降雨条件的不同表现出差异性和复杂性。

基于SWMM的杭州小和山区域LID措施

【目的】缓解杭州城西小和山区域涝水问题。【方法】基于海绵城市理念,利用层次分析法(analytic hierarchy process, AHP)针对研究区域设置的5种低影响开发(low impact development, LID)改造设施的效益指标权重进行判别,实现不同LID设施下的综合效益优选,并利用暴雨管理模型(storm water management model, SWMM)构建研究区域雨洪模型,比较LID设施布设前后的汇水情况。【结果】对研究区域中12%的学校和住宅区域用地增添雨水花园,25%的广场铺装改造为透水铺装,65%的道路设置渗渠,可使洪峰出现时刻延迟45 min,洪峰流量削减率达61.5%,径流系数削减率为19.2%。可见,改造措施对洪峰流量、地表径流系数和洪峰时间等均起到显著的削弱作用。【结论】本研究结果对缓解同类区域涝水问题及提升防涝治理技术具有参考意义。

产流风险与绿地分布相关性研究——以郑州市金水河片区为例

利用ArcGIS与SCS-CN、SWMM模型相结合对研究区产流状况进行模拟,通过莫兰系数分析研究区产流风险与绿地分布在空间上的联系。绿地分布与产流风险相关性显著,研究区域的产流风险与绿地分布呈基于产流风险的绿地失配现象,在城市尺度上对绿地空间进行合理分配与布局优化,更加高效地解决城市内涝问题。

下沉式道路排水系统设计研究

本文主要探究了下沉式道路排水系统的设计要点。在设计中首先要根据径流系数、设计暴雨强度等参数,计算下沉路段的雨水设计流量。同时结合实地勘察判断下沉式路段的类型,对于两个或多个连续的下沉式路段,可以在相邻集水点之间布置连通管道,然后在最低集水点处修建泵房进行统一排水,有助于减小工程规模、控制工程成本。从下沉式道路排水系统设计的应用实例来看,该道路的雨水设计流量为1308.6 m3/h,泵房设计流量为1.2倍的雨水设计流量,即1570.3 m3/h。泵房内安装2台额定流量为800 m3/h的潜水泵,可以满足排水需要。

地理环境差异对城市内涝灾害发生的影响研究

为达到城市建设中的合理规划,研究地理环境差异对城市内涝灾害发生的影响。以武汉地区为研究对象,对特定研究区域内地理环境数据展开采集。利用采集到的数据分析地表径流系数。引入景观格局指数,计算蔓延度指数、香农多样性指数、景观破碎度指数和斑块聚集度指数,评价该地区实际地理差异情况,根据评价结果划分土地利用类别。分析4类土地利用类型的城市内涝点密度的分布情况,证明地理环境差异影响着城市内涝灾害,不同土地利用类型对城市内涝灾害的影响严重程度为:建筑区域>绿地区域>其他区域>水体区域。

大通河流域径流演变特征及其影响因素

大通河流域是青海和甘肃两省重要的调水水源.它生态环境敏感脆弱,开展径流变化归因识别对区域生态环境、水资源开发和管理至关重要.采用气候倾向率、累积距平、滑动t检验、Hurst指数等方法探究了大通河流域1961—2020年气象水文要素的演变,基于Budyko假设的水热耦合平衡方程和累积量斜率变化率法定量评估了流域径流变化的主要影响因素.结果表明:近60年大通河流域气候暖湿化明显,气温、降水倾向率分别为0.39℃·(10 a)^(-1)、9.1 mm·(10 a)^(-1),未来一段时间这种趋势还将持续;年径流于1990年发生突变,上游增加,中下游衰减明显,受水库调蓄影响汛期径流比重减小,年内分配趋于均衡;大通河流域以草地为主,研究期土地利用、植被覆盖未发生明显变化.流域冰川萎缩严重,面积减小20.9 km^(2),储量减少2.99 km^(3),冰川年消融量0.37×10^(8) m^(3),约占径流的1.3%;气候变化为流域上游径流增加的根源,降水的影响远大于潜在蒸散发和气温,跨流域调水是中下游径流减少的主导因素,对中游的影响高于下游.

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随着中国城市化水平逐步提高,城市化对降雨径流过程的影响受到愈加广泛的关注,开展城市化对降雨径流过程的影响研究对防治城市暴雨洪涝灾害具有重要意义。基于广州市大坑河流域城市化前后多年的逐时降雨径流数据资料,采用数字滤波和Boussinesq方程对基流进行分割的方法,对城市化前后降雨径流过程变化特征进行了分析。结果表明:①随着大坑河流域城市化率提高,土地利用情况发生了改变,自然土壤转化为透水性较差的道路、建筑和其他人工设施,不透水面面积增加,下垫面硬化,进而导致流域地表径流量、洪峰流量、径流系数增大,流域滞时减少;②城市化后地表径流系数和洪峰流量增大幅度随着总降雨量的增加而提高,原因可能与城市内雨水管网对径流的减少能力和城市化对下渗作用的减弱效果在总降水量不同时对降雨径流过程的影响程度不同有关。这些变化将会对大坑河流域内水资源的管理和洪水防治等方面提出新的挑战。