A Rain Duration and Modified AMC-dependent SCS-CN Procedure for Long Duration Rainfall-runoff Events

This paper presents a rain duration-dependent procedure based on the popular Soil Conservation Service Curve Number (SCS-CN) methodology for computation of direct surface runoff from long duration rains. Curve numbers are derived from long-term daily rainfall-runoff data, and antecedent moisture condition (AMC) related with antecedent duration. Analysis of data from five Indian (large, in terms of area) watersheds reveals the calculated curve numbers to decrease with the considered duration, showing the existence of a characteristic value of minimum CN or maximum initial abstraction to occur in a watershed for a pre-selected AMC. The testing of the proposed procedure on the separate (measured) rainfall-runoff event data sets from the same watersheds suggests satisfactory workability of the method.     

SCS-CN模型中CN值的空间移用效果研究

SCS-CN模型因其曲线数CN值可以根据下垫面(土壤和植被)确定,近年来在分布式水文模拟和无/缺资料地区得到较为广泛的应用。美国土壤保持局提供的CN查算表在中国地区并不完全适用,如果直接采用,可能会带来较大的径流计算误差。选择资料数据较好的北京柏崖厂站作为假定的无实测径流资料的目标站,通过相似流域特性分析确定北山下站为参证站,利用参证站资料计算出CN值校正系数,并将该系数引用到目标站,利用校正前后的CN值分别模拟多场次洪水。结果表明,SCS-CN模型的参数CN值修正后,在空间上具备一定的外推能力;无论在确定性系数、径流总量精度和洪峰流量精度上,CN值修正后的洪水预报精度都要比修正前要高。     

On relationship between curve numbers and phi indices

The curve number and phi (φ)-index models each provide a simple one-parameter relationship between storm-event rainfall and runoff. It is shown that the curve number and φ-index models can both be used to segregate the rainfall hyetograph into initial abstraction, retention, and runoff amounts. However, the principal advantages of the φ-index model are that both rainfall distribution and duration can be explicitly taken into account in calculating runoff, and the φ index is more physically based than the curve number. The quantitative relationship between the curve number and the φ index is presented and validated with field measurements. Knowing the relationship between the curve number and the φ index is useful in that it facilitates using the extensive database of curve numbers in the more realistic φ-index model in calculating a runoff hydrograph from a given rainfall hyetograph. It is demonstrated that conventional adjustments to curve numbers can be largely explained by variations in storm duration, which suggests that variable rainfall duration can possibly be an essential factor in accounting for deviations from the median curve number of a catchment.     

Field Applicability of the SCS-CN-Based Mishra–Singh General Model and its Variants

The general soil conservation service curve number (SCS-CN)-based Mishra and Singh (Mishra and Singh, 1999, J. Hydrologic. Eng. ASCE, 4(3), 257–264) model and its eight variants were investigated for their field applicability using a large set of rainfall-runoff events, derived from a number of U.S. watersheds varying in size from 0.3 to 30351.5 ha, grouped into five classes based on the rainfall magnitude. The analysis based on the goodness of fit criteria of root mean square error (RMSE) and error in computed and observed mean runoff revealed that the performance of the existing version of the SCS-CN method was significantly poorer than that of all the model variants on all the five data sets with rainfall 38.1 mm. The existing version showed a consistently improved performance on the data with increasing rainfall amount, but greater than 38.1 mm. The one-parameter modified SCS-CN method (a = 0.5 and = a median value) performed significantly better than the existing one on all the data sets, but far better on rainfall data less than 2 inches. Finally, the former with = 0 was recommended for routine field applications to any data set.     

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R²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。     

Development of a GIS Interface for Estimation of Runoff from Watersheds

Development of accurate surface runoff estimation techniques from ungauged watersheds is relevant in Indian condition due to the non-availability of hydrologic gauging stations in majority of watersheds. Besides this, the high budgetary requirements for installation of gauging stations are another limiting factor in India, which leads to the use of surface runoff estimation techniques for ungauged watersheds. Natural Resources Conservation Services Curve Number (NRCS-CN) method is one of the most widely used methods for quick and accurate estimation of surface runoff from ungauged watershed. Also, the coupling of NRCS-CN techniques with the advanced Geographic Information System (GIS) capabilities automates the process of runoff prediction in timely and efficient manner. Keeping view of this, a GIS interface was developed using the in-built macro programming language, Visual Basic for Applications (VBA) of ArcGIS® tool to estimate the surface runoff by adopting NRCS-CN technique and its three modifications. The developed interface named as Interface for Surface Runoff Estimation using Curve Number techniques (ISRE-CN), was validated using the recorded data for the periods from 1993 to 2001 of a gauged watershed, Banha in the Upper Damodar Valley in Jharkhand, India. The observed runoff depths for different rainfall events in this study watershed was compared with the predicted values of NRCS-CN methods and its three modifications using statistical significance tests. It was revealed that using all the rainfall data for different AMC conditions, the modified CN I performed the best [R ² (coefficient of determination)?=?0.92; E (model efficiency)?=?0.89) followed by modified CN III method (R ²?=?0.88; E?=?0.87), while the modified CN II (R ²?=?0.42; E?=?0.36) failed to predict accurately the surface runoff from Banha watershed. Moreover, under AMC based estimations, the modified CN I method also performed best ( R ²?=?0.95; E?=?0.95) for AMC II condition, while the modified CN II performed the worst in all the AMC conditions. However, the developed Interface in ArcGIS® needs to be tested in other watershed systems for wider applicability of the modified CN methods.     

Modeling runoff from an agricultural watershed of western catchment of Chilika lake through ArcSWAT

Chilika lake is the biggest lagoon in the Indian Eastern coast and is a source of livelihood for peoples of the coastal region surrounding it mainly through fisheries. However, the deposition of sediments in the lake carried through runoff water from its drainage basins may alter this wetland ecosystem in future. Implementation of appropriate soil water conservation measures may reduce the sediment load in runoff water and thus may protect this lagoon ecosystem. Keeping in view these concerns, runoff water from a selected watershed of western catchment of Chilika lagoon was modeled through ArcSWAT with a purpose to estimate future runoff potential from western catchment. Effective hydraulic conductivity of main channel, base flow alpha factor, curve number corresponding to antecedent moisture content II, and roughness coefficient of main channel were found most sensitive parameters in decreasing order. Nash–Sutcliffe coefficient of predicted monthly runoff was 0.72 and 0.88 during calibration and validation period, respectively whereas root mean squared error of predicted monthly runoff was 54.5 and 66.1 mm, respectively. Modeling results indicated that about 60% of rainfall is partitioned to runoff water, which carry significant amount of sediment load and contributes to Chilika lake.     

Estimation of Width and Depth of the Wetted Soil Volume Under a Surface Emitter,Considering Root Water-Uptake and Evaporation

A cylindrical flow model that describes local infiltration from a surface point source, by incorporating evaporation and water extraction by roots, was used to obtain numerical results that were the base for the development and testing of an empirical method for determining the surface and vertical components of the wetting front. The implementation of the mathematical model took place against two of the twelve USDA soil classes, using three water application rates for each one. The empirical methodology consisted of two simple, time dependent empirical relationships: a power law for the stage of the infiltration, which was applied in both directions and a polynomial for the stage after the end of the irrigation, applied only for the vertical component, to account for percolation losses. The statistical criteria used for the evaluation of the method showed good agreement between the numerical results and the values calculated by the empirical relationships. Based on the limited availability of necessary experimental data for detailed analysis of multidimensional transient infiltration, the introduction of such an empirical model, as a design tool for trickle irrigation systems, may contribute to the selection of the optimum application rate and lateral spacing.     

西林县雨水情防汛服务平台设计概述

介绍了西林县河流及雨、水情遥测站的分布情况,分析了雨水情防汛服务平台建设的背景,论述了平台的结构、通信组网方式、后台数据库及服务平台的主要功能。     

雨水花园设计方法探析

雨水花园是一种有效的雨水自然净化与生物滞留处置技术。对目前国外雨水花园常用的三种设计方法进行了对比和分析,包括:基于达西定律的渗滤法、蓄水层有效容积法和基于汇水面积的比例估算法。根据我国多数城市雨水花园的建造特点,提出了一种基于水量平衡分析的设计方法,为雨水花园的设计提供参考。     

城市雨水径流量计算方法--修正RRL法

阐述了一种城市雨水径流量的计算方法--修正RRL法的原理和方法,并模拟实际的降雨过程,预测结果与实际观测值接近,从而验证了该计算方法的准确性,为预测城市雨水径流量提供了一种有效的计算方法.     

Comparison of potential water supply and demand in Taiwan

The authors estimated the potential water supply in Taiwan based on hydrologic and water resource data sets pertaining to 233 rainfall stations, 145 stage stations and 109 reservoirs. The comparison between potential water supply estimates and predicted water demand indicated a slight water shortage, even though Taiwan normally receives a large amount of rainfall. This predicted water shortage likely occurred due to the uneven distribution of rainfall in Taiwan. Taken together, the results of this study demonstrate the importance of conservation of forests and paddy fields for the maintenance of base flow and effective management of reservoirs in Taiwan.     

宝鸡市雨水径流岸边渗滤系统设计与应用

城市雨水径流污染对城市河湖水体污染的贡献越来越受到关注.针对城市雨水径流,采用岸边砂渗滤系统处理,进行了工程设计和建设,建成宝鸡市金渭湖雨水岸边渗滤系统示范工程.运行结果表明,渗滤池对水中有机物和悬浮物的去除率达80%以上.该工程将城市雨水管网、集蓄、处理及排放连为有机整体,为解决雨水径流污染城市河湖水体提供示范.     

城市雨水径流生态处理研究现状与进展

从城市雨水径流产生的问题出发,分析对城市雨水径流进行生态处理的必要性。对包括植被缓冲带、植被浅沟、生物滞留系统、滞留塘和人工湿地等在内的多项雨水径流管理与利用生态技术的优缺点、净化机理、适用条件等进行了综合比较。并对我国城市雨水径流生态处理技术的应用前景进行了展望,为生态城市建设和城市水环境改善提供借鉴。     

Stochastic Prediction of Drought Class Transitions

This paper aims at the stochastic characterization of droughts applying Markov chains modeling to drought class transitions derived from SPI time series. Several sites in Southern Portugal having updated data on precipitation available were considered. The drought class probabilities, the expected residence time in each class of severity, the expected time for the transition between drought classes and the drought severity class predictions 1, 2, or 3 months ahead have been obtained. Those predictions are then compared with observed drought classes for the recent drought periods of 2003–2006. In addition, the estimation of the cumulated precipitation deficits, amount of monthly precipitation needed to decrease drought severity, and foreseen SPI values depending on different precipitation scenarios are also presented as complementing the prediction of drought class transitions.     

模糊聚类在流域年径流规律研究中的应用

对水资源系统的规律研究通常是对系统进行聚类、识别来实现，目前可用于水资源系统的模糊聚类的理论和模型很多，但是每种方法都有各自的特点，本文介绍一种模糊聚类循环迭代模型和最佳聚类数的确定方法，通过直观的离散函数曲线确定最佳聚类数和循环迭代的方法确定聚类中心，达到对样本进行归类的目的，最后将模糊聚类循环迭代模型应用到流域年径流规律的研究中，这对认识流域年径流规律具有一定的意义。     

乡镇供水工程水量分析研究探讨

为2020年全面建成小康社会,随着城镇化建设步伐的加快,乡镇面积不断扩大,集镇人口剧增,但供水设施的建设速度却远远滞后于经济发展和集镇建设的速度,且由于乡镇现有供水设施供水量小,日供水能力不足,供水普及率低,配水管水管网被破坏严重,供水设施已基本报废,自来水的供需矛盾日益突出,如不加以改善,将会严重制约乡镇社会经济的发展,严重影响人民群众的正常生产、生活秩序和身体健康。基于以上原因,建设乡镇供水工程,以满足乡镇日益增长的生活和工业用水需求,彻底解决乡镇的用水供需矛盾是十分必要的,也是十分迫切的。     

近年浦东新区水资源量浅析

水是生命的源泉,是不可替代的宝贵资源。2011年中央明确实行最严格水资源管理,确立水资源开发利用的＂三条红线＂。通过对2007—2011年浦东新区水资源量的分析,研究现有水资源量的特点,对水资源开发利用和保护提出建议,促进浦东新区水资源利用的可持续发展。