Optimal design of unit hydrographs using probability distribution and genetic algorithms

A nonlinear optimization model is developed to transmute a unit hydrograph into a probability distribution function (PDF). The objective function is to minimize the sum of the square of the deviation between predicted and actual direct runoff hydrograph of a watershed. The predicted runoff hydrograph is estimated by using a PDF. In a unit hydrograph, the depth of rainfall excess must be unity and the ordinates must be positive. Incorporation of a PDF ensures that the depth of rainfall excess for the unit hydrograph is unity, and the ordinates are also positive. Unit hydrograph ordinates are in terms of intensity of rainfall excess on a discharge per unit catchment area basis, the unit area thus representing the unit rainfall excess. The proposed method does not have any constraint. The nonlinear optimization formulation is solved using binary-coded genetic algorithms. The number of variables to be estimated by optimization is the same as the number of probability distribution parameters; gamma and log-normal probability distributions are used. The existing nonlinear programming model for obtaining optimal unit hydrograph has also been solved using genetic algorithms, where the constrained nonlinear optimization problem is converted to an unconstrained problem using penalty parameter approach. The results obtained are compared with those obtained by the earlier LP model and are fairly similar.     

Influent generator for probabilistic modeling of nutrient removal wastewater treatment plants

The availability of influent wastewater time series is crucial when using models to assess the performance of a wastewater treatment plant (WWTP) under dynamic flow and loading conditions. Given the difficulty of collecting sufficient data, synthetic generation could be the only option. In this paper a hybrid of statistical (a Markov chain-gamma model for stochastic generation of rainfall and two different multivariate autoregressive models for stochastic generation of air temperature and influent time series in dry conditions) and conceptual modeling techniques is proposed for synthetic generation of influent time series. The time series of rainfall and influent in dry weather conditions are generated using two types of statistical models. These two time series serve as inputs to a conceptual sewer model for generation of influent time series. The application of the proposed influent generator to the Eindhoven WWTP shows that it is a powerful tool for realistic generation of influent time series and is well-suited for probabilistic design of WWTPs as it considers both the effect of input variability and total model uncertainty.     

State variable analysis of hydrological systems

The concepts of state and state variables are introduced. From a mathematical point of view the concept of state variables provides the means of transforming a differential equation of any order into an equivalent set of first-order equations. From a physical point of view the state of a system, specified by numeric values of the system state variables at a given time, contains all the relevant information about the system necessary to predict the behaviour of the system in the future. The state variable concept is thus very much suited for analysis of dynamic systems. Examples of the state variable concept applied to analysis of discharge from a reservoir and from two reservoirs operating in series are presented.     

纪录片在桥涵水文课程教学中的应用探索

桥涵水文课是土木工程类专业的一门重要专业基础课,起着连接前期基础理论课和后续专业课的关键作用。本文探索将视频资料中的一类——纪录片引入桥涵水文课堂教学中,通过启发式引导学生思考和学习。教学效果表明,纪录片教学不仅能够调动学生的学习积极性,拓展其视野和分析问题的角度,同时还可以培养学生的社会责任感和爱国情操,是一种很好的课堂教学补充方式。但同时这种方式也存在一定的局限性,需进一步的完善和提高。     

Doing the first loop of planning for sustainable urban drainage system retrofits: A case study from Odense,Denmark

The planning and implementation of sustainable urban drainage systems (SUDS) requires intensive collaboration between professions and institutions. To improve the conditions for such practice in Denmark, the first loop of a SUDS-based retrofitting project was completed in Odense over a 6-month period. The project involved officials from the City of Odense and Odense Water Ltd., as well as university researchers. Studies of hydrological, environmental and socio-cultural aspects were developed by disciplinary teams and used to draft integrated solutions for two selected city districts. Albeit sewer surcharge was the initial catalyst, the main driver for the drafted solutions was urban planning. An assessment of the impact 1.5 years after completion indicated that the employed approach is valuable. In Odense, a planning procedure reflecting the loop process has become new practice. The project represents a key reference for the introduction of SUDS in Denmark.     

同位素测年新发展:81Kr测定古老地下水年龄理论

自从1966年Loosli&Oeschchger测定出大气中的81Kr,就已经有人设想放射性81Kr(半衰期为(2.29±0.11)×105年)可能成为测定古老地下水年龄(105~106年)的有效工具。但一直没有付诸实践,直到2000年,Collon等人首次利用81Kr同位素确定澳大利亚大自流盆地(GAB)的古老地下水年龄。本篇文章中主要介绍了影响81Kr同位素测年的因素,81Kr的取样制样分析过程,回旋加速质谱仪分析81Kr同位素的原理。     

基于特色培养的水利工程类专业教学改革探析

以扬州大学水文与水资源工程专业人才培养,以及该专业目前的办学定位和培养规格分析为基础,从明确专业培养目标与任务、加强教学体系建设、注重实践教学环节、完善核心课程与主干课程体系设计、构建学科专业交叉融合机制、注重人才队伍培养与学科建设,以及完善教育质量评估与保障措施等方面探讨了以特色培养为导向的水文专业教学改革措施。     

Surface runoff estimation over heterogeneous foothills of Aravalli mountain using medium resolution remote sensing rainfall data with soil conservation system‐curve number method: A case of semi‐arid ungauged Manesar Nala watershed

Manesar Nala watershed, having an aerial extent of 71.53 km², was subjected to modelling of its hydrological behaviour for assessing its water resource potential. Modern tools and techniques of Remote Sensing (RS) and Geographic Information System (GIS) were used for assessment of runoff generating potential using the Hydrologic Soil Cover Complex (HSCC) Method [U.S. Department of Agriculture (USDA)‐Soil Conservation System‐Curve Number (SCS‐CN) approach]. RS and GIS were used in generation and integration of thematic maps [such as Land use/Land cover (using LISS‐III data) and Hydrologic Soil Group (HSG), (using soil map of study area) to derive the Curve Number (CN) for simulating Runoff (R_o)]. The daily rainfall (P) data for the study period 2002–2015 were acquired from NOAA Climate Prediction Center (NCPC). Corresponding R_o from the watershed for intense storm events for 14 years were calculated through RS and GIS. GIS and SCS‐CN model was employed for modelling the runoff production to study its hydrological behaviour. The study showed that the Manesar Nala watershed was having a composite Curve Number – II (CN_II) value of 82.5 for normal conditions. For dry and wet conditions these values were estimated at 66.44 (CN_I) and 91.56 (CN_III), respectively. This investigation showed that Manesar Nala watershed exhibited an annual average (of 14 years, 2002–2015) R_o volume of 4 542 514.37 m³ based on the average annual rainfall (P) of 0.72 m (720 mm). The average annual surface runoff (R_o) was predicted to be approximately 0.21 m with annual runoff coefficient (C_R) of 0.29. During the study, we also found a strong correlation ‘r’ between satellite driven P and R_o from NRCS‐CN method of the order of 0.94. The methodology so developed has the potential to be used in other similar ungauged watersheds in the same agro‐climatic conditions for the purpose of planning of watershed conservation measures and other developmental activities.     

城区路面雨水径流水文水质特征试验研究

鉴于研究城区路面径流水文过程与污染物变化特征可为有效利用城市雨水、控制非点源污染等提供参考依据,采用污染物分析方法对新乡市2010年城区路面3场降雨—径流的水文、水质过程进行采样分析。试验结果表明,路面径流系数在0.78～0.82之间,径流曲线形态与降雨过程线类似,两者波动幅度相对较小;径流初期污染严重,后期COD、SS浓度分别小于203、458mg/L;各指标的标准差率呈SS>COD>DO>pH值的趋势,这与各自浓度变化过程的指向性一致;径流中COD与SS之间的相关性较好,而DO与其之间的相关性较差。     

城市水文模型原理刘家宏

城市水文过程因强烈的人类活动影响而发生了深刻变化,科学精细地模拟城市区域的产汇流过程是解析城市水问题机理的科学基础。在系统剖析城市水文模型原理的基础上,将城市复杂下垫面根据其透水特性划分为不透水单元、透水单元、半透水单元、伪透水单元、强透水单元、水域单元等六类基本单元,并构建了不同类型城市水文响应单元的水文特性曲线,基于圣维南方程组和Navier-Stokes方程提出了城市管网与河湖水系水动力学模拟的技术方案。在耦合城市水文响应单元的降水—截留—蒸发—入渗—产流模块、地表汇流模块、管网汇流模块、水系一维水动力学模块等基础上,以水循环过程为主线,将水文模型的径流输出作为城区一维管网、河道水动力模型的输入边界,实现水文模型与一维管网、河道水力学模型的集成。将单元水文模型通过城市管网和河湖水系等连接方式集成到城市水文模型系统中,弥补了现有城市雨洪模拟在水文学机理上的不足,可为城市排水防涝和海绵城市建设提供科学基础。