Hydraulic analysis of water distribution systems can be divided into DDA (Demand-Driven Analysis) and PDA (Pressure-Driven Analysis). Many studies have reported the superiority of the PDA over the DDA in the realistic simulation of hydraulic conditions under abnormal operating conditions. Many of the developed PDA models rely on iterative processes to solve the equations, which is a timeconsuming task and even worse it is not possible to solve them in some cases. To improve the efficiency of the PDA, the present study proposes a new PDA model which interfaces a hydraulic simulator and an optimization algorithm with a customized searching scheme. The suggested model is applied to differently sized water distribution systems under abnormal operating conditions and its results are compared with ones by the DDA model and two other PDA models. As results, the DDA may generate unrealistic hydraulic results under the abnormal operating conditions while the three PDA models produce more realistic results. Moreover, the suggested PDA model with the new optimization process simulates the hydraulic conditions under the abnormal operating conditions in large water distribution systems efficiently compared to the other PDA models.

The main objective of sewer rehabilitation is to improve its function while eliminating inflow/infiltration (I/I). If we can identify the amount of I/I for an individual pipe, it is possible to find the distribution of the total I/I over the entire sewer system. With this information we identify which sub-area is more critical than others. However, in real, the amount of I/I for an individual pipe is almost impossible to be obtained due to the limitation of cost and time. For this reason, we suggested the rehabilitation weighting model (RWM) to determine it objectively or systematically. Based on the determined amount of I/I for an individual pipe, we also suggested the rehabilitation priority model (RPM), which is equipped with genetic algorithm, to determine the optimal rehabilitation priority (ORP) for sub-areas in term of minimizing the amount of I/I occurring while the rehabilitation process is performed. The benefit obtained by implementing the ORP for rehabilitation of subareas is estimated by the only waste water treatment cost (WWTC) of I/I which 1726 J.H. Lee et al.occurs during the sewer rehabilitation period. A decision making support system which is consisted of the RWM and the RPM was applied to an urban drainage area. The results of the ORP were compared with those of a numerical weighting method (NWM) and the worst order which are other methods to determine the rehabilitation order of sub-areas in field. The ORP reduced the WWTC by 22% compared to the NWM and by 40% compared to the worst order.

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A roaded catchment (RC) is a representative type of artificial catchment for rainwater harvesting. The rainfall–runoff threshold value of the RC is the main factor which influences the system efficiency and cost. Antecedent soil moisture condition is an important factor which impacts on the determination of the rainfall–runoff threshold value. In this study, rainfall–antecedent soil moisture condition–runoff relationships and the potential efficiency of RCs are presented. Rainfall and runoff data monitored at research sites in Merredin and Mount Barker are used to determine this relationship. Two antecedent moisture criteria; Antecedent Moisture Conditions (AMC) and Average Antecedent Precipitation (AAP) are used to analyse the relationship between previous rainfall and soil moisture for each RC. Monitored results show that AMC is not that suitable to show the relationship between rainfall and antecedent soil moisture condition of the RC in the dryland of Western Australia and it is recommended to use AAP to determine this relationship.

A washland can effectively reduce peak flow of a high flow event at a certain location. A number of washlands located in a basin influence each other's hydrological function, and hence, their hydrological role should be evaluated from a river network perspective. Here, we present an approach to determine optimal locations of constructed washlands in a basin, considering their mutual effect. The problem is formulated as a multiobjective problem with maximizing peak flow reduction effect as one objective and minimizing the total volume of washlands, which is associated with cost, as another. By simplifying modelling algorithm for hydrological routing, we show that consideration of all possible cases is feasible for the situation of a typical basin. This approach guarantees global optimum and shows a full spectrum of Pareto front, which will help decision-makers in problems of multiple objective functions. The proposed approach is demonstrated for the Anseong River basin. bs_bs_banner Water and Environment Journal. Print ISSN 1747-6585 Fig. 4. Developed model structure. HEC-HMS, Hydrologic Engineering Center Hydrologic Modeling System. Optimal location of basin-wide constructed washlands C. W. Baek et al.

Rainwater harvesting systems such as roof-raintank water harvesting systems for internal domestic use, and artificial catchment rainfall-runoff harvesting systems connected to farm dams for agricultural purposes, have many advantages as sustainable water resources. Rainwater harvesting systems can provide adequate high quality water across significant areas of Western Australia (WA) that do not have access to the comprehensive water supply scheme. Declining rainfall trends in southwestern Australia due to climate variability make rainwater harvesting systems more significant as a water resource for isolated farms and communities in arid and semi-arid areas (wheat-belt and pastoral areas) in WA. The design of catchment-dam systems, especially size of dam and catchment, will impact the efficiency and cost of construction of the system, in arid and semi-arid areas of WA and they are generally determined to satisfy the targeted demand reliability of catchment-dam systems. The reliability of catchment-dam systems can be defined as the probability that the system will supply a required demand of water during a specified time. The result of water balance simulations for the design of harvesting system can be affected by time interval for the water balance simulation such as daily, weekly or monthly calculation. The practical reliability of catchment-dam systems can be defined using available water supply demand or period with water supply failure. Determination of the modelling time interval and the definition of reliability will therefore be a critical design factor for water supplies. Evaporation from a farm dam will be affected not only by weather conditions (e.g. temperature, wind) but also by dam design characteristics such as surface area. Therefore, catchment-dam designs will return different water balance simulation results than those for roof-raintank systems, in arid and semi-arid climates. Farm dams undergo significant water loss through evaporation while roof-raintank systems (if capped) are unaffected by evaporative losses. The definition of the reliability of a rainwater harvesting system is a significant factor in determining the demand reliability that may result in the underestimation or over-estimation of supply efficacy and reliability, particularly in dry climates. Simulation process for the reliability of rainwater harvesting system has no great difference depending on which modeling time interval and the definition of reliability are applied. However, there is the variability in the calculated reliability considerably depending on regional conditions. This paper assesses this variability in the reliability of catchment-dam systems through an evaluation of the influence of the modelling time interval for the water balance simulations; and the definition of reliability. The reliability of catchment-dam systems for ten sites located in dryland agricultural areas of WA are evaluated using daily and weekly modelling time intervals and five definitions of reliability (volume-based estimation, daily, week...