IRAN-WATER RESOURCES RESEARCH
Year:2006 | Volume:2 | Issue:2|Papers Count:10

Shortage of water is the most important limiting factor for crop production in arid and semi-arid regions of Iran. Higher efficiencies for the present water supply can be obtained by deficit irrigation. Seasonal and intra-seasonal approaches for deficit irrigation for Sorghum are compared in this study. The data for deficit irrigation were collected at the Bajgah area, a semi-arid region, located 16 km north of Shiraz, in southern Iran. Time pattern distribution of applied water was not considered in their seasonal approach and the cost-benefit ratio analyses are performed on an annual basis. Decision making in the intra-seasonal approach is based on water allocation at different growth stages of crop. The results showed that there are some differences between the two approaches as far as the optimal water reduction is concerned. Seasonal approach showed a constant water reduction (18%) irrespective of water cost variation, while the intra-seasonal method offered higher allowable water reduction of 23% for unit water cost of 10 Rls m-3 which may lead to a more economical water use. However, the result obtained in the intra-seasonal method is sensitive to the unit water cost and the allowable water reduction becomes lower than that of seasonal approach at the higher unit water cost. These results confirmed a previous result on Corn about the differences for the two approaches. Meanwhile, there is a substantial difference between the results for Sorghum and Corn in two different approaches.

In this research finite elements approach and systems approach, are combined and a new framework for dynamic modeling of large problems and their solution by Decomposition-Coordination or Aggregation-Disaggregation algorithm is introduced. This framework enables the modeler to benefit from these two approaches in an integrated base and to simulate and optimize large water resources systems. To show applicability of this framework, software named FEWREM is developed in this research. This model is compared to MODSIM via a case study the results show that MODSIM results in more shortages compared to FEWREM. In other words, the effectiveness of FEWREM in operating the water system is more than MODSIM.  

This study is focused on two parameter estimation methods of Ordinary Least Square (OLS) and binary code Genetic Algorithm (GA) for estimating the k, n Nash conceptual model parameters. The efficiency of these methods is compared by applying the calibrated models in simulating seven rainfall-runoff events in Heng-Chi watershed in north of Taiwan. The results of the goodness of fit criteria indicate that GA method has better performance in terms of coefficient of efficiency and has reduced the coefficient of variation of error in simulated discharge and error in peak discharge.

Floods have caused extensive damages in the floodplain every year. An important issue in regions with construction sites of diversion dams is how to protect the project during the construction. In implementating flood management schemes, both non-structural and structural flood control options should be considered. The experiences show that nonstructural options are more effective than structural methods in reducing the damages of flood at a lower cost. In this paper, an algorithm is developed to define the best management scheme for flood protection. An economic analysis is undertaken which combines the analysis of probable floods and expected damages for different flood control options as well as a flood warning system. The case study is Shirgovaz diversion dam which is located 44 kilometers downstream of the Pishin Dam in South Baloochestan in southeast of Iran. The results show that considering a flood warning system for the Pishin Dam is an effective method to reduce the flood damages. This system could provide early warning to the Pishin Dam and the rest of the area. A simple flood warning system has been designed and could utilize the information obtained from upstream synoptic and hydrometric stations. This study shows the significant value of planning flood control schemes for flood damage reduction.

The main objective of this study is to develop a higher order numerical scheme to simulate the pollutant spreading in surface water resources. The new discretisation schemes in Finite Difference Method are presented in one and two dimensional domain to predict surface water quality. Moreover, the effect of dimensionless computational numbers on numerical processing and errors is investigated for several methods. The grid size sensitivity analysis is made based on numerical results which are obtained in several methods. A real case study is made for thermal pollutant released from cooling water outfall of a power plant into the adjacent river. The numerical results are compared with field measurements and a good agreement is obtained.

The successful application of a conceptual rainfall-runoff (CRR) model depends on how well it is calibrated. Generally, CRR model deals with many parameters that should be estimated through robust optimization tools. The degree of difficulty in solving a global optimization method is generally dependent on the dimensionality of the CRR model and certain characteristics of objective function. The purpose of optimization is to finalize the best set of parameters associated with a given calibration data set that optimize the evaluation criteria. In this study, a global optimization method known as the SCE (Shuffled Complex Evolution) has been developed for autocalibration of CRR parameters. This method is developed based on the nature of optimization problems in CRR models, combination of probabilistic and deterministic approaches, and clustering and competitive evolution. SCE method has shown promise as an effective and efficient optimization technique. Model verification and validation results indicated that automatic calibration was superior to other existing algorithms. Also, the proposed SCE algorithm was programmed via innovative ways to reduce the memory allocation and improve the speed of computations. In addition, a new method of storing very large matrices with small number of non-zero members was implemented. Thus, personal computers can also be used for automatic calibration of up to 35 parameters. In this study, the developed SCE technique has been applied for auto calibration of storage CRR model, namely NAM, in Gamasiab watershed within the greate Karkhe basin. The calibration and validation results and evaluating criteria shows the effectiveness and efficiency of this method for autocalibrating of CRR parameters.

Leakage is one of the most serious problems in water distribution networks. Limited resources of water and the increasing expenses of transport, treatment, pumping, storage and distribution of water, notify the importance of leakage reduction. Due to the direct relation between leakage and pressure, pressure management is a useful and cost effective method for leakage reduction. In this research pressure reducing valves are used to achieve this goal. An optimization procedure is applied to minimize the difference between the available head and minimum standard head at each node. Sum of square differences between the available and minimum standard heads at each node are minimized using linear and non linear programming. To analyze the hydraulic conditions of the system the head driven simulation method is used. In this method the available nodal outflows are not fixed and vary with nodal pressure fluctuations. Finally a test network, have been used to illustrate the validation of the proposed method. The results of this procedure define the PRV’s outlet values. Based on these optimized values, nodal heads tend to be very close to the minimum standard values which lead to the maximum leak reduction.

In recent years, many hydraulic, sediment, and environmental researchers focused their studies on river junction hydrodynamics. River junction is an important morphological element of river systems. The incoming flow from a minor branch causes extensive variation of flow velocity, flow discharge, and sediment discharge which results in flow turbulence in the main channel. The main characteristic of river confluence is the dimensions of flow separation zone. This zone is developed from the downstream edge where the minor branch enters and extends to some distance downstream into the main channel. There are few parameters affecting the separation zone extension including the discharge ratio (Qr) the width ratio (Br) and the downstream Froude number (Frd). The effect of these parameters has been investigated on the separation zone length (L) and width (H). Experimental tests have been conducted in a 90 degree junction. The results show that as Qr increase L and H increases and as Frd increases the value of L and H decreases. In this study relations were developed which can be used for prediction of separation zone dimensions. The mean value of separation zone shape index also has been determined.

Diverted flow has been the subject of interest for researchers and hydraulic engineers for many years. In general, diversion flow can be categorized as natural and artificial flow. Natural flow diversion usually occurs as braiding or cutoff in Meander Rivers, while artificial flow is man-made to divert flow by lateral intake channels for water supply. According to the research done so far, flow patterns have been identified to be non-uniform and three dimensional in the vicinity of the lateral intake. The rate of flow diversion is influenced by the separation zone, resulted from vortices. In most of the research works, the main hydraulic and geometric parameters that have been studied are intake location, diversion angle, main channel flow and Froude number. To assess the flow diversion rate in rivers, experimental studies were made on a rectangular fixed bed U-shape channel with a rectangular fixed bed straight channel as a lateral intake. Experiments were carried out for different Froude numbers, intake locations and diversion angles to obtain a relationship between the so-called hydraulic parameters and diversion flow rate.