مجله تحقیقات منابع آب ایران
پیاپی 1 (بهار 1384)

In mountain regions, snowmelt runoff is a key hydrologic component that controls flow regime. In such regions, it is usually impossible to sufficiently measure the climatic and hydrologic data in the spatial and temporal scale required for the simulation of uncertainty. Therefore, predicting snowmelt runoff is carried out with some unknown degree of uncertainty. When calibrated, Snowmelt Runoff Model (SRM) is a hydrologic model, capable of simulating daily discharge in case of minimum measured snow data. The SRM is applied in order to study the capability of this model in simulating the snowmelt runoff in a basin in Iran, which lacks sufficient data. Khersan a sub-basin of Karoon river is considered for this case study. An Advanced Very High Resolution Radiometer (AVHRR) data is also considered to determine the time series of snow-covered areas. The time-series of daily discharge in 1996 are used for model calibration. Accuracy of the parameters is evaluated based on the time series of daily discharge in 1997. Model accuracy in snowmelt and rainfall runoff simulation is 88% based on evaluation results. The determination coefficient R2 is 0.774. The difference between the simulated and measured total discharge is I% for the study period. Based on the results of this research, SRM can be considered as an effective tool to estimate the snowmelt runoff and the quantity of rain and snow contributions. The application of this model is recommended for basins with no measured data.

Excessive water withdrawal from the rivers due to growing population, agricultural and industrial development, along with increase in the wastewater discharge to this systems, have intensified the need for integrated planning for water pollution control in river systems. In this paper, a framework of a master plan for water pollution control in the river systems and the results of a case study for developing a master plan for Karoon River water pollution control in Khuzestan Province in Iran are presented. The main pollution sources in the domestic, industrial, agricultural and agro-industrial sectors are identified and the effects of these pollution sources on the river water quality are investigated using the water quality simulation model. A Multiple-Criterion-Decision-Making (MCDM) technique, namely Analytical Hierarchy Process (AHP) is used in order to determine the share of different sectors in polluting the water resources. Data deficiency and the relative weights of different water quality variables are determined using engineering judgments and the information gathered from brain storming sessions with experts, the agencies' officials, and the stakeholders of the system. Based on this study, specific major categories of water pollution reduction projects were defined and in each category, several projects were identified. The effectiveness of the proposed water pollution control projects is also assessed using the MCDM method and water quality simulation model. The total cost of implementation of the projects was also estimated and the projects were prioritized based on their potential impact on water pollution control. The results of this study show that the proposed methodology is of a significant in developing the master plans for river systems.

The assessment of water flow in unsaturated zone is of interest in many hydrological and environmental problems. In this paper, two different forms of governing equations of water flow in unsaturated zone are studied. The influences of discritization schemes, averaging methods of nonlinear interblock hydraulic conductivity, and different convergence criteria on the accuracy and performance of numerical models for these equations are investigated. It is shown that by choosing an appropriate form for determining the hydraulic conductivity and using the secant method for calculating the moisture capacity and implicit method for discritization, is chosen. By doing this, the type of Richards's equation that has pressure as its dependent term gives very close results to the mix type of Richards's equation. This later approach according to the previous studies had given better results.

In this paper, impacts of climate change on water resources and food productivity of Zayandeh Rud basin using HadCM3, GCM model data under SRES scenario; A2 and B2 for the periods of2010-2039 and 2070- 2099 are investigated. Meteorological analysis shows significant decrease in rainfall and increase in temperature and successive dry years up to the year 2100 Inflows to Chadegan dam was simulated Using Artificial Neural Networks (ANNs) model. Then ZWAM model was developed to. Allocate water to different water consumption sectors. The results show significant deficit in inflows to Chadegan dam and water for the agricultural sectors of the basin up to the year 2100 In the next step, the SWAP model was used to simulate staple food (Rice, Wheat, Barely and Potato) production of the basin using climate change information, which revealed decrease in food productivity and increase in coefficient of variation up to the year 2100. To alleviate the negative impacts of climate change, two strategies were evaluated; reduction of cropped lands by applying full water requirements and change in cropping patterns. The first strategy was beneficial only for rice. But changing the cropping pattern and substitution of wheat with rice not only produce more (33 to +48%) calories but also resulted in reduction of water consumption by 10%.

Inference from individual stream flow records can be extremely misleading, even for large samples. One is often tempted to trust information available from a stream flow record rather than to exploit regional average statistics of those records. This study has sought to understand the spatial and temporal characteristics of historical annual stream flow in the western watersheds of Iran (i.e., Karkhe, Dez and Karoun). The first goal of the study is to explore the regional and stochastic structure of annual flow records with an emphasis on characterizing the variability and persistence of flow records used in the regional stochastic stream flow models. The second goal is to develop regional hydroclimatological models of annual stream flow which relate mean annual stream flow to climatic and geomorphic characteristics. To achieve the first goal, parameters of regional autoregressive model of AR(1)-LN for each watershed were estimated from time series of annual stream flow at 84 gauging stations with record length of 17 years or more out of 213 total hydrometric Stations. Based on the same time-series, regional hydrologic regression equations were developed for each watershed.

In this paper, a framework for design and operation of hydropower reservoirs is presented. For this purpose, a dynamic programming model is developed to optimize the operation of a dual cascade reservoir system. The model has been applied to the Pa-alam and Karkheh Reservoir system in southwest of Iran. In order to decrease the computational burden of the problem, certain design parameters are selected based on the sensitivity analysis of the long-term simulation results. These Parameters include installed capacity and Plant Factor of the Power Plant and normal and minimum water levels in the reservoir. In order to evaluate the results of simulation based on the variation of these parameters, variations of firm energy, total annual power generation, and reliability of water supply are analyzed. Comparison of the results of the optimization model and the long-term simulation based on the optimal operating policies shows that the selection of design parameters can significantly affect the long-term performance of the system.

Coordination of operation of hydrothermal power systems is in line with optimum reduction of energy generation costs. Researches for preparation of operational models for planning of hydrothermal power systems have been started since 50 years ago. HTCOM software package as one of these models was developed in 1997 in McMaster University, Canada. This model determines long - term operational policies for a hydrothermal power system with multi-purpose reservoirs. This nonlinear model considers stochastic inflows by scenario analysis. However, energy demand is considered deterministic. Considering capabilities of this model in dealing with hydrothermal planning and to improve its performance, uncertain energy demand is applied to this model in this paper. The improved model has been utilized in a real world system in the Khuzestan province in Iran, comprising of multi-purpose reservoirs and thermal power plants.

In this paper different methods for analysis of pipes breakage in urban water distribution networks are investigated. At first, it is necessary to obtain complete and exact information about the failures in the networks. Thus, a suitable form was designed for gathering the required information including all the necessary parameters for the analysis. Then the rates of annual pipe failures were assessed based on the diameter, age and availability of pipes. Mechanical reliability (availability) of network components is the probability that component is performing well in the networks during its lifetime. The results show that the rate of breakage is decreased by increasing the diameter in all pipe types (e.g. Steel, Asbestos Cement). Assessing the availability of the pipes according to their diameter and length reveals an increase in availability by increasing the diameter but a decrease in availability by increasing the length of the pipes. It is also seen that the rate of water loss decreases by increasing the diameter of pipes. Furthermore, an increase in the rate of failures is observed when pipes are aging. The results of pipe breakage analyzed. Introduced in this paper provide helpful information to be used in design, operation and rehabilitation of pipe networks.

Wave induced hydrodynamics within the near shore region; sediment transport and the subsequent evolution of beaches under wave attack are important elements governing the stability of the coastal structures. Based on surf zone hydrodynamics, several efforts have been made to estimate the sediment transport and beach profile formation during storm conditions. Although there are advanced models of surf zone hydrodynamics for natural beaches, the behavior of the beaches in front of reflective structures (i.e. seawalls) under breaking waves still suffers from the lack of appropriate theoretical models and measured data. In order to consider the effect of reflective structures on beach profile evolution, experiments have been performed at laboratory model scale on a reflective seawall located in the surf zone. In this paper, the measurement data has been analyzed with Buckingham theory and certain equations have been derived the results obtained from utilizing the equations have been compared with the experimental data. For the cases simulated, the reflected waves have been found to have a great effect on the beach profile development. The results obtained from the experiments show a strong dependency of the surf zone hydrodynamics and beach profile formation on the location of the structure and the breaking point near the shoreline.

Insufficient information regarding the distribution of sediment yield during a storm is one of the old problems in soil and water conservation projects. Dotill now, the relationship between sediment and water discharge has only been investigated using the power equations and the position of samples have not been taken into account. In this paper, the concept of regression model was implemented to find out two separate equations defining the relationships between sediment yield and water discharge in two important segments of hydrograph namely, rising and falling limbs. The results revealed that the application of regression model is a suitable technique for the watershed is of Amameh and zamn Derakht in the study area.