Sharif Digital Repository

To investigate boiling heat transfer characteristics of nanofluids, transient quenching¬ experiments of a high temperature silver sphere in water-based nanofluids with Ag and TiO2 nanoparticles were performed. A silver sphere of 10 mm in diameter at the initial temperature of 700o C was quenched in the nanofluids at the temperature of 90o C. The results showed considerable reduction in the quenching ability of nanofluids compared to that of pure water. The presence of nanoparticles in water caused film boiling mode to vanish at lower temperatures depending on the mixture concentration. Computed heat transfer rates in nanofluids were lower than those in pure water. In the quenching... 

With altering natural state and increasing impervious surfaces, traditional urbanization leads to deteriorating the environment and water catchments. During the years most efforts in order to control the urban runoff outflow, have been focused on quantity; and awareness about improving water quality has been raised just in the last few years and, which emphasizes on pollution source control. Standard water quality sampling methods are time consuming, expensive and because of sampling in broad geographic areas, difficult; however modeling is a more efficient way in assessing water quality and as worries about non-point source pollution grows, different kinds of models have been used to... 

Maintaining the quality of water is of paramount importance for lakes with tourist attraction capacity. Inaccurate prediction of the quality state of lake in design phase may lead to some trouble in future. Kan River known as the main source of water feeding for the urban lake located in the north of Chitgar park passes through various villages and restaurants discharging nutrients via runoff and wastewater in the aforementioned river. Previous investigations reveal that phosphorous plays a central role in the water quality of this river and the associated downstream lake. In this research, Kan watershed,located in in the north-west of Tehran, was simulated. Considering the "Total Maximum... 

Evaporation is the initial process of losing water and heat from the surface of the lake. There are six well-known methods for estimating the evaporation of water from surface water including: the water balance method,the energy balance method, themass transfer methods, the combined mass transfer and energy balance method, the empirical equation and using pan evaporation. In this thesis, evaporation has been calculated with using different equations, in-site observation and remote sensing data. These results also have been compared with the results of the energy balance method. In addition, we have developed modified empirical equations of fresh water evaporation estimation with the... 

Evaporation is the most important water loss from terminal lakes which can influence the chemistry of lakes. In large lakes, the spatial distributions of meteorological and water quality variables affect the evaporation rates. Therefore, it is crucial to consider such variations in estimating evaporation rates from large lakes. This study aims at developing an evaporation estimation model for saline lakes considering salinity and spatial distribution of variables in/over the lakes and investigating the interaction between meteorological, hydrological and water quality variables in natural saline systems. To accomplish these objectives, first a distributed model was developed for estimating... 

Most of the surface and ground water resources are allocated to agriculture in Iran. Even though lots of water is used in this field, the level of crop production is not satisfactory due to mismanagement. Besides, environmental issues caused by surface and ground water overuse has brought the crucial situation into the governers’ attention. Over the past two decades, Lake Urmia water basin has encountered lots of environmental issues such as decrease in lake water surface. Any effort to improve water reources consumption can be very helpful to lake restoration process. Miandoab plain known as one of the main sub basins of Lake Urmia provides the lake with more than half of its surface water... 

Urmia Lake is one of the largest permanent hypersaline lakes in the world. Since Urmia Lake is faced with drying phenomena, the release of dust from its surface is expected. The most appropriate technique on dust storms is the remote sensing technique. One of the most popular parameter that provides the integrated information over a vertical column of unit cross section of this phenomenon is aerosol optical depth (AOD). Satellite remote sensing has been used to retrieve AOD over land and ocean at spatial resolutions of several to several tens of km. However, higher spatial resolution aerosol products for local scale areas have not been well-researched mainly due to the difficulty of... 

The direct impact of rainfall in human life and its fundamental role in water resources management cause the development of methods and algorithms to estimate the rainfall among the researchers. In the past decades the traditional methods were used to measure the amount of rainfall until the advent of Meteorological Satellites has sparked a revolution in this field. Significant temporal and spatial changes of rainfall and the small number of the synoptic stations caused negative impact on the actual distribution of the amount of rainfall in a vast area. The rainfall satellite data were somewhat overcome by existing deficiencies in Synoptic methods by providing a better rainfall distribution... 

Lake Urmia is the largest inner lake in Iran that has been dessicated continuously over the past two decades, and most of it has dried up. Urmia Lake basin is one of the country's agricultural and industrial pillars and has more than 5 million inhabitants. The conflict between people’s interests and the environmental ones besides increased demand for water harvesting has led to a reduction in water inflow to the lake. As the water resources management issues became more complex in last two decades with the entrance of political and socio-economical, the concept of water resources management has been promoted in the broader sense of water governance. The solution to the problem of Lake Urmia... 

The level of water at Lake Urmia has decreased dramatically in the last two decades. Lake-Urmia basin is one of the regions in which most of the consumption of water is based on groundwater resources. The annual withdrawal of groundwater in the Urmia Plain is about 468 MCM which is the highest rate of water extraction throughout the basin. In this research, interaction between surface and groundwater flow is simulated using MODFLOW and remote-sensing. METRIC algorithm is used for estimating the amount of recharge to groundwater. The model is calibrated in 24 months of 2008 and 2009. The results show that the main input to the aquifer is the return flow of agricultural lands and the main... 

Human as an important part of the natural environment and can exert their positive or negative effects in the form of long-term and short-term on a natural environment. Human impacts on the natural system are very complex and consist of various components. The most considerable among them from past to now are maybe land use and land cover change, although, the impact of dam construction, water pollution, air pollution and etc, can not be neglected. To quantify the impact of these changes, many researchers have studied meteorological and climatic parameters using statistical relationships, but one major problem always existed, the low spatial accuracy of meteorological data. In recent years,... 

At Lake Urmia (LU) greatest extent, it was the largest lake in the Middle East and the sixth-largest saltwater lake on Earth, with a surface area of approximately 5,200 km2. The lake has shrunk to 10% of its former size due to damming of the rivers that flow into it, and the pumping of groundwater from the surrounding area. Moreover, as the lake shriks its potentional to be a major dust sources increases. A Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to investigate and track the extent of dust emission and aerosol concentration over Lake Urmia marginal dust spots in order to identify the affected and critical areas. Also, percent movement, propagation... 

Tehran, the capital of Iran, like many megacities in the world is encountered with increasing freshwater demand and water resources limitation because of the rapid growth of population. In spite of the existence of neighboring water recourses; such as Karaj-Dam, Latian-Dam and Lar-Dam, and large usage of groundwater, the management of urban water demand is one of the biggest problems with this city. In this thesis, water reuse and wastewater recycling are considered as a sustainable solution for water supply and wastewater management of Tehran. A linear programming optimization model with the object of cost minimization is used to allocate water between users and resources, concerning the... 

One of the most important matters beside the shortage and requirement of water in big cities is how to dispose of wastewater. Also concerns with the continued use of centralized facilities include the capacity limitation, increased population growth, sustainable use of water, water shortages due to changes in global cycles and homeland security and disaster mitigation. Therefore the use of decentralized and satellite treatment systems is essential for big cities such as Tehran. One important matter pertaining to this issue is site selection of decentralized wastewater treatment plant. Multicriteria decision making is one of the methods that is used for site selection. By multicriteria... 

Detention basins have been used as one of the Best Management Practices (BMPs) for urban flood control during the last decades. In this study, rainfall-runoff modeling in Darakeh Catchment of Tehran for return periods of 50 and 100 years has been performed using Storm Water Management Model (SWMM). This modeling aims to evaluate the present drainage network in dealing with floods and to identify critical sections. Analytic Hierarchy Process (AHP) was used as analytical framework for siting detention basins considering hydrologic, hydraulics, physiographic and economic factors. First, weights for Criteria have been specified and then, site selection of detention basins has been performed.... 

Although surface water networks play a very important role in transporting runoff, they contain significant amounts of pollutants entered through the point or non-point sources which cannot be neglected. The goal of this research is quantitative modeling of Zargande reach located in Maghsoodbeyg-Sadr area using SWMM model and investigating the effect of variation of permeable surface on the volume of runoff. Analysis of a 7 hour precipitation with the total of 5 mm cumulative precipitation resulted in 1.6 mm per hour loss of watershed. We utilized a FORTRAN code which minimizes the difference between the Espey synthetic hydrograph and the observed hydrograph for the precipitation to obtain... 

Lake Urmia is the largest hypersaline lake in Iran, as well as a significant aquatic habitat. In recent decades, extreme increasing of extent plans and exploitation of water resources in this basin, cause decreasing inflow, water level and creating several environmental and economic issues. In recent decades, the excessive expansion in the development and exploitation of this basin's water resources has resulted in a drop in the flows into the lake, a decline in the lake's water level, and the creation of several environmental and economic issues. In recent years, these stressors have caused the lake's salinity to exceed 400 g/L, and salt deposits have emerged on the lake bottom and... 

Due to water resources restriction and increasing water demand, the optimal utilization of water resources in the country is more and more necessary. Optimal utilization of these resources highly require more precise prediction of the river's stream entering the dam with anticipated intervals of one to some months. In recent decades, identification of large-scale signals as predictors of hydrological climate changes has created great expectations and a lot of studies have been done in this area.One of the most important principles of planning and management of water resources in each country from the point of view of hydrological, the rainfall is forecast. In this study,using principal... 

Sustainable management of water resources is an important issue today, because it can play a role in achieving environmental protection and economic prosperity. Lake Urmia is a remarkable ecological system, because it includes a unique habitat with native and migratory species, maintains the temperature balance of the region, prevents the formation of dust in the region and is one of the largest Tourism and recreational destinations and a source of income for many people in the Area. However, over the past two decades, the intensification of agricultural activities, the indiscriminate use of water, and climate fluctuations have put significant pressure on it and have led to a gradual... 

Estimation of runoff in the ungauged basins is a challenge for hydrologists. The main objective of this research is to produce runoff coefficient map using SCS-CN (1972) and Kennessey (1930) as empirical models to for Urmia Lake basin between for 2006-2011.Both SCS-CN and Kennessey methods use slope, land use, and soil permeability data to estimate surface runoff. Accuracy of each model is tested along with the observed runoff using the Root Mean Square Error (RMSE).Urmia Lake basin includes about 400,000 hectares irrigated land, which constitutes around 10 percent of the entire basin area. To exclude the anthropological activities from the estimations, methods were applied only for 28...