IRAN-WATER RESOURCES RESEARCH
Year:2008 | Volume:4 | Issue:1 (10)|Papers Count:8

Estimation of reservoir sedimentation volume is necessary for design and hydraulic structure management purposes where different empirical and mathematical methods are employed in this regard. Due to different factors effecting sedimentation process and their stochastic process, uncertainties arise which cause failure and may force designers to consider safety factors in their designs. Therefore, uncertainty analysis may introduce a better understanding of the effect of different input parameters and their separate contributions to the whole output error. In this research, the sediment discharge rate was estimated by employing different methods such as USBR, average of classes, and the FAO modification coefficient. In these methods data collected from Yalfan hydrometry and Shakhe Dovom SAD stations were used. To calculate the trap efficiency the Brown method, and for specific weight Lane & Koelzer and Miller methods were used. The results of the FAO modification coefficient on average of classes and specific weight of Miller method compared to other corresponding methods show better agreement with the measured ones. In this research, Mont Carlo Simulation and Har's methods were investigated. Calculation of The Mont Carlo method and the uncertainty contribution of each parameter were conducted by a FORTRAN computer program introduced by the author. The results show that the sediment discharge rate and the flow rate introduce the highest contribution to the whole uncertainty of sedimentation volume, respectively. Also, Har's method show less uncertainty value compared to the Mont Carlo method.

Management Information Systems (MIS) are efficient tools for analyzing the structural problems in water resources and environmental systems management. This paper presents a MIS for river water quality data analysis. The MIS includes six modules, namely Data Management, Data Validation, Analytical Hierarchy Process, Water Quality Zoning, Water Quality Simulation, and Non-point Loads Estimation. The management of the data banks, statistical analysis and preparing different reports are the main tasks of the Data Management module. The Data Validation module uses statistical methods such as correlation analyses to verify and validate the input data related to the river water quantity and quality. Ranking pollution sources and determining their shares in river water pollution is done using the Analytical Hierarchy Process (AHP) module. The Water Quality Zoning module classifies the river reaches considering the concentration of different water quality variables. This module uses the fuzzy clustering method. In the proposed MIS, a river water quality simulation model is also used for determining the spatial and temporal variation of the water quality constituents in a river system. Finally, the characteristics of the non-point pollution sources are estimated using the Nonpoint Loads Estimation module. The proposed MIS has been used for water quality data analysis in the Karoon- Dez River system in southwestern part of Iran. The results show that the MIS can effectively support decision-makers in managing water quality in this river system.

Understanding the spatial variation of the flood source area within watersheds as they affect of the flood characteristics at the outlet is an important issue in flood control studies. Determining the flood severity index in a watershed requires study of hydrogeomorphic properties, recorded rainfall-runoff events and use of mathematical models in the context of the methodology to delineate various watersheds areas with respect to the flood downstream. In this paper, Roodzard watershed was selected as the case study since it has suitable rainfall-runoff record. The watershed consists of five tributary subwatershed and three intermediate subwatersheds. ModClark distributed hydrologic model was calibrated in subwatersheds with hydrometric stations. Using HECRAS routing model the whole of the Roodzard watershed model was calibrated at Mashin Hydrometric Station at the outlet. Following the “Unit Flood Response” approach, 2*2 km2 grid squares within the watershed were removed one by one in the simulation process and their effect on the flood peak at the outlet was determined. Such effect was quantified by a flood index and used for preparing the map of “flood severity”. Furthermore, the profile of flood index along the main stream was plotted in grid-scale as well as for each sub-basin.

The main goal of physical hydraulic modelling of plunge pools as energy dissipators at the toe of reservoir dams is the assessment of their performance efficiency. There is a limitation of using non-cohesive material at steep slopes. Accordingly a suitable combination of cohesive and noncohesive materials should be selected to simulate the scouring resistance characteristics in the plunge pool against complicated turbulent flow in a hydraulic model. In this study, the relative ability of rock to resist scouring in the plunge pool of Karoon-III dam on the Karoon River in south eastern Iran was simulated using a physical model. Eighty-six experiments in four series were carried out in a flume with an effective length of 10 meters with different combination of cohesive and non-cohesive materials, with uniform flow in different velocities. The threshold velocity of scouring was subsequently determined for each combination. Cement was eliminated from the test due to its high scour resistance and was replaced by bentonite clay. Experiments were then continued to determine a suitable fraction of clay bentonite in the combination. The erosive power of water was calculated using three methods: measured flow profiles, flow normal depths, and the Standard Step method. The Erodability Indices were determined by the Annandele method for each method. These Indices were used to determine the suitable class of bentonite clay for different parts of the Karoon-III dam plunge pool.

In this paper the H2D shallow water model is developed which employs terms like atmospheric pressure, wind stresses, tidal forces, and boundry friction status. Adding the algorithm of wetting and drying in boundry cells, along with the changing wind and pressure fields, a new model called Surge2D is developed. The numerical 2D model developed in this study estimates the shallow water currents. The landwater interface is treated as a moving boundary in which the flooding and draining rate depend on the both simulated current and the height of water in adjacent ‘wet’ cells. This ensures realistic and smoothly varying results. In this approach for the status of a boundary cell to change from dry to wet or wet to dry, the water level should become greater or less than a specified stage, respectivly. Furthermore the fluid must cross the length of the boundary cell according to the flow velocity in the adjacent cell. The results of this model were compared to both analytical solutions and MIKE21 results. The result of the 2D model indicated an excellent agreement with the analytical solutions (differences less than 0.1%). This model is used to study the effects of Shahid Kalantary causeway on the current pattern and characteristics in Urmia Lake, in north-western Iran.

One way to reduce the effect, of water hammer in hydraulic conduits is to build a proper surge tank. Surge tanks dissipate the mass oscillation and reduce the transmitted pressure into hydraulic conduits. The design of Differential Surge Tanks usually includes the proper determination of diameter of the main tank and the riser, the heights of the main tank and the riser, and the area of orifices such that they guarantee the acceptable hydraulic performance. In this paper, the design of differential surge tanks has been formulated in the form of an optimization problem in which the objective function is to minimize the total cost. Hydraulic conditions that have to be satisfied for a good performance of the system, comprise the constraints of the problem. The optimization problem has been solved using the Barrier method. The outputs are the basic design parameters that make detailed design of surge tank possible. To show the capabilities of the method, the surge tank of Appalachia dam has been designed by the proposed algorithm and compared to similar design of other research.

Measuring of daily maximum and minimum temperatures is the oldest method to estimate mean daily temperature which has been a global standardized method since the ninteen century. Unfortunately this method is not precise. In this research we selected all climatology stations over the Khorasan province and drew a sample of temperature-graphs by a systematic sampling method to establish an accurate method. Mean daily estimates by integration of graphs and measuring daily maximum and minimum temperatures are calculated. Finally we introduce a new model for estimating mean daily temperatures by regression from daily maximum and minimum values.

This research was conducted for recognizing affective watershed physical characteristics on morphometric parameters of bed sediment aggregated during recent floods in Vaz River located in Mazandaran Province, Iran. To achieve the study purposes, 7 cross sections were selected along the river where the bed sediments were sampled using combining technique. Then the morphometric characteristics of bed sediments were determined through applying sieving method and with the help of GRADISTAT software package. The entire data were analyzed by cluster and principle component analyses using SPSS12 software. The affective watershed physical characteristics on bed sediment morphometry were ultimately recognized using collected data and standardized correlation coefficient (β) in better performed multiple regression equations. The results of the study revealed that the area of upstream watershed and distance from upstream were most affective watershed physical characteristics on bed sediment morphometric variables.