نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Modified IUDRN as a Tool for Annual Streamflow Stochastic Simulation (Case Study: Arieh River- Khorassan)
1
8
FA
farhad
daliri
MAHAB GHODSS Con.Eng
majid
kholghi
University of Tehran
In this study, the Independent Uniformly Distributed Random Numbers (IUDRN) method as a hydrologicsynthetic data generation technique has been modified to simulate the streamflow in annual time scale.A hybrid approach based on hydrological conditions-random number combination has been developed andproposed. The three hydrologic conditions as wet, normal and dry conditions have been defined in onethird of each of random number that varies from 0 to 1. The annual mean values of 52 years discharge ofArieh River situated in North of Neyshaboor in Khorassan province of Iran has been applied for validationof proposed approach. The comparison between the results of two methods (IUDRN and proposed method)shows that the error estimation has been reduced from 25% to 17%. This result indicates that new approach(MIUDRN) can be applied to simulate the streamflow data with a high efficiency.
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Simulation of Direct Run-off Hydrograph Using Nash's Linear Reservoir Model in Jafar-Abad Watershed, Golestan Province
9
16
FA
raouf
Mostafazadeh
Gorgan University of Agricultural Sciences and Natural Resources
abdol reza
Bahremand
Gorgan University of Agricultural Sciences and Natural Resources
Estimation of runoff hydrograph from ungauged catchments has been an important subject of research forplanning, development and operation of different water resources projects. In this study, Nash's linearreservoir model was applied to predict direct runoff hydrograph characteristics in Jafar-Abad watershed(109 km2) located in Golestan province. Using hourly hydro-meteorological data, the Nash model parameters(n and k) calculated by Moment method for 33 storm events. Then the mean value of n and k, wereused for simulation of second subset of storm events as model validation. The efficiency of Nash modelwas evaluated by statistical comparison with the observed hydrographs. The results indicated that themodel predicts direct runoff hydrographs with good accuracy, 70 % according to the Nash-Sutcliffe criterion.Also mean relative error of peak discharge, relative error of time to peak, model bias for water balanceand RMSE are 10 %, 10 %, 25% and 3.94, respectively. The good agreement between observed andsimulated hydrographs shows that n and k were calculated reasonably by Moment method. Results showthat the Moment method in estimation of n and k parameters gives good results. So that regionalization ofNash's model parameters (n and k), in ungauged catchments is suggested for development and applicationof this hydrological model.
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Comparison of Interpolation Methods in Study of Bed Topography on Channels Bend
17
26
FA
mohammad
Vaghefi
Persian Gulf University-Bushehr, Iran
ali
Ahmadabadi
Tarbiat Modares University, Iran.
amanollah
Fathnia
Tarbiat Modares University, Iran.
masoud
Ghodsian
Tarbiat Modares University, Iran.
The study of changes of sediment beds is of the issues which has attracted River engineers. Attention toinvestigate the rate of scour and sedimentation is significant in bend of rivers rather than straight rivers.The change of bed topography, scour and sedimentation pattern have caught the attention of hydraulicengineering profession. This paper examines the topography changes using experimental data in 90 degreebend and bend with T shape spur dike in outer bank. For this purpose interpolate methods such as IDW,KRIGING and SPLINE Tension used to convert point measurement to continuous surfaces. Accuracyassessment accomplished by validation method. The result showed that KRIGING methods have bestaccuracy to create surfaces for studying bed topography in Bend Rivers.
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Experimental Investigation on the Effects of Horizontal Footing on Topography of Bed in 90o Bend
27
38
FA
Ali Reza
Rezania
Shahid Chamran University, Ahwaz, Iran
mahmood
Shafai-Bejestan
Shahid Chamran University, Ahwaz, Iran
said mahmood
Kashefipour
Shahid Chamran University, Ahwaz, Iran
The outer banks in river bends are subject to sever bank erosion due to secondary flows. Therefore, itis essential to have some measurements for protection. The protection must be based on maximum scourhole. Any measurements to reduce the scour hole would be beneficial for protection. In this paper the effectof horizontal footing on reduction of scour hole has been investigated. To reach such goals, an experimentwith a 90 degree flume was carried out and series of horizontal footing were installed at outer bank in fourdifferent elevations of 0, 20, 40 and 60 percent of maximum scour depth.By comparison of the bed topography with and without footing a maximum scour reduction of morethan 44.5% was obtained with footing installed at elevation of 40% of the maximum scour depth. Theresults of this study reveal that the point of maximum scour hole has been displaced from the outer bankto the center of the flume.
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Flushing Sediment Removal Optimization Using Reservoir Operation Model: Sefid-Rud Case Study
39
48
FA
said said
Ashraf Vaghefi
University of Amir Kabir, Tehran, Iran
banafshe
Zahrai
University of Tehran
bahram
Malek Mohammadi
University of Tehran
mohammad ali
Bani Hashemi
University of Tehran
Operation optimization of the reservoirs has been mostly carried out based on general objectives, includingwater demand supplies, power generation, flood management, and environmental constraints. In mostof the previously developed models, sediment removal from reservoirs has not been included. Flushing isone of the most important and common ways of retrieving the lost volume of reservoirs due to sedimentation.Despite its adverse effects on the environment of downstream rivers, this method has received lots ofattention by engineers and researchers in the past. One of the main drawbacks of the previous studies inthe field of reservoir operation optimization has been lack of modeling tools for considering the relationbetween sediment removal and other objectives of reservoir operation. In this paper, a new approach hasbeen developed for monthly reservoir operation optimization. For this purpose, a model has been formulatedto minimize the total deficit in supplying demands and to maximize the total volume of sedimentremoved from the reservoir. The objective function for sediment outflow has been developed using theflushing method. The optimization model has been formulated using Varying chromosome Length GeneticAlgorithm (VLGA). The efficiency of the model has been tested in the case study of Sefidrud Reservoir inNorth of Iran. The results of the optimization model for a 5-year period have been compared with the historicalrecords of the operation of the reservoir. The results of the case study have been summarized in theform of practical operating rules for flushing and operation management
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Erosion and Sedimentation Pattern at the Spur Dikes Endings on the Floodplains
49
58
FA
babak
Aminnejad
Islamic Azad University, Iran
mojtaba
Saneie
Conservation and Watershed Management Research Center, Tehran, Iran
said reza
Sabbagh Yazdi
K.N. Toosi University of Technology,
naser
Talebbeydokhti
Shiraz university
Soil erosion and its associated impacts, is one of the most important of today's environmental problemsbecause, agricultural land is seriously degraded. Erosion is the removal of solids in the natural environment.Water is the most important erosion agent and erodes most commonly as running water in streamsand rivers. Also when flow speed in rivers is halted, the river deposits its sediments and may cause someproblems. In rivers with flood plain, the erosion happens when the flow contact strongly to bank of river.To prevent these, spur dikes have been widely used to protect eroding stream banks and causing sedimentationto change the flow direction away from river banks to the river center. However, much is yet to beresearched about the influence and effects of spur dikes during large amount of flow (floods). For thesereasons some experimental tests are designed to predict the behavior and influence of length and shape ofspur dikes. In this paper the result of scour at spur dikes ending, which are installed in floodplain in a seriesas single side of flood plain with the length of 10 and 20 centimeters of spur dikes. The scour and sedimentationpattern and also maximum scouring at the end of spur dikes are measured and the experimentalresults are analyzed and discussed.
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
The Effects of Different Grazing Intensities on Nitrogen, Phosphorus, Potassium and Organic Matter in Step Rangelands
59
65
FA
asghar
Kohandel
Jihad University of Tehran
hossein
arzani
University of Tehran
morteza
Tavassol
Jihad University of Tehran
The present study has analyzed the effects of different grazing intensities on soil chemical propertiesincluding nitrogen, phosphorus, potassium and organic matter content in different conditions of referencearea, key and critical areas located in Savojbolagh, Iran during 2004-2005. Data produced based on randomizedcomplete block design plot. In this case, study area, time and depth of sampling were appropriatedfor main plots and sub-plots, respectively. Statistical analysis was done using SPSS version 12. If significantdifferences were found between treatments then Duncan test was used for comparison of means.According to the results, there were significant differences between NPK rates during two years. The rateof organic matter, nitrogen and phosphorus was increased in second year and the amount of potassium wasdecreased. Animal grazing significantly affected soil chemical characteristics in all areas (reference, keyand critical). There were significant differences between content of nitrogen, phosphorus, and potassiumin two years, during the grazing season and between the two depths.
نشر دانشگاهی
Iranian Journal of Watershed Management Science and Engineering
2008-9554
3
6
2009
4
1
Regionalization of Rainfall Temporal Pattern in Iran
66
68
FA
abozar
Hatami Yazd
Ferdowsi University of Mashhad, Iran
bijan
Ghahraman
Ferdowsi University of Mashhad, Iran
said reza
Khodashenas
Ferdowsi University of Mashhad, Iran
Rainfall temporal pattern has a marked influence on design of dams, urban water harvesting, culverts,drainage design, flood potential and soil erosion. In this research we used data of 146 autographic rainfallstations of Iran to implement the rainfall temporal pattern. Rainfall depth were calculated for each timeinterval from rainfall charts and were categorized to four quarters. The ranking method was used to arriveat rainfall temporal patterns corresponding to time intervals of 1,3,9 and 12 hours. After normalizing therainfall mass curves, every quarter of rainfall was ranked, number 1 for the highest. The final pattern wasderived by averaging the quarter ranks and percentage of rainfalls corresponding to each duration.Adopting Ward method, 5, 9, 9, and 8 homogeneous regions were detected for short (<3 hr), medium (3-6hr), and long (6-12, and >12 hr) rainfall time period, respectively. Design rainfall temporal pattern wasderived for every homogenous zone. There is a danger for mis-used temporal pattern by type patterns.