Ali Mollaie; Abdol Rasoul Telvari
Volume 1, Issue 2 , July 2009, Pages 70-77
Abstract
The first step for design flood estimation of a watershed is determination of the design rainfall characteristics. One of rainfall characteristics is its distribution over the rainfall duration. This is known as the temporal pattern of the design rainfall. In the present study, the data of four synoptic ...
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The first step for design flood estimation of a watershed is determination of the design rainfall characteristics. One of rainfall characteristics is its distribution over the rainfall duration. This is known as the temporal pattern of the design rainfall. In the present study, the data of four synoptic stations in Kohkiloyeh and Boyerahmad province have been used to determine the temporal pattern of rainfall, using the Pilgrim (ranking) method. Rainfalls of various durations less than 30 hours were classified into 1, 2, 3, 6, 9, 12, 18, and 24 hour durations, and then dimensionless temporal pattern were derived. In ranking method, each event is divided into a number of equal periods. Then, each individual burst is ranked according to the amount of rainfall in that period. The percentages of rain in all periods could be then ranked. The average percentages of rainfall among all recorded rainfall are estimated. The results show that, short duration rainfalls have maximum intensity in the second quarter, while longer duration rainfalls (12, 18, 24 hours) have maximum intensities in the third and fourth quarters. Thus, as rainfall duration increases, the maximum rainfall intensity moves towards the second half of time duration.
Seyed Hamid Reza Sadeghi; Seyedeh Laleh Razavi; Mohammad Mahdavi
Volume 1, Issue 2 , July 2009, Pages 78-86
Abstract
Many different runoff prediction methods are being used among which SCS model has been applied throughout the globe. It is therefore very important to evaluate the circumstances and input specifications under which such models could be applied. The present study was conducted to investigate the role ...
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Many different runoff prediction methods are being used among which SCS model has been applied throughout the globe. It is therefore very important to evaluate the circumstances and input specifications under which such models could be applied. The present study was conducted to investigate the role of rainfall main characteristics on accuracy of SCS model in runoff prediction for Kasilian and Darjazin watersheds. For this purpose, the simultaneous rainfall-runoff data were selected and the storm runoff was estimated using determining rainfall characteristic, providing Curve Number map and calibrating the model. In order to determine the effects of rainfall characteristics on model output, the standardized values of regression coefficient (β) of the best fitted multiple regression, developed between rainfall circumstances and maximum storage index coefficient, were determined. The results of the study showed the depth, maximum rainfall in concentration time, maximum 30 minutes intensity, 2nd quartile and 1st quartile have the highest rate of effectiveness on model output respectively.
Hossein Saadati; Shaban Ali Gholami; Foroud Sharifi
Volume 1, Issue 2 , July 2009, Pages 87-98
Abstract
Lack of hydrometric data is the main issue for research and executive plans. In the present study in order to solve this issue, the capability of SWAT model has been studied in terms of daily discharge simulation in un-gauged watersheds. This model can simulate six hydrological and biological processes ...
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Lack of hydrometric data is the main issue for research and executive plans. In the present study in order to solve this issue, the capability of SWAT model has been studied in terms of daily discharge simulation in un-gauged watersheds. This model can simulate six hydrological and biological processes such as daily discharge, daily sediment, yearly and monthly water balance, water quality, agricultural products and estimation of vegetative cover for different animal grazing management systems. Simulation has been done for both gauged and un-gauged basins in Kasilian catchment for two time periods as calibration and validation of model. Calibration has been done using data derived from 4 years recording data (1987-1981) while validation has been done using 6 years data (1981-1986). Results show that, ABF, CN2 and REVAPC parameters are most sensitive and also Z and T-Laps parameters are low sensitive among other parameters. The model simulated runoff reasonable with r2=0.69, PBIAS=-2.5, and NS=0.72, whereas, the validation of model for the same data showed that r2=0.57, PBIAS=4.3, and NS=-0.54, which indicates that the performance this model is not quite valid for low stream flows because of sensitivity of hydrological parameters. The new version of SWAT model, modified during 2000 to 2005, has a capability in using GIS, thus it can be used in the same study area.
Maral Khodadadi; Mohammad Sadegh Askari; Fereydoon Sarmadian; Hossein Gholi Refahi; Ali Akbar Norouzi; Ahmad Heidari; Hamid Reza Matinfar
Volume 1, Issue 2 , July 2009, Pages 99-110
Abstract
Salinity is the major factors of soil degradation in semi arid and arid regions. The main aim of this study was to evaluate the capability of Landsat ETM+ data for soil Salinity mapping in the selected part of the Qazvin plain, an area of arid environment. In this study spectral classes carried out on ...
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Salinity is the major factors of soil degradation in semi arid and arid regions. The main aim of this study was to evaluate the capability of Landsat ETM+ data for soil Salinity mapping in the selected part of the Qazvin plain, an area of arid environment. In this study spectral classes carried out on remotely sensed data and with the help of field observation and soil analysis were regrouped to soil salinity classes to prepare soil salinity map.. Soil sampling was implemented using stratified random sampling method, depending on landscape complexity and homogeneity as well as on the representativeness of Landsat ETM+ data. Also in each soil map unit at least one profile was studied for subsoil salinity variations. Field samples taken by using augur and profiles were analyzed in laboratory for Na+ , Ca2+ , Mg2+ cations, as well as soil texture, ECe and pH. We have analyzed the effectiveness of additional data such as digital elevation model to improve the accuracy of classification. Also NDVI, SRVI, PVI, SAVI, SI, BI and NDSI indices, PCA and Tasseled cap were analyzed. Soil salinity map of each selected bands produced and with ground truth map crossed. The results indicated that combination of DEM with ETM+ bands has highest accuracy. This study addressed that thermal band of ETM+ can increase the classification accuracy which illustrated its effective role to classify the soil salinity. Tasseled cap and other indices had almost high accuracy among studied image processing techniques. The SI and BI indices had the highest correlation with EC and could distinguish the saline and non saline soils while the optimum index factor had overall low accuracy.
Kourosh Kamali; Mohammad Hossein Mahdian
Volume 1, Issue 2 , July 2009, Pages 111-118
Abstract
Knowledge of the moisture content is important for making decision for seeding, irrigation, soil management and other soil, water and natural resource projects. Conventional methods such as gravimetric or neutronmetry methods for measuring soil moisture are time consuming and sensitive application, respectively. ...
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Knowledge of the moisture content is important for making decision for seeding, irrigation, soil management and other soil, water and natural resource projects. Conventional methods such as gravimetric or neutronmetry methods for measuring soil moisture are time consuming and sensitive application, respectively. The Time Domain Reflectometry is commonly known as TDR, is a new method for determining volumetric water content. The probes of TDR are two types, connector and burial types. Use of connector probe for soil moisture measurement in the coarse sand and in the natural resource lands is disappointed, so use of burial probes are advised. But those are expensive. Therefore those must be manufactured. Manufactory and Calibration of burial probes is the main objectives of this study. After choosing cable testers, BNC port and suitable stainless steel for two parallel metallic rods, the burial probes were manufactured, and then those calibrated. To calibrate manufactured type of probes, measurements were made using the TRACE system (soil moisture equipment corp.) with the conventional rod-type probes (or standard type) and manufactured types of probes in three difference types of soil texture classes, these were sandy loam, loam and silty clay, respectively. The bulk densities for sandy loam, loam and silty clay texture were, 1.66, 1.47, 1.30 gr/cm3, respectively. There was a good linear correlation between the two estimates. The highest relation determination was observed in sandy loam texture in 10 ns capture windows. Calibration equations for sandy loam, loam and silty clay texture were , and , respectively.
Hamid Reza Moradi; Nayereh Ghazanfarpour; Sadat Feiznia
Volume 1, Issue 2 , July 2009, Pages 119-127
Abstract
One of the effective factors in soil erosion is geological formations of the drainage basin from the view points of their erodibility and the amount of runoff and sediment yield. In this investigation a part of Segzi- Kuhpayeh subdrainage, located in Zayandeh-Rood Drainage Basin with 67091.7 ha area ...
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One of the effective factors in soil erosion is geological formations of the drainage basin from the view points of their erodibility and the amount of runoff and sediment yield. In this investigation a part of Segzi- Kuhpayeh subdrainage, located in Zayandeh-Rood Drainage Basin with 67091.7 ha area was chosen for studying erodibility and sediment yield of Quaternary Formations. For doing this, the map of Quaternary Formations was prepared. Then in each unit a field rainfall simulator was used and runoff and sediment were collected from the plots and erodibility and sediment yield factors were obtained. Soil samples were taken adjacent to each micro plot for laboratory tests and the data were analyzed statistically. The results of regression analyses have shown that erodibility and sediment yield are significantly different in various Quaternary Formations. The most important physical and chemical parameters in sediment yield in different formations are Silt, Sand, very Fine Sand, Wetness, Caco3 and in erodibility of different formations are Silt+ very Fine Sand, Caco3, Silt, Clay, very Fine Sand and EC.
Ali Rezaei
Volume 1, Issue 2 , July 2009, Pages 128-139
Abstract
The TDR device is implicating to monitor soil and hydrology of flood spreading stations all over the country. Along this concept, the surveying of errors that caused by long-term installation of sensors, have been realized in Zanjan flood spreading station. For this purpose, six profiles in flood spreading ...
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The TDR device is implicating to monitor soil and hydrology of flood spreading stations all over the country. Along this concept, the surveying of errors that caused by long-term installation of sensors, have been realized in Zanjan flood spreading station. For this purpose, six profiles in flood spreading and two others in non flood spreading area have been dug with 1.5 m depth and totally 36 bury able sensors installed in different layers. The soil moisture was determined along two years with time interval of one week. The results show some interruptions in the data time series that caused by the device’s message of “time measurement failed”. The temporal and spatial analyses of data series, state increasing of missed data from primary to second year because of leaching and from west to east zone for the reason of high volumetric concentration of water in that area. With dividing the data collection period to three nearly 70 days periods at every layer indicated that, the percent of missed data increased twin along with time and declination of moisture. The main source of error is leaching the particles around the electromagnetic guide rods of sensors and adding to the pores and interfacial distance of rods and soil particles.
