Davood Nikkami; Peyman Razmjoo; Farzad Bayat Movahed
Volume 2, Issue 2 , July 2010, Pages 65-72
Abstract
The amount of water erosion is basically related to rainfall erosivity and its consequent runoff. In soil erosion and sediment yield models, intensity and energy of rainfall are mostly considered. In this research, some parameters such as the amount of rainfall, maximum intensity and energy in different ...
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The amount of water erosion is basically related to rainfall erosivity and its consequent runoff. In soil erosion and sediment yield models, intensity and energy of rainfall are mostly considered. In this research, some parameters such as the amount of rainfall, maximum intensity and energy in different basic times are correlated to the amount of runoff and sediment outflow from erosion plots to investigate rainfall erosivity index. For this purpose two years of precipitations of Sohrain-Gharacharian flood spreading research station were monitored by recording raingauge. During 2003-2004 period, two plough treatments of parallel and perpendicular to slope direction on three slope classes of 0-12, 12-20, and 20-40 percent with three replicates and randomized complete block design were studied under regional wheat planting and fallow conditions in 1.8x22 sq. meter erosion plots. The correlation between the amounts of runoff and sediment, as dependent variables, resulted from 12 rainfall events and the amounts of rainfall, maximum 1, 5, 15, 30, 60 and 120 minutes of rainfall intensity, rainfall energy and rainfall erosion index, as independent variables, computed by different methods were analyzed with the SPSS V11. Two variables of the amount of rainfall and the maximum rainfall intensity in different base times had the maximum correlation with the amount of runoff and sediment at the levels of 99 to 95 percent.
Majid Soufi; Hossein Esaei
Volume 2, Issue 2 , July 2010, Pages 73-82
Abstract
Gully erosion is more important than both rain splash and sheet erosions due to both higher sediment productions. Estimation of the volume of gully erosion requires some indices that could be measured easily in the field. This research aims to present simple models to estimate the volume of gully erosion ...
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Gully erosion is more important than both rain splash and sheet erosions due to both higher sediment productions. Estimation of the volume of gully erosion requires some indices that could be measured easily in the field. This research aims to present simple models to estimate the volume of gully erosion with minimum cost. After determining influenced regions, using anecdotal, historical and field surveying, two regions in each modified Dumartin climate zone and region, three representative gullies were selected. Then, morphometric and edaphic characteristics such as length, depth, top and bottom width, clay, silt, sand, Ca, Na and Mg percentages of the gullies were measured both in their heads and cross sections in 25, 50 and 75% of their length from the headcut. The volume of gully erosion was calculated by the sum of partial volumes in each gully. The results revealed that gullies were initiated and developed in two arid and semi-arid climates on the loess sediment with little cohesion. Gully widening is higher than deepening and silt has an important role in it. Statistical analysis indicated that linear relationship with R2 of 0.86 is more suitable than power relationship with R2 of 0.54 for estimation of the volume of gully erosion. Results indicated that the volume of the gullies had a significant linear relationship with gully length, depth and top width in 0.01 level. Results also, revealed that gully length with 86% interpretation of changes in gullies volume and had the most impact among the variables. These results prove that suggested comments in literature using gully length to sediment yield estimation in EGEM is applicable in the northeast of Iran.
Raouf Mostafazadeh; Amir Sadoddin; Abdolreza Bahremand; Vahedbordi Sheikh; Habib Nazarnejad
Volume 2, Issue 2 , July 2010, Pages 83-93
Abstract
Assessment of flood control projects in the same conditions is essential in order to improve decision making that assist us in watershed management purposes. Focus of this study is on assessing hydrological effects of the Jafar-Abad watershed management project. The study area (109 km2) located in north ...
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Assessment of flood control projects in the same conditions is essential in order to improve decision making that assist us in watershed management purposes. Focus of this study is on assessing hydrological effects of the Jafar-Abad watershed management project. The study area (109 km2) located in north of Iran in the Golestan province. Paired t-tests were performed for Indicators of Hydrologic Alteration (IHA) in Taghi-Abad gauging station, located in the outlet of the catchment, before and after construction of 58 check dams. HEC-HMS model was calibrated using 12 storm events and validated for study area. Calibrated HEC-HMS model was applied to rainfall-runoff modeling in sub-catchments and Level-pool method used for reservoir elements. Design flood hydrographs for 2-100 year return periods were simulated for both before and after check dams construction periods. The results of statistical analysis indicate that existing flood control measures had no significant impact on the hydrologic characteristics measured by IHA in 95% confidence level. The results indicated that constructed structures do not have important effect on IHAs and the amount of these effects was less than 1.5 percent in all cases. Also, by increasing in return period, the effects of structures on peak discharge and flood volume were reduced.
Abbas Pourmeydani; Abolfazl Khalilpour; Hossein Tavakoli Neku; Mohammad Hassan Marefat
Volume 2, Issue 2 , July 2010, Pages 95-101
Abstract
One of the important problems is erosion and soil degradation in watershed areas. Polymer usage is a way for both erosion control and soil and water conservation. In this research the effects of the BT53 polymer application for moisture storage in soil, reduction of runoff and erosion and prevention ...
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One of the important problems is erosion and soil degradation in watershed areas. Polymer usage is a way for both erosion control and soil and water conservation. In this research the effects of the BT53 polymer application for moisture storage in soil, reduction of runoff and erosion and prevention of loss soil are studied for 1998-2001. The research plan was CRBD and factorial method. First factor included polymer levels of 0, 2 and 4 gr/m2. Second factor included Secale montanum species planted and not-planted. After every rainfall event both runoff volume and sediment amount were measured. Analysis of variance showed there was significant difference between polymer levels and sediments amount (P<0.01). Compression of averages by Duncan's method in first factor showed all polymer levels fall in one group from runoff volume point of view, and in three groups based on sediment amounts. The most effect of polymer usage was on sediment amounts reduction rather than runoff. This means that polymer BT53 is suitable more for soil protection besides runoff reduction. Polymer level 1 had most amounts and polymer level 2 had least amounts of sediment. So application of polymer BT53 in level 2 (4 gr/m2) was suggested for sediment control. Polymer level 2 with non-planted treatment had least effects on runoff volume and sediment amounts among six treatments of polymer levels and planted or non-planted.
Seyedeh Maryam Alibakhshi; Mohammad Mahdavi; Shahram Khalighi Sikaroudi
Volume 2, Issue 2 , July 2010, Pages 102-110
Abstract
Approximation of precipitation and design of a rain-gauge system with minimum initial cost and robustness against measurement uncertainties requires finding the relationship between various stations equipped with udometers .On the other hand, in areas where the issues of erosion and sediment exist, it ...
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Approximation of precipitation and design of a rain-gauge system with minimum initial cost and robustness against measurement uncertainties requires finding the relationship between various stations equipped with udometers .On the other hand, in areas where the issues of erosion and sediment exist, it seems necessary to know the amount of rainfall. Among the possible solutions, increasing the number of rain gauges can be adopted which is expensive. In the present study, rainfall data of 16 base stations by Ministry of Power recording precipitation data of Tehran Province on a common date (1622 rainfalls) were extracted. In each measurement, a station was chosen as base, the rainfalls of other stations were ignored, so the rainfall of each of them were reconstructed according to base stations, which were finally compared with observed rainfalls. Then, the curve of reconstructed and observed rainfalls was transformed into a dimensionless form, and rainfall percentage in the three quarterlies and the surface under each curve were calculated. Eventually by figuring out the error percentage of them, the frequency of error percentage in anticipating the rainfall amount and the three quarterlies for both curves were calculated. In order to determine the ratio of sensitivity of the model, distance index with statistical estimation of percentage of variation coefficient was used. Results demonstrated that there is no elevation effect within the 900 to 1800 m from sea level, but, there is a jump in the amount of error that this situation reduces gradually up to 2000 m height.
Seyed Hamid Reza Sadeghi; Bahar Salavati; Abdolrasoul Telvari
Volume 2, Issue 2 , July 2010, Pages 111-115
Abstract
Population ever increasing and consequent demands in recent decade have encouraged farmers to utilize unsuitable and marginal lands such as forests and ranges for agricultural purposes. However, these lands have high soil erosion potential and low productivity and their proper management is therefore ...
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Population ever increasing and consequent demands in recent decade have encouraged farmers to utilize unsuitable and marginal lands such as forests and ranges for agricultural purposes. However, these lands have high soil erosion potential and low productivity and their proper management is therefore a vital task. In the present study, the land use areas have been evaluated in Garan watershed in Kordistan Province, Iran, from 1995 to 2002 by using three digitized images and corresponding changes have been then assessed. The effects of land use changes on changing annual runoff were ultimately evaluated with the help of moving average and hydrological regime analyses. The results of the study revealed that the variation in water discharge thoroughly followed the annual rainfall oscillation which itself affected land allocation to different land uses.
Mohammad Shabani
Volume 2, Issue 2 , July 2010, Pages 116-122
Abstract
Increasing and preserving water quality requires sufficient data of the location, value as well as spatial distribution of the chemical factors. Preparation of the updated maps of groundwater salinity variation and salt concentration is an important step for appropriate management and its exploitation. ...
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Increasing and preserving water quality requires sufficient data of the location, value as well as spatial distribution of the chemical factors. Preparation of the updated maps of groundwater salinity variation and salt concentration is an important step for appropriate management and its exploitation. Selection an accurate method for zonation and mapping groundwater quality parameters variation depends on regional condition and availability of data which is an important stage for groundwater management. The purpose of this research is evaluation of geostatistical techniques accuracy for determination of EC, NO3, pH and TDS of groundwater and mapping them using geographic information systems in Arsanjan plain, northwest of Fars province. For this aim, different techniques of geostatistics including Ordinary Kriging (OK) and Simple Kriging (SK) as well as deterministic techniques such as Inverse Distance Weights (IDW), Radial Basis Function (RBF), local polynomial interpolation (LPI) and Global Polynomial Interpolation(GPI) were used. The result based on lowest root mean squared error (RMSe) and Mean Absolute Error (MAE) showed that Simple Kriging (SK) technique is the most appropriate technique for salinity (EC) mapping (RMSe=724.8 and MAE=513.41) and TDS mapping (RMSe=463.9 and MAE=328.58) among all techniques in the study area. Also the results revealed that OK with RMSe=0.197 and MAE=0.139 for pH parameter and RMSe=7.92 and MAE=6.29 for nitrate parameter has the highest priority among other techniques and is selected for pH and nitrate variation mapping. Finally, the results of this research indicated that Geostatistical techniques have higher priority than deterministic techniques and thus are selected as suitable methods in Arsanjan plain.
