مجله مهندسی و مدیریت آبخیز
سال دهم شماره 1 (بهار 1397)

Soil and water are the most valuable national resources. Unfortunately in recent decade, due to land use change and vegetation cover degradation, most of the rainfall changed into runoff and in addition to loss of this vital resource, causes abundant loss of life and property by creating enormous floods. The aim of this study is to assess the effect of land use change from range land to agriculture with different percent of vegetation cover on runoff and soil erosion. For this purpose, three types of land use included preserved range land with 100 percent of vegetation cover; range land with 50 percent of vegetation cover and agricultural land (range land changed to agriculture) were identified in the study area. Then, in each land use, three slopes were determined (10, 15 and 24%). This study was carried out split plot experiment based on completely randomized design. In each land use and slope, runoff and erosion were measured in plots randomly using rainfall simulator with 1.5 mm.min-1 intensity and 15 min duration with 3 replicates. Results showed that the maximum of runoff, sediment mass and sediment density were in the range land changed to agriculture with 24% slope and the minimum of them were in the preserved range land with 10% slope. Also the results showed that the change of range lands to agricultures increase runoff 5 times. In the other hand, with increasing slope from 10 percent to 24 percent, runoff increased 1.7 times. Runoff coefficient was determined for 3 land uses and 3 slopes level. The maximum and minimum runoff coefficient were found 0.72 and 0.06 for the range land changed to agriculture with 24% slope and preserved range land with 10% slope, respectively.

Land use and its fluctuations is one of the most important factors that affects on the natural cycle in the ecosystem. Land use changes cause change in watershed hydrological cycles, water balance between precipitation, evaporation, infiltration and runoff response. Understanding the relationship between land use changes and its factors and secondary effects on the hydrological regime provides the necessary information for planning of land use and sustainable management of natural resources. At first, land use maps related to years of 2000 and 2014 were prepared, then CLUE-s model was applied to simulate land use map of 2025. For simulating runoff, WetSpa model was employed to simulate daily runoff with land use maps related to years of 2000, 2014 and 2025. According to the results, the Nash-Sutcliffe evaluation criterion was calculated 68.26 % and 66.75 % for the calibration and validation periods, respectively. In addition, model Aggregate Measure (AM) was calculated 64 % and 54.15 % for the calibration and validation periods, respectively. Land use maps comparison showed, the main land use changes in Nojian Watershed was the conversion of forest and rangeland areas to agricultural lands .As a result of these changes the annual runoff volume, peak discharge, mean daily discharge increased to 16.20, 11.35 and 9.15 percent, respectively. Results of statistical analysis using paired t-test showed that land use change has effect on discharges in the study area at the level of 1%.

Sediment entering lateral intakes depend on flow pattern in intake entrance. Using a structure in front of the intake entrance can change this pattern and as a result the entering sediment. One of the effective methods to change pattern and manage sediment entering lateral intake is using skimming wall. By removing sediments from intake entrance, the skimming wall reduces the volume of sediments entering the intake. To direct the flow towards intake and increase skimming wall efficiency, a spur dike is used on the opposite side of the intake. The length and angle of the spur dike were 0.25B and 60° and was located at distances 2b from intake center. In this study, the effect of skimming walls angle with the bank, a combination of spur dike and skimming walls and discharge changes on controlling sediments entering the intake, intake ratio and bed topography were investigated experimentally. The effect of the skimming walls with three angles (β1=10, 14, and 18 degrees) and a combination of skimming walls and spur dike on opposite sides of the intake was investigated. Conducting dimensional analysis, non-dimensional ratios were extracted and test variables were specified. Results showed that in the case of having a skimming wall combined with spur dike, the amount of sediment entering the intake has decreased to 81%, 78.5% and 76% on average in walls with an angle of 10, 14 and 18 degrees respectively. The combination of using skimming wall and spur dike has a superior effect on reducing enterance sediments to intake than employing skimming wall alone, namely about 15% for three angles.

Watershed resident's benefit increasing and soil erosion controlling are the main goals of agricultural sustainable development. Landuse optimization operation is an effective solution in order to maximizing the benefits, as well as minimizing soil erosion damages. Current research was executed in southern parts of Ahar Chaey Watershed in East Azerbijan Province. In this research, Multi-Objective linear programing based on Simplex method applied for optimizing landuse in form of three different scenarios: current landuses, implementation of management into current landuses and performance of the standard landuses by WinQSB software. Results showed that due to landuse optimization, irrigated orchards could be increased from 1.736 to 6.629 km2. In addition, based on suitable soils and adequate rainfalls, it is expected to expand the rainfed orchards up to 9.72 km2. Also, the weighted average of soil erosion reduces from 16.3 to 14.8 and from 10.11 to 9.5 tha-1year-1 within the first and second scenarios, respectively. This rate will reduce up to 6.8 tha-1year-1 in the standard landuse situation. On the other hand, maximizing results showed that the annual net benefits increases from 6.6 to 12.9 and 8.46 to 14 million Rails per unit area in the first and second scenarios, respectively. This rate increases up to 15.67 million Rails per unit area for standard landuse situation. Sensitivity analysis results showed that irrigated and rainfed orchards are of high sensitivity in maximizing profit functions due to high profitability of these landuse in unit area. In contrast, the rangelands, forests and drylands are of high sensitivity in soil erosion minimization, so that with increasing their area, soil erosion will increase significantly in the region.

Study of effective factors on runoff quantity to achieve optimum measures for runoff controlling is an essential subject in watershed management. This study aimed to investigate the effects of land use type and land slope degree on runoff quantity using an artificial rainfall simulator in Kakasharaf watershed from branches karkhe watershed (Lorestan Province). Based on the land use map, at 6 work units (sub basins), three land use types of pasture, forest and agriculture; and three land slope degrees of 10, 20 and 30 percent was chosen. In total 93 tests were run using an artificial rainfall simulator and the runoff quantities were collected and measured. Artificial rainfall simulator was a plexiglass non-pressure rainfall simulator with a plot size of 83.5 × 119 cm2 and height 160 cm. Statistical analysis was done using SAS software. Results showed that the average, minimum and maximum runoff quantity were 1499, 0, and 9100 cm3, respectively. Analysis of variance showed a significant difference (p

The flood water spreading is one of the suitable ways for the control and efficient use of flood water in arid and semiarid regions. By this way, the flood sediments are reused and soil fertility increased. The floodwater spreading is an suitable way to exploit deposits of nutrient-rich water that have some important uses include more fertile soil with nutrients supply. Floodwater spreading in the aquifer and sedimentation in surface soil cause large changes in soil characteristics on the surface and at the depth. This research is about Tigh Syah, Hashtbandi floodwater spreading network located in the 165 km in the South-east of Bandar Abbas on a shallow alluvial apron. In this plain, floodwater spreading plan began in 2005 with an area of 165 hectares. The purpose of this research was to study the changes in some features of the topsoil affected by floodwater and to compare its results with the control area. In this study three floodwater spreading network were implemented and in any network soil was sampled from 0-30 cm top soil and from three sections of upstream, middle and downstream of a control area. The study area was located in Tigh Syah in Hashtbandi, Hormozgan Province. For measuring changes on soil properties, 20 samples were selected from inside and outside of the station. The results were analyzed in a completely randomized design. Results of t test, showed that the average percentage of clay, silt, soil saturation moisture, organic carbon and electrical conductivity, total N, phosphorus and potassium were increased at the level of %1 (P≤ 0.01). Results also indicated that electrical conductivity and sand and pH were decreased (P≤ 0.01) in flood spreading area compared to control site. The results of this research indicates that in general, soil condition improves by floodwater spreading as a positive operation.

Estimating the runoff coefficient that is influenced by morphometric, geologic and hydro-climatologically factors are the most important issues in hydrology and information of its role in the planning and management of water resources is more important. Clustering catchments is the best method for the analysis of hydrological parameters in the absence of full coverage of hydrological data. In this research, twenty two hydrometric stations with common period from 1974 to 1999 were selected. Physiographic parameters of the catchments were extracted. Runoff coefficient was calculated and then base flow was extracted from using one parameter recursive digital filters. Lithological units using digital geological map, with the scale of 1: 250,000, based on expert opinion divided on two classes and area covered by each unit in each catchment were calculated. Factor analysis using 15 parameters were conducted. Catchments using independent factors in different hierarchy methods includes: nearest neighbor, furthest neighbor, median clustering, centroid clustering and Ward method were classified. Then, the regional equations using linear regression at 1% significant level were determined. To compare and evaluate the accuracy and efficiency of the models, independence errors, colinerity and normal distribution of error were tested. The results of factor analysis showed that all variables are to be classified in terms of five factors which 85.9% of the variance was included. Results of homogeneity showed that the basins in homogeneous methods of nearest neighbor, furthest neighbor, centroid clustering and median clustering, were all the same and classified in two groups with the similar components. The results of accuracy assessment showed that the accuracy of nearest neighbor methods was more accurate, and because of low relative error (25.4%) and MAE of 7.85 and RMSE of 9.62 was diagnosed as the best method for regional analyzing of runoff coefficient in the study area.

Wind erosion has high potential for damage, especially in arid region due to continuity and extent of erosion in time and space. Therefore, the damage to economic resources is impressive especially soil and vegetation. So, a comprehensive understanding of its formation, function, effects and affected areas is essential. This study was implemented for finding the source of wind erosion and sand movement direction in Khezrabad region, Yazd Province. In this study, Yazd synoptic station anemometer data was analyzed over a period of 15 years (2001-2015) using Sand Rose Graph 3.0, WD convert and Wrplot View. The results of the spatial analysis of data from the anemometer (wind rose) showed that the dominant wind direction of Khezrabad Plain is Western with 18.77 percentage of calm wind with speed less than a knots (0.54 meters per second). The results of the calculation and drawing Storm Rose provided based on wind erosion threshold velocity of 6.5 meters per second showed that erosive winds mainly blow from the West-North West (WNW) and North West (NW) and West winds (W) less frequency. According to Storm Rose drawn, the frequency of calm winds (less than 6.5 m/s) in the region is about 96%. This indicates that erosive wind include only about 4 percent of views. Storm Rose provided based on speed threshold showed that North-West (NW), South-West (SW) winds have the most Drift Potential (DP) respectively. The Resultant Drift Direction (RDD) is around 74 degree (Northeast).

One of the important reasons of soil erosion and sediment production in irrigation and drainage canal networks is the soil instability. Erosion mechanism in this type of channel starts with the impact of raindrops and soil aggregation, so that broken fine particles lead to blockage the pores. In this condition, soil permeability is reduced compared to the initial state and runoff that is increasing. Increased runoff on slopes of moderate to steep, rises shear stress sharply which causes soil destruction and produces sediment production. To overcome this problem, suitable vegetation cover deployment is appropriate, but in some situations, vegetation cover establishment is not possible simply due to special circumstances and it is not the best solution in the short term as well. One of the ways of controlling erosion on slopes is the use of various mechanical structures, commonly used in engineering projects, that is associated with expensive costs. Another solution that was tested in this research, is the use of natural corrective materials such as organic mulch and natural rectifier materials. In this study, by using four types of various organic mulch, soil erosion resistance of various parameters of the drain canal bank was studied using simulated rainfall in the rainfall laboratory of Soil Conservation and Watershed Management Research Institute. In this article, the results of using bio mulch for erosion control, on the drainage channel bank are provided. This study aimed to determine the most appropriate type and density of different mulch on canal bank erosion reduction for irrigation and drainage network channel project that is located in Arayez plain of Khuzestan. With the use of four organic mulch, at least 40 experiments on soil samples were done. For the all laboratory tests, 25 kg soil samples were pressed inside the steel basins, to imply the bulk density of soil in nature. Treatments in the flume with a slope of 1 to 1.25, similar side slope drains, in both 30 and 80 mm per hour rainfall intensity were simulated. Each treatment was applied at three densities. The results showed that all mulch treatments compared with control samples had a significant effect on sediment and it confirmed that the bio mulch are effective in the erosion control of the bank drainage channel. The results showed that the mulch will lead to reduce sediment more than 90 percent. Therefore, the use of mulch 1 and 4 in the highest density, have the greatest impact on the rate of erosion. It was also found that by increasing density of mulch, the amount of sediment reduced significantly.

This research aims to study temporal and spatial variations of groundwater quality of Marvast Plain to manage these recourses. For this purpose, total anion and cation, a percentage of sodium, Ca, Cl, EC, HCO3, K, Mg, Na, pH, SRA, So4, TH parameters were prepared and a statistical period of 14 years (1377_1390) was selected using the evaluation of incomplete data. Semivariograms and cross semivariograms were potted to perform geostatistcal methods and the best model was selected with regard to more R2, less RSS and a strong spatial structure, and an exponential model was fitted for most parameters. Then, interpolation methods, such as Radial Basis Function (RBF), Inverse Distance Weighting with powers of 1 and 2 (IDW), Kriging and coKriging were used. The most accurate method was selected for parameters using cross validation method and error estimation indexes such as Mean Absolute Error (MAE), Mean Bias Error (MBE) and Root Mean Square Error (RMSE). The results showed that coKriging is the best method for estimating most parameters (total anion and cation, EC, Cl, Ca, K, Mg, Na, TH). Kriging is defined as the most suitable method for estimating SRA, So4 and pH, and RBF and IDW with power 1 are the most fitted methods for a percentage of Sodium and HCO3, respectively. The results showed that the density of most parameters increases from west to east and south to north of the study area. Also, decreasing underground water quality is observed over the time.