WATERSHED ENGINEERING AND MANAGEMENT
Year:2016 | Volume:8 | Issue:3 |Papers Count:10

Crop pattern has significant effect on optimum use of water resources and agricultural management. Present research accomplished to achieve optimum crop pattern in Aharchai Basin located in the downstream of Sattarkhan Dam. The study area is about 3000 ha using traditional irrigation method, wherein low irrigation efficiency and water shortage are the most important problems. In order to determine optimum crop pattern and to provide a suitable way to increase agricultural benefit and productivity, a linear programming model in both cases of the current and improved irrigation system conditions was simulated in the Mathematica software. After simulation, in order to maximize benefits, the area of each product was determined through two different simulation states. Results showed that if agricultural lands employ modern irrigation methods, the benefit of agricultural activities would increase by 30%, i. e. it would rise from 98 to 128 billion Riyals in a year.

Gully erosion is a type of water erosion that causes significant sedimentation in watersheds and damages in agricultural lands, rangelands, and infrastructures. This study was conducted to determine the potential of gully erosion by artificial neural network. The Levenberg-Marquardt (LM) algorithm and Multi-Layer Perceptron were used employing soil, geology, land use, distance to fault, slope, aspect, distance from roads, distance from drainage, and elevation data as its variables. Results showed that the structure of 1-13-9 with sigmoid activation function in the hidden layer is more suitable for gully erosion potential assessment. Zonation of gully erosion revealed that the watershed area was divided into different classes of different extent, including 70. 26% in very low, 1. 71% in low, 2. 45% in medium, 2. 65% in high, and 22. 93% in very high potential class. Furthermore, results indicated that slope less than 10%, 50 m distance from the stream, rangeland area, and lithological units of EM and M2 had the greatest impact on the occurrence of gully erosion.

The main objective of water spreading projects is recharging aquifers. In this study, changes of soil surface permeability in Yazd water spreading projects, including Sirizi in Bafgh, Herat and Miankouh in Mehriz were investigated. Using a double ring, 12 Permeability tests (in first and fourth strips and three tests for each strip) were performed. Using measured data the performance of permeability equations such as Kostiakov, Kostiakov-Lewis, Horton, SCS, and Philip were compared in estimating cumulative infiltration and infiltration rate in the study areas. Results showed that average permeability for Bafgh, Herat and Mehriz water spreading projects were about 1. 06, 1. 52 and 2. 94 cmhr-1, respectively. The best equation for estimating cumulative infiltration in Bafgh was the Horton equation with RMSE and Nash Sutcliffe coefficients of 0. 097 and 0. 992, respectively, while in Herat and Mehriz the best equation was the Kostiakov-Lewis equation with Nash-Sutcliffe coefficient and RMSE of 0. 385, 0. 994, 0. 081 and 0. 991 respectively.

Process erosion is one of the most important degradation process, particularly in semi-arid climate. Identify the sediment of the issues is important for watershed managers and planners. The main purpose of evaluating and comparing the potential contribution of this research has been deposition of marl formations. This study was conducted in hablerood basin and in the northern city of garmsar. for this reason, constructive map lithological was prepared as a unit in geographic information systems. then, the potential value erosion on sediment collected simulators rain comforts' with intensity4mm and continuing 10 minutes in the category marl and none marl has been determined. the results showed that in hablerood basins contribution marl and none marl land respectively59. 4 and 40. 6 percent. While in terms of lands area. marl and none marl land respectively 21. 4 and78. 6 percent. particularly sedimentation marl lands was 2. 38 ton in hectares, that twice none marl land. this study showed that the use of simulators rain in order to determine the contribution of sediment formations suitable method for watershed planners, to estimate the erosion rate is correct.

Social and economical evaluation of watershed management activities, is an important criterion for its validation. The main objective of present study was, identification and analysis of socio-economic impacts of watershed management operations implimented in Gosh village wich is located in 60 km north of Mashhad. The sample data of this study was consisted of 38 extension workers were randomly selected from the study area based on Cochran’ s sampling methodology. The research instrument consisted of three parts in Likert scale. The validity of the questionnaire was analyzed and reliability coefficient was calculated for the questionnaire using Cronbach's alpha ratio of 0. 745. These amounts showed that questionnaire has an acceptable ability for data gathering. Factor analysis was the major statistical method. The results offactor analysis indicated that socio-economic effective parameters are increasing garden and farm area, increasing qanats water discharge, increasing rangeland area, and preventing lands flood damages. These four factors, in general, had more than 60 percent of the total variance. Final results indicated that watershed management activities have improved qanats water discharge by flood control and aquifer rechrge and increased the area of Agricultural and garden lands. Also, conseving activities in rangelands caused improving of vegetation cover density and the area of rangelands.

Floods water contain sediments that affect the fertility of coarse grain alluvial fan and flood plains after deposition, through increasing their nutrients. In this study, the effects of flood spreading were investigated on the recovery of soil nutrients at the Poldasht flood spreading station of west Azerbaijan during 10 years., The first three bands that have been flooded, were selected at the flood spreading channels. In each strip, six soil samples of of 0-20 cm depths, were taken and total nitrogen, phosphorus, potassium, and soil organic carbon were measured. For statistical analysis, t-test non-parametric tests were used where the data had normall distribution or not, respectively; . According to the results, the amount of soil organic carbon and total nitrogen increased from 0. 23 to 0. 33 and 0. 027 to 0. 039 percent, respectively during the implementation years. Exchangeable phosphorus and potassium were significantly increased from 2. 69 to 5. 32 and 145. 93 to 206. 52 parts per million, respectively. On the other hand, there was a significant difference for some factors of the spreading bands at 5% probability. Amounts of phosphorus, soil organic carbon and nitrogen in the upper strips were significantly more than lower bands. However, there was no significant change on the amount of potassium. The results showed that the flood spreading increased soil nutrients which reduce the fertilizers application.

In this study, rainfall, percolation and hydrogeological processes relationship were evaluated using geochemical tracers to determinate paleoclimate in the Ardabil Plain. The occurrence of dry and wet periods was also determined with the help of tracer used in six profiles. The Dry and wet periods were then evaluated by the Edmund-Allison equations based on interpretation of soil water chloride concentrations and long– term precipitation measured in different periods. Applying the chloride mass balance technique to soil water chloride profiles improved the boundary conditions associated with wetter and drier climate in last times. The estimated ages through sediment cores chemistry varied from 737 years in Imijah core to 4511 years in Gharahlar core with two recorded dry and wet periods. Precipitation of recently drier climate was estimated around 202 mm in 116 last years and second drier climate was estimated around 83 mm in 473 last years. Precipitation of recently wetter climate was also estimated around 451 mm in 210 last years and second wetter climate was estimated around 703 mm in 735 last years. The second wetter had the highest amount of precipitation in 3600 years period. The Ardabil plain had a moderate drier climate since 1100 to 2900 years ago. In addition, the results showed that the wetter climate happened during last 2900 to 3550 years. According to this results, the present climate moves towards drier climate. A comparative analysis of data from six profile sites indicated that there were short term oscillations of wetter and drier climate.

The land use programming is vital since inappropriate land use can endanger soil and water resources in a region and reduce their quality and quantity for future generations. While land development based on its ability are always facing limitations. This research is conducted with a sustainable approach to manage water resources and land programming in line with make optimal use of limited land, soil and water in the watershed. For this purpose, the required information to prepare a development model based on the land potential, were collected. Using the ArcGIS software, essential maps including map of slope, altitude, driving directions, land form, hydrographic, soil and vegetation, and density, were derived. By combining layers of information, the lands abilities were extracted in term of 107 ecological units. The meteorological data, hydrometer and the sources and consumptions of water resources of the watershed were collected and analyzed. The results showed that 88. 2 percent and 11. 6 percent are currently the area of agriculture and orchards. While the watershed potential for these practices are as 78. 9 and 19. 1, respectively. However, lack of attention to the potential water resources of the region, which is mostly as groundwater, caused a drop in groundwater level about 0. 85 m per year and consequently the risk of soil and water resources in the region. The results indicate the importance of integrated water resources management and natural potentials in sustainable development in the watershed.

The aim of this study was to evaluate the effects of mechanical watershed management measures implemented across the Boostan Dam Watershed on reduction of flood peak. To this end, the Watershed Modeling System (WMS) was used to compare peak flow before and after of implementation of the measures. The mechanical measures have been implemented during 2000– 2007. The major soil and water conservation measures in the Boostan Dam Watershed were mechanical and biological measures implemented in a limited area. To determine the effect of these measures, the watershed has been modeled in WMS environment. Five flood events occurred before implementation of the measures were used for calibration and validation of the model. Three other flood events occurred after completion of the measures were then used for the evaluation. The results showed that the mechanical measures, despite the fact that their reservoirs are full of sediment, decrease the average peak flow 1. 79 % compared to the absence of these measures and if some structures would not be destructed, the reduction would reach 5. 95 percent. It should be noted that if the structures were out of sediment, the average peak flow rate would decrease 3. 25 % in comparison with current situation and 7. 64 % when compared to absence of structures.

The study aimed to evaluate the regional models in estimation of probable annual water yield in hydrologic units of Karkheh, Dez and Karun watersheds, located in south-west of Iran. Afterward, observational data of discharge and precipitation were used from 108 hydrometeric stations and 208 rain gauges. Area, equivalent rectangle length, slope, Gravilios coefficient, precipitation, main stream length, main stream slope, mean watershed elevation, drainage density and perimeter were accounted in regional analysis. The cluster analysis and discriminate function was used in homogeneity analysis of hydrologic units. The results of multiple regression showed a high correlation between observed and computed data (0. 98 and 0. 99). It was also found out that annual discharge had a direct correlation with the first four above variables, and an inverse correlation with the other factors. The results showed that the annual yield can be precisely predicted by the area. Finally, the results showed that the annual depth of runoff yield over watershed had a high correlation with area and precipitation in a bi-variable regression model with regression coefficients of 0. 52 to 0. 8.