فصلنامه حفاظت منابع آب و خاک
سال چهارم شماره 4 (پیاپی 16، تابستان 1394)

Gate plate slope has an important role on hydraulic characteristics of sluice gates. In the previous studies, the influence of gate plate slope on hydraulic characteristics of sluice gates has not investigated theoretically. By applying the results of this theoretical study, the theoretical relations for discharge characteristics of sluice gates will be obtained depend on the gate plate slope. These theoretical and simple relations can be used to radial and top hinged flap gates, instead of long and complicated empirical and dimensional analyses-based equations. In this order, Euler’s equation was used to relate the specific energy of inclined sluice gate with specific energy of vertical sluice gate in rectangular channels under free orifice-flow condition. The gate plate slope was considered in the streamwise component of the gravitational acceleration in Euler’s equation. The ratio of inclined to vertical sluice gates specific energies obtained depends on the gate plate slope. The equation allows for the gate plate inclinations into the upstream pool. By applying the relation for specific energies ratio along the surface streamline, the water depths ratio at the vena contracta obtained depends on the gate plate slope with assuming negligible energy loss and approach velocities. Experimental data were used to validate the proposed equation for water depths ratio at the vena contracta, which showed good agreement with the measured values. Also, other equations presented for contraction and discharge coefficients variation with the gate plate slope. The proposed relation for contraction coefficient developed to radial and top hinged flap gates.

To protect from the risks of drought and water crisis in the future is needed that guidelines and rules for utilization of limited water resources be taken. In this context, mathematical programming models are used to help solve problems related to water resources management widely. In the present study in order to proper exploitation of groundwater and surface water resources and the optimal allocation of these resources in agriculture sector and also to determination an optimal cropping pattern that conducive to achieve the maximum possible profit for farmers of Roudbar Alamout region, from Fuzzy Goal Fractional Programing (FGFP)model and statistical data related to year 2010-2011 were used. The proposed model was solved in GAMS software version 23/9. The results showed that utilization optimal cropping pattern and optimal allocation of existing water resources in case study region in addition to reducing water used in farms level, the product cost in per hectare of lands reduced, the utilized labor force increased and efficiency indicators "profit ratio to water used" increased about 13 percent. In the end, according to obtained results planning and modeling from bottom to up for development agricultural sector of Qazvin province was proposed.

Headcut erosion is a sudden change in height or slope, which creates gullies and valleys and depending on different factors, it may vary from a height range of less than one inch to some feet and move upstream. This is one of the most significant types of erosions in soil losses and the major sources of sediment yield. Therefore, knowing this phenomenon, migration rate and sediment yield are important. In this study, seven samples of cohesive soils with different compositions of clay and silt, tested under different circumstances of waterfall height and flow velocity, and discussed migration rate and sediment yield. Tests were continued to reach a constant migration rate. One of the effective phenomenons in all tests was tensional cracks on soil surface. The size and number of these cracks have inverse relation with clay percent. The higher is the adhesion of sediment, the more vertical is the angle of waterfall migration upward. Waterfall slope angle under pure clay conditions was 34.6 degrees, but it increased to 40 degrees in the soil with 50 percent clay. With the 50 percent clay reduction, headcut movement and its average velocity were 3 times more than the one with 10 percent reduction of clay. Moreover, waterfall decline, its mean velocity, and average flow rate of sediment increased by 3.5, 4.5, and 3 times, respectively.

Analysis the flow in unsaturated soil is very complicated and is dependent on two nonlinear functions K(h) and θ(h) which are the nonlinear functions of soil hydraulic behavior. There are various methods for estimation of soil hydraulic parameters which using the infiltration test is one of them. In this study, the collected data from disk infiltrometer experiment (pressure head and cumulative water infiltration) used for estimation and optimization of soil hydraulic parameters by applying HYDRUS-2D software. The estimations done by inverse solution and Van Genuchten-Mualem model used for hydrodynamic assessing of soil sample. In addition, it is assumed that there is no hysteresis in soil sample and porous media is completely homogenous and isotropic. The silt loom soil sample with 20.7 cm in length and diameter equal to 20.7 cm selected for this experiment. The recorded data in 150 hours used as experimental observations in inverse solution of problem and the soil hydraulic functions estimated. Model ran in two discrete part, using pressure head and cumulative infiltration respectively, and results were compared. Results show that using the pressure head in depth 4 cm cannot lead to precise estimation of soil hydraulic parameters. Using the cumulative infiltration show the successiveness of this part of experiment in inversely estimation of parameters.

Forecast and evaluate the effects of climate change can be very useful in planning future managers. Various tools used to achieve this goal. In this research, the SWAT model is used to simulate and evaluate the climate change impacts on the crop yields in Simineh Rood basin and the changing cropping pattern strategy is evaluated as a comparative plan. To model the climate change conditions in the region, under the A2 and B2 scenarios, the HadCM3 atmosphere-ocean general circulation model outputs’ are used. Using the SDSM model, the outputs are downscaled and the minimum and maximum temperature and precipitation data are obtained for the years 2010 to 2033 and the data are used as inputs for the SWAT model. Afterwards, the values of water and temperature tensions, crop yields and the inflow of Urmia Lake in the climate change conditions are estimated and it is named as BAU. The results showed the increase in the average tensions of water and temperature and also the reduction in the crop yields. After evaluating the climate change impacts in the basin, changing the cropping pattern to wheat and barley is evaluated as a comparative strategy that showed 32% and 24% reduction in the water tension under the A2 and B2 scenarios compared to BAU condition. Also the produced calorie and the inflow of the lake showed 15.6% and 15.8% under the A2 scenario and 11.8% and 12.1% under the B2 scenario increase, respectively, compared to the BAU condition.

Quantitative evaluation of soil compaction to improve agricultural management practices and reduce the problems caused by compaction in the environment and production is essential, and such factors as compaction effort, soil type (%clay and soil plasticity) and water content condition have a significant impact on soil compaction. This research was conducted to study the effect of soil type and compaction on soil water characteristic curve with factorial experiment using randomized complete block design and 27 treatments were provided. Treatments consisted of three soil types: clay, clay loam and sandy loam under three compaction conditions: reduced, standard, and modified were performed. The compactions were performed in the three moisture conditions: dry, optimum and wet and undisturbed samples were provided as control. Mean comparison was conducted using Duncan's test and statistical analysis was performed by SAS statistical. The results showed that at all potentials, the influence of soil type on soil water retention was significant at the p Quantitative evaluation of soil compaction to improve agricultural management practices and reduce the problems caused by compaction in the environment and production is essential, and such factors as compaction effort, soil type (%clay and soil plasticity) and water content condition have a significant impact on soil compaction. This research was conducted to study the effect of soil type and compaction on soil water characteristic curve with factorial experiment using randomized complete block design and 27 treatments were provided. Treatments consisted of three soil types: clay, clay loam and sandy loam under three compaction conditions: reduced, standard, and modified were performed. The compactions were performed in the three moisture conditions: dry, optimum and wet and undisturbed samples were provided as control. Mean comparison was conducted using Duncan's test and statistical analysis was performed by SAS statistical. The results showed that at all potentials, the influence of soil type on soil water retention was significant at the p