فصلنامه حفاظت منابع آب و خاک
سال چهارم شماره 1 (پیاپی 13، پاییز 1393)

Nowadays optimal management and conservation of water and soil resources seems to be more essential than ever before. The issue of surface irrigation systems as a major consumer of water in the country is very important. Accurate prediction of the advance phase is important for the design and evaluation of these systems. The main objective of this study was to evaluate the accuracy of solving methods of Volume Balance Model (VBM) in the estimation of the water advance of furrow irrigation. In this study، Michel، Philip، Power functions and Return functions solving methods were used and also new models were proposed. For each method، a computer program was written in Matlab and to measure the precision of solving Methods mentioned above، gathered data of seven fields in two-time irrigation (A: water-soil and B: middle growth) in Chaharmahal and Bakhtyari province were used. The statistics of solving methods mentioned were obtained by use of root mean square error (RMSE)، coefficient residual mass (CRM) and model efficiency factor (EF). The results showed that Michel method has a lower RMSE (27. 6 and 57. 6 meters values for two-time irrigation respectively) and CRM (0. 06 value) and the higher EF (-1. 07 value) than the other solving methods of volume balance model. Other methods have close results for RMSE (33. 3 and 61. 4 meters values for two-time irrigation)، CRM (0. 21 value) and EF (-2. 65 value). As a result، the best method to solve VBM is Michel''s method. Accurate determination of infiltration coefficients and selection of infiltration equation are effective factors for model accuracy. Therefore، considering subsurface shape factor effect، the best suggestion for this coefficient is Kiefer equation.

Water resources systems as a set of structures and equipment، strongly need proper operational programming in order to optimally supply demands and perform suitable water conservation. Water reservoirs are the most commonly used water resources systems for supplying domestic demands whose incorrect management may lead to unsuitable water resources protection and huge financial losses. Approximately in all of the reservoir design، operation and management problems، real reservoir system case studies are studied and analyzed according to the existing conditions and their objectives. Under these conditions، it can be very useful to define and introduce a sample reservoir system which can be investigated for all conditions and objectives. In this research، a three-reservoir system is presented for the first time، considering all physical and hydrological parameters beside three general objectives of generating hydropower energy، supplying downstream demands (agricultural، municipal and industrial) and flood control. The obtained results are quite logical، with a natural trend based on the logically defined data for the sample reservoir system. Therefore، this sample case study is capable of showing the performance of reservoir systems in different states of single or multi reservoirs and single or multi objectives. As a result، the presented reservoir system can be used as a sample case study for introducing and developing different methods in solving water reservoir system problems.

AbstractTreating problematic soils at the location of irrigation and drainage networks in order to prevent hydraulic structure failure and thus water losses is considered an important issue regarding water and soil conservation. Expansive soils are found in many parts of the world and are considered a worldwide problem as they cause extensive damage to structures (especially hydraulic). This paper presents the laboratory results of wetting and drying cycles for expansive clay prepared with saline (sodium chloride with a concentration of 50 g/L) to improve its quality. Soil samples were prepared by static compaction using saline water and wetting and drying cycles by a modified and conventional Oedometer apparatus. Results indicated that axial deformation caused by consecutive wetting and drying cycles decreases and reaches equilibrium after five consecutive cycles thus causing the amount of swelling and shrinkage to be equal. Furthermore swelling and shrinkage paths (void ratio versus water content paths) indicate that the general shape of a wetting or drying cycle is an S-shaped curve which will reach equilibrium thus eliminating hysteresis caused by wetting and drying in the final cycle causing identical swelling and shrinkage paths.

Stilling basins with sudden expansions are one of the energy dissipater structures. This structure has many applications downstream of hydraulic structures، such as spillways، sluice gates and chutes. In the jump، the pressure fluctuations resulting from intense macro-scale turbulence must be carefully considered during the design of the structure. Roughness can also cause changes in the behavior of stream line and vortices. So far its effects on the hydrodynamic characteristics of the jump have not been studied. In this study many tests are conducted in a relatively large flume size of 0. 8 meter wide and 12 meter length. Channel expansions ratio (B1/B2) was 0. 33 and data are presented for Froude numbers from 4-9. 2. Measurements were conducted in the bed of flume by means of pressure transducers systems. The final results of this study show that roughness decreases Intensity of fluctuating pressure in sudden expansion stilling basin. Test results were compared with those of smooth sudden expansion jump and classical jump which indicates that the peak values of RMS dimensionless pressure fluctuations (Cp'')، are 53% lower than smooth sudden expansion jump and are reduced 70% compared with classical jump. Intensity of fluctuating pressure at the position of about (0. 15-0. 3) Lj، can reach the maximal value. Peak values of RMS dimensionless pressure fluctuations C''p max up to 0. 023 and maximum positive (negative) deviation Cp-and Cp-values up to 0. 08 were obtained. In addition to dimensionless coefficients of pressure fluctuations، the longitudinal distribution of pressures and determined pressure fluctuations and extreme values occurring during flow are obtained.

Research carried out so far indicates that oxygenation is capable of effectively increasing crop yield because of supplying sufficient oxygen in the rhizosphere. However، the severe non-uniformity associated with the distribution of emitter air flow rates along laterals is a major deficiency. This research explored the effect of individual and/or concurrent use of surfactant with a final concentration of 32 ppm to irrigation water and/or insertion of turbulence-inducer sealing plugs preceding connectors on the uniformity of emitter air flow rate distribution. The results indicated that addition of surfactant raised the CUC of the emitter air flow rates from -83% to 37% for the asymmetric connectors and from 1% to 23% for the symmetric connectors، respectively، over the controls without surfactant. Addition of surfactant to oxygenation systems with symmetric connectors of 9. 5 and 7 mm long led to a rise in CUC from 1% to 23%، and from -41% to 39%، respectively. Compared to aerated water without surfactant or sealing plugs، concurrent use of surfactant and turbulent-inducer sealing plugs in oxygenation systems with symmetric and asymmetric connectors caused a rise in the CUC of air bubble deliveries from -82% to 48%، and from 1% to 53%، respectively.

Water resources management، forecasting، and decision making require reliable estimates of precipitation. Therefore، a normal and an inevitable part of any hydrological or water management project before starting the research is analyzing the accuracy of time series. For this purpose by using statistical tests، the time series are analyzed heterogeneous and improbable fluctuations of data and if needed are corrected or omitted. Although usually passing the statistical tests، scientifically verifies the efficiency of the data، more precise verifications on the data may lead to different results. Therefore، in this study by choosing precipitation data of Urmia basin as a case study، final results of some statistical tests on the efficiency of the data are analyzed. Careful and precise analysis of the time series especially in comparison with neighboring stations shows that full reliance on the statistical tests alone is not enough for analyzing the efficiency of the time series and the results of these tests may mislead users on the true condition and efficiency of the data. Based on the results of this study، only 2. 4 percent of the data need correction or must be omitted; nevertheless، more precise analysis through data shows that about 12. 6 percent of the data are completely unsuitable and must be omitted.