فصلنامه مهندسی منابع آب
پیاپی 19 (زمستان 1392)

Due to potable water shortage، groundwater pollution and an increase in water demand as a result of population growth، many Iranian communities، especially the coastal cities، are facing water crisis. Rainwater collection from the rooftops of residential buildings in towns and villages for non-potable water and greenery irrigation demand would be a practical solution to reduce the growing crisis of water supply for citizens. As the wide examples of ​impervious surfaces of cities are formed by the rooftops، the volume of rainwater harvested from the area is significant، which could be considered as a valuable alternative in water resources management. The rooftop rainwater harvesting system and the water tanks’ performance for storage and enhancement of daily non-potable water demand were analyzed in residential buildings in four coastal cities، namely Rasht، Gorgan، Bushehr and Bandar Abbas. Results of this study showed that if the tanks’ volume and daily non-potable water demand of residents calculated based on the physical and hydrological conditions of buildings، then rainwater storage in them would reach its maximum and the water demand. Large and small tanks could supply satisfied for a longer time. At least 75% of the non-potable water demand in 70 and 50 percent of the year، respectively in the City of Rasht. This will be 39% and 32% for the City of Gorgan، 15% and 11% for the City of Busher، and 10% and 7% for the City of Bandar Abbas.

Different loss models of Soil and Conservation Services (SCS)، Green and Ampt، Initial – Constant، Deficit – Constant، Constant Fraction، Exponential and Soil Moisture Accounting (SMA) methods have been compared using the HEC-HMS event-based rainfall–runoff simulation with respect to the effect of precipitation loss on the runoff generation in the Karoon III basin. The SMA method، with the maximum N. S.، 0. 81 and 0. 69 and the minimum PW RMSE، 148 and 143 in calibration and verification was the best in the stream flow simulation and the SCS and Constant Fraction were better than others in validation، following the SMA. A comparison between the simulated and observed key variables showed that the SMA method with minimum average percent difference of simulated volume، peak flow and hydrograph time of peak occurrence، was the best one in calibration. In verification، the SMA was the best in hydrograph volume simulation، SCS and SMA in the peak flow، and Initial and Constant and Green and Ampt in time of peak occurrence.

Hydraulic jump type stilling basins with abrupt drop are used to reduce the basin length and to ensure the start of jump at the front of basin immediately downstream of gates. In this type of basin، four different types of jumps can develop of which the most occurred type is the B-jump. On the other hand، it has been shown that the bed roughness can reduce both of the jump length and the required tail-water depth too. Therefore، in the present study، the B-jump in a roughened bed of an abrupt drop basin was simulated by the three dimensional numerical model of Flow-3D and the results are compared with experimental data. The characteristics of B-jump in a roughened bed such as sequent depth، flow velocity distribution، and bed shear stress were obtained from both numerical and experimental models and compared. For numerical simulation of the B-jump، the method of control volume in free surface water and the RNG k-ε turbulent model were applied. The results show that the RNG k-ε is a better simulation than the k-ε turbulent model. The results of both numerical and experimental models proved that for the B-jump in a roughened bed stilling basin، the sequent depth reduces، which can be due to roughness and an increase in the bed shear stress، as a result of both the bed and the abrupt drop.

The climate change (CC) shall certainly affect the water resources. As the presumed negative effects are serious matter of concern to countries experiencing water shortage، these phenomena have to be studied. Therefore، a new probabilistic approach was taken to evaluate the CC impacts on stream flow. To generate climate change scenarios in the foreseeable future and under A2 emission scenarios، the HadCM3 model was employed. By introducing climatic variable time series in future periods to the IHACRES hydrological model، long-term stream flow simulation scenarios were produced. By fitting the statistically different distributions on the runoff produced by using the goodness-to-fit tests، the most appropriate statistical distribution for each month was chosen and relevant statistical parameters were extracted and compared with the statistical parameters of runoff during the base period. Results showed that the long-term average annual runoff during the three future periods will decrease compared with the base period. Despite the reduction in the total runoff volume in the future periods compared with the baseline period، the decrease was concerned with the medium and high flow. The low flow rates، the total volume of runoff for the future periods compared with the baseline period will increase 47، 41، and 14%، respectively. To assess the further impact of annual average runoff on flow rates، it is necessary to examine the correlations of time series using the stream flow transmission probability. To compare the stream flow probability in each of the future periods with base period stream flow in each month، the stream flow was discretized and the performance criteria were used. This approach was used for the Aidoghmoush River، East Azerbaijan. Results show a low coefficient of correlation and high error indicators.

Water must be uniformly distributed over the whole farm field if a uniform growth of irrigated plants is desired. Therefore، achieving acceptable uniformity using a center pivot irrigation system is of utmost importance. This may be achieved by using an appropriate model to fine - tune the system by adjusting pressure، nozzle diameter، lateral spacing، revolution velocity، etc. Currently، suitable simulation models for fine- tuning the sprinkler irrigation are available. These models are useful tools for predicting operation parameters such as uniformity coefficient for various combinations of operation pressure and different meteorological conditions. The ballistic principle is the most common theory used in modeling water distribution uniformity in sprinkler irrigation systems. This principle and the necessary experimental and computational steps taken necessary for calibration and validation of the model for determination of sprinkler irrigation uniformity are presented in this paper. Experimental set-up for the determination of uniformity coefficient (UC) for different wind speeds included two operation pressures and two brands of sprinklers. The experiments were conducted on a farm adjacent to the Yaniq Village in the East province of Azarbayjan. Practical implications of the results indicated that relatively high UC may be achieved by the proper adjustment of pressure، the nozzle diameter and correct spacing of sprinklers.

Gabion structures are commonly used in water- related projects، especially as weirs. The unique structure of these weirs increases the rate of energy dissipation and reduces the construction costs of stilling basins. The permeable gabion weirs might have less negative impacts on the environment than most of the solid weirs. In this paper، the ability of M5 model in estimating energy dissipation over gabion-stepped weirs has been assessed. The M5 model has two options: M5P and M5Rule، although very similar، they differ in the manner of yielding of outputs. To assess the precision of these 2 models، the data collected on energy dissipation over 8 physical models were analyzed. Results showed that the M5Rule model، as a technique of data mining، had a good performance in predicting energy dissipation over gabion-stepped weirs. Moreover، the discharge and the height of the weirs were the most effective parameters in energy dissipation. Comparing the results of M5 model and the logistic linear regression method proved the rigorous power of M5 method in predicting energy dissipation over and through gabion-stepped weirs.

Food cycle creates a mechanism through which nutrients and other components of life are available for the living organisms. Improper function of the cycle may lead to disruption in the life cycle of organisms. In this paper، the dynamic flow of phosphorus، which is essential for plant growth، was studied considering three state variables: productive organisms (organic phosphorus)، dead organisms (organic phosphorus) and inorganic phosphorus. According to the three state variable’s feedbacks، phosphorus and phytoplankton simulation model was developed using the system dynamics approach and considering governing equations، feedback loops، and input and output streams. The behavior of each state variable was evaluated during a year for Lake Ontario. The result revealed that the model benefits from the desired performance in simulating and estimating the variable concentrations. It can be clearly seen that stratification and completely mixing of the lake during two periods (day 100 to 158، and day 315 to 335) have paramount impact on the variable concentrations.

The importance of inter-basin water transfer project is its ability to balance the non-uniform temporal and spatial distribution of water resources and demands، especially in arid and semi-arid regions. A water transfer project can be executed if many economics and environment criteria are satisfied. In this research، a methodology is proposed for inter-basin water allocation using the virtual water concept. Thus، a model based on the virtual water estimates the benefit of the inter-basin water transfer. SWAT simulation model was applied in order to estimate the virtual water potential of the receiving basin. The water related revenues of the basins that receive transferred water and the initial basins and related virtual water are estimated. The results show efficiency and benefits based on value of water and production. The effectiveness of this methodology is examined by applying it to a large scale case study of inter-basin water transfer from the Solegan to the Rafsanjan Basin in southeastern part of Iran.