IRAN-WATER RESOURCES RESEARCH
Year:2012 | Volume:7 | Issue:4 (22)|Papers Count:9

A cyclic storage system integrates a surface water subsystem (i.e., river and surface reservoir) with a groundwater subsystem (i.e., aquifer) in an interactive loop to satisfy prespecified demands. Modeling these systems need to consider the hydraulic relationship between all components. This paper presents an optimization model for design and operation of a cyclic storage system. A generalized and modified unit response matrix method is developed and embedded into the optimization model to develop design and operation parameters. This method were also used to create the link between the groundwater simulation model and the system optimization model to compute system responses to different excitations. Solution to the proposed model, in addition to the design parameters, provides the optimal operation for the defined cyclic storage system. The Abhar River and Aquifer, Iran, were used as case study. One of the key results of this study is that the release from the surface reservoir does not necessarily follow a storage rule curve as might be expected in a single reservoir system.

In water distribution networks the initial and rehabilitation design are usually perform separately. However, it seems that the influence of the initial design upon the future condition of the network performance during operational years and rehabilitation activities are undeniable. Therefore, by combining the initial and rehabilitation designs, a new method is presented in this paper. This method called Dynamic Design of water distribution networks is capable of introducing cheaper and more reliable long term designs in comparison with normal initial design and rehabilitation design of networks. To assess this method, a fuzzy reliability index is introduced. Then by developing the multi objective version of the honey-bee mating optimization algorithm and applying it on two sample networks, final results of the multi objective dynamic design method is presented. Finally, this paper showed the positive performance and influence of dynamic design method on decreasing the design costs and increasing system reliability.

Study of the snowpack in the mountainous catchments is important from different aspects including the assessment of river yield or the avalanche control. Lack of data and low accuracy models for distributed simulation, especially on issues related to snow depth and cover, are however serious obstacles in such analysis. This research aimed to develop an appropriate algorithm for snowmelt and snow pack distributed simulation, in ungauged snow capped catchments. In this regard the snowpack of the region was spatially simulated, using snow balance equation and SRM (Snow Runoff Model) snowmelt algorithm. Additionally, the SWIFT algorithm was embedded in the model incorporating slope and aspect for calculation of radiation. Finally, the model is linked to the SWAT model to use its data generation capabilities and also calculate runoff. Comparison of the model with observation data in Imamzadeh Davoud catchment, Iran, showed acceptable performance of developed algorithm in mountainous basins relying only on readily available data.

Actual evapotranspiration (ETa) is one of the major components in the hydrologic cycle and its accurate estimation is of paramount importance for many studies concerning hydrologic water balance and water resources planning and management. Evapotranspiration is a complex nonlinear phenomenon depending on several interacting climatological and crop factors. This paper determines the minimum climatic data required for estimating ETa in a representative catchment (Emame, Iran) using artificial neural networks (ANNs) technique. Four combinations of weather parameters were considered as input data and the resulting values of ETa were analysed and compared with those of water balance method. The study indicated that maximum and minimum air temperature, relative humidity, and wind speed are the minimum climatic data required for estimating ETa. With these input data, the root mean square error (RMSE) and the coefficient of determination (R2) for the comparison between observed and estimated ETa are 0.17 mm d-1 and 0.95, respectively. Plotting measured values of ETa versus predicted values suggests that 82 percent of the values lie within a scatter of ±15%.

Soil erosion and sediment yield from watershed are among key limitations to achieve sustainable land use and to maintain the water quality. Development of the sediment graph (SG) is essentially required for accurate estimation of sediment yield from the watershed. However, development of SGs for watersheds is a tedious and time consuming task. Development of the sediment graph models based on easily accessible physical characteristics of a watershed and precipitation data is therefore a viable and convenient tool for designing the efficient soil and water conservation measures. In this regard, driving synthetic SGs using instantaneous unit sediment graph (IUSG) is an applied approach in watersheds where detailed discharge and sediment data are not available. However, the performance of this approach in watershed scale with different governing conditions has rarely been evaluated. The present study formulated IUSG for Kojour watershed comprising an area of some 500 Km2. The Watershed located at east of Nowshahr City in Mazandaran Province, northern Iran. The suspended sediment samples were taken from Kojour River during eight storm events in 2008 and corresponding SGs were then developed. The results showed that the IUSG model is unable to predict observed SGs components of peak, time to peak, total sediment yield, and the base time having respective estimation errors of 764, 111,750 and 101%.

Despite the fact that the quality of forecasts from numerical weather prediction (NWP) models has increased in recent years, yet exact forecast of precipitation is a difficult and challenging task. In order to obtain more accurate precipitation forecasts, efforts have been made to improve the models, formulations, and the accuracy of the initial conditions. One important alternative is to improve the model output via postprocessing.In this paper, the WRF model was applied for a six month period from 1 November 2008 to 30 April 2009 with two nests using 45 and 15 Km grid. The model outputs were then postprocessed for 24-hour precipitation forecasts for 205 synoptic stations over Iran using two methods of the moving average (MA) and the best easy systematic estimator (BES). Data for the first three months were used for training and the rest of data were used for the test and comparison. Statistical scores including degree of mass balance (DMB), mean absolute error (MAE) and its corresponding skill score were calculated for both direct and postprocessed outputs.Results showed that both methods improve the direct outputs of the model. The MA method decreased MAE for different stations from 5 to 50 percent. The mean of MAE decrease for all stations was about %25. In the BES method the average value of MAE for all stations is around 13 percent.

In many water engineering studies, there is a need to fill lost rain data using mapping tools. In this research this has been done by 5 types of RBFs; the data used were extracted by 3 test functions in which the support domain varied from 0.1 by 0.1 meter net to 0.5 by 0.5 meter net with different numbers of stations in a unit area domain. The c parameter was optimized by cross validation method and the Normalized Mean Square Error (NMSE), Percent Average Estimation Error (PAEE) and Coefficient of determination (R2) were the statistical controlling tools for choosing suitable RBF function type. Compared to other works in literature, this work had a better performance in mapping. It is also shown that the c parameter that optimizes the RBF function is highly dependent on the support domain size; the finer the resolutions of support domain, the better the results achieved. The attribute was also found for an arbitrary station point, Z (0.25, 0.35) to show the model capability for an irregular domain. This work may be compared with meshless methods for further research.

In this paper, the 3-D flow pattern around the pier with different sections is simulated using Fluent software. The pier sections modeled in this study included circular, spindle, oval, rectangular, square, and combined (rectangle - circle) sections. The software solves the flow equations using finite volume and pattern of cell centralism. Prismatic networks were used for computational lattice field. These networks were produced using the pre-processor Gambit. The computational field was then analyzed using the Fluent software. The Fluid Volume Method (VOF) is used to involve the free surface in three-dimensional modeling. Flow turbulence has been entered in the calculations using k-e model. In three-dimensional models, the effect of changes in water surface profiles and piers shape were investigated on decreasing shear stress and thus reducing scouring. The results indicated that spindle and elliptical cross sections have the largest effect in reducing shear stress and thus scouring around piers. The low velocity flow is formed around these piers and no large disturbance and no return flow, as important factors in scouring, are observed for spindle shaped piers.

Geographic information systems and remote sensing techniques have been increasingly applied in watershed runoff estimation in recent years. In this research, the runoff curve number map of Birjand’s Mansourabad watershed, eastern Iran, was prepared using geographic information system (GIS), landsat images, and the Indian remote sensing (IRS) images based on the factors of hydrologic soil group, land use, land cover, and the hydrologic conditions. The land cover map was determined using Normalized Difference Vegetation Index, (NDVI); the watershed land use map was produced by satellite data; and the hydrologic soil group map was produced using field survey and watershed soil, slope, geology, and land use maps. Results showed that during the period of 2002 to 2006, land coverage density has decreased and consequently the curve number of watershed and its runoff production potential has increased.