IRAN-WATER RESOURCES RESEARCH
Year:2012 | Volume:8 | Issue:2 (24)|Papers Count:9

Optimization of reservoirs operation is one of the most important tasks in the field of water resources management.In fact, vital requirement for beneficial use of water and energy resources clear the necessity of doing integrated planning and right operation of dams. recently, research has been made focusing on a shift from traditional single objective models to multi-objective models for the planning of multiple reservoir systems in a river basin. In this study the three objectives of meeting irrigation and environmental demand, flood control and recreation (sometimes in conflict with each other) are referred to for a two reservoir system by Goal Programming.Within this framework, the mathematical model of two reservoirs system in Sefidrud watershed (Northern Iran) with the three objectives is formulated and the system parameters and decision variables are defined. The problem involves finding desired water releases from each reservoir in the system in order to satisfy the multiple objectives.With comparing results of optimization models of this study, the model with the higher reliability indices was chosen as the best model. Due to the considerable advantages of linguistic rules in better inferring and interpreting the systems, an adaptive neural based fuzzy inference system (ANFIS) approach is used to consider uncertainties and to achieve a general method for multipurpose multi reservoir systems. The results of the Adaptive Neural Fuzzy Inference System (ANFIS) models shows that they can be applied successfully to provide high accuracy for the management of the reservoir systems.

A Cooperative Water Allocation Model (CWAM) as a comprehensive model for efficient and equitable allocation of water in a river basin is designed. This model comprised of two steps: first the initial allocation of water using Lexicographic Minimax Ratio of Water Shortage (LMWSR), and second, water reallocation and net benefit for an efficient and optimal allocation of water transfer model. The second step can usethe followings: Irrigation Water Planning Model (IWPM); Hydrologic-Economic River Basin Model (HERBM) and Cooperative Reallocation Game (CRG).This study is performed in order to optimize the allocation of water resources of Chahnimeh natural reservoirs in a 12 month term (April 2005 to March 2006) using Game Theory.The results of LMWSR model showed a satisfaction ratio of 1 to 0.89 for domestic water and 1 to 0.49 for agricultural sector. For allocating water to the reservoirs this ratio is less than 1 for all months.The HERBM model results showed that the total allocation and profit of domestic water is increased in the optimal allocation compared to the initial allocation. These are decreased for agricultural compared to the initial allocation.The reallocation of benefits based on the concept of Shaply value showed that the maximum benefit obtained for the domestic water of Zahedan City which drew the maximum side payment and added value from other stakeholders in the whole period. The least benefit belongs to the agricultural sector.

Friction coefficients of river banks and floodplains are influenced by two major factors which are the flow conditions and the characteristics of vegetation. The most important parameters of vegetation characteristics are its density and flexibility. Many research focused on the effects of vegetation on the friction factors of rivers and floodplains.Less attention has however been given to the effect of vegetation density. This research was performed using laboratory flume and three kinds of Non-Submerged vegetation, to evaluate the effect of the density and the flexibility of vegetation on friction coefficients. The effect of these parameters on friction factors was investigated in four density conditions. This research revealed a linear relationship between the friction coefficients and the vegetation density. For same flow conditions; same velocity and same depth of flow (submerge ratio), the amount of friction coefficient for the less dense vegetation was seven to ten percent less than that of the dense condition. Also in same flow and vegetation conditions, different friction factors were obtained because of the difference between flexibility of vegetation.

This research was aimed to investigate the changes of runoff considering the uncertainty of AOGCM models and emission scenarios that may occur due to climate change in the period of 2010-2039 (2020s). First, the monthly temperature and precipitation data of AOGCM models (models of TAR reports) were provided for the baseline period (1971-2000) and the future period (2010-2039) under the SRES emission scenarios, namely A2 and B2. Then, these data were spatially and temporally downscaled to Gharanghu basin by proportional and change factor methods. Results showed that the temperature increased and the precipitation decreased in the future compared to the baseline period. The monthly probability distribution function of the temperature and the precipitation in the period of 2020s was constructed using weighting method; comparing observed and modeled temperature and precipitation. A semi- conceptual model (IHACRES) was calibrated for simulation of the monthly runoff of the basin. Using the Monte Carlo approach, 2000 samples of temperature and precipitation were generated by the probability distribution functions and were introduced to IHACRES. Finally 30-year time series of monthly runoff were simulated in 2020s. The results were compared to the baseline result which indicated that the climate change will affect the runoff in the basin.

This study presents verification of the Weather Research and Forecasting (WRF) model for the 24-h accumulated precipitation forecasts in Iran for the period of November 2008 to June 2009 for 24, 48, and 72.houre-ranges.Verification is done separately for three precipitation ranges and nine different regions in the country via 2×2 contingency table and quantities attributed to it. Though precipitation is the most difficult parameter to forecast, results show the good skill of WRF Forecasts. However regarding the bias, the model has over-forecasting.In northern parts of Iran with the highest rainfall rate, the value of TS is more than 0.50 and shows the highest accuracy of precipitation forecasts in different regions. In the regions with the lowest rainfall rates (east and southeast of Iran) TS is less than 0.40 and the model results show the least accuracy.Economic value of the forecasts reaches 60% for the cost to loss ratios of less than 0.40. This recommends the operational use of this model.

Changes in the rainfall trends can be a sign of the global climate change. The study on the hydroclimate trends can be conducted at both station and regional scales. Fewer studies have however paid attention to this subject at the regional scale. In this study, existence of a trend in both mean annual rainfall amounts and maximum 24-hour rainfall amounts over a 30-year period for 35 raingauge stations located in Mazandaran Province, northern Iran, is investigated with nonparametric Mann-Kendall test at both local and regional scales. The Trend Free Pre-Whitening approach (TFPW) was used to remove the effects of serial correlation in the time series on Mann-Kendall test. Removal of auto correlation in the time series is also performed by the same approach. The results of the regional Mann-Kendall test showed that if Mazandaran Province is considered as a unit region, no trend in the time series of maximum 24-hour rainfall is observed in 5% significance level. But if Mazandaran Province is divided into hydrologic regions using Fuzzy cluster analysis, it is observed that a significant trend exists in the western part of the province at 5% significance level. The investigation of the mean annual rainfall time series indicates an upward trend at 1% significance level for the whole province.

Spur dikes are one of the protective and stabilizing tools of river banks by deviating the flow from the banks toward the central axis of the flow. This can however cause scouring at the head of the spur dike.If the depth of the scour extends to the foundation of the structure, the spur dike may be destructed. In this experimental study, the effect of the length of a spur dike and the grain size is investigated on the scouring around a Tshaped spur dike at 90 degree bend. Results showed that the dimensions of the scour hole is directly related to the length of the spur dike while the maximum depth of the scouring and the length of the scour hole in the upstream showed an indirect relation to the grain size.

This study has dealt with the groundwater pollution using Arc GIS 9.3 and has identified the areas with high, moderate, and low pollution risk by the help of modeling and some parameters of the DRASTIC method taking into account the population growth rate in the urban areas. Although DRASTIC is often applied to the large alluvial plains, the contamination rate of the aqufer can be assessed in the urban area with a semi-drastic model if some of DRASTIC parameters are modified and also other effective factors are taken into account. In this study the parameters of depth to water, net recharge, aquifer media, soil media, topography, impact of Vadose zone, and hydraulic conductivity were evaluated to assess the risk of groundwater contamination.The site specific conditions pertaining to the urban areas were also considered; the impact of the texture of surface soil on the contamination of aquifer in the urban areas has been highlighted. Considering the role of urban sewer in aquifer contamination the parameter of population density has also been determined as a vital parameter and has been added to the DRASTIC parameters. In general the findings showed that the most vulnerable areas in Mashhad city include central, southern, and southeastern parts of the city.

The present research aimed to study the relationship between the water discharge and some main components of water quality using the experimental Forest Watershed of Tarbiat Modares University.61 water samples were taken through depth integration method during October 2007 and July 2008 in different hydrological conditions, and corresponding analysis was consequently made. The results of the regression modelling ultimately proved the relationship between the water discharge with chloride concentration in the base flow, hardness and nitrate during base flow and flood occurrences, and hardness and alkalinity in the sand mining period with respective correlation coefficients of 0.509 (p<0.001), 0.063 (p<0.01) and 0.508 (p=0.01), respectively, and the estimation error of less than 64%.