IRAN-WATER RESOURCES RESEARCH
Year:2013 | Volume:8 | Issue:3 (25)|Papers Count:12

Natural phenomena usually seem irregular at the first glance, however, with changing the scale and the noise they can become regular and therefore it is possible to predict their behaviors. This idea is the main base of the Chaos Theory that deals with studying of unstable and non-periodic behavior of nonlinear and swinging dynamic systems. The time series of drought, as a major natural disaster, has a dynamic nature. and therefore the Chaos Thero can play a significant role in capturing the detailed changes. Refinement of the indicators, standardized precipitation index (SPI) is now widely used in the world. The obtained SPI data are noisy, and therefore the predictions made based on this data are not very accurate. Wavelet algorithm is able to describe a signal in time and frequency domain and also analyze a signal locally. Hence in this study, it is used in order to de-noise time series of SPI of Tabriz city for the past 40 years. The nature of the chaotic time series was evaluated using the Lyapunov exponent and correlation dimension parameters.The results indicated a very chaotic time series behavior for the studied data. The behavior of the system is non-random, and then the time series are not portion of the stochastic and the noise process. To predict the SPI values by the Chaos Theory, the algorithm of the false nearest neighbors is used.Validation of the results indicated the high accuracy of the predictions of the Chaos Theory. According to the proposed method the severity of the droughts and the SPI of the Tabriz city are predicted for the next 3 years.

Undesirable effects of droughts on the agricultural and economical sectors and especially on the natural resources are intense. Different methods have been presented to predict the main factors of drought such as precipitation and during the recent decades some new computer based models have been developed for drought prediction. In most cases these models have presented quite satisfactory results. Decision tree, as one of these models, produces rules based on evaluation of the parameters from portion (component) to the whole, and finally reaches understandable knowledge from the existing statistical data. In this research, decision tree model has been used as a data mining method to predict precipitation and evaluation of drought in Yazd synoptic meteorological station. Simulations were carried out in four different conditions. Related variables including previous monthly precipitation, mean temperature, maximum temperature, humidity, wind speed, wind direction, and evaporation were used as independent input variables for all these four conditions and the amount of precipitation was predicted 12 months in advance. Finally for evaluation of the model performance in different conditions, statistical criteria were employed. Results indicated that the decision tree model is able to presents suitable prediction of precipitation especially when 5-year moving average of data is used. Precise prediction of precipitation and the accurate evaluation of drought conditions are of great importance for a better management and planning for drought damages reduction.

In this research the effect of Sugarcane straw and Phragmites australis anion exchanger nano adsorbents have been investigated for removal of nitrate from aqueous solutions.The effects of operating conditions such as pH, contact time, adsorbent loading, initial anion concentration, and the presence of competitive ions on the adsorption performances were examined. The results showed that the equilibrium time was 2 hours and the pH was 6. With pH of the solution varying from 2 to 10, the nitrate removal efficiency for sugarcane straw and Phragmites australis nano adsorbent increased up to maximum of 45% to 76% and 60% to 86% reached at pH 6. With an increase in the nitrate concentration from 5 to 120 mg/L, the removal efficiency decreased from 86% to 66% and 90% to 67% for sugarcane straw and Phragmites australis nano adsorbent, respectively. For Phragmites australis nano adsorbent, with an increase in the adsorbent dosage from 0.1 to 0.3 grams, the removal efficiency increased from 60% to 85%, but remained almost unchanged when adsorbent dosage ranged from 0.3 to 1grams. For sugarcane straw nano adsorbent as the adsorbent dosage increased from 0.1 to 0.5 grams, the removal efficiency of nitrate increased from 45% to 75%, but remained almost unchanged for the increase of 0.5 to 1 grams. Adsorption kinetics of nitrate ions could most successfully be described by Freundlich isotherm. This study indicated that sugarcane straw and Phragmites australis nano adsorbents could be used for the removal of nitrate ions in water treatment and Phragmites australis nano adsorbent has higher adsorption than sugarcane straw nano adsorbent for nitrate removal.

Extreme precipitation in every given point is defined as rare and abnormal precipitations in which could happened far from the center of frequency distribution. The high extreme and upper tail of distribution of precipitation has been taken a lot of experts’ attentions. The thresholds values for extreme precipitations that have been chosen are varied by geographical locations. One of the most usage indices is based on deciles of any given distributions.The current paper has analyzed tempo-spatial characters of extreme precipitation of northwest of Iran based on daily observations database created from of 729 synoptic, climatology and rain gauges stations by using90th percentiles of precipitation distribution. The period under investigation is 41 years which started in 1967to 2007 (14975 days).The 90th percentiles of precipitation probability distribution have been estimated for every single pixel as extreme threshold. The numbers of pixels have experienced the extreme threshold or more, had been calculated. Many kinds of coverage of this character have been recognized. Based on analyzing temporal and trends characters it has cleared that there is a significant decreasing trend in 20-30 percent coverage of extreme precipitation. Meanwhile there are stationary in other extreme coverage except for 60% -70% coverage’s. The coverage of 40%-5% and 50% - 60% in March is the second order in extreme precipitation events.Monthly analyses showed the months with most extreme (two times in every month) are April, May, March and October r.

A major problem with which most of the lateral intakes are faced is sedimentation and sediment delivery. This process causes many problems in irrigation systems such as reduction flow discharge capacity in irrigation canals and even threat of blockage of water during low water flow. Therefore an intake with higher flow discharge and low sediment delivery should be considered in the design. In previous research the same attention has not been given to the lateral intakes installed at trapezoidal canals, as for rectangular canals. The main goal of this study was to investigate sediment delivery to an intake from trapezoidal canal. Sediment tests were carried out for different hydraulic conditions at a 30 degree water intake installed at a main canal with inclined bank. It was found that the flow patterns at the upstream of the intake has been modified in such a way that more water from surface layers are diverted. Therefore less suspended sediment enters the intake. Also it was found that in all tests the amount of sediment enters the intake reaches its minimum value at Froude number between 0.35 to 0.4. For high friction coefficients, the rate of sediment entering the intake decreases as the flow ratio increases.

Bank erosion is one of the important management issues, especially in meandering rivers. Bendway weirs have recently become among the most popular structures in erosion control along the meanders. Bendway weirs are the stone structures constructed in outer bank to change the flow direction from outer bank to the center of the channel so as to prevent erosion. In this study it has been attempted to investigate the effect of angle of bendway weirs on the pattern of erosion and sedimentation. Three angles of 60o, 75o and 90o and three flow rates of 120, 180 and 230 liter per second were examined. Other structural parameters such as length, height, and distance were kept constant. Continuous injection of sediment with d50=1.6 mm formed a live bed.The results of this study showed that the cross-section area of sedimentary bar in the inner bank decreased by an order of 13 to 48 percents as a result to the construction of weirs. The minimum and maximum of decrease were corresponded to the angles of 90o and 60o, respectively. The maximum scour depth to weir height ratio in the outer bank wall was very evident for the angle of but not so noticeable for other two angles. The maximum amount of this ratio was 4.6 at 90o.Sedimentation and scouring patterns showed that the sedimentation between weirs and thereby protecting the outer bank were better for the angles of 60o and 75o. Angle of 90o is not recommended for construction of bendway weirs.

A survey of research findings related to the assessment of training programs according to the international standard (ISO) 10015 is indicated that one of the key factors of ineffectiveness of on-the job training programs is the lack of accurate need assessment technics and procedures. Instances such as personal preferences and unnecessary needs of personnel,, presenting numerous unrelated training programs, distrust and less cooperation of the personnel and managers, and developing merits not desired by the orgnization and therefore wasting the financial resources are all corroborating the hypothesis. The need assessment has been the focal point of many researches and books in the recent years. It is of utmost importance for managers and educational experts that with regard to the purposes, the budget, time, and the need assessment, choose and employ a proper technic in order to identify the training needs of their organization according to macro - organiational decisions. To this end 160 job titles have been assessed by the standard method of skills in the Iranian Water Resources Management Company. In this article it has been attempted to identify the training needs of the River and Coastal Conservation Department by the standard method.

Aging in urban water distribution networks would lead to an increased number of bursts. Beside leakage control and pressure management, the last solution in this regard is rehabilitation and replacement of main pipes in the networks.In this research the optimum time for pipe replacement in water distribution networks is obtained by an optimization model applying genetic algorithm, which minimizes the present value of the total costs. According to the obtained results, the economic constraint increases the total costs of replacement while the hydraulic constraint would decrease it.Additionally, considering the cost of water losses and grouping replacement would increase the total costs.

Nitrate in high dosage may cause serious diseases for both human beings and animals. WHO has set 45 mg/l as the maximum permitted level for nitrate in drinking water. High concentrations of nitrate in drinking water of the Mian Jungle region of Fasa, located 120 km south east of Shiraz, caused inhabitants to avoid using groundwater as the source of drinking water. Main objectives of this study were i) to determine the main sources of nitrate in the groundwater and ii) to introduce a feasible nitrate removal method in the region. Monthly groundwater sampling were carried out from April 2010 to March 2011 for 15 sources including water wells and outcropped springs. Nitrate, EC, and pH were measured in situ, however remaining parameters were determined in the lab using standard methods. Amounts of nitrate changed from 3.1 mg/l to 259.4 mg/l in diferent times and locations in this region. Results showed that an internal and external background of nitrate in groundwater are originating from the geologic formations and the animal husbandry activities as the main sources.