فصلنامه مهندسی منابع آب
پیاپی 34 (پای ی ز 1396)

The declining groundwater resources have jeopardized food security in many marginal drylands. As Iran is dependent on this immensely precious resource that provides some 60% of its needs in hydrologically normal years, and undoubtedly more during droughts, the populace, particularly their irrigation farmers have to be concerned with this dwindling resource. Therefore, the farmer's attitudes towards utilization of groundwater resources are of utmost importance. The purpose of this study, which was implemented through questionnaires, was an assessment of some effective factors, which govern the farmer’s attitudes towards water resources management behaviors in Hamedan-Bahar Plain. Of the 476 farmers who operated wells deeper than 150 meters, 250 were randomly selected for this study. The data were analyzed using the multiple regression analysis based on their answers. The results indicated that understanding of vulnerabilities (β=0.48), realization of the damage (β =0.55), perception of the barriers to water conservation (β =0.57) and acceptance of responsibility for mismanagement of groundwater resources (B=0.42) had significant correlation coefficients (p

One consequence of a significant increase in the man-made greenhouse gases in recent decades has been a global rise in air temperature with the commensurate rise in the atmospheric heat energy, which in turn affects the hydrologic cycle. Thus a drastic change in the amount, distribution and timing of the hydrologic events is logical. Therefore, preparation for the future water-related events dictates an implication of detailed studies on the prediction of the future rise in temperature and the resultant change in precipitation. The Atmosphere-Ocean General Circulation Model (AOGCM) is considered to be the most reliable software for the predicting the weather-related events. The statistical downscaling method (SDSM) and the Artificial Neural Networks (ANN) were tested to remove the uncertainty related to the AOGCM. Of a few software used for downscaling, SDSM was proved to be the most reliable for predicting the 2011-2040 changes in air temperatures and precipitation under the A2, B2 scenarios of the HadCM3 for the Qorantalar Watershed. Results indicated that there would be an increase of 7% and 6% in the precipitation amount, and 0.34 and 0.86 degrees Celsius in temperature using the A2 and B2 scenarios, respectively.

The Babolroud watershed has experienced different climate related events such as flooding and drought in recent years that emphasize the urgent need to investigate the impact of climate change on meteorology and hydrology of the watershed. Two general atmospheric circulation softwares were used to predict these changes. However, the large scale computational grid of such software discourages their application to meteorology parameters prediction in small scales. Therefore, an interface tool called the LARS- WG model has been developed to facilitate assessment of such parameters in more manageable scales and at the desired localities. The data generated by the HadCM3 general circulation of the atmosphere software were incorporated into the LARS-WG software under a similar scenario for the 2046-2065 periods. They were downscaled, compared and evaluated the four climatic variables related to the statistical base period of 1982-2011. These data were introduced into the LARS-WG software for calibration and verification. Furthermore, the relationships between the collected data were established between rainfall depth, maximum and minimum temperatures and radiation to simulate the future events. It was observed that the ECHO-G software prediction was lower for precipitation and higher for temperature under the similar scenario as compared to those predicted by the HadCM3 software. Precipitation depth as predicted by this software for the Babolroud watershed ranged from -52 to %. The results indicated a moderate increase in precipitation in the rainy season and an extreme decrease in the summer month. The highest reduction was related to the August rainfall (43 mm) as predicted by the ECHO-G software. The highest increase in precipitation was related to October (27 mm) as predicted by the HadCM3 software.

Evapotranspiration (ET0), a major component of the hydrologic cycle, is important in water resources development and irrigation planning. The ET0 for west and northwest of Iran was estimated using the FAO Penman-Montieth method (FAO-56) as the reference. The performance of four different data-driven methods, namely the Artificial Neural Networks (ANN), Adaptive Neuro Fuzzy Inference System (ANFIS) with grid partition (GP), ANFIS with subtractive clustering (SC), and Gene Expression Programming (GEP) were investigated on the ET0 estimation. Latitude, longitude and altitude of stations, and the periodicity component were used as inputs to the applied models to predict the long-term monthly ET0 using the data from 12 stations in the west and northwest of Iran. The maximum coefficients of determination (R2) were found to be 0.994, 0.998 and 0.997 for the ANN, ANFIS-GP and ANFIS-SC models at the Sanandaj Station, respectively. The highest R2 (0.982) of the GEP model was calculated for the Khoy Station. The root mean squared error ranged 0.311-1.551, 0.368-1.319, 0.450-1.80 and 0.435-0.833 mm/day for the ANN, ANFIS-GP, ANFISSC and GEP models, respectively. The results revealed the high accuracy of the GEP in the prediction of ET0. Therefore, the GEP model can be applied as a simple method in future studies as an alternative to the use of empirical relationships for the ET0 estimation.

Weirs are the most important and very applicable barriers built across channels to control the flow of water or change its direction. They are also widely used in current measurement in open channels and many hydraulic engineering studies. The advantage of the semi-cylindrical and circular crested weirs as compared with other structures and measuring instruments is their higher discharge coefficient, stability of flow pattern, non-obstruction by floating materials, simplicity of design, durability, wide applicability and economics. One of the newest and most useful software in the field of computational fluid dynamics is Ansys CFX, which provides fairly reliable results. This software, which benefits from the continuity and momentum equations and the application of a turbulence model, was used to simulate flow over three semi cylindrical weirs with different radii in a laboratory study. After selecting the optimum mesh size for simulating the flow in the multiphase form of the fluid model, the k-ε, RNG k-ε and k-ω turbulence models were used to simulate the flow, and the results of the numerical solution was compared with the collected data extracted from experimenting with the physical models. The mesh size selection was based on the optimum mesh, root mean square error, mean absolute error and the coefficient of determination. The results showed that for cylinder with 4, 6, 7 cm radius, the discharge coefficient ranged from1.2 to 1.4. Furthermore, both the flow and the discharge coefficient increased with an increase in the radius. Moreover, the location of minimum pressure on the weir moved upstream with incremental discharge in conformity with previous studies.

Stability of streambeds is dependent on different factors some of which maybe destabilized at any moment. Dam erection on the riverbed is the most important among those factors. Some morphological changes of a meandering river, the most obvious of which are the gradient change and the area deducted or added to the riverbed, were studied downstream of the Karkheh Dam. To delineate the areas, which had been taken from or added to the riverbed due to the lateral and longitudinal displacement of the meanders, morphology of the downstream river bed prior to and after the dam construction were studied employing satellite imagery, and their extent was calculated using the CCHE2D model. Slope reduction, as expected, follows an increase in the riverbed breadth. The average width of the riverbed was reduced from 273 m to 60 m (78% reduction) after the dam construction. The land taken off the streambed was almost 21 hectares for each kilometer of the length of the river. Mean, maximum and minimum horizontal thalweg displacements were 340,768 and 53 meters, respectively; 56% of the displacements were towards right (west) and 59% of the displacement took place out of the original streambed. The mean annual lateral displacement of the riverbed was 34 meters after the dam construction. This finding illustrates the instability of the terrain through which the river flows.

Serious attention to agricultural water supply management is inevitable due to an increase in demand for this most precious resource. Water demand management is a strategy that reduces the demand for, increases its use efficiency of, and prevents the waste of its resources. Various laws, pertaining to the prudent water management, have been passed; however, many of them have never been enforced. Therefore, the existing structure was investigated by polling a group of water- related experts. The questionnaire, which was employed for this research, was answered by38 eminent water experts. The calculated Cronbach's alpha coefficient of the polling was 0.701 that pointed to the strong reliability of the questionnaire. Those water experts were in agreement with reorganization of the water resources management and maintained that a “lack of coordination among relevant agencies” and the “legal difficulties in reforming the consumption patterns” have greatly affected the emergence of the existing water crisis. Therefore, a countrywide organizational chart, consisting of five levels, was proposed: 1. Providing a framework and adapting a firm policy on logical water management in coordination with the judiciary bodies; 2. Enabling the managers of large watersheds to adapt their own policies; 3. Enabling the managers of sub-watersheds to adapt their own policies; 4. Implementing the confirmed policies employing the existing hardware and software and looking for the new methods; 5. Implementing the adapted policies at the local scale. We strongly recommend an assessment of this chart by the concerned water authorities.

The Fourth Assessment Report of the Intergovernmental Panel on Climate Change presents four general circulation models under the SRES emission scenarios of A2 and B1. The take-home message of these documents is the expected change in the atmospheric temperature, which undoubtedly would affect the hydrology of watersheds. These warnings dictate the necessity of prediction of the future change in the flow of rivers and the vulnerability of the people who depend on them for their water supplies. Results indicated that the average temperature variations are from -0.13 to 0.96°C and 0.72 to 1.85°C for 2016-2038 and 2039-2061 periods, respectively. Furthermore, the average monthly rainfall variations in the baseline period in comparison to the observed period (1988-2010) are from -3.5 to 182% and -20.7 to 123 % for those two periods, respectively. The daily rainfall- runoff simulation using the IHACRES model yielded the R2 of 0.684 and 0.635 for the calibration and validation stages, respectively. Overall, the mean volume of annual runoff into the Doroodzan Reservoir would decrease by 8.4 and 28.15 % as compared with the baseline period for the 2016-2038 and 2039-2061, respectively. Furthermore, the most decrease in the mean volume of monthly runoff of the basin in comparison with the baseline period has been predicted for November to be 42.34 and 54.13 % for those two periods, respectively.