Journal of Water Resources Engineering
Year:2013 | Volume:5 | Issue:15|Papers Count:8

A significant portion of the annual precipitation of the mountainous West Azarbaijan (WA) of the I.R.of Iran occurs as snowfalls. Therefore, an assessment of the water equivalent of the snowpack and its density is of utmost importance in estimating the water yield of the WA basins. AS snowfall gradually increase with latitude and elevation, and since establishing snow courses and regular snow sampling in extensive areas is both costly and difficult, it is prudent to use a limited amount of data, suitable algorithms, and modeling to predict these 2 parameters for inaccessible places in WA. In this study, using the artificial neural network, variable snow density and snow water equivalent in the basins were estimated. In designing the artificial neural network three independent variables of longitude, latitude and altitude of the snow survey are used as the inputs. Artificial neural network design consisted of three neurons in input layer, two neurons in output layer, 6 to 18 neurons in one or more of the middle layers.The results showed that the structure of 2-6-3 to 2-6-6-3 and 2-6-6-6-3, yielded more logical answers. Thus, in the 2-6-3 structure, network design were converged after 270 iterations. Using the Levenberg-Merquate algorithm and the results obtained from the 2-6-3 structure, the neural network successfully estimated 92% of variations in snow density and snow water equivalent in WA. Furthermore, the stability results indicated that the 2-6-3 structure when used for analyzing the data from 35 snow measuring stations could satisfactorily predict 91% of variations in snow density and snow water equivalent for the 2009-2010 period. As the neural network uses fewer, easily accessible inputs as compared with the models used in similar studies, it has a better merit in snow-related hydrological studies.

Hydrological modeling is a major approach for prediction of hydrological responses of watersheds to different management scenarios. A GIS-based flood hydrograph modeling (GFHM) has been developed for simulation of event-based flood hydrographs using the PCRaster GIS and dynamic modeling language for The Jafarabad Watershed. The GFHM model is a spatio-temporally distributed hydrologic model. DEM, land use, and soil type maps as well as the precipitation hyetographs are the main input data required by this model. Regarding the temporal discretization of the model, a time interval of as small as seconds has been implemented. This minute time interval enables to the model, simulate the flood hydrograph of small watersheds with spatial discretization of a few meters. To this end, a conceptual model, including methods and relationships for simulation of different elements of the hydrologic processes, assumptions and limitations were defined. The GFHM uses the well-known method of curve number (NRCS) to calculate the rainfall excesses. The kinematic wave routing approach was used to route the generated excess rainfall of cells towards the outlet of the watershed. The one factor at a time (OAT) method has been used to carry out the sensitivity analysis. Based on the results of the sensitivity analysis, the CN and the Manning’s coefficient were chosen for the manual calibration of the model. Various assessment criteria were used to evaluate the model results. Results showed that the Nash-Sutcliffe efficiency criteria for the GFHM model were 0.718 and 0.777 for the calibration and validation datasets, respectively. Although the Nash-Sutcliffe criterion indicated the satisfactory of the model, resolving the time shift between the simulated and observed flood hydrographs through improvement in the model structure will enhance the performance of the model.

Climatologists have predicted that there will be decreased precipitation and increased temperature in many parts of the world. Therefore, achieving a sustainable agriculture requires a reliable knowledge of the local climate change. Means and standard deviations of the monthly mean values of the minimum and maximum temperature, relative humidity, wind speed, solar radiation and precipitation at five climatic stations were analyzed for the period 2040-2069relative to the base period (1980-1999) in the Qazvin Irrigation and Drainage Network. Five different groups of climate change scenarios were assessed. In the first group, all of the climate change scenarios were combined and analyzed together. Other four groups each consisted of one of the SRES scenarios, namely the A1B, A2, B1 and Commit. The magnitudes of variations were estimated using the inverse distance weighting (IDW) method at all selected stations. The results indicated an increase of 1.61oC in the minimum temperature, an increase of 1.93oC in the maximum temperature, a decrease of 2% in the relative humidity, a decrease of 1% in the wind speed, and a negligible change in the solar radiation. Furthermore, no significant trend was detectable through the year. It was concluded that the standard deviation of monthly average values of all of the variables increased, especially those of the maximum temperature and precipitation.

Soil saturated hydraulic conductivity (ks) is one of the most important soil physical properties. Information on spatial and temporal variations of the property is necessary for improvement of soil and water management. The double ring infiltrometer (DR), single ring infiltrometer (SR), guelphpermeameter (GP) and tension infiltrometer (TI) methods were compared in a silty loam soil of a farm field on the Shahrekord University campus. The water level during the experiments was kept constant at 11 cmin both of the double and single ring methods. The successive constant pressure heads in the Guelph permameter method were 11 and 19 cm. The experiment with tension infiltrometerwas performed at the tensions of -15, -10, -6, -3 and -1 cm. The mean saturated hydraulic conductivity using the DR, SR, GP and TI methods were 0.300, 0.246, 0.011 and 0.295 cm min-1, respectively.Statistical analysis using the Duncan's test showed that there was no significant difference between the measured ks values with the previously mentioned methods; however, hydraulic methods; except GP (P<0.01). Conductivity as measured by the GP method was much low, than those obtained using the other methods. The main reason for the large difference in ks value between the GP and other methods was a hard layer with low infiltrability at a depth of 25- 30 cm.

The purpose of this study was to identify the most important effective solutions in improving of management of the Qazvin Network water resources from the water users’ viewpoint. The sample size was determined using the Cochran formula. The samples were selected using the multi-stage sampling method (n=127). Questionnaires were used to collect the data. Validity of the questionnaire was assessed by panel of faculty members and experts. In order to measure the reliability of the questionnaire, the Cronbach Alpha coefficients were calculated for their main scales (0.92). The results showed that the most important barrows in improving the management of water resources were: the lack of a strong law in water resources management and the needed power in the enforcement of the drilling regulations؛ i.e., prevention of drilling wells without obtaining the legal permits. By using the exploratory factor analysis, effective solutions in improvement of management were summarized through 4 factors: reforms in pricing and training, development of a comprehensive partnership in agriculture, reduction of bureaucracy, and improvement in technology, extension, supervision. These factors explained 60% of the variations. The most important effective factor was the reform in the pricing system and training.

Seepage under hydraulic structures built on permeable foundations may cause internal erosion, boiling and piping, and in the extreme cases, overturning of the structure due to the development of the uplift pressure. Therefore, predicting the location of the seepage line, the uplift pressure, and exit hydraulic gradient are vital in the safety of such structures. Installation of the cutoff walls underneath such structures is an approved method of seepage loss and hydraulic gradient reduction. The Seep/3D software, which employs finite differences, was used in this study to developed more than 1000 models to pinpoint the location of cutoff walls and their depth of installation that minimizes the uplift pressure and exit hydraulic gradient. It was revealed that a cutoff wall installed at the lower toe of the structure theoretically presents piping, and one located of the upper toe reduces the uplift pressure. These results are depilated in a series of curves, which allow a designer to anticipate solutions to the seepage problem without a computer code and, to obtain the flow characteristics and achieve an optimum design by spending less time for making a quick and correct decision.

Soil is one of the most important natural resources and perhaps is the most fundamental factor in formation of civilization. In addition to food supply, the soil will also provide other human necessities such as clothing, residence, bury wastes, wild life, recreation and etc. Climate plays a very important influence on enhancing and processes of soil formation, and in addition the climatic factors play a considerable influence on plant growth, production and land use. In each region, topographic factor also influence soil characteristics. Its influence on soil development and plant growth depend on its direction and elevation. In other to study the effects of topography and depth of ground water on soil genesis, Dasht-E-Arjan plain with xeric and mesic soil moisture and temperature regimes, were selected. Based on aerial photographs and also topographic maps, the location map of the study area was drawn. Then on two transversal sections, six profiles were dug. Among them four representative profiles were selected for detailed studies. The results of field studies and also profile description showed that Entisols and Inceptisols orders were developed on alluvial-colluvial fans, while on piedmont plains and lowlands only Inceptisols were formed. The physico-chemical characteristics of studied soils showed that, among the studied profiles, there are remarkable differences in soil texture, organic matter, saturation percentage, pH, EC, and CEC. The most important soil forming processes were accumulation of surface soil organic matter and also formation of Cambic and Calcic horizons. Because of extensive cultivation, the color and thickness requirements do not satisfy for the formation of MollicEpipedon, which show great future hazards for all Mollisols of the country. The XRD results of clay minerals showed more smectite mineral with respect to kaolinite, illite and chlorite minerals. This could be due to its higher content in parent materials and also transformation of illite to smectite due to more wetness of low lying physiographies.

Stepped spillways are used in flood control activities and designed to reduce energy dissipation and stilling basin dimensions at their downstream terminal. It’s compatibility with the roller-compacted concrete technology, gabion construction techniques and precast concrete, made this structure to be very popular. Hydraulic modeling is a form of physical modeling using a scale model to simulate the flow. The advantage of this model is its potential in complex flow simulations. In this study, using physical modeling in a flume, one model with downstream slope of 1: 0.7 (V: H) was constructed. The Spillway crest was selected from the WES standards and the spillway had 6 steps. Six models were tested and evaluated. The results showed that most of the energy loss occurred in the described model. The results were confirmed by using Flow3d-10 the software.