مجله سامانه های سطوح آبگیر باران
سال پنجم شماره 3 (پیاپی 16، پاییز 1396)

Rainwater harvesting is one of the most important techniques for collecting water. Harvesting and using rainfall runoff can help with better management of water resources. The purpose of this study was investigating the economy and potential of rainwater harvesting from the rooftops in Fasa University. Daily rainfall data for 30 years (1987-2016) at the Fasa station was collected and used to create monthly statistics. After analyzing the data in terms of accuracy and homogeneity, time series data were fitted to the different functions. After selecting the best distribution function with respect to the residual sum of squares, daily rainfall on 2 return periods was calculated. Using empirical equations and available parameters, the volume of the reservoir needed to store the harvestable water was determined. Finally, using the net present value, the time of return on capital and the economics of the project were studied. The results showed that the maximum volumes of water that can be harvested in daily precipitation is 24.6 m3, occurring in February. Therefore, according to the purpose and the selected method, we need reservoirs to store 24.6 cubic meters of harvested water. Also, the results of economic analyses showed that the return on investment of 250 million Rials occurred in the 6th year. Therefore, it is suggested that this project be implemented as a technical and economic plan at Fasa University.

Due to the short period of statistical data for other stations only the rainfall level of Bojnurd station was used to determine the coherent pattern of extreme precipitation in North Khorasan. In order to determine the patterns of rainfall, data related to sea level pressure, specificity, vertical velocity (omega), wind component (U), wind velocity component (V), geopotential height and air temperature at different levels, collected four times a day, were used. Also, Outgoing Longwave Radiation (OLR) prepared daily by the National Center for Environmental Forecast from two days before the rainfall was entered into GrADS software along with the previous parameters and analyzed using the software’s capabilities. The findings show that the prevailing atmospheric patterns during the occurrence of rainfall is the existence of a nave with a north-southwest axis in the southern part of the Caspian Sea, which causes instability, raising and transferring moist air to the studied area, causing heavy rainfall in the area. According to the vertical maps of atmospheric moisture, it was determined that the highest amount of moisture in the atmosphere was at lower levels of the troposphere. By studying the maps of the convergence nuclei of moisture at different levels, the role of the Caspian Sea in providing the moisture of such heavy rainfall is visible. The status of the atmospheric river at upper levels of the atmosphere also contributes to more severe ascent of air, increased instability, and elevated atmospheric turbulence in the region. On the other hand, falling cold air has higher latitude, which creates a frontier, increases its intensity, and stretches the frontier to the upper levels of the atmosphere.

Snow and snowmelt are important factors controlling flow regimes in mountainous basins and provide most of the water. As a result, snow hydrology is of great value in mountainous areas. Estimation, simulation and prediction of flow resulting from rain and snowmelt has applications in provision of drinking and irrigation water, water control in rivers, flood control and flood warning systems, and estimations of flood damage in a basin. In this study, flow resulting from snowmelt was simulated using the MLP neural network and support vector machine (SVM) models for the Baladarreh Kandovan, Marand ski resortand, and Sandoghlu ski resort stations in the East Azerbaijan Province in the 2006-2013 period. The coefficient of correlation, root-mean-square error (RMSE), and mean absolute error (MAE) were used to evaluate accuracy. The results indicate that the neural network model had better accuracy compared to the SVM model. Among the different arrangements of neural networks, the 3-6-1 arrangement with snow density, length of snow sample, and snow depth had the highest accuracy.

The current research was carried out to study the amount of soil erosion and soil moisture storage in cultivation of two species from the Gramineae family . The study area was located 45 km north of Khorramabad in the village of PereskOlia, in the province of Alashatar in the Honam basin. Most of the cultivation in the area is wheat, cultivated on land with a slope of up to 18%, and in rangelands that have been converted to dry farmland. In order to promote the correct principles of crop cultivation and soil tillage, and in order to highlight the effects of land use change on soil condition and water loss, two sites were selected with identical conditions. On the control site wheat, the region’s most common crop, was cultivated and in the treatment site rye (Secalemontanum) was grown. The reason for selection of rye is the natural abundance of this species in the rangelands of the region, its resistance to harsh ecological and climatic conditions, its permanence and the extensive use of this species in the food industry and its several other industrial applications. To determine the amount of soil erosion, special geotextile fabrics were installed at the end of each site. To ensure the accuracy of soil erosion measurements, erosion pins were used in the both sites. Also, soil moisture content from the soil samples with depths of 0-25 centimeters was determined by weighing and drying samples in 20-day intervals during growth period. The three-year results after the implementation of this plan indicated that the amount of rye barley per unit area in the third year was 19.91% higher than the wheat yield in the control site. Soil erosion of the treatment site compared to the control site (wheat) decreased by about 53%, and soil moisture content of the rye site was 91.3% higher than the control site (wheat) in the third year. In addition, the cost of agricultural inputs in the treatment site was reduced to one-fifth in the treatment condition. Along with the scientific and investigative results of this project, its extensional results include the level of participation and interest in this project among farmers. Observing the project accomplish its objectives lead to farmers’ implementation of this plan at a large scale in agricultural fields. Finally, this study increased farmers’ willingness to change the cultivation pattern from wheat to rye in the study area.

The aim of the present study is to investigate the amount of salt in the Musian plain and its relationship with falling water table during the time span of 2001-2013. To conduct this research, statistics from 7 observation wells were used. Then, the zoning maps of EC, SAR, TH and TDS were drawn. In order to clarify the relationship between these maps and the drop in water table levels, the hydrograph and the groundwater drawdown map of the plain were prepared. The results showed that the observed groundwater drawdown in the plain has led to an increase in all four parameters in the studied area so that EC, TH and TDS have exceeded world standards in most parts of the studied area. Low amount of rainfall in the area, successive drought and ultimately, the existence of Aghajary clastic formations can be mentioned as factors influencing the unfavorable quality of groundwater in the plain.

In the past decades, urban development and the increase of impervious surfaces have caused an increase in the volume and peak discharge of runoff along with an increase in its pollution. Bojnord is one of the cities affected by flooding. This study is an attempt to analyze the feasibility of using the infiltration trench system in some parts of Bojnord and predict its effects using SWMM. Runoff generation volume was calculated with return periods of 2, 5 and 10 years using SWMM. Then, the results were compared with two conditions using and not using infiltration the trench system and the reduced runoff generation volume was analyzed in the case using the infiltration trench system. The results of this study indicated that the reduced runoff generation volume with return periods of 2, 5 and 10 years are equal to 6.51, 6.26, and 6.18%, respectively.

Having the values of rainfall characteristics (intensity, depth, duration) in different return periods is highly important in many of the projects related to water resource management, drought studies, flood management, and design of water structures. These parameters are also the main inputs in hydrological models. In this study, different available software for frequency analysis and the properties of several related packages presented in the R programing platform were reviewed and the best distribution functions fitted on each rainfall characteristic was determined using the L-moment method through lmomco package. Further, quantile values of each variable were determined for different return periods based on the selected distributions. For this purpose, 40-years rainfall data recorded in Minoodasht station in Chehelchay watershed located in Golestan Province was used. The results showed the most appropriate distribution fitted on intensity and depth of the rainfall to be the Wakeby distribution and the Weibull distribution for duration. Furthermore, the quantile values were computed for each variable in return periods of 2 to 1000 years. The results indicated the application of L-moment through lmomco package in the R software platform as a very useful tool for achieving the best fitted distributions on the sample data, showing high efficiency in determination of the governing distribution on each variable and its quantile value for a given return period.