مجله سامانه های سطوح آبگیر باران
سال نهم شماره 4 (پیاپی 31، زمستان 1400)

The flow duration curve (FDC) represents the frequency distribution of water flow over a period of time, which is widely used in hydrology to evaluate different ranges of river water flow applications. Therefore, it is necessary to develop a suitable estimation model and method in un-gauged watersheds. To this end, in the present study, a modeling method based on nonlinear regression, for the preparation of FDC based on water flow (Q) and precipitation (P) data in the statistical period 2002-2013, area (A) and mean slope (S) of upland watersheds of 30 stations of Ardabil Province were used. For nonlinear regression analysis, about 70 and 30% of the stations were considered for calibration and validation, respectively. The development of the FDC estimation model involved several steps, including nondimensionalization of flow data, normalization, definition of the parameters of nonlinear regression equations, and calculation of required quartiles. According  to the results, after testing different equations, the equation Q=0.00002385(AP)0.571S0.845  considering all input variables with a coefficient of determination (R2) 0.78 and mean absolute error (MAE) 0.021, was introduced as the final equation for FDC modeling in watersheds without statistics.

Every year, large amounts of the country's water resources leave the country through political borders. Subsurface water is part of these resources that flows on the dry bed of rivers and becomes inaccessible without proper exploitation. Since Iran has many common borders with neighboring countries, it is necessary to pay attention to this issue. One of the appropriate solutions to prevent the outflow of subsurface water from the country is the construction of an underground dam that the first and most important step in the construction of an underground dam is to locate the suitable areas. The purpose of this study is to identify suitable sites for subsurface flow harvesting in the border areas of Torbat-e-Jam County. Therefore, using the analytical hierarchy process (AHP), the effective factors in identification of suitable sites for the underground dam were weighted and potential areas were identified. Finally, through a field visit and considering the issues in the region, suitable areas were determined for the construction of an underground dam. The results show that 26.6% of the study area has lacks subsurface flow harvesting potential. Among the parameters weighted by AHP, geology and slope have the highest weight and the distance from the road has the lowest weight. Furthermore, with the field studies, three suitable points for the construction of an underground dam in the study area were identified. Since locating an underground dam is time consuming and costly, using the AHP can be a good way to reduce the time and cost of locating.

Arid and semi-arid regions with highly variable rainfall and periods of drought or unpredictable floods have severely affected residents' water shortages and they are often living in insecure areas. Rainwater catchment systems are one of the available solutions to overcome water shortage and runoff management in these areas. Surface runoff is a potential source of water that, with proper management and rainwater extraction methods, can be used to meet demand in various sectors, including agriculture and drinking. This study was conducted with the aim of introducing suitable places for establishing rainwater catchment systems in Latyan Watershed. Essential maps of the watershed for this study included land cover coefficient, permeability of formations and soil, average long-term rainfall, slope, land use, and drainage network were prepared. The mentioned maps were each divided into five categories and by overlaying in ARC/GIS 10.7.2 environment, finally suitable places for runoff production of the watershed were obtained to create catchment levels. The results showed that slope percentage, type of land use, NDVI and climate in this watershed were effective factors for runoff production. In addition, the map of runoff production potential classes showed that the frequency percentages related to runoff production potential classes were very high, high, medium, and low, respectively 3.2, 22, 33.6 and 23.5%. For the construction of these systems, priority is given to areas that have the potential and frequency of upper class in terms of runoff production, which areas with medium runoff production potential have this feature. Introducing suitable places to establish rainwater catchment systems can maximize the probability of success of rainwater harvesting projects.

Rainwater harvesting is one of the available, low-cost, and complementary methods for groundwater use, which is highly important in arid and semi-arid regions. The purpose of this study is to estimate the amount of water that can be extracted from the annual rainfall of Aryan Shahr for non-drinking purposes. In this study, in the first stage, the rainfall data of the Aryan Shahr climatology station, located in the city, for the period 1975-2016 were studied and analyzed and the average rainfall of Aryan Shahr was calculated to be 183 mm. In the second stage, based on detailed studies of Aryan Shahr municipality, the amount of the city area, as well as different uses of the city, was determined, and based on the runoff coefficient of each user, the volume of extractable runoff was determined on a monthly, seasonal, and annual basis. The results of this study showed that due to the occurrence of precipitation in winter and spring, the maximum volume of water can be extracted from December to April, and seasonally in winter and spring can be extracted. Annually, the amount of 141636.2 cm3 of runoff can be extracted from the city, which can be used in various applications according to the needs of the city.

Prediction of daily evaporation is a valuable and determinant tool in sustainable agriculture and hydrological issues, especially in the design and management of water resources systems. Therefore, in this study, the ability of artificial intelligence models of multi-layer perceptron (MLP), support vector regression (SVR), and the hybrid model of support vector regression-firefly optimization algorithm (SVR-FFA), to predict daily evaporation at Takab Station during the period 2002-2020 based on four statistical criteria have been assessed In all three models, the best scenario was the model whose input included the parameters of average temperature, minimum temperature, maximum temperature, average relative humidity, minimum relative humidity, maximum relative humidity, wind speed, and sunny hours. Among the input parameters, the sunny hours was one of the effective components on the evaporation prediction, which reduced the errors in all models. The results showed that the sixth scenario of the MLP model provided the best performance with the least error (2.18) compared to other models. It was also concluded that the sixth scenario of the SVR-FFA model had a lower error (2.20) than the other models. Among the SVR model scenarios, the sixth scenario showed the lowest error (2.27) compared to other SVR combinations. The results of this study showed that the sixth scenario of the MLP model had the best performance and the hybrid firefly algorithm improved the performance of support vector regression in estimating daily evaporation.

The trend of river discharge changes in arid and semi-arid regions is mostly decreasing and this trend can be influenced by climatic factors and rising temperatures in recent decades in these areas. This reduction in discharge could have a significant impact on the water storage of the Nahrin Dam and agriculture, industry and drinking water in Tabas City, which should be considered by experts. The aim of this study was to determine the trend of discharge, precipitation and temperature in the watershed of Nahrin Tabas Dam using Mann-Kendall method, Sen's slope and linear regression. After data investigation and validation the data, the statistical period of 1987 - 2017 was selected. The results of all methods showed that the discharge decreased in all scales of annually, seasonally, and monthly. Precipitation has also decreased and in this 31-year period, it has annualy decreased by 0.8 mm, in average. The temperature has been increasing and on average, it has warmed up to about 1.5 °C during this period. The declining trend of river discharge has been due to climatic factors such as drought and rising temperatures. So that, according to the standardized precipitation index (SPI), the region suffers from severe drought in the last years. There is no water extraction for agriculture and industry above the hydrometric station, and the land use of the region has not changed. Therefore, declining trend of river discharge reduces  the agriculture and other exploitations at the downstream of the Nahrin Tabas Dam, which already exists.