جستجوی مقالات مرتبط با کلیدواژه "آب نمود" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

 One of the most important features of any watershed is the threshold of the start of runoff, which can reflect the different characteristics of the watershed and is an important factor in identifying and determining the flood status of the watershed. Accurate estimation of the amount and duration of runoff due to rain events, followed by the starting point of the flood, is one of the main points of interest in hydrological studies of watersheds. The runoff threshold is the amount of effective precipitation that is required during a certain period of time at the level of a certain watershed to start a flood at the outlet of the drainage channel of that level. The purpose of this research is to determine the minimum rainfall, or in other words, the effective rainfall on the start of runoff, in the Sanij watershed in the province of Yazd. By determining the height of the minimum rainfall for the start of runoff in the mentioned basin or other basins, one of the main and effective components in studies related to flooding and flood risk zoning is provided.

 The study area in the current research is the Sanij watershed, 30 km from Yazd city in Taft city, Yazd province, with an area of 153.173 square kilometers and geographic coordinates 31°32°48 to 31°18°42 north latitude and 36°54° north latitude. 53 to ˝54 ˊ03 ° to east longitude. Its annual rainfall is 220 mm, the average annual temperature is 11.2 degrees Celsius and the average relative humidity of the basin is 42%, the maximum height of the basin is 4036 meters and the lowest point is 2020 meters high. The concentration time of the area (Tc) according to the Bransby-Williams method is 5.18 hours. The stations targeted in this research are the Faizabad hydrometric station at the outlet of the Sanij watershed to provide flood discharge data, the Bidakhoud rain gauge station for hourly rainfall data and the Faizabad climatology station to provide 24-hour rainfall data. daily) whose data was available for the period from 1370 to 1400. To achieve the goal of the research, the relationships between maximum 24-hour rainfall and runoff threshold were investigated. Also, the compatibility of the corresponding hydrographs and hyetographs was studied in order to estimate the minimum rainfall for the start of runoff, and the intensity of rainfall was checked in the time base of 1 hour.   Then EXCEL software was used to analyze statistics and information.

 The results of investigating the relationship between the runoff threshold and the maximum 24-hour rainfall, whose data was a combination of 24-hour rainfall and torrential rainfall, showed that their function is y=0.9131x+ 14.01 and the minimum amount of precipitation with 82% of  R2 is equal to 14.01 mm. It also showed the results in the adaptation section of water patterns and corresponding rain charts; The average height of precipitation for the start of runoff is 18.9 mm. Finally, the average value for the minimum precipitation height in both study methods was 16.45 mm. Also, the intensity of precipitation in the time base of 1 hour was estimated as 13 mm; Therefore, if the intensity of precipitation is more than 16 mm in the time bases above 1 hour, it is expected that runoff will be produced at the outlet of the basin.

 The aim of the present research is to determine the threshold of effective precipitation that leads to the flow and start of runoff in a complete basin in the arid regions of central Iran..By knowing the threshold of the start of runoff in watersheds, one of the main components in hydrometric studies and optimal flood management is provided. The results showed that if the duration of rainfall in the basin is more than one hour and its amount is more than 16 mm, the runoff will flow at the outlet of the basin. It is also important to know the threshold of effective precipitation in the beginning of runoff in watershed plans, optimal use and management of precipitation, as well as the design of rain catchment surfaces to absorb precipitation. It should be noted that the results of this research depend to a large extent on the direction of the entry of rain-producing systems as well as its distance from the outlet of the basin, which is suggested to be investigated in future researches.

Flood hydrographs preparation and estimation are considered a comprehensive information for managers and planners. While, it is not simply possible preparing it for all watersheds. Therfore, suitable flood hydrograph estimation and modeling seems to be necessary using available rainfall data. The study area is located in Kasilian representative watershed in Mazandaran province comprising 66.75km2 in area. For the accomplished present study, 15 characteristics of hyetograph as independent variables and 8 characteristics of hydrograph as dependent variables were considered for 60 storms from 1975 to 2009. For estimation flood hydrograph, aadaptive neuro-fuzzy inference system with two methods i.e., grid partitioning and subtractive clustering was used. Variance inflation factor (VIF) was used to select the input variables. The ANFIS results showed that subtractive clustering was found to be superior to grid partitioning.

In undeveloped and less developed countries of arid zones, the easiest way for water supply is withdrawal of groundwater. The negative perception of this method of water discharge is clear. Spreading floodwater is one of the water resources management strategies in arid and semi-arid zones that has positive impacts on groundwater resources. The aim of this research was to demonstrate the impact of floodwater spreading on quantity of groundwater in Gareh Bygone Plain, Fasa, Fars province, Iran. Annual changes of water level was determined by reviewing water level of monthly data (1992-2013) of four piezometric wells. Despite to the spreading floodwater, the general trend of groundwater level was declining. Thus, for demonstrating the role of the floodwater spreading in groundwater recharge, changes in groundwater levels were investigated in the years of increases and decreases of floodwater. Results showed that the least recession is in piezometric wells 1 and 3. Piezometric well 1 due to the effect of fault and piezometric well 3 due to the effect of floodwater spreading. Results of Principal Components Analysis (PCA) of monthly water level in four piezometric wells showed that the first component as the most important indicator of recession of water level in the region is more than 83% of the variance. Sorting PCA loadings on the first component, represents a high recession in piezometric wells 2 and 4 that corresponds with the results of recession map of the plain. Piezometric well 2 due to evapotranspiration of trees and piezometric well 4 due to excessive extraction of water for agriculture in the area showed the most recession.