مجله سامانه های سطوح آبگیر باران
سال چهارم شماره 2 (پیاپی 11، تابستان 1395)

As the study area is situated in warm and dry climate, the very strong anomalies should occur in the atmosphere to form snow spreading widely, one of the condition is atmospheric cut-off. In order to study snowfall in Kerman province, the data were used from 10 meteorological stations within the province. To explain they structure and movement of the precipitation system, the data from web- site of National Climate and Environmental Prediction and the Atmospheric Research (NECP/NCAR) from the upper atmosphere stations were used and synoptic maps were drown at the time of occurrence of the phenomenon. The results showed that on the day before rainfall, there was the poor instability in the region, but the next day's instability in atmosphere the becoms intense in different layers. Synoptic maps are indicated a very deep landing in central of Iran in the core of cut-off with an average temperature of -25 degrees. Cold air fall in the upper troposphere and its contact with lower latitude air, caused a deep frontal in the region. Other major reasons include a placement area beneath the jet stream core divergence and strong eddy in central Iran. With the establishment of the anticyclone over Pakistan, and by entering the system in the region, and subsequently by passing through the Oman Sea and the acquisition of sufficient humidity which is providing the heavy snow in the region.

In recent years the importance of flood control and management in urban areas has increased due to the development of urbanization and environmental pollution. The green roof technology is used in many parts of the world and seems an appropriate technique to reduce runoff. The lack of surface water collection systems has caused the flow of water on the streets in Tehran. The aim of this study is to simulate the effect of extensive green roof of residential buildings to reduce urban runoff in Tehran. For this purpose, a survey of the study area was performed in GOOGLE EARTH, and the area of the roof of buildings were analyzed using AUTOCAD software. Then, simulated green roof performance based on mass balance for a typical roof and three extensive green roofs with the soil thickness of 25 mm and the vegetation area of 25%, 50% and 75% and the hydraulic relationships between water and soil were compared using CROPWAT software. The results show that the highest decrease in runoff for extensive green roof with the vegetation of 25%, 50% and 75% is respectively 12/59%, 24/59% and 36/58% in comparison with the typical roof. The study shows whenever the vegetation area of the green roof is more; the run-off from the similar rainfall will be less. Thus, the green roof can be raised as a method to reduce runoff in Tehran.

About 70 percent of earth's surface is covered with water, but "water crisis" in many countries increasingly takes on more complex dimensions. The crisis is more sensible in countries located in the arid belt of the earth especially Iran. Climate change and mismanagement of water resources are the factors affecting water crisis. The use of different methods for efficient use of rain water and water harvesting, is one of the ways to compatibility with the effects of the climate change. Cloud seeding technology is one of the ways to increase water harvesting rain and atmospheric water resource management, which has been used for many years at international level, and it has a 18-year history in Iran. On the other hand, the economic feasibility and cost-effectiveness of water harvesting is also necessary and important. The aim of this study is to determine the unit cost of each cubic meter of water extracted with the help of cloud seeding technology. For this purpose, two scenarios of 10 and 20 percent of the increase in rainfall for the watersheds of Hamadan employed in, and cost of one cubic meter water obtained using the runoff coefficient and operating costs of cloud seeding projects. The results show that for every cubic meter of water extracted from cloud seeding under the scenario of 10% and 20%, 278 and 186 Rials will cost respectively.

Runoff generation threshold dependent on the different parameters such as rainfall features, geometric characteristics of the basin, soil characteristic basin, vegetation and primary humidity. Runoff outbreak in big basins is determined by using the rainfall data and the recorded data by hydrometric stations. In small basins, estimating the runoff outbreak is challenging due to the lack of hydrometric station. In this research, the rainfall events and runoff were measured in Sanganeh Kalat watershed (the studied sub basins are small and their area is about 1 ha and the whole area is about 7 ha). The rainfall was recorded by a rain gauge system and runoff were recorded by five lymonograph systems which four of them were installed in the output of sub basins and the remaining one was installed in the main output basin to record data for two years. Different effective factors in runoff outbreak were studied including rainfall intensity, basin area, channel slope and basin slope, channel density and rainfall in some days ago. Results show that the rainfall intensity and basin area play the most in runoff outbreak. There is a relationship between runoff outbreak and these two factors which have high precision.

Severe lack of rainfall and its unfavorable distribution, very high evapotranspiration rate and the low water-holding capacity in some of the soils are the most important challenges for the establishment of plants in arid areas. This research was aimed at comparing efficiency of different water harvesting methods for establishment of six native plant species in Chahdar rangeland of Mashhad. It was designed in a completely randomized design block, splitted in time and space. Experiments contained two major treatments that were assessed during two consecutive growth seasons. First major treatment, included different water harvesting methods i.e. contour furrow, pits and small basins. For the second treatment, six perennial range plants of Agropyron elongatum, Secal montanum, Sanguisorba minor, Medicago sativa, Onobrychis khorasanicum and Krashninkova ceratoides were sown and compared. Seeding emergence and survival were recorded three times (spring 2014, autumn 2014 and spring 2015) and data were analyzed by using SPSS software. Results indicated significant differences between water harvesting treatments and between plant species. Highest survival rate, at the end of the second growth season, was respectively found for Onobrychis khorasanicum and Krashninkova ceratoides. Highest establishment rate was found in pits, mainly because of higher water soil accumulation as compared to that of contour furrow and small basins. According to the results of this research, best restoration practice for Chahdar rangeland is sowing seeds of Onobrychis khorasanicum and Krashninkova ceratoides within the small pits.

The aim of this project is to study the effect of mechanical structures on flood control of rainwater catchment systems in Taftan Catchments to identify the weak points and find a scientific approach to useful function of these mechanical structures. In this research , the capacity of the check dam reservoirs was calculated and measurements were laid in check dams reservoirs to determine the level of water in each flood. The result shows that the capacity of these mechanical structures is 145744m2. During this research, 4101090m3 precipitation have occurred that caused 939434 m3runoff in this area. The construction of these check dams reservoirs runoff has resulted in harvesting and infiltration of 320535 m3 floods although618899 m3of that have left this area. The period while the absence of these reservoirs, 939434 m3 runoff left this area and the destructive power of the floods were increased as well, that caused more erosion and less infiltration in main streams. Reviews show that the construction of these check dams reservoirs will reduce the amount of run off from 22.9 to 7.8 percentages. Before the construction of these structures, the record-high flood level was 145cm which reduced to 72cm after that. Statistical analysis of the data shows thatthere is a significant differenceat the 0.01 level (P

The Artificial recharge of aquifer in order to improve and develop underground water resources is a strategy. Iran pays a lot of finance to construct the artificial recharge project. Watershed Projects are the most important activates that entails a lot of expense yearly. So evaluation the effect of these projects is essential. This investigation was performed to consider the effectiveness of Zoroom dam on the groundwater quantity in the Tokahor plain. Therefor we used water table data from two control wells and three wells trial in a 14-year- old static period(1997 – 1998 to 2010-2011) . Statics period was divided into two parts before an after the dam construction (1997-2004) to (2004-2011). Despite no change in the amount of rainfall The results indicated water table increased in test wells and decreased in control ones before and after performing this project. This shows the positive impact on the water table by performing this project in Tokahor plain.