مجله سامانه های سطوح آبگیر باران
سال دهم شماره 3 (پیاپی 34، پاییز 1401)

Due to the heterogeneous distribution of precipitation, predicting its occurrence is one of the primary and basic solutions to prevent possible disasters and damages caused by them. Considering the high amount of precipitation in Sardasht County, the people of this city turning to agriculture in recent years and not using classification models in the studied station, it is necessary to predict the daily precipitation parameter as accurately as possible. On the other hand, although the optimal performance of lazy algorithms and tree models has increased their use for predicting various hydrological phenomena, these algorithms have not been used in Sardasht County. Therefore, in this research, four models Kstar, M5P, learning algorithm with local weighting, and random forest are used to predict the daily precipitation of Sardasht Station. In this study, seven input parameters of average temperature, maximum temperature, average relative humidity, maximum relative humidity, average wind speed, maximum wind speed, and sunshine hours which were the same time as daily rainfall were used for the models. The comparison and evaluation between the input parameters showed that the sunshine hours was one of the most important input parameters, which played a significant role in the prediction accuracy of the used models. The obtained results showed that the M5P tree model had the best performance in the seventh scenario with the highest correlation coefficient (0.734 mm/day) compared to other models. In addition, the seventh scenario showed a high performance compared to the rest of the scenarios. Therefore, it can be said that increasing the input of the models has a direct relationship with their accuracy. In general, it can be said that the M5P tree model is suitable for modeling and forecasting daily rainfall in Sardasht City and it is recommended for future use.

Drought and grazing rangelands play an important role in changing the structure of vegetation and losing the biodiversity of natural ecosystems. In this research, in order to determine the effects of drought and livestock grazing on the vegetation structure of rangelands located in the Nakhab Forest of South Khorasan Province, species abundance, biodiversity, and range condition and trend were evaluated. For this purpose, sampling was done in 80 plots (2×2 m) located on four transects of 150 m using conventional methods in a two-year period (between the water years of 2019-2020 and 2020-2021). According to the standard precipitation index (SPI) and the normal percentage index (PN), 2019-2020 was very wet and 2020-2021was a mild drought. According to the physiognomy method, the plant type of the study area is Hammada salicornica and the important species include Aeluropus littoralis, Haloxylon persicum, and Zygophyllum atriplicoides. In terms of the percentage of vegetation, litter, bare soil, and stones and gravel, there is no significant difference between the grazed rangeland and enclosure in two years. The results show that in the two sampling years, the grazed rangeland has a higher species density than the enclosure. Enclosure rangeland has benefited class I and III species and livestock grazing has caused a significant decrease in class I and III plants and an increase in class II plants. Livestock grazing caused a significant decrease in the density of grass, forb, and shrub plants and did not affect the density of shrubs. The results showed that in the very wet year, there is no difference in species richness between the grazed range and the enclosure. Nevertheless, the enclosure has more species diversity than the grazed range. However, in the mild drought year, all biodiversity indices were not different between the grazed range and the enclosure. This indicates that in drought conditions, the enclosure does not help to improve species diversity.

Atmospheric precipitation is one of the most important sources providing water for various purposes. Their optimal use, especially snow and rain in arid and semi-arid regions, can play a significant role in meeting water needs in low water seasons, which can be collected and stored before they come into contact with the soil surface and become contaminated so that in times of water shortage, To provide the water needs of industries and factories, green spaces and drinking water for humans and animals. One of the methods of harvesting water from precipitation, including snow and rain, is to make the surface of the earth impermeable and maximize the runoff caused by them. Impermeable surfaces can exist naturally like stone surfaces or by covering the ground surface with materials such as asphalt, concrete, and insulation sheets such as plastic, geomembrane and decamond can be created artificially. In this research, 2 treatments with 3 repetitions were considered, which included the Catchment of geomembrane cover and plastic cover with sand protection, each in a square shape with an area of 4 m2, and were implemented in lands with an average slope of 36%. The total rainfall on the mentioned surfaces during the statistical collection period was 747 mm, of which 430 mm (52 events) was in the form of rain and 317 mm (26 events) was in the form of snow. The results of 26 winter snowfall events during two years of statistics showed that the runoff from normal precipitation in winter for geomembrane and plastic covering with sand protection is equal to 89 and 80% of precipitation, respectively. Therefore, according to the normal rainfall of the winter season (65.4 mm), the volume of runoff collected for the geomembrane cover and the plastic cover with sand protection will be 58.2 and 52.3 lit m-2, respectively in the winter season, if from the short-term statistics. The statistical period should be used, according to the annual rainfall (373.5 mm) and the winter season (158.5 mm), the volume of runoff collected in the winter season for the catchment surfaces covered with geomembrane and plastic cover with sand protection reaches to 141 and 127 lit m-2, respectively.

This research aims to introduce the water supply method required for pistachio orchards in semi-arid climatic regions using the rainwater harvesting technique. For this purpose, a rain catchment system with an area of 1000 m2 was constructed at the Tasuj Station site. Based on the mean annual rainfall of the region, runoff threshold, runoff coefficient for insulation surfaces and the area of the catchment system, water storage pool was designed and constructed with a nominal capacity of 280 m3. In addition, a geomembrane cover is used to insulate the surfaces of the rain catchment system and the water storage pool. To reduce agricultural water consumption and increase productivity, the drip irrigation method with gravel filters was used to irrigate pistachio trees from harvested rainwater. The results showed that from the total rainfall of 267 mm, about 227 m3 of water was harvested from rainfall in the year 2021. According to the findings, the per capita water consumption of each fruitful pistachio tree has decreased from 8.65 m3 in the usual drip method to one m3 in the drip irrigation method with gravel filters; without having a negative effect on production yield. The simultaneous use of rainwater harvesting techniques and drip irrigation methods along with gravel filters will reduce the pressure of groundwater resources exploitation and increase the irrigation water efficiency. The results of this research were introduced to the farmers of the region in the form of educational-promotional workshops, which have been well accepted.

The lack of water resources in Iran has increased concern about water consumption in the country. The agricultural sector is known as the largest sector of water consumption, and saving in this sector will save significant water resources. One of the solutions for the optimal use of water resources is the use of modern irrigation methods with proper design and implementation. Therefore, the purpose of this research is to evaluate sprinkler irrigation systems implemented in Khorram Abad city. For this purpose, in this research, three sprinkler irrigation systems were evaluated based on the parameters of uniformity of water distribution, irrigation efficiency, and uniformity of pressure distribution in pipes. The results showed that in Khorram Abad sprinkler irrigation systems, although there are design and implementation problems in many cases, a large part of the causes of low performance is poor management and exploitation of these systems, which has caused excessive irrigation in some cases, and while reducing the actual application efficiency, it has caused an increase in deep penetration losses.

Bandsar is a traditional and Intelligently method of exploiting floods in arid and semi-arid areas, which can be implemented in a wide area with the participation of watershed residents. This structure, in addition to controlling floods and feeding the aquifer, expands flood agriculture in the region, and by collecting sediments from floods, it leads to soil enrichment. To this end, in this research, the structure and function of Bansadrs in the Shahid Parsa Dam watershed in the north of Sarayan city in South Khorasan province were investigated. First, using topographic maps and satellite images, the Bansadr's location was determined. Then, with field visits, measuring the dimensions of the Bansadrs, the way of construction, and land use, samples were harvested from the soil inside the Bansadrs. The results showed that Bandsars in the region are divided into two groups, mountain and plain, and according to their structure, they are divided into four types. Thus, the dewatering of Bandsars started in March, and usually, it is done two to three times a year. The time for land preparation and planting is from mid-May to mid-June. The amount of crop production in the years of relatively good rainfall is at least 3.5 t of plantation product and 1 t of fodder per ha, the average annual income is up to 6.11 billion Rials from all farms. The depth of sediments in Bansadrs varies from upstream to downstream and has a decreasing trend so that the thickness of sediments was 25 cm in one year in the beginning and less than 2 cm in the end dams. Therefore, Bansadrs can be suitable structures for flood and sediment control, flood irrigation, and soil regeneration in the region.