مجله ترویج و توسعه آبخیزداری
پیاپی 30 (پاییز 1399)

Estimating runoff from atmospheric precipitation and its quantitative understanding of various production processes is considered as one of the important issues in hydrology knowledge. Since runoff in the watershed, due to several factors influencing it, is a complex issue, therefore, it is estimated that many researches, studies and various plans for development, use of water resources and hydrostructure. According to the above mentioned it was used, rain and discharge daily data of the Bar-Ariyeh area of Razavi Korasan province were used to estimate runoff from the extracted number curve method from the Natural Soil Conservation Service (SCS-CN). For this purpose, rainfall and discharge data of Bar and Ariyeh stations during the period of 56 years and in the daily scale, the value of the curve number in the three conditions of previous moisture in low, medium and high antecedent moisture conditions of soil was evaluated. The results showed that the maximum, minimum and average values of the curve number in summer and autumn were 93, 91, 92 and 85, 81, 83 percent, and in the spring and summer were 81, 79, 80 and 78, 76 and 77 percent in The domain was studied. The highest and lowest monthly average number of curve number for April and January were 93 and 76 respectively. In addition, the maximum and minimum amount of runoff was calculated for April and September with a numerical value of 12.45 and 1.29 mm in the statistical period.

Rivers are eco-hydrological dynamic systems contribute to agriculture, industry and tourism activities as well as environmental sustainable. However, rivers and their flow are impacted and contaminated through landuse change, urban sludge, agricultural waste, reservoir dam building and drought impacts. The objective of this research was to assess factors affecting the catchment landuse change and riverside plant removal seven different reaches of Dinavar river (upper sub-catchment of Karkheh basin), Kermanshah province, Iran during 2016-18. The results explored that due to dominant clay and silt deposits of Quaternary in the plain areas, meander and riparian are the dominant morphology in four reaches improper sand and gravel harvesting and converting river bank and its groves (willow and spruce) to arable lands cause development of Tamarix. Sp and some unpalatable plant species in the river bed and furthermore river bank erosion. In these reaches, the river is contaminated by disposal of rubbish, plastic, animal manure and agricultural waste. In upper River branched, severe soil disturbance through improper civil activities, road construction and up-down the slope tillage practice attributed in considerable siltation phenomenon which quickly delivered to river system by runoff during rainfall occurrence. The upper reach (upper Jamishan Dam that was built in 2018) urban and industrial wastes are main river water pollutant sources. It is concluded that the Dinavar river morphology is changed and its water also is contaminated through improper tillage practice (up to down slope), landuse change, improper civil activities, local tourism as well as waste, and rabbles disposal that are being accelerated.

Due to the logistical challenges of large-scale rainfall simulator, most studies to date have used small scale rainfall simulator with a nozzle height of less than 3 m and a plot area of less than 5 m 2. Performing such small-scale studies is valuable for investigating the rate of soil erodibility, soil infiltration, the impact of herbaceous and shrub cover on water erosion and runoff. But there is a need for larger rainfall simulator to better understand and deepen the water cycle process and the interactions that occur on a larger scale. The rainfall simulator should be designed to simulate rain from top of canopy. In this case, raindrops can reach their final speed. For this purpose, a 15-meter anchored tower (controlling tower by several cable is called anchoring) with multiple nozzles is need. The most important component of any rainfall simulator is the type of nozzle used. The most common type of nozzle is a rotating plate nozzle with a 360 ° rotation angle in two linear mounting patterns and H mounted on top of the mast. The nozzles are connected vertically to a water tank and pump motor via a plastic pipe. After setting up the system and calibrating the rainwater, a windmill collector with a radius of 5 meters (about 80 m 2) of thick nylon, thin rods and zippers is used to collect throughfall, interception, and stemflow. In water erosion of soil, the most important stage that the soil is washed is rutting stage. In small-scale rainfall simulator, the low dimensions of plots causes runoff doesn’t have enough time to rut the soil, so in this condition true knowledge about soil erodibility cannot be achieved.

The reduction and or control of soil erosion has the very important in the conservation of soil and water resources. Accordingly, various methods is being used for control of soil erosion. Studies have shown that the application of organic and chemical mulches is the available and useful methods for soil and water conservation. Therefore, in the present study was conducted the effects evaluation of bean straw mulch (as an organic mulch) with levels of 25, 50 and 75 percent, polyvinyl acetate (as a chemical mulch) with level of 3 perecnt on parameters of soil erosion and sediment concentration. The experiments were conducted in laboratory conditions and under rainfall simulator with rainfall intensity of 80 mm h-1 in duration of 10 min. The results of statistical analysis with GLM method showed that the treatments effects of used mulches were not siginificant on changes of soil erosion and sediment concentration. Also, the results showed that the concentration present of bean straw mulch was variable on soil erosion from 30.37 to 60.99 percent and sediment concentration from 12.87 to 23.11 percent. The polyvinyl acetate effect in level of 3 percent on reduction of soil erosion and sediment concentration measured 56.02 and 16.14 percent, respectively. Finaly, Application of polyvinyl acetate and bean residues in used levels, given that, these have not the effects of adverse environmental, and these can be suggested to reducing the soil erosion.

Building underground dams is one of the most effective and effective ways to provide small-scale water supply and improve groundwater storage. These structures can be used in arid and semi-arid climates to provide water and cope with dehydration and drought in many valleys and seasonal rivers at low cost. The construction of these dams can lead to improved aquifer status and environmental protection. In this research, the methods of underground dam construction as an optimal watershed design have been studied. Office studies and existing information have been used for this purpose. Investigations by researchers in various areas indicate that groundwater reserves have faced a serious crisis with water resources. Therefore, it is inevitable to adopt sound methods and policies for the conservation and management of water resources. Implementation of underground dams in Iran is a relatively new topic that can be used in watershed management activities. Implementation of these structures can prevent subsurface flow from catchments.

Rainfall as a meteorological variable is studied in daily, quarterly, monthly and annual time scale, therefore understanding the changes in rainfall over different time periods is important to assess the risk of flooding and water resources managemnet. Occurance of a high percentage of rainfall in a short rainy day can increase the risk of flooding and soil erosion. Therefore, in this study, the spatial pattern of rainfall concentration was evaluated using daily rainfall concentration index (CI) and monthly rainfall concentration index (PCI) on an annual and seasonal scale in 26 rainfall stations of West Azerbaijan province for 41 years (1397-1356). Then, the zoning map of the concentration index on annual and seasonal scales were prepared using the Co-Kriging method and elevation data. According to the annual CI index, Alasgal station in the southeast of the province and primitive stations, Siah Cheshmeh and Razi in the west of the province had a uniform rainfall concentration, but according to PCI index, the northern and northwestern parts of West Azerbaijan province have more uniform distribution of monthly rainfall than the other study areas. The CIs at other stations had relatively similar values and did not differ much, indicating a positive correlation between the CI and PCI. The results also showed that annual changes in CI values are most associated with the percentage of annual rainfall that occurs during 15% of rainy days. Therefore, the daily heterogeneity of rainfall during a year is related to the best percentage of rainfall of 15% of rainy days in the study area, and the seasonal distribution of rainfall over a year can be justified to some extent by the heterogeneity of daily rainfall.

In recent years, the growing trend of population and overuse of groundwater aquifers and subsequent events such as droughts are causing irreparable damage to the country's socio-economic infrastructure. Therefore, the purpose of this article is to investigate the impact of groundwater level on rainfall fluctuations in Rafsanjan plain from 1992 to 2016. Drought periods were determined based on meteorological drought index (SPI) and groundwater (GRI) at three time scales (12, 24 and 48 months) and correlation and trend were determined using Pearson correlation and Mann-Kendall test, respectively. The results of meteorological and groundwater drought analysis showed that the highest drought classes in these two indices in the relatively normal class were 12, 24 and 48 months at 33.56, 41. 87 and 49.01 for SPI and 29.75, 29.96 and 29.64 for the index, respectively. GRI occurred The study of the effects of meteorological drought on the changes in groundwater aquifers indicated that the drought showed the highest correlation with the GRI index of 0.414 in the 48 month period, so that this scale is the most consistent since 2003. With the aquifer drop variations, and then showed the highest correlation on a 24 month scale of 0.256. The bottom is relatively high doses correlation between SPI and GRI indicators show that groundwater levels are influenced by significant changes. The results also showed that the Rafsanjan plain groundwater loss trend was significant at 99% level and all Mann-Kendall test statistics indicated that the aquifer level changes in these areas had a negative and negative trend such that the groundwater level during this plain The 25 year old dropped 20.75 meters.