مجله سامانه های سطوح آبگیر باران
سال هشتم شماره 1 (پیاپی 24، بهار 1399)

In arid and semi-arid regions of the world including Iran, floodwaters are the main resource to supply irrigation water. Floodwater spreading also plays an effective role in replenishing groundwater, stabilization of alluvial soil, and vegetation restoration. Qazvin traditional garden is an example of such floodwater spreading mechanism, dating back to over a thousand years ago, according to historical sources. The city of Qazvin is located at the foothills of the Aborz ranges and on the alluvial fan of the seasonal rivers. The traditional garden was built as a protective green belt around the city against floods. These unfenced gardens have been established as the largest aquifer in the region and an efficient flood spreading system to protect the city against floods. The gardens cover a vast area of around 2500 ha on three sides of the city. The unique practice of floodwater irrigation stabilizes the alluvial soil and recharges water in underground reservoirs. The gardens are placed next to each other in the form of ponds and are separated by borders with a height of about one meter. During the rainy season, the gardens are alternately filled with water up to the height of the ponds, which allow the water to infiltrate gradually into the soil. Almond, pistachio, and grape trees are irrigated once or maximum twice in months with very low evaporation. With such little irrigation, these trees survive and have economic efficiency. It is expected that the unique floodwaters irrigation of Qazvin traditional garden achieves its status in the strategic priorities of water management in the province.

Low rainfall and its poor distribution in the West Azerbaijan province have hampered agricultural production in dry-land. One of the important solutions in this regard is converting rainfall into runoff. In this study, a field experiment in Khoshalan village of Urmia on grapes in rainfed conditions with supplementary irrigation and rainwater harvesting was carried out in a split-plot design based on randomized complete blocks for six years from 2000 to 2006. The first four years were for seedlings of plants, and recording of yield was possible in 2005 and 2006. The three factors studied include fertilizer application factor in 30 and 70% of the usual recommendation for irrigated cultivation, watershed area factor in areas of 12, 20, and 30 m2, and runoff surface status factor including normal traffic, plastic cover, and paving stones. In this study, the benefit is calculated based on the cost and income of 2019. The results showed that with increasing fertilizer consumption, yield decreased from 1755 to 1461 kg/ha, and benefit decreased from 81.2 to 46 million rials. This result indicates that under semi-dry conditions, fertilizer, cannot be consumed in large quantities. With decreasing watershed area, yield and benefit increased from 1018 to 2451 kg/ha and from 6.2 to 148 million rials, respectively. Plastic with 2208 kg/ha and 113.6 million rials had an increase in yield and profit of 54 and 86% compared to the control. Also, paving stones compared to the control, experienced 1 and 49% yield reduction, and profit respectively. According to the results of this study, an area of 12 m2, with plastic cover with 70% of the usual fertilizer recommendation for irrigated cultivation, increases the yield of rainfed grapes.

Rivers play an important role in the economy and agriculture, but climate change and improper management have affected these resources. In order to better manage rivers, it is necessary to know their discharge trend and the factors that create the trend. The severe decrease in rainfall and the resulting dry periods have many negative effects on water resources. The continuation of droughts is a consequence of climate change. This study investigates rainfall and discharge changes in the Aras catchment located in the northwest of Iran. For this purpose, after data validation, 9 hydrometric stations and 5 rain gauging stations were selected with the statistical period of 1987-2016. The purpose of this study was to evaluate the trend of time series variations of precipitation and discharge variables using Mann-Kendall and Sen’s slope estimator tests. The results of the trend analysis showed that precipitation at two stations increased, however other stations did not experience any trends. Furthermore, there has been a downward trend in the discharge trend analysis at the six stations and no trends in the other three stations.

Most of the rainfall in arid and semi-arid regions, which becomes runoff immediately after rainfall, eventually evaporates and becomes inaccessible. Harvesting water from impermeable rock surfaces and storage in reservoirs or aquifer feeding is an effective way to prevent evaporation losses in these areas. The purpose of this study is to model the amount of runoff in sub-basins with impermeable surfaces in the Haft Bagh Alavi area of Kerman to estimate the volume of harvestable runoff in this area. Haft Bagh Alavi watershed is located 26 km from Kerman and has an area of 14923 hectares. About 18.3%, equivalent to 2732 hectares of the basin area has a rock mass level of more than 90%. HEC-HMS software has been used to model rainfall-runoff in the basin. The area curve number of soil, slope, and land use information was entered into the model. 30-year mean evapotranspiration data, with the 30-year mean of 10-minute precipitation data, were collected from the automatic station and used as input. The results showed that by harvesting only 10% of the total average annual cumulative runoff of four sub-basins, it is possible to collect 8.055 million cubic meters of water and provide water for supplementary irrigation of 16,110 hectares of gardens.

One of the most suitable and efficient solutions for proper use of flood potential and saline ephemeral rivers in arid and desert areas is the use of flood spreading networks with a special design that while separating the saline base flow from the flood, water also increases forage production and improves the quantity and quality of pastures and desertification control. The purpose of this study is to show the aspects of this process in the flood spreading project of the Bafgh Sirizi Station. In this study, for soil sampling, drilling three profiles in the flooded area and three profiles in the control area, as well as rangeland vegetation within four flood spreading areas and adjacent areas as control, were done randomly. The results showed that the percentage of canopy cover, density, and percentage of species of Hammada salicornica, Seidlitzia rosmarinus as well as the percentage of total canopy cover, total density, and the total percentage of species were significantly different at 1% error level. Flood spreading has also caused the presence of Zygophyllum eurypterum, Salsola yazdiana, and Artemisia sieberi species with good palatability value. The percentage of cover and the presence of litter also showed a significant difference at 5% error level. Also, a comparison of changes in soil properties in the natural and floodplain areas indicates a decrease in soil salinity and an increase in silt and clay in different soil horizons, which has provided an important role in improving fertility and moisture-holding capacity.

Groundwater is one of the most important resources of water in the world. Studies show that low rainfall, persistent droughts, and over-exploitation have caused economic and environmental damage. Therefore, this study was conducted to evaluate the effects of rainfall and drought on the groundwater of Kashmar plain as one of the most important fertile plains of Khorasan Razavi in eastern Iran, using Man-Kendall and Petit time series. In this study, from the 30-year statistical period (1989-2017), the rainfall data of Kashmar meteorological station were used to evaluate the effects of meteorological drought, with SPI index. Furthermore, the statistical data of 17 piezometer wells in the study area in 23 years (1996-2017) were used to assess groundwater drought, with PSI index. The results of the time series analysis of the SPI index in different ranges of 3, 6, 12, and 24 months in 1989-2017 showed that the gradual changes in the range of 6 and 12 months at the five percent significant level (p-value = 0.05), which the point of change was 1999-2000, however, it was not significant in 3 and 24 months. Since p-value≠ 0.05, the time series of the PSI index in Kalat-e-Rahim and Khalilabad wells (in the southern and northern parts of the region) is not significant, but the other wells are significant. This means that Kalat-e-Rahim and Khalilabad wells were in better condition during droughts due to aquifer operations in the area. Therefore, Kashmar plain has suffered from groundwater drought from 1996 to 2018. According to the SPI and PSI indices, meteorological drought has affected groundwater resources, but a more important factor in groundwater drought is the over-exploitation of groundwater, which has led to declining 40 cm groundwater levels per year in Kashmir plain.