Mojtaba Shahnazari, Zahra Hejazizadeh, Mohammad Saligheh,
Volume 20, Issue 59 (12-2020)
Abstract
Abstract
In this research, while studying climate conditions in the current period and analyzing changes in temperature, precipitation level, and the sunlight received, current conditions were also analyzed based on daily data from synoptic stations in the region, which had meteorological data recorded for at least 30 years. Given the environmental conditions necessary for the growth of rice, the availability of its phenological data, its high-low temperature thresholds, the Degree Day systems needed for the completion of its life cycle, and the phenological processes related to its economic production, a suitable agricultural calendar was specified. During the March-July period, this calendar showed variations in different provinces. Based on the current temperature conditions and the probable continued warming trend of the planet in the decades to come, nwoDscale was applied to the output from the atmospheric general circulation model MCdaH3 under scenario using LARS-WG5 model. In this study, years between 1969 and 1990 were used as the base period, while years between 2046 and 2065 were studied as the future period. Temperature and precipitation conditions for the future period were simulated. Obtained output was then studied and compared with temperature conditions that were suitable for the plant to grow in the region. With some differences, results showed that the agricultural calendar for rice in Gilan and Mazandaran provinces will shift to winter. Given the different temperature conditions of Golestan province, its agricultural calendar will shift to spring.
Seyd Fateme Hashemi, Ali Shahnazari,
Volume 25, Issue 78 (9-2025)
Abstract
The catchment area of the Talar River in Mazandaran Province is subject to annual flooding events that facilitate the transport of substantial quantities of silt. To investigate sediment transport dynamics within this watershed, samples were collected at five designated sections along an 11-kilometer segment of the Talar River. The sampling intervals were delineated as follows: 24.7–22.4 km, 18.2–20.5 km, 17.5–18 km, 16.75–17.5 km, and 11.5–16.75 km, measured from the urban area of Malakala-Najjarkala to Arab Roshan, with all distances calculated from the shoreline. This study aimed to analyze sedimentation and erosion patterns over a five-year period (2016–2021) employing the HEC-RAS model. Sediment transport and volume were assessed based on long-term data obtained from the Kiakla hydrometric station, with a specific focus on flood conditions associated with return periods of 2, 10, 25, 50, and 100 years. The findings indicate that the cumulative sediment input at the beginning of the monitored section is 0.9 million tonnes lower than the total sediment at the end. The river exhibits a pronounced tendency towards erosion. In the first section (22.4–24.7 km), the mean sediment height is 11 cm, accompanied by significant sedimentation totaling 6 million tonnes. The second section reflects an approximate deposition of 1 million tonnes. The third section demonstrates a relatively stable sediment pattern. In the fourth section, the conditions for erosion—both in terms of depth and volume—are deemed unsuitable for sediment harvesting. The fifth section (11.5–16.75 km) records erosion amounting to approximately 8.3 million tonnes, with height variations ranging from 10 to 20 cm. Under these circumstances, sediment removal is impractical; However, the implementation of flood management strategies and river engineering interventions is strongly recommended.
