Document Type : Research Article
Authors
1 Mazandaran Water regional company
2 Mazandaran Regional Water Company
Abstract
Abstract
The imbalance between water availability and water consumption is a critical challenge to sustainable development, particularly in water-dependent regions. This study examines the Tajan River Basin in northern Iran to evaluate the balance between water resources and sectoral water demands, focusing on agriculture, aquaculture, drinking, and environmental needs. Using hydrological data from river monitoring stations, ten years of inflow and outflow data from the Shahid Rajaee Dam (2011–2021), and regional groundwater information, the study assesses water availability under different hydrological conditions. Annual water demands are estimated at 598 million m³ for agriculture and aquaculture, 68.7 million m³ for drinking, and 100 million m³ for environmental sustainability. Available resources include regulated water from the Shahid Rajaee Dam, the flow of rivers in the middle basin, groundwater extraction, and surface water from ponds. Water availability was analyzed under three scenarios: normal, dry, and very dry years. In the first six months of the year, Shahid Rajaee Dam can supply 231 million m³ (normal), 194 million m³ (dry), and 122 million m³ (very dry). Annual contributions from ponds and wells are estimated at 12.8 million m³ and 176 million m³, respectively. Comparative analysis shows that the Tajan Basin experiences significant water shortages of 166 million m³ (normal), 231 million m³ (dry), and 324 million m³ (very dry). These findings highlight the urgent need for improved water management, better allocation strategies, and infrastructural developments to mitigate the effects of water scarcity and support long-term sustainability in the region.
Keywords: Water resources, basin, Tajan River, water uses, Shahid Rajaee Dam
1) Introduction:
Water is essential for survival, economic growth, and industrial development, and its optimal allocation is crucial for sustainable progress. Effective water management, especially in agriculture, requires understanding the dynamic relationship between water supply and consumption. This study focuses on the Tajan River Basin, aiming to evaluate and compare available water resources and their uses—agricultural, drinking, industrial, and environmental—across the Tajan Plain and the upstream basin during the exploitation season. The goal is to identify potential water shortages throughout the year. The study builds upon data and findings from a 2023 report by Pandam Company on the basin's water needs.
2) Materials and Methods:
The Tajan River is one of the important rivers of Mazandaran Province, which originates from the Hezar Jarib Mountains and flows into the Caspian Sea after passing through the city of Sari in Farahabad. The entire catchment area of this river up to the entrance to the plain with an area of about 4050 square kilometers and the Tajan Plain with an area of about 800 square kilometers, has been considered as the study area to investigate water resources and uses. In this study, long-term statistical data from hydrometric stations of the Zaremroud (Garm Rud Station), Lajim (Vastan Station), Chahardangeh (Varand Station), and Tajan (Kordkheil Station) rivers, as well as the inflow and outflow statistics of Shahid Rajaee Dam (during the ten-year operation period of 1390-1400) as the main source of water supply for the Tajan basin, have been used. For groundwater resources (wells), information obtained from the Mazandaran Regional Water Company in 1400 and basic water resource studies have been used. Regarding water ponds, the results of the interpretation of new satellite images in the form of a land use map have been used.
3) Results:
Surveys in the Tajan River Basin, including the Tajan Plain and upstream areas, reveal approximately 119,800 hectares of agricultural land, with 74,500 hectares irrigated and the rest under dry-land farming. Additionally, there are 550 hectares of fish farming ponds in the plain, mostly for warm-water species, some of which also support aquaculture. The total annual water requirement is 492 million cubic meters for agriculture and aquaculture in the Tajan Plain, and 106 million cubic meters for upstream areas. Drinking, industrial, and tourism-related water needs across Sari, Miandoroud, and Kiasar counties total 7.68 million cubic meters per year. The environmental water demand of the Tajan River is estimated at 100 million cubic meters annually. Available water sources include regulated releases from the Shahid Rajaee Dam, seasonal flows of middle basin rivers, pond water storage, and groundwater. Water availability is assessed under three hydrological scenarios: normal, dry, and very dry years. In the first half of the year, Shahid Rajaee Dam can supply 231 million m³ (normal), 194 million m³ (dry), and 122 million m³ (very dry). Annual extraction from ponds and wells is estimated at 12.8 and 176 million cubic meters, respectively.
5) Discussion and Conclusion
A comparison of the needs and available water resources shows that the amount of water shortage in the entire area (Tajan basin) in normal, dry and very dry years is 166, 231 and 324 million cubic meters, respectively. A comparison of the resources and uses of the study area shows that the amount of water shortage in normal, dry and very dry years in the Tajan Plain area is 147, 212 and 305 million cubic meters, respectively. In other words, in a normal or normal water year, there is a water shortage of about 150 million cubic meters in the irrigation network and the Tajan Plain area. Water shortage due to the reduction of available water resources, including the outlet of Shahid Rajaee Dam, leads to resource constraints and, as a result, water shortage in the lands of the Tajan Plain. In the dry water year, the water shortage was mainly due to the decrease in discharge from the Shahid Rajaee reservoir dam and the rivers of the middle basin. Therefore, in addition to the necessity of managing water distribution and scheduling, as well as improving the Tajan irrigation network, which will partially reduce the amount of damage caused by water shortage, the construction of the planned dams on the Zaremroud and Chahardangeh rivers is very important in regulating the monthly discharge.
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