Investigating the Impact of Increasing Cultivated Area and Population Growth on the Surface Water Resources of the Mahabad Dam Basin Using the WEAP Model

جغرافیا و مخاطرات محیطی

Article 14, Volume 14, Issue 1 - Serial Number 53, March 2025, Pages 299-324   

Document Type: Research Article

DOI: 10.22067/geoeh.2024.85119.1425

Authors

Nezamoddin Mahmoudi¹; Hirad Abghari^{* 2}

¹PhD student in watershed management, Faculty of Natural Resources, Urmia University, Urmia, Iran

²Associate Professor, Department of Range and Watershed Management, Faculty of Natural Resources, Urmia University, Urmia, Iran

Abstract

Today, because of population growth, improvement of public health and welfare, development of industry and growth of economic and agricultural activities, per head water consumption has greatly increased, and due to the deficiency of water and the imbalance between supply and demand, the management of water resources is very complex and important. The WEAP model evaluates the effect of changing the amount of water allocated to different consumers on the economic benefits of water consumption. This advantage is very important, especially when it is necessary to evaluate the long-term effects of changing allocation in water resources. That is why WEAP has been used in this research. The purpose of this research is to investigate the status of water resources in the Mahabad dam and the impact of an increase in demand on meeting the needs. In this research, after collecting and completing the required information, the input file was created and the WEAP model was calibrated for a statistical period. Then, exploitation scenarios for the dam reservoir were developed and implemented, and the obtained results were evaluated. The simulated scenarios include the increase of cultivated area by 10, 20, and 30 percent and the population growth scenario. The results show that according to the reference scenario, Mahabad Dam will face a shortage of 18.8 million cubic meters, and according to the scenarios S4, S3, S2, S1, it will face a shortage of 30, 41, 52, and 21 million cubic meters, respectively. The selected scenario is the reference scenario that provides better conditions for the reservoir in terms of reliability and supply of water demands, and the maximum volume of water stored in the reservoir.
Extended Abstract
Introduction
Water resource allocation determines consumption priorities in various sectors, such as drinking, industry, and agriculture. The use of effective solutions for optimal water resource allocation and simulation of the decision-making process in prioritizing development and sustainable use of water and soil resources is of great importance. Therefore, many regions of the world face serious challenges in managing freshwater resources. Limited water resource allocation has led to environmental concerns, planning for water diversity, and the need for sustainable water consumption strategies. Supply-oriented simulation models are also always insufficient for examining water resource management options (Loucks and van Beek, 2017). In the past decade, an integrated approach to water resource development has emerged that directs water supply methods towards demand management, water quality preservation, and ecosystem protection. Due to population growth, improvements in public health and welfare, industrial expansion, and growth in economic and agricultural activities, water demand has increased significantly. Also, considering the severe water scarcity and imbalance between supply and demand, water resource management has become very complex and crucial. Various models, such as the WEAP model, have been developed to simulate integrated water resource management and evaluate how to allocate limited water resources among different consumers. The aim of this research is to examine the status of water resources in the Mahabad Dam Basin and the impact of increased demand scenarios on meeting the needs.
Material and Methods
The Mahabad Dam Basin is located in the northwest of Iran, in West Azerbaijan Province, covering an area of 1384 square kilometers. This basin extends between the geographical coordinates of 45°25’59" and 45°53’59" East longitude and 36°22’59" and 36°59’59" North latitude. The study area includes two sub-basins, Koter and Beitass (upstream of Mahabad Dam), and the Mahabad Plain (downstream of Mahabad Dam). The Koter sub-basin, with an area of 467 square kilometers, is located in the western part of the study area. The Beitass sub-basin, with an area of 285.87 square kilometers, is located in the eastern part of the basin. In this study, weather data, including daily precipitation and minimum and maximum daily temperatures, hydrological data, including daily flows, and physiographic characteristics of the basin were collected to form the WEAP model. The reservoir storage volume and levels of the Mahabad reservoir from 1992 to 2011 and 2012 to 2021 were used for calibration and validation. Subsequently, scenarios were designed and implemented, and the results were evaluated. The scenarios used are increasing agricultural land area by 10%, 20%, and 30%, and population growth.
Results and Discussion
The results indicate that the Mahabad Dam will face a deficit of 8.18 million cubic meters according to scenarios S1, S2, S3, and S4, with shortages of 30, 41, 52**,** and 21 million cubic meters, respectively. Notably, the deficits highlight significant challenges in meeting the projected water demand. The highest water demand over the 17-year horizon is for agricultural use, underscoring the critical role that agricultural activities play in the region's economy and food security. This heavy reliance on water for agriculture necessitates careful planning and resource management to prevent agricultural losses and ensure sustainability. Among the operational scenarios analyzed, the reference scenario was chosen as the preferred scenario due to having the highest water supply percentage and reliability index. This choice indicates a strategic prioritization of water resources to maximize efficiency and support agricultural needs**,** while also promoting long-term sustainability. The implications of adopting the reference scenario could lead to a more resilient water management framework, allowing stakeholders to navigate challenges more effectively in the face of varying demand and supply conditions.
Conclusion
In the current study, water resources were simulated using the WEAP model, analyzing various scenarios to compare water allocation during the base period and projections of population growth and increased cultivated areas. The results indicate that during the summer, when agricultural water demand peaks, not all needs can be met, leading to unmet demand that could increase from 18 million cubic meters per year to 52 million with expanded cultivation. As urban demand is prioritized, the water allocated to agriculture, the environment**,** and industry will inevitably decrease unless urban needs are fully satisfied. While potable water supply for Mahabad is likely to remain adequate, agricultural demands have the lowest reliability among all needs assessed. The reliability index shows that increasing cultivated areas will result in a 9% decrease compared to the base period, highlighting the urgent need for effective water management (Hellmann et al., 2010). Continued population growth and rising cultivation levels make achieving a balance in water supply and demand in the Mahabad Dam watershed unlikely.
 

Keywords

Population Growth Scenario; WEAP Model; Water Resources Management; Mahabad Dam Basin; Agricultural Land Expansion

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