Document Type : Original Article
Authors
1
Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, 45137-66731, Iran
2
Institute for Advanced Studies in Basic Sciences (IASBS)
10.22034/IWRJ.2025.15438.2714
Abstract
Extended Abstract
Introduction:
Integrated Water Resources Management (IWRM) is defined by the Global Water Partnership (GWP) as “a process that promotes the coordinated development and management of water, land, and related resources to maximize economic and social welfare equitably without compromising the sustainability of vital ecosystems and the environment.” Recently, a physical index has been proposed to quantitatively evaluate water resource management by accounting for environmental water requirements. This index, based on the concepts of water accessibility and water supply, allows for a more integrated and comparative assessment of management performance. The Sefidrud watershed, covering an area of 58,452.84 km², is located in northwestern Iran. This study aims to: (a) assess the management levels of surface and groundwater resources across the Sefidrud watershed during the 1995–2017 observation period, and (b) examine the impacts of observed climate changes on water resource management levels during the study period.
Materials and Methods:
To evaluate and quantify the management levels of surface and groundwater resources in the Sefidrud watershed, SWAT hydrological model was employed. The watershed was delineated into 15 subbasins based on elevation, hydrometric, and dam data, and the model was run with inputs of soil, land-use, slope, and daily dam outflows. The model was implemented over the 1995–2017 period in two stages: a 16-year calibration period (1995–2010) and a 7-year validation period (2011–2017). Level of Management (LOM) for river water was estimated using a physical index that accounts for available water and total water supply. In this context, total water supply is defined as the volume of water withdrawn from the river. To calculate LOM, which denotes the management level of either river or groundwater resources, the available water volume (AW) of the river or groundwater and the water withdrawn from the river or groundwater for use in sectors (TWS ), were considered. The Environmental Flow Requirement (EFR) is also defined as a percentage of the river’s long-term annual mean flow. In this study, 80% of the river's long-term annual mean flow was allocated to EFR, and the remaining 20% to human needs and Accessible River Water (ARW). EFR for groundwater was determined based on the river’s baseflow contribution. River and groundwater management levels may vary from negative values up to +1, where negative values indicate mismanagement and positive values reflect acceptable management. The management levels of both river and groundwater resources during the observation period were computed under two scenarios: (1) the real scenario (reflecting actual climate and land-use conditions), and (2) the climate scenario (using daily precipitation and temperature data with trends removed, i.e., de-trended), and were subsequently compared.
Results and Discussions:
The performance evaluation of the SWAT model during the calibration period (1997–2010) indicated an acceptable level of accuracy in simulating monthly river flows at the subbasin scale. The coefficient of determination (R²) and the Nash–Sutcliffe Efficiency (NSE) exceeded 0.7 in most subbasins. To investigate the effect of precipitation changes, the annual mean precipitation derived from the observed time series was compared with the corresponding values from the detrended series. The impact of precipitation changes was estimated as the difference between the mean annual observed precipitation and the detrended values (observed minus detrended). Spatial analysis of the distribution of climate stations showed that decreasing precipitation trends predominantly occurred in the southwestern and eastern parts of the basin, whereas the central and northern regions experienced increases in annual precipitation during the period 1995–2017. Analysis of annual minimum and maximum temperature trends revealed that the entire study area experienced warming during 1995–2017, with the exception of the minimum temperature at the Tabriz station. The effect of climate change on river flow in each subbasin was determined by calculating the difference between simulated river flows under the actual scenario and those under the no-climate-change scenario (flow in actual scenario minus flow in no-climate-change scenario). Climate impact mapping showed that most subbasins experienced reductions in river flow due to decreased precipitation, although a few subbasins exhibited increases in flow associated with increased precipitation during 1995–2017. Because total water withdrawals in both the actual and no-climate-change scenarios remained constant, the observed changes in LOM values were attributable to variations in water availability. Consequently, climate change improved LOM in subbasins that experienced increased precipitation and river flow during the study period, whereas LOM declined in subbasins with decreased precipitation and flow. The impact of climate change on groundwater recharge in each subbasin was assessed by calculating the difference between simulated aquifer recharge under the actual scenario and that under the no-climate-change scenario (recharge in actual scenario minus recharge in no-climate-change scenario). Evaluation of climate change effects revealed that most subbasins experienced reductions in groundwater recharge due to decreased precipitation, whereas some subbasins showed slight increases in recharge rates as a result of higher precipitation during 1995–2017. The groundwater LOM declined in most of the study area because of reduced precipitation, although some areas exhibited increases.
Conclusion:
In this study, the impact of climate change on the Level of Management (LOM) of surface and groundwater resources was evaluated in the Sefidrud watershed, Iran, during the period 1995–2017. The watershed has experienced an increase in annual temperature; however, annual precipitation has been shown to increase or decrease depending on geographical location. The assessment of river and groundwater management levels indicated that the river management level in eight subbasins and the groundwater management level in three subbasins had negative values, indicating that water abstraction exceeded the volume of available water resources. Subbasins with negative management levels were recognised as ecological hotspots. Surface and groundwater resources respond to climate change in a coordinated manner. As precipitation is the main source of accessible water for both river and groundwater systems, long-term climatic trends continuously influence long-term water availability and management levels. In the evaluation of management levels of Sefidrud watershed, ecological hotspots were identified. These results can serve as a model for water resource decision-makers to propose management strategies adapted to local conditions. For example, in sustainable management approaches, special attention should be paid to areas where ecosystems dependent on water resources are stressed. To achieve an acceptable management level, appropriate strategies should be implemented such as reducing abstraction from surface and groundwater resources, improving irrigation efficiency, cultivating crops with lower water requirements, and enhancing agricultural land productivity.
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