1- Agricultural Sciences and Natural Resources University of Khuzestan
2- University of Birjand
3- Ardakan University
2- University of Birjand
3- Ardakan University
Abstract: (69 Views)
Introduction and Objective
At a global level, land degradation is a serious challenge to the productive capacity of water and land resources. Soil erosion, water loss, vegetation cover reduction, biodiversity loss, and nutrient depletion are all signs of land degradation. The most significant indicator of land degradation is soil erosion. Soil erosion due to the water and nutrient loss is one of the most important indicators of soil degradation. Soil erosion and sediment production are influenced by the interplay of climate, land cover, and land use. Due to this complexity, models are often used to support soil and water management, such as Soil and Water Assessment Tool (SWAT) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). In the present study, the InVEST Sediment Delivery Ratio model was used for sediment modeling. Research on sediment modeling and soil retention in South Khorasan Province is essential due to the region's arid and semi-arid climate, which poses serious challenges of soil erosion and land degradation. Conducting these studies can help identify critical areas and provide effective management strategies to preserve natural resources and improve the region's environmental sustainability. Estimating the economic value of functions and services of natural resources is a challenging and complex task but essential for economic management. In recent years, the necessity of determining the value of ecosystem services and biological resources has been firmly established worldwide, and efforts have been made in this regard as well. The present study aims to quantitatively assess the ecosystem service of sediment retention using the InVEST-SDR model and its economic valuation in the watersheds of the eastern border regions of the country, located in South Khorasan Province. No research in the study area has utilized the InVEST model, highlighting a significant research gap.
Materials and Metho The study area includes 10 watersheds in the eastern region of South Khorasan Province, covering an area of 2,008,357 hectares. In this study, soil erosion and sediment yield modeling were initially conducted. The InVEST Sediment Delivery Ratio (SDR) model, a spatial model operating at the resolution of the digital elevation model (30 m), was used to estimate soil erosion, retention, and sediment yield annually in the northeastern part of South Khorasan Province. The model first calculates the annual soil loss using the soil loss algorithm, then determines the SDR as a function of the hydrological connectivity of the basin, and finally performs the economic valuation. For economic valuation of sediment retention, the cost replacement or restoration method was employed. Thus, in this research, the economic value of preserving soil fertility was defined based on three elements: nitrogen (N), phosphorus (P), and nitrogen (N). Surface soil is the first part susceptible to soil erosion, and the nutrient content of the soil at this level decreases significantly. This decrease results in a reduction in organic nitrogen (N), phosphorus (P), potassium (K), and other elements.
Results The findings of this study reveal that the most substantial sediment retention is observed in dense forests, with dense pastures ranking second within the region. This aligns with the conclusions drawn in similar research. Asadollahi et al. (2015) stated that sub-watersheds with dominant forest cover played the most significant role in soil retention in the eastern part of the Gorganrood watershed, Golestan Province. Zabihi et al. (2021) also mentioned the lowest rate of soil erosion in the Flord sub-watershed compared to other sub-watersheds in the Talard watershed, Mazandaran Province, due to its predominant forest cover and lower soil erodibility factor. The highest provision of ecosystem service, annual soil retention, was recorded in high-density forest areas, and the lowest was in agricultural and built-up areas in the Lahijan Chaboksar and Astaneh-Kuchesfahan watersheds, Gilan Province. On the other hand, areas without vegetation cover (especially built-up areas) have the lowest sediment retention capacity and highest sediment export.
The results of economic valuation in the present study indicate that the average value of sediment retention service per pixel (900 square meters) is equivalent to 2731.48 Iranian Rials, which amounts to 30,349.77 Iranian Rials per hectare. Comparing with Hanareh Khalilian (2016), who estimated the annual value of sediment control function at 23,158.7 Iranian Rials per hectare, the values are close.
Conclusion The Esfadan and Shahrakht Watersheds, with over 13 and 12 million tons respectively, had the highest sediment prduction among the other watersheds. The Namakzar Khaf Watershed showed the lowest sediment amount with 737,504 tons. The average slope in the Namakzar Khaf Watershed is 1.6%, which has the lowest sediment production and the lowest slope among the other watersheds. In contrast, the average slope in the Esfadan Watershed, which has the highest sediment production, is 14.7%, and it has the second highest slope after the Ghaen Watershed. At the pixel level, sediment amounts in the eastern border watershed of the country ranged from 0 to 747.6 tons. The highest sediment retention was observed in the Esfadan Watershed with 22,626,499 tons, and the lowest in the Namakzar Khaf Watershed with 1,316,208.6 tons. The minimum and maximum soil loss were obtained for the Namakzar Khaf and Esfadan Watersheds, respectively, ranging from 4,845,857 to 6,385,471 tons.
At a global level, land degradation is a serious challenge to the productive capacity of water and land resources. Soil erosion, water loss, vegetation cover reduction, biodiversity loss, and nutrient depletion are all signs of land degradation. The most significant indicator of land degradation is soil erosion. Soil erosion due to the water and nutrient loss is one of the most important indicators of soil degradation. Soil erosion and sediment production are influenced by the interplay of climate, land cover, and land use. Due to this complexity, models are often used to support soil and water management, such as Soil and Water Assessment Tool (SWAT) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). In the present study, the InVEST Sediment Delivery Ratio model was used for sediment modeling. Research on sediment modeling and soil retention in South Khorasan Province is essential due to the region's arid and semi-arid climate, which poses serious challenges of soil erosion and land degradation. Conducting these studies can help identify critical areas and provide effective management strategies to preserve natural resources and improve the region's environmental sustainability. Estimating the economic value of functions and services of natural resources is a challenging and complex task but essential for economic management. In recent years, the necessity of determining the value of ecosystem services and biological resources has been firmly established worldwide, and efforts have been made in this regard as well. The present study aims to quantitatively assess the ecosystem service of sediment retention using the InVEST-SDR model and its economic valuation in the watersheds of the eastern border regions of the country, located in South Khorasan Province. No research in the study area has utilized the InVEST model, highlighting a significant research gap.
Materials and Metho The study area includes 10 watersheds in the eastern region of South Khorasan Province, covering an area of 2,008,357 hectares. In this study, soil erosion and sediment yield modeling were initially conducted. The InVEST Sediment Delivery Ratio (SDR) model, a spatial model operating at the resolution of the digital elevation model (30 m), was used to estimate soil erosion, retention, and sediment yield annually in the northeastern part of South Khorasan Province. The model first calculates the annual soil loss using the soil loss algorithm, then determines the SDR as a function of the hydrological connectivity of the basin, and finally performs the economic valuation. For economic valuation of sediment retention, the cost replacement or restoration method was employed. Thus, in this research, the economic value of preserving soil fertility was defined based on three elements: nitrogen (N), phosphorus (P), and nitrogen (N). Surface soil is the first part susceptible to soil erosion, and the nutrient content of the soil at this level decreases significantly. This decrease results in a reduction in organic nitrogen (N), phosphorus (P), potassium (K), and other elements.
Results The findings of this study reveal that the most substantial sediment retention is observed in dense forests, with dense pastures ranking second within the region. This aligns with the conclusions drawn in similar research. Asadollahi et al. (2015) stated that sub-watersheds with dominant forest cover played the most significant role in soil retention in the eastern part of the Gorganrood watershed, Golestan Province. Zabihi et al. (2021) also mentioned the lowest rate of soil erosion in the Flord sub-watershed compared to other sub-watersheds in the Talard watershed, Mazandaran Province, due to its predominant forest cover and lower soil erodibility factor. The highest provision of ecosystem service, annual soil retention, was recorded in high-density forest areas, and the lowest was in agricultural and built-up areas in the Lahijan Chaboksar and Astaneh-Kuchesfahan watersheds, Gilan Province. On the other hand, areas without vegetation cover (especially built-up areas) have the lowest sediment retention capacity and highest sediment export.
The results of economic valuation in the present study indicate that the average value of sediment retention service per pixel (900 square meters) is equivalent to 2731.48 Iranian Rials, which amounts to 30,349.77 Iranian Rials per hectare. Comparing with Hanareh Khalilian (2016), who estimated the annual value of sediment control function at 23,158.7 Iranian Rials per hectare, the values are close.
Conclusion The Esfadan and Shahrakht Watersheds, with over 13 and 12 million tons respectively, had the highest sediment prduction among the other watersheds. The Namakzar Khaf Watershed showed the lowest sediment amount with 737,504 tons. The average slope in the Namakzar Khaf Watershed is 1.6%, which has the lowest sediment production and the lowest slope among the other watersheds. In contrast, the average slope in the Esfadan Watershed, which has the highest sediment production, is 14.7%, and it has the second highest slope after the Ghaen Watershed. At the pixel level, sediment amounts in the eastern border watershed of the country ranged from 0 to 747.6 tons. The highest sediment retention was observed in the Esfadan Watershed with 22,626,499 tons, and the lowest in the Namakzar Khaf Watershed with 1,316,208.6 tons. The minimum and maximum soil loss were obtained for the Namakzar Khaf and Esfadan Watersheds, respectively, ranging from 4,845,857 to 6,385,471 tons.
Type of Study: Research |
Subject:
فرسايش خاک و توليد رسوب
Received: 2024/03/27 | Accepted: 2025/04/21
Received: 2024/03/27 | Accepted: 2025/04/21
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