Extended Abstract
Introduction
Increasing pressures from land use change, overexploitation of water and soil resources, climate change and population growth, reduction of vegetation cover, soil erosion, decline in the quality and quantity of water resources, and reduction of biodiversity have reduced the efficiency of ecosystem services and threatened the health and sustainability of watersheds. The complexity of health and sustainability indicators and the simultaneous existence of quantitative and qualitative criteria highlight the need to use Multi-Criteria Decision-Making (MCDM) methods. Among these methods, the VIseKriterijumska Optimizacija Kompromisno Resenje (VIKOR) method, as a method based on adaptive optimization, allows for prioritizing options based on maximizing group satisfaction and minimizing individual dissatisfaction. On the other hand, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method, in its advanced version, using Mahalanobis distance, is able to take into account the effect of correlation between criteria in calculating the distance. The main objective of this study is to prioritize the sub-watersheds of the Atrak River watershed in northern Golestan Province based on health and sustainability indicators using VIKOR and TOPSIS-Mahalanobis methods.
Materials and Methods
The Atrak River watershed is located in Golestan Province with geographical coordinates of 53° 50' to 56° 30' North longitude and 36° 50' to 38° 20' North latitude and has an area of 819,000 hectares. In this study, a total of 16 health and sustainability indicators categorized into five classes of vegetation (percentage of canopy cover), hydrology and climatology (per capita available water), environmental (Environmental Performance Index (EPI) and Total Dissolved Solids (TDS) indices), social (life expectancy, population density, household size, population growth, human development index, gender ratio, and urbanization ratio), and economic (per capita agricultural and horticultural land, per capita livestock, per capita other (honey, silkworms, fish, and poultry), per capita wheat area, and average wheat yield per hectare) were measured to prioritize the sub-watersheds of the Atrak River watershed. In this study, two methods, VIKOR and TOPSIS_Mahalanobis, were used for prioritization. Mahalanobis distance evaluates environmental variables without change and intact, so that all variables are assumed to be unequal. In the Mahalanobis distance method, there is no need to normalize the data, on the other hand, the covariance operator in the computational formula of this method considers the correlation between variables. Due to having 16 indicators and forming a matrix with large dimensions, all calculations were performed in the MATLAB environment.
Results and Discussion
Based on the results of the VIKOR, it was determined that the Gomishan has the worst condition. Therefore, the Gomishan was ranked last in terms of health and stability. On the other hand, the Maraveh Tapeh was ranked first in terms of all three indicators R, S and Q, meaning the best condition. However, the numerical value of Q between the first and second sub-watersheds is very close and does not seem statistically significant. This important issue in the first condition (C1) of the Vikor method showed itself, so that the condition Q2-Q1≥DQ was not met, so the first and second sub-watersheds had to be introduced as the best options together, and as a result, Chat and Gomishan were ranked second and third, respectively. According to the TOPSIS-Mahalanobis results, the Dashli-Brun is in the best condition and Gomishan is in the most critical condition. However, studies show that the numerical values of the first three sub-watersheds are relatively close to each other, but the Gomishan is in the last rank with a large difference. In other words, there is high confidence in the criticality of the Gomishan and the need to allocate watershed management measures to this sub-watershed. The numerical values of the indices in a ranked manner in each sub-watershed showed that the Maraveh Tapeh with seven 1st and only one 4th, was in a better condition than the other sub-watersheds, although the Dashli-Brun sub-watershed was in competition with Maraveh Tapeh with only two 4th and four 1st ranks.
Conclusion
In this study, two multi-criteria decision-making methods, VIKOR and TOPSIS-Mahalanobis, were used to prioritize the sub-watersheds of the Atrak River watershed based on health and sustainability indices. Comparing the results of the two TOPSIS-Mahalanobis and VIKOR methods shows clear similarities and differences, and the source of error can be searched in the structure of the first decision matrix. The results showed that the output of the VIKOR method can be considered more logical than the TOPSIS-Mahalanobis method, because assigning the third rank to the Maraveh Tapeh sub-watershed by the TOPSIS-Mahalanobis method reduces the validity of this method. Therefore, based on the findings of this study, the two Maraveh Tapeh and Dashli Brun sub-watersheds can be jointly introduced as superior sub-watersheds in health and sustainability indicators, and only if it is required to separately allocate management measures to each sub-watershed, Dashli Brun sub-watershed will be given a higher priority, because Maraveh Tapeh is in a relatively better situation. On the other hand, the first and second priority of management measures to improve health and sustainability indicators should definitely be assigned to the Gomishan and then Chat sub-watersheds, respectively. Finally, in solving complex problems such as the present study, one must both reduce the number of indicators and limit oneself to the most basic indicators that represent the overall status of the target sub-areas, or use more flexible methods in introducing and prioritizing target sub-areas such as VIKOR. |
