چكيده به لاتين
Various aspects of water, including quantitative, qualitative, socio-economic, water hazards, etc., are defined in the concept of water security. In this study, water security frameworks have been studied. The framework introduced by Babel, has been applied to study the water security index in Ajichai watershed as the Lake Urmia sub-basins. According to Babel framework, the water security index is divided into five dimensions: water availability, water productivity, water-related disasters, watershed health, and water governance. Each of these dimensions is divided into different sub-indices. SWAT model, as a semi-distributed process-based hydrological model, has been applied to derive some variables included in the mathematical formulations and/or concepts of water security sub-indices. SWAT model was calibrated and validated based on runoff and crop yield criteria in spatiotemporal scale with the aid of SUFI-2 algorithm in SWAT-CUP tool. The observational runoff data in Akhola, Merkid and Mirkoh-Haji hydrometric stations, have been used as field data in SWAT model calibration/validation. The average values for statistical indices such as NSE, P-Factor, R-Factor and R2 in the calibration process of the Ajichai SWAT model were 0.6, 0.72, 0.94 and 0.62, respectively. The aforementioned statistical indicators in validating process were equal to 0.64, 0.74, 1.86, and 0.66, respectively. Next, according to the water availability and the sustainable basin exploitation aspects in the Ajichai sub-basin, the per capita water availablility in the east, west and middle of the Ajichai basin were 1,209, 679 and 59 cubic meters per person per year, respectively. According to SWAT model result analysis, the green water scarcity indices in the east, west and middle sections were 0.34, 0.32 and 0.31, respectively. The blue water scarcity indices in the aforementioned sections of Ajichai sub-basin, were 1.74, 1.12 and 3.71, respectively. Based on the analysis of the historical record of precipitation, in the South and North sections of the Ajichai sub-basin, the water variability indices were equal to 42% and 29%, respectively. Study on the water disaster aspects demonstrated the drought index (the proportion of the area affected by drought) was equal to 50% for the study area. Furthermore, the ratio of the irrigated areas to the total cultivated areas the Ajichai sub-basin was equal to ten percent. In the last 35 years, the flood frequency in the East and West parts of the the Ajichai sub-basin were 8 time and 6 time, respectively. In terms of water economic efficiency and water economic value aspects, the agricultural income in the whole basin and in the per water drop have been calculated as 1,218 billion Tomans and 4,431 Tomans/per cube meter, respectively. The simulation-optimization approach based on coupled SWAT-PSO optimization algorithm was developed in the current study to improve the water security index while supplying the minimum river flow. The proposed approach was applied in the Ajichai sub-basin to study the economic effects of a hypothetical dam and different scenarios on minimum river flows. This hypothetical dam with a volume of 100 MCM is located in the East section the Ajichai sub-basin. 30% of the irrigated areas in the Ajichai sub-basin were affected by dam operation. In the current scenario, the agricultural incomes in the affected downstream agricultural areas by the dam were equal to 523 billion Tomans (1,218 billion Tomans is the income from the entire basin lands). It should be considered in the current scenario; no water is allocated to minimum river flow. In the scenarios of allocating minimum river flow as 30%, 50%, 80%, 120% and 200% of the average annual flow of each river, the agricultural incomes were equal to 485, 463, 417, 363 and 317 billion Tomans, respectively (the scenario of non-operation of the dam). In dam operation scenarios; adjusting the monthly water release with the aid of SWAT-PSO tool, the economic incomes were changed to 562, 543, 516, 485 and 435 billion Tomans, respectively. The agricultural water consumptions in downstream lands, affected by dam operations, were decreased by 55% (~100 MCM/year) in comparison to the not dam operation scenario. Furthermore, the agricultural income per water drop has changed from 2,900 to 6,500 Tomans/ per cubic meter (with a 124% increase). Therefore, the dam operation in spite of allocation to the minimum river flow, has led to the improvement of the water security index in the basin.
