چكيده به لاتين
Nowadays, the water-energy-food (WEF) nexus has attracted increasing attention in research communities due to high concerns on water, energy and food securities in futures. In this research, some definitions for the nexus concepts, the series of events and conferences on nexus concepts, and the increasing trends on the nexus significance have been introduced. Then, integrated water resources management (IWRM) approach and WEF nexus have been compared. In this research, the SWAT-MODFLOW model has been used in order to quantify the relationships between WEF components as the main axes of the system. The SWAT-MODFLOW model, has been applied in WFE nexus study. To SWAT-MODFLOW model calibration, in the first step, the SWAT and MODFLOW models were setup and calibrated, separately. The SWAT model was calibrated for the years 2009-2015 and the MODFLOW model was calibrated for the years 2009-2014. Then the two models coupled, and re-calibration for the coupled model for the years 2009-2014 have been performed. The flow discharges in various hydrometric stations and the annual average of crop yields were calibrated in SWAT environment. The statistical measures, R2 and PBIAS indices, have been set in SWAT model for calibration of flow rates and the crop yields, respectively. The SWAT model calibration has resulted in R2 coefficient greater than 0.6 and the PBIAS index less than 0.15 for the flow rates and the crop yields, respectively. Therefore, SWAT model calibration was acceptable. The spatial and temporal ground water surface elevation (GWSE) in MODFLOW model were calibrated according to the recorded observational data in various wells in the study area. The RMSE index as a statistical measure for GWSE adjustment in MODFLOW was 1.908, which is an acceptable ranges considering extensive wells in the study area. Then, the hydrological indices (flowrates and GWSE) and agricultural crop yields have been calibrated in SWAT-MODFLOW model. In the coupled model, the R2 coefficient for all hydrometric stations is greater than 0.58, which is a favorable value. The PBIAS index has not changed in the coupled model, because the average yield calibration is done using the plant parameters. The calibration error measure in SWAT-MODFLOW model for GWSE were less than 4 m in 60 simulation months for various wells around the watershed, which indicates the acceptability of the calibration process. In this study, 6 various scenarios were defined based on the irrigation water supply sources (surface water/groundwater) as well as the crops patterns in the study area. The results indicated that the greater dependences of the irrigation scenarios on groundwater, have led to more energy consumptions for the crop products. Furthermore, the energy consumptions in the study area represents increasing trends during time horizon due to GWSE declines. In addition, the amount of water used for the cultivation of different crops has been obtained in irrigations that have been done from surface water and groundwater sources.
The results show that in the cultivation of crops using surface water, due to the changes in river flow, the amount of water defined for the plant is not fully available at some times. But in the irrigation done by ground water, all the defined water is fully supplied and the amount of product is more than the irrigation using surface water. The results show that in surface irrigation, less water is used to produce one kilogram of product. In other words, in crop irrigation using surface water, water efficiency has been higher.
