New Designing The Relationship Between The Water-Energy-Food Nexus With Environmental Objectives At The Basin Level For Sustainable Agricultural Management


 Accomplishing the objectives of optimal and sustainable management in the agricultural sector is increasingly getting complicated, which includes increasing the sustainable productivity of water and energy resources, ensuring food security, decreasing contaminations from fertilizers and chemical pesticides, and environmental destruction. The present research deals with designing the relationships between the water-energy-food (WEF) nexus approach with economic and environmental objectives to accomplish the aforementioned objectives. Hence, a multi-objective programming model was developed to maximize the water-energy-food nexus index and farmers' gross margin, minimize the use of chemical fertilizers (nitrogen and phosphate), and minimize the use of chemical pesticides (herbicides) by considering the balancing constraint to groundwater resources. Afterward, the proposed multi-objective model was solved using the augmented ε-constraint method, and then the total of strong and efficient Pareto solutions was extracted. Then, the best solution was chosen using the TOPSIS method and assigning a weight of equal importance to the desired objectives. The irrigation network of Jiroft plain in Kerman province in Iran was chosen as the study area to implement such a system. The obtained results indicated that the optimal and sustainable management in the agriculture sector can be hopeful using the proposed approach in the current research. On the other hand, the results revealed that despite considering the economic objective in the proposed system, the farmers' profits can be significantly decreased. Thus, the realization of optimal and sustainable management in the agricultural sector is not possible without the implementation of policies for increasing the economic incentive of farmers.


74
The constraint of water and energy resources in food production along with some phenomena 75 including land destruction, climate change, increasing population growth, and rapid 76 urbanization, has caused several challenges in terms of increasing food production and 77 sustainable resource management (Hoff, 2011;Bizikova et al. 2013;Alloisio, 2015; El-Gafy, 78 An investigation of reviewing studies revealed that several methods have been employed to 146 implement the water-energy-food nexus approach for optimal agricultural management. Most 147 studies on the water-energy-food nexus in agriculture considered a combination of water and 148 energy consumption benefit functions and environmental benefit functions as objective 149 functions to design an optimal pattern regarding constraints of water and energy resources  Nevertheless, the balancing of groundwater resources was not performed. 175 The present paper aimed at maximizing the water-energy-food index, maximizing gross 176 margin, minimizing the use of fertilizers and chemical pesticides, regarding the constraints of 177 balancing groundwater resources to reduce pollution and environmental destruction for the 178 optimal and sustainable management of the resources in the agricultural sector. So far, no such 179 comprehensive analysis has been conducted to take into consideration all the criteria of the 180 water-energy-food nexus, and environmental pollution caused by using fertilizers and chemical 181 toxins, and environmental destruction due to excessive consumption of the groundwater 182 resources. To assess the performance of the approach proposed in this paper, the irrigation 183 network of Jiroft plain of Kerman province located in Iran was considered as the study area.

184
Jiroft plain, known as one of the important agricultural areas in Iran, has always encountered 185 the constraints of water and energy resources and several environmental challenges. Hence, in 186 the second section, the study area was demonstrated. In the third section, the study 187 methodology was described. Then, the obtained results of the study were analyzed in section 188 4, and general conclusions and some suggestions were provided in section 5.

210
In the current research, first, the water-energy-food nexus index was calculated for different 211 crops in the irrigation network of Jiroft plain. Then, the optimal allocation of resources and the 212 extraction of the optimal cultivation pattern were demonstrated by GAMS software using a 213 multi-objective planning model for maximizing water-energy-food nexus index and gross The relationship between water and food can be analyzed using the criteria of water 221 consumption, water physical productivity, and water economic productivity. The relationship 222 between energy and food can be measured through the criteria of energy consumption, energy 223 physical productivity, and economic productivity (Sadeghi et al., 2020). Regarding the 224 relationship between energy and water, energy consumption is needed to extract groundwater 225 resources, in which reducing the water resources would lead to increasing the costs of energy 226 (Nabavi, 2018). Hence, considering the relationship between the three components of water-227 energy food, the optimal allocation of resources can be performed.

228
Nevertheless, the optimal agricultural management with the water-energy-food approach   248 To calculate the WEF index, a combination of water and energy consumption criteria, physical 249 water and energy productivity, and water economic productivity and energy was employed. In 250 this regard, water consumption (W) of different products of Kerman Regional Water Company 251 was provided as a collection of irrigation and drainage reports (Kerman Regional Water  Hence, it is essential to consider balancing the water table of the aquifer. In this matter, a 309 balance must be generated between the discharge rate and the aquifer supply to balance the 310 groundwater resources of the study area. According to Mirzaei and Zibaei (2021) in this region, 311 a 20% reduction in groundwater discharge could be effective to achieve such balance. Thus, 312 the constraint of groundwater and energy consumption for the extraction of these resources was 313 formulated using Eqs. (12) and (13):

Calculating the WEF index
Where Wat and E indicate respectively the amount of water and energy required to extract 317 groundwater resources in the production of one hectare of product c. gwc, swc and ec denote 318 the total current consumption of groundwater resources, surface water, and energy required to 319 extract groundwater resources, respectively. To balance the groundwater resources and prevent 320 environmental destruction in the study area, the constraints of the groundwater consumption 321 and energy required to extract groundwater resources were considered less than 80% of current 322 consumption. Furthermore, the constraint of the available area under cultivation (land) was 323 formulated using Eq. (14): The gross margin coefficients of different products in the objective function f2 (Eq. 9) were 326 obtained from the difference between revenue (multiplication of price and product yield) and  Table 1 cover 17968 ha of these lands (more than 98%). Physical water productivity is an essential criterion, which leads to more food production,  (Table 2). To do so, the relative weight of the criteria was calculated using the 404 pairwise comparison matrix of criteria and the AHP method. The results indicated that the weight of importance, water consumption, water physical 408 productivity, and water economic productivity criteria were 0.12, 0.22, 0.35, respectively, 409 whereas the weight of importance, energy consumption, energy physical productivity, and 410 energy economic productivity criteria, were 0.04, 0.10, and 0.17 respectively. Thus, in the 411 irrigation network of Jiroft plain, water-related criteria have higher relative importance, as 412 compared to energy-related criteria. In the end, the WEF index (WEFI) was achieved for 413 different products using Eq. (7) ( Table 3). It should be mentioned that the coefficients of other 414 objective functions are also provided in Table 3.   to water consumption in the current pattern). The Augment ε-constraint method was used and 427 then the set of strong and efficient Pareto solutions was obtained (Fig. 4). 428 In the following, the TOPSIS method was employed to choose the best solution from the set of After that, the optimal management of the agricultural sector was performed based on the  In the current cropping pattern of the Jiroft plain irrigation network, the average water-energy-469 food nexus index, gross margin, chemical fertilizer application, chemical pesticide application,

472
The results of the optimal cultivation pattern achieved from the two-objective model 473 simultaneously satisfied the objectives of maximizing the water-energy-food nexus index and 474 the farmers' gross margin without considering the objectives and environmental constraints. It 475 was revealed that the amount of water-energy-food nexus index was increased by about 46% 476 at the regional level, as compared to the current condition. However, in this pattern, the gross 477 margin is decreased by about 30%, as compared to the current condition. Besides, by increasing 478 the water-energy-food nexus index, it can be concluded that the optimal management of 479 resources, particularly water, is possible by adopting the optimal cultivation pattern of the two-480 objective model. In this regard, the water consumption of the optimal pattern is decreased by 481 57%, as compared to the current pattern, which is stronger than the reduction of gross margin,  The optimal pattern does not lead to a significant reduction in energy consumption, as 487 compared to the current pattern. The reason is that owing to the crisis of water resources in the 488 region, the experts and specialists consider the issue of water more than energy. Hence, they 489 pay more importance to the criteria related to water resources in the water-energy-food nexus 490 approach. Therefore, it is obvious that in the water-energy-food nexus approach, optimal 491 energy management will be challenged due to more attention to the issue of water. Thus, one 492 of the knowledge gaps in the water-energy-food nexus approach is to consider the reduction of

525
The optimal cultivation pattern extracted from the four-objective optimization model was 526 illustrated and compared with the current pattern in Fig. 6. As seen, in the optimal pattern, the 527 share of three crops of dates, wheat, and citrus, is strongly decreased, such that two crops of 528 wheat and citrus have no place in the optimal pattern. However, these crops have a high share 529 of the current cropping pattern. In contrast, the share of barley crops in the optimal cultivation 530 pattern shows a strong increase, as compared to the current pattern. This is because the 531 production of barley is very favorable in terms of water resources, energy, and fertilizers, and 532 chemical pesticides, as compared to other products. Nevertheless, the remarkable point is the 533 low gross margin of this product, in comparison to other products, which is known as a threat 534 to the livelihood of farmers.

539
In the present work, the recent researches on the optimal resources management in the 540 agricultural sector based on the water-energy-food nexus approach were reviewed. It was 541 indicated the relation between this approach with other dimensions such as economic and 542 environmental dimensions should be further designed. In this paper, it was attempted to achieve 543 optimal resources management in agriculture and environmental sustainability through We wish to confirm that there are no known conflicts of interest associated with this publication 570 and there has been no significant financial support for this work that could have influenced its 571 outcome. We confirm that the manuscript has been read and approved by all named authors 572 and that there are no other persons who satisfied the criteria for authorship but are not listed. 573 We further confirm that the order of authors listed in the manuscript has been approved by all 574 of us. We confirm that we have given due consideration to the protection of intellectual 575 property associated with this work and that there are no impediments to publication, including 576 the timing of publication, with respect to intellectual property. In so doing we confirm that we 577 have followed the regulations of our institutions concerning intellectual property. 578 We understand that the Corresponding Author is the sole contact for the Editorial process El-Gafy, I., Grigg, N., Reagan, W., 2017. Water-food-energy nexus index to maximize the economic water and energy productivity in an optimal cropping pattern. Water Int. 42, 495-615 503.