Neural Comput & Applic DOI 10.1007/s00521-017-3160-z ORIGINAL ARTICLE Cuckoo optimization algorithm in optimal water allocation and crop planning under various weather conditions (case study: Qazvin plain, Iran) Omolbani Mohammadrezapour1 • Icen Yoosefdoost1 • Mahboube Ebrahimi2 Received: 20 June 2016 / Accepted: 7 July 2017 Ó The Natural Computing Applications Forum 2017 Abstract As inferred from its biological nature, agriculture is a key consumer of water resources in many countries. Hence, today, water management plays an important role in the use of water resources of these countries. The present study aimed to optimize cultivation area, to manage irrigation water, and to optimize total income gained from the cultivation area of special crops in Qazvin plain (the central plateau of Iran) under various weather conditions using cuckoo optimization algorithm (COA). Under the same objective function, the performance of the COA was accessed through comparison with the genetic algorithm (GA). The results of two models showed that because of its high water requirement and low yield, the cultivation area of sugar beet in every four different condition reduced (by over 80%); that is, it is not wise to plant it in all different weather conditions of the study area. Comparison of the model results indicates that the COA can provide better and more reliable optimal results in relative yield of crops, higher farm income. So, in comparison with GA, less water is allocated. Following the new cropping pattern delivered by COA model, the water volume stored in the dam reservoir at the end of the operation under wet, normal, dry, and hot–dry conditions rose, respectively, by 264,745.3, 2,865,387, 275,789, and 655,918 m3. Meanwhile, the farmers’ profit increased, respectively, by 6.2, 2.6, 1.27, and 1.48% compared to the previous optimization occurred & Omolbani Mohammadrezapour mohammadrezapour@uoz.ac.ir; omohammadrezapour@gmail.com 1 Department of Water Engineering, University of Zabol, Zabol, Iran 2 Department of Agricultural, Payame Noor University (PNU), Tehran, Iran at the end of the operation. To conclude, COA is quite promising in a cultivation area of crops optimization problem in terms of its simple structure, excellent search efficiency, and strong robustness. Keywords Meta-heuristic algorithm Optimization Agricultural water management 1 Introduction Due to its biological nature, agriculture is the largest consumer of water resources in many countries. Nowadays, irrigation plays a vital role in economy; hence, water management in agricultural sector has its highest effect on raising efficiency during drought and relieves its economic and social damage. Iran is located in the south of the northern temperate zone, and because of its unique geographical location and its sparse roughness and other influential factors such as air masses, it is regarded as an arid area. In fact, low rainfall has caused so severe fluctuations in the surface water that with the advent of heating season, especially in the summer, its rate often drops dramatically. On the other hand, in order to achieve higher profit, the farmers are willing to cultivate plants such as rice, sugar beet, and corn, which require more irrigation. However, considering the climatic conditions of the country, this indiscriminate consumption of the water resources would lead to irreparable damages in the regional water potential. As one of the central plains of Iran, Qazvin plain is among the areas in which water resources are threatened seriously due to non-optimal operation, and if continued, it would leave irreversible economic and environmental consequences in the region. Hence, implementing proper 123 Neural Comput & Applic planning and management of irrigation and cropping patterns in the study area seems quite urgent. Nowadays, a universal agricultural problem facing most developing arid regions is the limited supply of water used for irrigation in which the crop yield is unable to reach its potential. For optimal allocation of irrigation water under a limited water supply, there have been successful models developed. The objective of most studies was to maximize economic benefits, based on developing for optimal land and water resources, maintaining the existing cropping patterns or expressing farmers’ propensity to pay for irrigation water [1–5]. It was concluded that these problems can be solved through mathematical programming methods. Recently, most researchers use heuristic methods such as genetic algorithm (GA), particular swarm optimization (PSO), leap-frog (LF) and linear programming commonly applied for optimal utilization of water resources and cropping pattern. In this case, Azaiez and Hariga [6] offered a linear programming model in order to optimize utilization of water resources and efficient use of groundwater and surface water and to assess optimum cropping model under water shortage conditions in Chitradorgay, India. To optimize reservoir performance of a single-purpose reservoir, Nagesh Kumar et al. [7] used genetic algorithm and linear programming for irrigation of crops to show the similarity between the yields of the genetic algorithm and those of the linear programming. Azaiez [8] developed a hybrid LP-DP model for optimal use of farmland for a crop in northern Saudi Arabia. Georgiou and Papamichai [9] used nonlinear programming model [simulated annealing (SA)] in Northern Greece to determine the optimal cropping patterns under diverse weather conditions. Moghaddasi et al. [10] prepared a 3-layer nonlinear programming (NLP) to manage the agricultural water demand in Zayandeh-Rud, Isfahan (the central part of Iran), in drought conditions to minimize the damage and to allocate water distribution in the dam’s downstream. Dima et al. [11] used linear programming model to study irrigation water optimization in five regions of the West Bank of Palestinian and to indicate that changing cropping patterns under water and land restrictions could decrease irrigation water consumption by 10%. Likewise, FallahMehdipour et al. [12] used the linear and nonlinear programming models such as GA, PSO, and leap-frog (LF) to optimize water used for agricultural irrigation and multicrop cultivation patterns. The results indicated the superiority of linear to nonlinear algorithm as well as the LF to other algorithms. Dai and Li [13] used a multistage stochastic programming model for water allocation to determine the optimum culture pattern under uncertainty conditions in the Basin of Wang Zhang River. Khanjari and Sabohi [14] also used a genetic algorithm to determine the 123 appropriate allocation of water and suitable cultivation pattern for the farming areas irrigated with Droudzan dam located in the southwest of Iran. Recently, an effective meta-heuristic optimization algorithm namely cuckoo optimization algorithm (COA) was proposed by Rajabioun [15]. Since the COA, commonly versatile in many fields, is helpful in optimization and is easy in application mainly due to its straightforward structure. For example, COA was used by Gandomi et al. [16] in structural optimization, by Kanagaraj et al. [17] in reliability optimization, and by Marichelvam et al. [18] in hybrid flow shop scheduling. More recently, Ming et al. [19] applied the cuckoo search (CS) to the optimal operation of multi-reservoir system (OOMRS) to maximize the energy production in China’s Wujiang multi-reservoir system. The performance results of the C, analyzed through comparing with the GA and the particle swarm optimization (PSO) under the same objective function, showed it can provide better and more reliable optimal results than those of GA and PSO. The aims of present study to optimize cultivation area of some main crops and management of irrigation water, realis of reservoir and maximum total farm income in cultivating a part of Qazvin plain farms. The study area located in the central Plateau of Iran, where they provide their required water through Taleghan dam. This is conducted under various weather conditions (wet, normal, dry and hot – dry) with the help of cuckoo optimization algorithm. 2 Materials and methods 2.1 The study area With an area of 440 thousand ha is Qazvin plain located in the central plateau of Iran (Fig. 1) which has a semi-arid climate with hot summers and relatively cold winters. One of the most significant rivers providing water for this plain is Taleghan River across which Taleghan dam is built. The dam is 135 km northwest of Tehran, and its geographical coordinates are 50° 37’ -51° 51’ Longitude and 36° 5’ -36° 25’ latitude on Taleghan River in the rural area, Rowshanabdar. Its capacity is 460 million m3, whereas its dead capacity is 210 million m3. However, due to its severe loss of inflow current, it has never been able to reserve over 210 million m3 water. 2.2 Statistical data and cropping pattern Cultivation optimization and optimal release of the reservoir aimed to provide irrigation in the study area needs accurate weather data about its weather conditions. These Neural Comput & Applic Fig. 1 Location of the Qazvin plain in Iran data include minimum and maximum temperature, relative humidity, sunny hours, wind speed, rainfall, evaporation, estimated volume of the river inflow, volume of stored water in the reservoir while irrigating, and characteristics of the cultivated plants. For the annual crops (corn, wheat, sugar beet, barley, and alfalfa), a series of critical data for the indicated crops along with the main parameters required for the optimization procedure, i.e., cultivation area, some key traits of cultivated plants, production cost, and cultivation date of the regional strategic crops within the crop year 2010–2011 are given in Table 1. It is worth to note that crops like alfalfa, corn, and sugar beet are summer specific, whereas wheat is just a winter crop and barely grows in both winter and summer. Growth stage durations for different crops were chosen based on local observations. During cost calculations, it was assumed that farmers own the land; thus, the fixed cost (B) equaled zero. The variable cost (C) for each crop was computed from data supplied by the Region of Qazvin, Iran (2014). Table 1 shows that the irrigation season starts in April and ends in December. The year is divided into 36 periods; each month consisted of three periods; yet, the last 9 periods of the year, i.e., the 28th–36th periods, have no irrigation activity. Although the proposed optimization model can handle heterogeneous soil, the considered soil under study was homogenous. It consists of one layer characterized as clay loam (L) with FC = 0.25 cm3/cm3 and PWP = 0.12 cm3/cm3. Due to higher rainfall during the no irrigation season, it is assumed that soil water content at the beginning of the irrigation season is at FC, so the values of Ky in the establishment stage are assumed to be equal to zero, as also proposed by Tsakiris [20] and Kotsopoulos [21]. The reference crop evapotranspiration was derived from daily climatic data (mean temperature, radiation, relative humidity, and wind speed) at Qazvin meteorological station provided by the FAO Penman– Monteith equation [22]. 2.3 The definition of the model and related variables The model, a nonlinear program, aims to introduce the most appropriate use of the dam reservoir, to regard its optimal allocation between different plants, and to rise profits gained from the crops. The time span of the balance equations is considered fixed for the whole model and is equal to the irrigation cycle of Qazvin area (10 days). The used objective function is also based on Eq. (1). The objective function maximized the total gross income of the area to achieve the optimal yield of Taleghan dam for irrigating n crop in the j period during the irrigation period [23]. n X Z ¼ Max Pi ðYcÞi Ci Ai ð1Þ i¼1 where Z* = total farm income (Rial), P = production price (Rial/kg) C = variable cost (Rial/ha), A: cropped area (ha), i: cultivation crop and YC is the relative yield. In 123 Neural Comput & Applic Table 1 Some characteristics of the annual crops under study in the Qazvin region Growth stage parameter Corn Sugar beet Wheat Barley Alfalfa Establishment Ky 0.01 0.12 0.01 0.01 0.85 d 30 30 20 20 10 Vegetative Ky 0.4 2 0.2 0.2 0.95 D 40 50 35 45 10 Flowering Ky 1.5 0.6 0.6 0.6 1.1 D 20 25 20 20 15 Yield formation Ky 0.5 0.36 0.5 0.5 1.1 D 30 50 40 40 15 Ripening Ky 0.2 0.12 0.01 0.01 1 d 20 50 20 10 10 Maximum root depth (cm) Variable cost C (Rial/ha) 120 1,976,343 100 3,873,256 110 3,160,421 110 1,273,198 110 2,183,652 Product price P (Rial/kg) 2000 2700 11,000 8500 7500 Planting day 4 May 20 March 5 December 5 August and 5 December 15 May Maximum yield Ym (kg/ha) 8612.76 39,215.12 1639.9 2763.52 9402.9 fact, irrigation function of the crop, which is calculated using the seasonal production, will function where the sensitivity and evapotranspiration coefficients are regarded in different growing stages of the plant. Jensen et al. [23] suggested the relationship between the relative yield and relative evapotranspiration as shown in Eq. (2). n Y Ya ETa ci YC ¼ ¼ ð2Þ Ymax i¼1 ETmax 2.4 Model’s constraints This equation, initially introduced by Rao et al. [24], is also provided in other forms. The main problem of these models is associated with sensitivity coefficients in different stages of growth. Careless selection of these coefficients would lead to problems in implementing the mathematical models and estimating the production [25]. To resolve this problem, Ky coefficients for different stages of growth of many plants are reported in the 33rd journal of Food and Agriculture Organization (FAO) entitled ‘‘Yield Responses to water’’, where: Ya: is actual yield (kg/ha), Ymax: is maximum yield of the crops under given management conditions that can be obtained with unlimited water supply potential (kg/ha), ETa: is actual evapotranspiration (mm), ETmax: is maximum evapotranspiration (mm), ki: is crop sensitivity index to water stress, by the following formula: In this study, ETREF software, which is based on the Penman–Monteith formula, is used to calculate the reference evapotranspiration. The maximum evapotranspiration, ETm, coincides with both crop evapotranspiration, which is the product of a crop factor Kc and the reference evapotranspiration [22, 26, 27]. k ¼ 0:2418 K 3 0:1768 K 2 þ 0:9464K 0:0177: ð3Þ In this formula (3), k is the yield reaction coefficient to water stress in different growth stages and is presented in the FAO-56 magazine for each crop and during different periods of growth. 123 Normally, every objective function has a series of restrictions that match the performance of the model with actual conditions of the area. The following constraints are used in model to make the objective function practical. 2.5 Crop evapotranspiration 2.6 Soil moisture balance The first constraint, soil moisture, was the amount of water available in soil surface. In the beginning of the irrigation season, soil moisture is assumed to be known. Here, it is assumed to be at field capacity for all soils and crops. Soil water balance equation for a given crop i and time interval j are given by Vedula and Mujumdar [28], Ghahraman and Sepaskhah [29], and Georgio and Papamichail [9]. ðSMin Þi;jþ1 ¼ ðSMin Þi;j þ ERAINi;j þ IRi;j ðETa Þi;j þ ðTAWi;jþ1 TAWi;j Þ ð4Þ where SMin = initial soil moisture level (mm), ERAIN = effective rainfall (mm), IR = irrigation water allocated (mm), ETa = actual evapotranspiration (mm), Neural Comput & Applic TAW = total available soil water (mm), i = cultivation crop and j = time interval. ðRmax Þij ¼ ¼ ðIRmax Þij ME 1 Pij TAWij þ ðETm Þij ðSMin Þij ERAINij 2.7 Water requirement ð9Þ The second restriction is water requirement of i plant in j time displayed as ðIRmax Þij . The following formula was used to calculate the plant’s water requirement: ðIRmax Þi;j ¼ 1 Pi;j TAWi;j þ ðETm Þi;j ðSMin Þi;j ERANi;j ð5Þ In this equation, ðIRmax Þij = is the maximum water requirement (mm) of the crop i in the time interval j, Pi,j = is the soil moisture depletion factor under non-water stress conditions of the plant i at the period j which depends on specific crop, and the maximum evapotranspiration ETm can be extracted from FAO 24 [25]. ERAINi = is the effective rainfall (mm), and (ETm)i, = is the maximum evapotranspiration, ðSMin Þij = is the soil moisture level (mm), and TAWi, = is the amount of total available soil water accessible to the plant. If due to low irrigation the plant’s yield drops by more than 70%, the crop production will not be economically feasible for farmers. This issue is also shown as restriction (6) to the model. Ya 0:7: ð6Þ Ym i 2.8 Reservoir release The third limitation Rij is the release from the reservoir used for irrigation of the i crop in the j period. It was calculated using Eq. (7), as also used by Georgiou et al. [9, 30]. P RijAi : ð7Þ ðRÞij ¼ ME Rij = is the release from the reservoir to meet irrigation requirement, so it should be always smaller than the maximum amount of water released from the reservoir. It is obvious that this value must always be greater than zero. This limit is shown as follows: 0 Rij Rij max ME ð8Þ At any time, the released maximum from the reservoir is in accordance with the amount of water allocated for irrigation of each crop per period as well as the irrigation efficiency that are based on the formula [30]: IRmax = maximum irrigation requirement (mm), Pij is the depletion factor of soil moisture in terms of the i plant’s water stress during the j period extracted from FAO’s 24th magazine, and ME is the average efficiency including application efficiency and conveyance efficiency, both determined according to the regional experts’ opinions. 2.9 Reservoir storage The fourth limitation applied to the objective function is the water balance of the reservoir where Si is the amount of water stored in the reservoir for any time period between the maximum storage volume, Smax, and the minimum storage volume (dead volume), Smin. Smin Si Smax ð10Þ Hence, Sj is calculated based on the continuity Eq. (11). Sjþ1 ¼ Sj þ Qj Rj EVPj þ SPj þ Rainj ð11Þ In this equation: Sj and Sj þ 1 are the volume of water stored in the dam (m3), respectively, in the j period and j þ 1 and Qj are the volume of inflow (m3) to the dam in the j period, SPj is the volume of water overflow (m3) in the j period, RAINj is the amount of precipitation on the dam (m3) in the j period, Ri is the volume of release from the reservoir for irrigation (m3) calculated based the following equation: Ri ¼ n X ¼1 10 Ai Rij ð12Þ i where Ri is the amount of water released from the reservoir for irrigation of the i crop (mm) in the j period. Ai is the cropped area of i crop (ha) (a factor of 10 for conversion of hectares in mm into m3). EVPj is the volume of water evaporated from the reservoir during the j period in terms of cubic meters. It is calculated based on Eq. (13). EVPj ¼ 0:001 Ei f ðSi Þ ð13Þ where f ðSi Þ is the dam’s level (m2) during the j period and Ej is evaporation rate from the dam level (mm) in the j period (a factor of 0.001 for converting millimeter into meter). By substituting Eq. (13) in Eqs. (14), (15) is achieved. 123 Neural Comput & Applic Sjþ1 ¼ Sj þ Qj n X 2.12 Weather condition classification ¼1 10Ai Rij 0:001Ej F ðSi Þ SPj i þ RAINj ð14Þ Sjþ1 ¼ min Smax; Sj þ Qj n X ¼1 10Ai Rij 0:001Ej F ðSi Þ i ð15Þ In Eq. (15), the reservoir water volume in each period was limited to two volumes: the maximum volume and the dead volume of the dam. Thus, the volume of water overflow is deleted from Eq. (15). 2.10 Actual evapotranspiration Eq. (16) is the limit of evapotranspiration. Actual evapotranspiration is always less than or equal to maximum evapotranspiration. This limitation shows that when soil moisture is higher than a critical value, ETa ¼ ETm but in cases of lower moisture levels, both ETa and ETm depend on the residual moisture in soil; hence, the actual evapotranspiration would be smaller than a proportion of its maximum value. In this study, the actual rate of maximum evapotranspiration is given by Doorenbos and Kassam [31], Georgiou et al. [9, 30]: ETa ðX; T Þ ¼ dx=dt ¼ f ð xÞETm ðtÞ ð16Þ ( ) 1ð1 pÞ . . . x TAW x f ðxÞ ¼ . . . 0 x ð1 pÞTAW : ½ð1 pÞTAW ð17Þ In Eq. (16), ETa = is actual evapotranspiration, X = is soil moisture in the root zone, t = is time period, and F ð X Þ is water drain from the soil and ETm = is maximum evapotranspiration. Other relevant parameters were described earlier. 2.11 Cropped area The last constraint is the limit-cropped area. Obviously, the area under cultivation for each crop should be between the maximum Amax and the minimum Amax cultivation. According to Eq. (18), this limit is displayed. Amin Ai Amax ð18Þ Most of these constraints and relationships are accessible in the references (Khanjari and Sabohi [14] and Ghadami et al. [32] and Ghahraman and Sepaskhah [33], Georgiou et al. [9, 30]. 123 The irrigation scheduling is provided to offer the farmers guidelines for adjusting irrigation schedules with actual weather conditions. In fact, developing such plan requires information on rainfall as well as evapotranspiration levels expected with different probabilities. Interestingly, the probability of rainfall coincides with probabilities of inflow. Four weather conditions are distinguished through combining the various probability levels of rainfall, evapotranspiration, and inflow [34]: wet, normal, dry, and hot–dry weather conditions along with the probability levels of expedience of rainfall and evapotranspiration. To find the base year upon which the weather conditions are simulated, the models were first implemented without regarding the weather conditions for the 8-year operation of the reservoir, which was daily recorded. The most optimal solutions offered by the cuckoo algorithm were witnessed in the base year, 2010–2011. Moreover, considering past data, various probability values of rainfall, reference evapotranspiration, and water inflow were estimated for the irrigation year, 2010–2011. Based on rainfall probability, the inflow to the dam, and the reference evapotranspiration (Table 2), four weather conditions, hot–dry, dry, normal, and wet, are considered for the model as follows. Based on the above probabilities and the frequency curves, the rainfall and evapotranspiration levels of a 10-day period are shown in Fig. 2. In addition, the 10-day inflow levels are shown in Fig. 3. 2.13 Cuckoo optimization algorithm Inspired by cuckoo’s life style, Rajabion proposed COA in 2011. The basic idea of this algorithm was taken from the way it lays eggs as well as the specific way it grows. Unlike most other birds, these kinds of birds avoid nesting and parenting and leave the nurture of its chicks effortlessly and subtly to other birds, so they are a socalled brood parasite. Cuckoo is the most famous brood parasite. A cuckoo destroys one of the host bird’s eggs and lays her egg among the eggs in the nest. Thus, the host bird will be in charge of maintaining the egg. Cuckoos do this by imitating the color and pattern of the eggs in each nest in order for their eggs resemble the actual eggs of the host. The more similar the eggs, the greater their opportunity to grow and survive. Two kinds of cuckoos are used in this model: mature cuckoos and laying-egg cuckoos. The following steps summarize the pseudo-code of the optimization algorithm: Neural Comput & Applic Table 2 The four different weather conditions Weather condition Probability level of expedience Evapotranspiration (%) Rainfall (%) Inflow (%) Hot and dry 80 0 0 Dry 60 20 20 Normal 50 50 50 Wet 40 80 80 Fig. 2 Ten-day rainfall and evapotranspiration with various weather conditions Fig. 3 Ten-day inflow with various weather conditions 1. 2. 3. Determine the primary habitat of the cuckoos (initial response) with selecting several random points on the function. Assign some eggs to each cuckoo. Identify egg laying radius or ELR for each cuckoo. ELR rate for each cuckoo is calculated according to the number of eggs and its distance to the destination using the following equation: ELR ¼ a ðnumber of available cuckoo’s eggs=total numbers of eggsÞ ðVarhi Varlow Þ where Varhi and Varlow are the maximum and minimum values of the variables, respectively. a is an integer that controls the maximum ELR. 4. 5. 6. 7. 8. Set cuckoos lay eggs within their respective ELR. Remove eggs with low target function. Determine the target function for any adult cuckoo. Limit the maximum number of the cuckoos available in the environment. Classify the cuckoos and determine the superior habitat. 123 Neural Comput & Applic The parameters, determined by trial and error, are used in the COA and are shown in Table 3. 3 Results and discussion The model was solved as a two nonlinear programming namely cuckoo optimization and genetic algorithms in 4 weather conditions namely wet, normal, dry, and hot–dry. MATLAB software was used to write the codes. Here, the results of implementing the model for different weather conditions for both algorithms are expressed. Furthermore, the COA optimization model was used to compute the irrigation scheduling and optimal cropping pattern for five crops (corn, alfalfa, wheat, barley, and sugar beet) with data gathered from all weather conditions. The time interval was 10 days for all five crops, and the irrigation period (from April to December) was sub-divided into 27 periods. 3.1 Relative yield Fig. 4 The flowchart of cuckoos algorithm [15] Table 3 Parameters of cuckoo optimization algorithm Title of parameters Selected value Initial number of cuckoos 50 Minimum number of eggs per cuckoo 2 Maximum number of eggs per cuckoo 5 Maximum number of alive cuckoos 50 Maximum number of iteration 100 Number of groups or categories 3 X p/6 Convergence criterion 1 9 10-10 Their classification is performed by K-means clustering method, where k group (usually 3–5 groups) is selected and based on the variation range of profit function in cuckoos, the average income of each group is determined, and each cuckoo will belong to a group that is closest to the average of the group. 9. Migration of new cuckoos toward superior habitat. In its migration toward the target habitat, the cuckoo does not fly all the way through. It flies k% of the path with u radian deviation (Fig. 4), so these two parameters search more spots of the problematic space. For each cuckoo, k is a random number between zero and one (equally distributed) and u is a random number between x and -x (x of about p/6 is appropriate). In case of occurrence of stop conditions, the algorithm will end; otherwise, go to the second step. In Fig. 4, the cuckoos algorithm flowchart is presented. 123 One of the most efficient outputs is the relative yield of crops under different weather conditions. In cases where the water allocated to the crop equals its maximum water requirement, the relative yield is one. However, in cases with less water requirement, the relative yield is less than 1. Two algorithms have calculated the yields of wheat, barley, and alfalfa in wet weather as one, so in this weather, the water allocated to these crops is sufficient to meet its water requirements. The relative yields under the four weather conditions are given in Table 4. As shown in Table 4, the crops’ yields differ greatly in different climatic conditions. In other words, reduced rainfall and hotter condition would lower their yields so significantly in hot–dry conditions that the estimated yields made by the cuckoo and genetic algorithms for crops such as sugar beet, barley, and alfalfa are significantly less than their economical rate (0.7). It is inferred that mainly due to their high water demand and reduced yield, their cultivation in these weather conditions is not economical. Moreover, in terms of reduced rainfall, sugar beet had the least yield of all. However, due to its high water demand, this result was quite expected. 3.2 Total farm income in optimal cropping patterns The main output of the model corresponding with the objective function of the model includes the output of the profit and the level of cultivation per crop. The calculated amounts prepared by using COA and GA for hot–dry, dry, normal, and wet weather conditions, allocation of water from reservoir and cropped area for various weather Neural Comput & Applic Table 4 Relative yield of cultivated crops in the Qazvin plain for various weather conditions (Ya/Ym) Crop Wet GA COA Normal Dry GA GA COA Hot and dry COA GA COA Corn 1 1 1 0.97 0.98 0.92 0.75 0.7 Alfalfa 1 1 0.81 0.82 0.79 0.79 0.7 0.63 Barely Sugar bee 1 0.99 1 0.97 1 0.95 0.99 0.94 0.98 0.79 0.95 0.81 0.78 0.63 0.58 0.53 Wheat 1 1 1 0.98 0.97 0.91 0.81 0.71 conditions are represented in Table 5. It should be noted that in the models, the rates of the farmer’s profit in different weather conditions are calculated immediately before and after optimization. As shown in Table 5, in hot–dry condition, due to lack of rainfall and input current in one hand and increased evaporation on the other hand, the dam reservoir used for irrigating the crops reduced. It was followed by a decreased rate of the acreage of the crops consuming high amounts of water. Yet, in case of the crops requiring less water, it increased significantly in two models. Consequently, wheat and corn, respectively, have taken the first and the second positions. In addition, the acreage of sugar beet dropped from 1425 ha to 0 and 31 (ha), respectively, in COA and GA, mainly due to its extremely high water demand. Following the new optimal crop pattern provided by the models, under hot–dry weather conditions, the volume of water consumption witnessed a great increase by the end of the operation. It was also economically beneficial for the farmers so that implementing the model would increase the relative profit of the farmers by 6.2 and 3.63% in COA and GA models. In dry weather conditions, the first place of cultivation was allocated to wheat, and corn and alfalfa had the following ranks. As it can be seen, the cultivation of sugar beet dropped significantly by 147 (ha) in COA and by 137 (ha) in GA compared to the previous optimization. Here again, the benefits increased by 2.6 and 2.55% in COA and GA, respectively. In normal weather conditions, the maximum area under cultivation was devoted to wheat, alfalfa, barley, and corn. The acreage of sugar beet in this condition, which was less than the period prior to implementation of the model, dropped to 204 and 157 (ha), and the farmers’ profit increased 1.27 and 4.96% in COA and GA models, respectively. As shown in Table 5, in wet weather conditions, rainfall and input flow to the dam are higher than other conditions, so it is expected that the acreage of all crops with high water needs increases more than other weather conditions. For example, in this case, the increased cropped area of sugar beet [by 271 and 174 (ha) in COA and GA models] signifies its significant increase compared to other weather conditions. This is due to increased yield of sugar beet in wet conditions. By contrast, the overall benefit of the farmers only decreased in COA and GA by 1.46 and 1.58%. As shown in Table 5, the allocated water increased in hot–dry and dry conditions because the crops required the highest depth of irrigation water in both models. By contrast, in wet and normal conditions, the allocated water Table 5 Total farm income, allocation of water from reservoir, and optimum cultivation area for various weather conditions by COA and GA Crop Cropped area (ha) before optimization Wet Normal Dry Hot and dry Cropped area (ha) Water (m3) Cropped area (ha) Water (m3) Cropped area (ha) Water (m3) Cropped area (ha) Water (m3) Wheat 34,583 34,929 1.011 34,949 1.27 34,966 1.56 35,702 1.97 Corn Barley 9608 9893 9723 10,123 0.815 0.549 9730 10,137 1.037 0.719 9735 10,148 1.259 0.738 10,229 6596 1.689 1.23 Sugar beet 1425 271 1.316 204 1.629 147 1.968 0 0 Alfalfa 9548 10,009 0.326 10,036 0.412 10,059 0.499 11,155 0.750 COA Total income (10 Rial) 150,670,907,040 131,970,730,080 124,307,287,233 68,562,559,902 GA Wheat 34,958 1.01 34,963 1.278 34,866 1.57 35,001 2.14 Corn 34,583 9608 9732 0.81 9734 1.03 9835 1.24 9747 1.7 Barley 9893 10,143 0.515 10,146 0.718 10,158 0.921 10,171 0.822 Sugar beet 1425 174 2.05 157 2.132 137 2.144 31 2.677 Alfalfa 9548 10,048 0.321 10,055 0.411 10,050 0.509 10,105 0.833 Total income (10 Rial) 150,861,600,000 137,094,675,876 124,229,887,233 66,697,894,772 Total income before optimization (10 Rial) 148,473,169,701 130,287,334,273 121,054,220,961 64,274,856,196 123 Neural Comput & Applic Fig. 5 Water values stored in the reservoir after optimization during the operational period dropped. For example in COA model, the water allocated to wheat increased from 1.011 in wet to 1.97 in hot–dry condition. The results of two models indicated that wheat crop could adopt well in all weather conditions because of its low water requirement and appropriate yield, so it is optimal for the study area. In contrast, sugar beet has lost 80% cultivation area in all climatic conditions; hence, given the current water shortage and high water requirement of sugar beet and its low profitability, it is not suitable for cultivation. In other words, it is recognized as a plant with high water requirements and low yield. 3.3 The volume of water stored in the dam in different weather conditions Figure 5 shows the water values stored in the reservoir by the difference of water storage in reservoir before and after optimization during the operational period. During wet weather condition, the volume of the stored water increased mainly due to increased rainfall and inflow into the dam. Likewise, the potential of the output flow in the reservoir rose. Consequently, more water is allocated for the crops with high water demand, so the area was 123 highly dedicated to cultivation of these crops. Therefore, compared to other conditions, less water was stored in the reservoir (Fig. 5). On the other hand, in dry conditions, extremely high temperatures would result in increased evaporation. Reduced rainfall will also lower the inflow to the dam. Of course, it is possible to release water for the least amount of acreage. In normal conditions with increased rainfall and inflow, the acreage of cropped area with high water required less expansion; therefore, the stored value in reservoir is more than other conditions. This model would decrease the acreage of the crops requiring high irrigation. In fact, the model is designed in a way that during the critical (low water) years, the cultivation area allocated for high-consuming crops would reduce, so the area would be left to crops requiring less water with higher economic profit, resulting in both proper consideration of the farmers’ profit and optimal monitoring of the dam water allocated to irrigation. Following the new cropping pattern extracted from these models, the volume of water stored in the dam reservoir in wet, normal, dry, and hot–dry conditions will increase, respectively, by 264,745.3, 2,865,387, 275,789, and 655,918 m3 for COA and 262,045.2, 2,862,686.6, 273,089, and 955,542 for GA compared to the previous optimization occurred at the end of the operation. Neural Comput & Applic Fig. 6 Effective rainfall (ERAIN), maximum evapotranspiration (ETm), reservoir release to meet irrigation requirement (R), and actual evapotranspiration (ETa) for wet, normal, and dry weather conditions for two crops (wheat and sugar beet) under study by COA In comparison with GA, the results showed that COA could provide better and more reliable optimal results in relative yield of crops, higher farm income, and lower water consumption. So, the results of COA are presented below for allocation of irrigation water. 3.4 Allocation of irrigation water Allocation of irrigation water and the cropped area for each crop depends mainly on factors such as net profit per unit yield (price, maximum yield obtainable per unit area, profit, cost, and net profit for maximum yield) (Table 1). According to the formulas introduced in the Materials and Methods, calculating water allocated to these crops requires information on soil moisture, potential evapotranspiration, and irrigation efficiency. The model is designed in a way that in cases when the crop’s water need is provided by rainfall, no more irrigation is required. In other words, the model initially provides the plant’s irrigation need through green water. If not sufficient, it will 123 Neural Comput & Applic Fig. 6 continued allocate water from reservoir. Therefore, the allocation of irrigation water to the crops in normal and wet weather conditions is less than that of dry weather. In addition, using the coefficient ky in designing the model has made it to reconsider the growth periods of the plant, so more water is allocated to this period than the output and harvesting stages. During the sleep (dormant) period, no irrigation is done. In Fig. 6, the amount of water allocated per hectare, the effective rate of rainfall, potential and actual evapotranspiration of wheat and sugar beet (with high water requirement) and wheat (with low water requirement) in each period and under three weather conditions (dry, wet, and normal) are shown. 123 According to Fig. 6, it can be seen that following weather pattern variation, increased rainfall, and reduced evaporation, the irrigation rates needed for the crops reduces alike. Therefore, under wet conditions, the model would reduce the maximum required water of wheat and sugar beet to less than 80 and 100 mm, respectively. Likewise, in dry conditions, due to significant reduction of rainfall volume and increased temperature, followed by increased evaporation, these values for wheat and sugar beet are, respectively, higher than 120 and 160 mm. As water loss increases, ETa will lessen more to less than ETm values. Yet, due to unequal yield sensitivity indices, these declines differ greatly at different time Neural Comput & Applic Fig. 7 Comparison of the convergence trajectories of cuckoo and genetic algorithms in wet conditions intervals. It is necessary to note that as expected, for the time intervals with nonzero effective rainfall, the corresponding release is adequately small or even null (Fig. 6). 3.5 Convergence performance of Cuckoo algorithm Figure 7 shows a sample graph of maximum objective function for cuckoo and GA with maximum iteration. As shown in Fig. 7, cuckoo algorithm in wet weather conditions with 25 of iterations and genetic algorithm with 65 of iteration has led to optimal solution iteration. Figure 7 indicates that the convergence speed of the COA is obviously faster than the GA. 4 Conclusion In this study, the COA is used for better management of water resources of Taleghan dam and for determination of maximum profit gained from the crop cultivation under various weather conditions in Qazvin plain located in Iran’s central plateau. Meanwhile, under the same objective function evaluation, COA and GA performances were accessed. The results of cropped area in two models showed that regardless of whether condition, the net profit for maximum yield of wheat is much higher than all other crops. Regarding variety of the weather conditions and the rate of water available, the acreages of sugar beet will decrease sharply, for it requires extremely deep irrigation. Comparison of the results of two models indicated that the COA could provide better and more reliable optimal results in relative yield of crops, farm income, and lower water consumption than GA. Following the new cropping pattern offered by COA model, in wet, normal, dry, and hot–dry conditions, the volume of stored water of the reservoir at the end of the operation will increase, respectively, by 264,745.3, 2,865,387, 275,789, and 655,918 m3. Meanwhile, farmers’ profit will increase, respectively, by 6.2, 2.6, 1.27, and 1.48% compared to the previous optimization occurred at the end of the operation. Therefore, it can be summarized that COA is quite promising in cultivation area of crops optimization problem because of its simple structure, excellent search efficiency, and strong robustness. 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