Juan Reca

Optimisation model for water allocation in deficit irrigation systems. I. Description of the model

Abstract In this paper, an economic optimisation model for hydrologic planning in deficit irrigation systems is proposed. Irrigation water allocation between agricultural demands is carried out following an economic efficiency criterion with the aim of maximising the overall economic benefits obtained, allocating available water to each user as a function of the water’s profit margin. Water resources constraints in the system are considered. Aggregated economic functions for each irrigation district are generated optimising the water used for the cropping pattern. Stochastic nature of water availability and irrigation requirements have been taken into account. Due to the complexity of the system, the problem has been broken down into three independent optimisation sub-problems that perform hierarchically. Each of these sub models takes into account a different resolution level of the system: crop, irrigation district and the whole basin. The proposed model has been used in a subsequent paper to optimise water allocation planning in a small basin in southern Spain; the Bembezar system.

A memetic algorithm applied to the design of water distribution networks

The optimal design of water distribution networks is a real optimization problem that consists of finding the best way to convey water from the sources to the users, satisfying their requirements. Many researchers have reported algorithms for minimizing the network cost applying a large variety of techniques, such as linear programming, non-linear programming, global optimization methods and meta-heuristic approaches. However, a totally satisfactory and efficient method is not available as yet. Many works have assessed the performance of these techniques using small or medium-sized benchmark networks proposed in the literature, but few of them have tested these methods with large-scale real networks. This paper introduces a new memetic algorithm for the optimal design of water distribution networks. In order to establish an accurate conclusion, five other approaches have also been adapted, namely simulated annealing, mixed simulated annealing and tabu search, scatter search, genetic algorithms and binary linear integer programming. The results obtained in three water distribution networks show that the memetic algorithm performs better than the other methods, especially when the size of the problem increases.

Optimisation model for water allocation in deficit irrigation systems: II. Application to the Bémbezar irrigation system

Abstract In this paper, the proposed optimisation model is applied to optimise water management in the Bembezar system, a small hydrological basin belonging to the Guadalquivir River basin in southern Spain that supplies water to the Bembezar River Irrigation District. In order to apply the model, the irrigation methods and performance in the irrigation district have been analysed through a set of field irrigation evaluations. Cropping patterns, crop productivity and other relevant agronomic and economic data have been collected. The influence of irrigation uniformity and the type of distribution of irrigation water on the crop yields, as well as the relationship between crop yields and irrigation scheduling have been analysed using the proposed model. A deterministic analysis has been carried out in the irrigation district in order to compare optimum water and cropping patterns management with actual ones. In order to account for the randomness of both climatic and water availability variables, a stochastic data generation has been carried out which considers the correlation between these hydrological series. The system is then analysed in a stochastic environment. Several simulations of the optimisation process have been carried out using generated data on climatic and water availability variables. The result of this analysis demonstrates that when only the satisfaction of the internal demands is considered, high quantities of water are allocated to the irrigation districts resulting in low economic benefits per unit of water used and lower irrigation efficiency. This situation has been compared with the solution provided by the hypothesis of a proposed water market in which it is possible to transfer part of the water of the system to other alternative uses at a fixed price. In this second hypothesis, water consumption in the irrigation districts was reduced.

Implementation of scatter search for multi-objective optimization: a comparative study

Abstract Interest in the design of efficient meta-heuristics for the application to combinatorial optimization problems is growing rapidly. The optimal design of water distribution networks is an important optimization problem which consists of finding the best way of conveying water from the sources to the users, thus satisfying their requirements. The efficient design of looped networks is a much more complex problem than the design of branched ones, but their greater reliability can compensate for the increase in cost when closing some loops. Mathematically, this is a non-linear optimization problem, constrained to a combinatorial space, since the diameters are discrete and it has a very large number of local solutions. Many works have dealt with the minimization of the cost of the network but few have considered their cost and reliability simultaneously. The aim of this paper is to evaluate the performance of an implementation of Scatter Search in a multi-objective formulation of this problem. Results obtained in three benchmark networks show that the method here proposed performs accurately well in comparison with other multi-objective approaches also implemented.

Optimal Pumping Scheduling for Complex Irrigation Water Distribution Systems

AbstractThe establishment of an optimal pumping schedule is a cost-free, efficient measure that is easily adopted to reduce energy costs. This paper proposes an optimal pumping scheduling model for complex irrigation water distribution systems (WDS) for the case in which head and efficiency are independent of flow rate. The proposed model utilizes a simplified pumping scheme and a determinist linear programming (LP) optimization algorithm. A robust and versatile software application was also developed that is useful for WDS managers in adopting optimal pumping scheduling decisions for a specific electricity tariff structure and to satisfy all system performance constraints. The model also provides the option of testing and comparing different alternative electricity tariffs and allows managers to select the most cost-effective tariff for their system. The model is applied to a real WDS located in the province of Almeria in southeastern Spain. The optimal pumping scheduling during an entire year is obtaine...

A Memetic Algorithm for Water Distribution Network Design

The majority of real optimization problems cannot be solved exactly because they have very large and highly complex search spaces. One of these complex problems is the design of looped water distribution networks, which consists of determining the best way of conveying water from the sources to the users, satisfying their requirements. This paper is to present a new memetic algorithm and evaluate its performance in this problem. With the aim to establish an accurate conclusion, other four heuristic approaches have also been adapted, including simulated annealing, mixed simulated annealing and tabu search, iterated local search, and scatter search. Results obtained in two water distribution networks demonstrate that the memetic algorithm works better when the size of the problem increases.

A Pareto-based memetic algorithm for optimization of looped water distribution systems

Looped water distribution networks have traditionally been used in urban and industrial water supply. Nowadays, they are also being introduced in certain irrigation water distribution systems, such as in greenhouse horticultural systems. The design of looped networks is a much more complex problem than the design of branched ones, but their greater reliability can compensate for the increase in cost. Most articles found in the literature try to minimize the network investment cost, while other designing objectives are considered as constraints. This article introduces a multi-objective memetic algorithm that simultaneously optimizes the total investment cost, and also the reliability of the network in terms of total surplus power at the demand nodes. This memetic algorithm uses the Pareto-dominance concept to determine the quality of the solutions. The results obtained in two small water supply networks, and a large irrigation water supply network denote the good performance of the memetic algorithm here proposed in comparison with other well known meta-heuristics.

Determinzation and analysis of Regional Evapotranspiration in southern Spain based on remote sensing and GIS

Abstract Evapotranspiration estimations are essential in irrigation schemes, reservoir water losses, water balance computations, runoff predictions, and meteorology and climatology studies. The new techniques called remote sensing and geographical information systems (GIS), allow a spatially distributed calculation of this parameter. A new rational model, SEBAL (Bastiaanssen, 1995), based on the energy balance equation, has been applied in this study. In this model, a lower number of empirical relations is needed. Besides of this, the SEBAL model has many other advantages. This model has been calibrated and validated in an area located in the Guadalquivir Valley (Spain), from a satellite image Landsat-TM5 and climatology data. Afterwards, the model was used in a smaller resolution than the original one, through an aggregation procedure of the original TM image. This resolution change was made to check the possible use of others type of satellite images. Crops, soils and digital elevation model maps of the study area have been included for studying some of the parameters obtained in the previous determination of the ET.

New Adaptive Hybrid-Automatic Irrigation Control System for Soilless Culture

AbstractIn soilless culture, irrigation scheduling is an important and difficult task, as water and nutrients must be frequently and precisely applied, due to the reduced volume and low water holding capacity of most of the substrates. This paper describes an efficient control system for irrigation management of soilless culture based on an irrigation tray and a new adaptive hybrid automatic irrigation control algorithm. The proposed irrigation scheduling criteria are based on applying constant amounts in every irrigation application and variable timing as a function of crop water consumption. The control system analyzes the water balance in the control tray from the information provided by the sensors on the measured inputs and outputs of water from the tray. A hybrid algorithm composed of two stages is proposed. An estimation of the irrigation interval between irrigations is made by using an average daily crop water uptake pattern obtained from the feedback information of the tray. Short-term variations...

Yield and Nutritional Status of Cucumis sativus under Different Growing Conditions in the Pacific Coast of Ecuador

ABSTRACT The growth of cucumber under open field conditions in the coast of Ecuador results in low yields being the growth under protected conditions a tentative solution, but there is little information about the nutritional status of this crop in this region. The objectives were to determine the yield, nutritional status as well as the water and nutrient use efficiencies. The different growing conditions were: multitunnel greenhouse with soilless system (GSL), multitunnel greenhouse with soil system (GS) and open field conditions with soil system (OFS). Cucumber plants grown under GSL had the highest yield. The nutrient concentration in leaf showed different trends: nitrogen (N), calcium (Ca) and iron (Fe) remained unchanged. Phosphorus (P), potassium (K), magnesium (Mg), copper (Cu), zinc (Zn) and manganese (Mn) showed variations according to the growing conditions and phenological stages. The highest values of water and nutrient use efficiencies under GSL were related to the highest yield.