Distribution systems


Design and performance analysis of distribution systems

Pressurized irrigation systems were the object of considerable attention in the sixties and the seventies and a considerable number of them was designed and implemented in the Mediterranean basin mainly but also in other parts of the world.  They offer a considerable potential for efficient water use, reduce disputes among farmers and lessen the environmental problems that may arise from the misuse of irrigation water.  With the current strong competition for water resources, modernization of irrigation systems is becoming a critical issue and one of the alternatives to modernize is the use of pressurized systems to replace part of the existing networks. This approach is being actively pursued in many Mediterranean countries.

Much of the work done in the past concentrated on the design and optimization of such systems and FAO, through its Irrigation and Drainage No. 59: "Design and Analysis of on-Demand Irrigation Systems" (Lamaddalena & Sagardoy, 2000), substantially contributed to this area of knowledge. The present research line was started with the idea of developing tools based on the great capacity of computers to randomly generate many scenarios  which could be statistically analyzed and provide clear indications of where the network is not functioning satisfactorily. This approach immediately highlighted that the same criteria could also be used to analyze an existing network designed according to traditional criteria for improving the modernization techniques. This research leads to the conclusion that design criteria need revision and this additional task is part of the present research line.

In addition, one of the most important uncertainties in an on-demand system is the calculation of the discharges flowing into network. As farmers are the ones who control irrigation, it is impossible to know, a priori, how many and what hydrants are operating simultaneously. In fact, variability in discharge flow occurs in such systems in relation to scheduling decisions over time depending on the cropping pattern, the crops grown, meteorological conditions, on-farm efficiency and management strategy.  This variability may produce failures related to the design options. The advent of on-demand large scale irrigation systems fostered the development of statistical models to compute the design flows.  Examples of such models are the first and the second formula of Clément (1966). Although these models are theoretically sound, the assumptions governing the determination of the parameters do not take into account the actual functioning of an irrigation system.

In view of these limitations a number of researchers tackled the problem by simulating irrigation strategies (CTGREF, 1974; CTGREF, 1977; Béthery, 1990; Lamaddalena & Ciollaro, 1993). Maidment and Hutchinson (1983) modelled the demand pattern over a large-scale irrigation system. Abdellaoui (1986) proposed a demand model based on the queuing theory. The Environmental Protection Agency (EPA) of the United Stateshas developed a model called EPANET (Rossman et al., 1993; Rossman 2000) that performs an extended period simulation of hydraulic and water quality behaviour within pressurised pipe networks. Teixeira et al. (1995) presented a simulation model to calculate the crop irrigation requirements in the peak period according to the soil type, the cropping pattern, the irrigation method efficiency and the percentage of the irrigated area.  Walker et al. (1995) developed the Command Area Decision Support Model (CADSM) for estimating an aggregated demand and studying management options for irrigated areas.  Lamaddalena (1997) and Lamaddalena and Sagardoy 2000, developed a new integrated methodology for the optimisation and the performance analysis of on-demand irrigation systems considering the Several Flow Regime Approach (SFR).  Khadra and Lamaddalena 2006 developed a soil water balance for generating an on-demand large scale irrigation system. All the above shows that the existing models need to be improved for generating information on the multiple discharges that can flow into the irrigation network

Therefore, this research aims at generating the demand hydrographs at the hydrant level and at the upstream end of the distribution network, which can be used for the design of new distribution networks as well as for the analysis of the existing ones.  This research allows integrating many different aspects including crops, soil, on-farm and distribution networks.

Within the framework of such research line, new technologies for water delivery systems are also developed, tested and implemented in the field.

Timing:
Starting: 8.01.1993
Scheduled ending: 23.09.2019
Real ending: 23.09.2019
Objectives:

The main objective of the present research is the development of a computer tool that permits the diagnosis of performance of pressurized irrigation systems, but also provides new and revised criteria for the design of such irrigation networks.  Therefore, the research has two main components: the first one deals with the revision of criteria for design and optimization, and the second concentrates on the analysis of performance of existing systems. 

The computer program (COPAM), developed within the framework of the present research and published in the FAO I&D paper n. 59 (Lamaddalena & Sagardoy, 2000), makes these calculations in a matter of seconds or fractions of seconds and helps the user fully understand what is being done by the program and develops his/her capacity to verify the results.

Within the framework of such research line several field situations in the Mediterranean basin were tested by quickly identifying the weak points of the network but also by identifying the power requirements of pumping stations needed to satisfy varying demand situations and often proving that the power houses were well not suited (over designed or under designed) to meet the requirements of the network.

Justification:

The present research is intended to provide new methods for the design and analysis of performance of pressurized irrigation systems, and should be of particular interest to district managers, consultants, irrigation engineers, construction irrigation companies, university professors and students of irrigation engineering and planners of irrigation systems in general.

This research line was officially demanded by all the Mediterranean partners, members of the networking activities coordinated by the IAM-B L&W Division, as described in the background paragraph.

Potential:

This research allows defining new design criteria aiming at maximizing the performance of the distribution irrigation systems and it allows the analysis of existing irrigation systems by identifying failure zones. It helps designers and managers better understand the hydraulic behaviour of an irrigation system and therefore, better act for solutions. In addition, the software packages with GIS interface that are currently under development, will give great visibility to the MAIB L&W activities.

Results:
Notes:
  • Strengths

This is one of the most consolidated research works carried out at the L&W Division, as it started more than 15 years ago within the framework of the MAIB networking activities (CIS-Net). Therefore, as demonstrated in many years, this research represents a very important step in the modernization of large scale irrigation systems This approach implies a strong interaction among engineering, agronomic and socio-economic aspects, which produces real innovations.

  • Weaknesses

The weakness is mainly related to the complexity in developing simulation models taking into account the farmers’ behaviour. This behaviour represents a stochastic that component considerably affects the model results. Therefore, the only way to calibrate the models is to have access to historical data sets often not available and/or not reliable.

Reference person/s: Lamaddalena Nicola /
Collaborators: Khadra Roula / Zaccaria Daniele /
Thesis: Optimisation des réseaux d’irrigation avec les critères de fiabilité
Experimental analysis on gabion-stepped weirs in irrigation open channels
Energy saving through variable speed pumping in on-demand irrigation systems
Assessment of potential water scarcity and water delivery performance in large-scale pressurized irrigation scheme
Experimental analysis on hydraulic jump in irrigation open channels
Optimisation du fonctionnement des réservoirs dans les systèmes d’irrigation à la demande par l’emploi des algorithmes génétiques
Algorithme génétique pour l’optimisation de régulation des réservoirs d’eau dans un système d’irrigation à la demande
Surface irrigation for cotton and wheat at Ras El Ain: assessment and issues for improvement
A comparative analysis between simulated and measured water deliveries at farm level in an irrigation district managed by the water users association
Energy saving criteria for optimal design of a pumping station serving an on-demand irrigation system
Etude expérimentale d’un écoulement à surface libre en présence de végétation submergée et rigide en particulier
Experimental study on open channel flow in the presence of submerged vegetation, with special focus on flexible vegetation
Management, operation and maintenance of large scale distribution systems in the GAP Region (Southeastern Anatolia Project)
Developing monitoring and evaluation systems for Water Users Organizations. The case study of District 4 « Sinistra-Ofanto » irrigation system (Consorzio per la Bonifica della Capitanata)
Experimental study of the scour hole downstream of bed sills
Evaluation of large-scale irrigation structures
Operation and performance analysis of a pseudo-looped irrigation scheme
Analyse des performances d'un réseau maille-ramifie d'irrigation à la demande
Mise en place d'un système de suivi-évaluation des performances hydrauliques d'un réseau d'irrigation sous pression. Application d'un modèle COPAM (FAO 59)
Modélisation et SIG pour l'analyse des performances des systèmes collectifs d'irrigation sous pression fonctionnant à la demande (Cas du sous-secteur A du Loukkos-Maroc)
Economie d'eau et d'énergie dans les périmètres modernes publics du Souss Amont (Maroc)
Prototype d'outil d'aide à la décision pour les grands systèmes d'irrigation
Amalgamation of GIS and environmental indicators for decision making in water resources management
Analyse des performances d’un réseau maillé-ramifié d’irrigation à la demande
Institutions involved: Institut Agronomique et Vétérinaire Hassan II of Rabat (IAV-Rabat)
Institut National Agronomique de Tunisie (INAT)
Technical University of Lisbon
 
 
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