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The estimation of crop evapotranspiration (ETc) from the reference evapotranspiration (ETo) and a standard crop coefficient (Kc) in olive orchards requires that the latter be adjusted to planting density and height. The use of the dual Kc approach may be the best solution because the basal crop coefficient Kcb represents plant transpiration and the evaporation coefficient reproduces the soil coverage conditions and the frequency of wettings. To support related computations for a super intensive olive orchard, the model SIMDualKc was adopted because it uses the dual Kc approach. Alternatively, to consider the physical characteristics of the vegetation, the satellite-based surface energy balance model METRIC™ – Mapping EvapoTranspiration at high Resolution using Internalized Calibration – was used to estimate ETc and to derive crop coefficients. Both approaches were compared in this study. SIMDualKc model was calibrated and validated using sap-flow measurements of the transpiration for 2011 and 2012. In addition, eddy covariance estimation of ETc was also used. In the current study, METRIC™ was applied to Landsat images from 2011 to 2012. Adaptations for incomplete cover woody crops were required to parameterize METRIC. It was observed that ETc obtained from both approaches was similar and that crop coefficients derived from both models showed similar patterns throughout the year. Although the two models use distinct approaches, their results are comparable and they are complementary in spatial and temporal scales info:eu-repo/semantics/publishedVersion

Research Paper This study explores the use of drip and surface irrigation decision support systems to select among furrow, border and drip irrigation systems for cotton, considering water saving and economic priorities. Data refers to farm field observations in Northeast of Syria. Simulation of drip irrigation was performed with MIRRIG model for various alternatives: double and single row per lateral, emitter spacing of 0.5 and 0.7 m, six alternative pipe layouts and five self-compensating and non-compensating emitters. Furrow and border irrigation alternatives were designed and ranked with the SADREG model, considering lasered and nonlasered land levelling, field lengths of 50e200 m and various inflow discharges. A multicriteria analysis approach was used to analyse and compare the alternatives based upon economic and water saving criteria. Results for surface irrigation indicate a slight advantage for long non-lasered graded furrows; non-lasered alternatives were selected due to economic considerations. For drip irrigation, the best ranking is for systems having lower costs, mainly with double rows per lateral and larger emitter spacing. Comparing surface and drip irrigation systems, despite low cost, drip alternatives may lead to 28e35% water saving relative to improved graded furrows, and increase water productivity from 0.43 kg m 3 to 0.61 kg m 3, surface irrigation provides higher farm returns. Drip irrigation is selected only when high priority is assigned to water saving. Deficit irrigation does not change this pattern of results. Apparently, adopting drip irrigation requires appropriate economic incentives to farmers, changes in the structure of production costs and increased value of production info:eu-repo/semantics/publishedVersion

The water footprint of a crop is the volume of water that is necessary to produce, therefore relating crop water requirements and yield. The components of water footprint, blue, green and grey water footprints refer to the volumes of respectively, surface and groundwater, rainfall, and water required to assimilate pollution, which are used to produce the crop yield. Determining blue and green water footprints is generally achieved using estimates of evapotranspiration. In the present study we have used evapotranspiration measurements to estimate the water footprint of a super-intensive olive grove in southern Portugal. Crop water requirements were measured using a sap flow technique, to determine transpiration and the eddy covariance method for direct measurement of evapotranspiration. This technique was used for a short period, while the sap flow measurements were performed for long periods, hence allowing the extension of the data series. Evapotranspiration measured directly was in average close to 3 mm d-1 and the ratio of actual evapotranspiration to reference evapotranspiration approached 0.6 for the same period. The water footprint of the olive crop under study was lower than those reported in literature. A possible reason relates to the density of plantation, yield and irrigation management. The irrigated grove under study produced a high yield, which compensates for high water use, leading to a water footprint lower than for rainfed or less dense groves. Furthermore, as evapotranspiration measurements were used to calculate water footprint instead of the common procedure, this might have also caused some differences. As recently discussed in literature, remote sensing techniques can provide estimates of actual evapotranspiration and water balance terms when associated with modeling. For the present study, water footprint estimates using in situ evapotranspiration measurements were further compared with water footprint estimates obtained with remote sensing.

A pegada hídrica de uma cultura representa o volume de água necessário para produzir, relacionando as necessidades hídricas da cultura com a produção. As suas componentes, pegadas hídricas azul, verde e cinzenta, referem-se respectivamente aos volumes de água superficial e subterrânea, precipitação e de água necessária para assimilar a poluição utilizados pela cultura. A determinação das pegadas hídricas azul e verde é normalmente conseguida através da estimativa da evapotranspiração cultural, aplicando coeficientes culturais a uma evapotranspiração de referência, calculada a partir de dados meteorológicos. No presente estudo foram utilizadas medições da evapotranspiração para estimar a pegada hídrica de um olival super-intensivo na região de Évora. As necessidades hídricas foram medidas utilizando um método de fluxo de seiva para determinar a transpiração e o método micrometeorológico das flutuações instantâneas para medir directamente a evapotranspiração. Esta técnica foi utilizada durante um período de tempo limitado, enquanto as medições do fluxo de seiva, que foram efectuadas para períodos alargados, permitiram a extensão dos registos. A evapotranspiração medida directamente apresentou valores de cerca de 3 mm d-1 e o quociente entre evapotranspiração real e evapotranspiração de referência é próximo de 0,6 para o mesmo período. Comparou-se a estimativa da pegada hídrica obtida com o procedimento habitual com a resultante de medições in-situ e utilizando técnicas de deteção remota. A pegada hídrica do olival sob estudo foi inferior às simulações encontradas na literatura, o que pode ser explicado por diferenças na densidade de plantação, produção e gestão da rega. O olival em estudo obteve uma produção elevada, com um azeite que preencheu as características essenciais à classificação de azeite extra virgem, o mais valorizado, o que contraria o efeito do elevado consumo de água, resultando numa pegada hídrica inferior à de olivais não regados ou com menor densidade de plantação.

MIRRIG is a decision support system (DSS), developed to design and evaluation of microirrigation system under operation. This DSS comprise a database and the models: design and evaluation. The database contains information on emitters, pipes, soils, as well as plants and the systems under design. Design models allow creating and comparing a set of design alternatives based upon an integration of technical, economic and environmental criteria, and may be useful to maximize the beneficial use of water for irrigation of golf courses and public landscape areas. The evaluation component is a tool to advise decision maker about how to improve their microirrigation systems when using data obtained during field evaluation of systems under operation. This article describes the DSS MIRRIG and presents the results of its application in two different landscapes in Portugal (Esposende and Faro)

The use of irrigation in the cultivation of papaya is increasing in recent years. Thus, there is the need for improved knowledge of the most appropriate irrigation scheduling practices to be adopted as well as the more adequate estimation of crop water requirements. With this objective, the simulation model SIMDualKc was adopted and calibrated. The model performs the calculation of crop evapotranspiration (ETc) with the methodology of the dual crop coefficient (Kc = Kcb + Ke), i.e., using a basal crop coefficient to estimate crop transpiration and an evaporation coefficient to estimation soil water evaporation. The research was conducted at the Experimental Station of Irrigation and Drainage, located in Alquízar, Havana, Cuba. The experiments were carried out between March and November 1997 with the papaya var. "Maradol red". The calibration consisted in searching the crop factors relative to the different stages of crop development that minimize the differences between the simulated and observed soil moisture content. Various goodness of fit indicators were used to evaluate the model predictions. It can be concluded that the model was properly calibrated and can be used to generate alternative irrigation schedules that improve water use and productivity of papaya in the considered soil and climate conditions

Droughts are natural but temporary imbalances of water availability, consisting of a persistent lower-than-average precipitation, of uncertain frequency, duration and severity, of unpredictable or difficult to predict occurrence, resulting in diminished water resources availability and impacts on natural and man-made ecosystems. To successfully cope with drought there is a need to understand the characteristics and consequences of related phenomena; however, differences in the perception of drought lead to difficulties in adopting risk management. The effectiveness of drought risk management depends upon drought monitoring, drought prediction and warning capabilities, and means to provide information to users, as well as on related awareness of populations. For drought monitoring and warning, drought indices are useful. The SPI has been extensively used in Portugal and stochastic methods have been developed for prediction of drought class transitions to be used for early warning. For agricultural purposes, the PDSI was modified and successfully referred to the rainfed olive crop, thus originating the MedPDSI. Its evaluation against the SPI and PDSI shows the appropriateness of this index. Relative to information systems, a variety of approaches were used to support deficit irrigation. However, its economic feasibility is questionable and more studies are required to assess ways to improve irrigation under drought info:eu-repo/semantics/publishedVersion

A identificação das necessidades de rega do milho, uma das principais culturas regadas em Portugal Continental, constitui uma medida de preparação para enfrentar as secas e a escassez de água. Definiram-se várias estratégias de rega com o objectivo de redução da procura de água de rega com impactos aceitáveis na produção. O modelo de balanço hídrico e de simulação de calendários de rega SIMDualKc, anteriormente calibrado e validado para a cultura do milho em Portugal, foi utilizado para simular as necessidades de água para condições de seca severa e extrema. Este estudo foi realizado para milho regado por aspersão e aplicado a várias localidades: Vila Real, Bragança e Miranda do Douro no Norte, Coimbra e Viseu no Centro, e Beja, Évora e Elvas no Sul. As alternativas de rega foram avaliadas tendo em consideração a poupança de água de rega e o impacto nas produções; para inferir a viabilidade económica da rega deficitária foram determinados indicadores da produtividade física e económica da água recorrendo a dados sobre o valor da produção e desempenho de sistemas. Os resultados mostram que as estratégias de rega deficitárias poderão ser viáveis quando os défices hídricos forem muito baixos. Como alternativa poder-se-á optar pela satisfação das necessidades totais da cultura mas diminuindo a área cultivada.

The SADREG decision support system was developed to help decision makers in the process of design and selection of farm surface irrigation systems to respond to requirements of modernization of surface irrigation—furrow, basin, and border irrigation. It includes a database, simulation models, user-friendly interfaces, and multicriteria analysis models. SADREG is comprised of two components: design and selection. The first component applies database information, and through several simulation and computational tools, produces a set of design alternatives in agreement with the user options. These alternatives are characterized by several hydraulic, economic, and environmental indicators that allow appropriate selection and ranking. The selection component bases upon multicriteria analysis using composite programming and ELECTRE II ranking models, which support the decision maker to select the best alternative. The decision maker participates in all decision processes through a user-friendly interface that allows expressing design options and priorities. SADREG was tested with data collected from field experiments. In addition to describing the modeling approach, an application to a sector of the Lower Mondego Irrigation Project, Portugal, is presented

The decision support system (DSS) MIRRIG has been developed to support the design of microirrigation systems and to advise farmers as a result of field evaluations. It is written in Visual Basic 6.0, runs in a Windows environment, and uses a database with information on emitters and pipes available in the market, as well as on crops, soils and the systems under design. MIRRIG is composed by design and simulation models and a multicriteria analysis model that ranks alternative design solutions based upon an integration of technical, economic and environmental criteria. User friendly windows are adopted for handling the databases and to manage the sub-models. The model allows creating and comparing a set of design alternatives relative to the pipe system and the emitters, either drip or microsprinkling emitters. For each alternative, the pipe system is sized and the irrigation system is simulated to produce performance, environmental and economic indicators. These include uniformity of water application, potential for contamination with agrochemicals due to water percolation, and installation and operation costs. Those indicators are used as attributes of the selected criteria. All alternatives are then compared and ranked through multicriteria analysis where the weights giving the relative importance of the adopted criteria are defined by the user. These procedures allow selecting the best design alternative and solving the complexities involved in the design of microirrigation systems. The model is available from the website www://ceer.isa.utl.pt/cms