The evapotranspiration of vegetation (ET) is a key component of the hydrological balance. Various tools and models have been proposed to estimate evapotranspiration in fruit crops. Among them, the most widely used approach is that proposed by the Food and Agriculture Organization (FAO), which considers climatic variables included in reference evapotranspiration (ETo), as well as the type of crop and its characteristics represented by a single crop coefficient (Kc). However, there is evidence that in tall and discontinuous canopies, such as citrus orchards, with a high degree of interaction with the environment, Kc can change depending on local environmental conditions and the amount of vegetation. Other methods, such as measurements of stem water potential, sap flow sensors, and moisture probes, allow for determining the water status of the crop, but only for a limited number of trees, and uncertainties arise when extrapolating values. Remote sensing fills this gap if spatial and temporal resolutions suit the monitored crop. A successful approach in water management is using models that calculate latent heat as a residue of the surface energy balance (SEB). This study applied an energy balance to calculate ET in an irrigation district. The study site is located in the Valencia region (Spain; 39º22'43'' N, 0º28'20'' W) with localized irrigation, where most crops are citrus. A total of 182 images from the Landsat satellite constellation for the period 2013-2018 were used to estimate instantaneous ET by extrapolating daily actual ET (ETSEBAL) values using climatic data. These climatic data correspond to predictions the Global Forecast System (GFS) provides. This way, climatic predictions are used for scheduling instead of the classical methodology that uses past data to estimate evapotranspiration. The study's objective is to analyze the results using a dynamic Kc obtained from the actual state of the crops and climatic predictions for each plot, compared to a generic Kc obtained for standard conditions and past climatic data. The results suggest that, for the studied plots, the relationship between drained water and the actual volume provided by irrigators would be reduced by 20% to -30 %. A point agrohydrological model calibrated with capacitive moisture probes was used to monitor soil water balance. In the same way, the methodology allows for determining the stress level of crops and maintaining it within recommended limits.

The amount of open data offered by different numerical weather prediction (NWP) systems is growing due to the increase in the capacity of computing systems. This rise has enabled the development of improved and user-tailored forecasting services and products. However, one key variable in agricultural systems not usually provided by the forecasting services is the reference crop evapotranspiration (ETo), which requires ad-hoc computation and proper identification of the factors that condition it. This work develops a spatially-distributed ETo forecast in the Jucar river basin (Eastern Spain), to support crop management in agricultural plots. ETo was determined from forecasted meteorological variables using the Penman-Monteith methodology described in FAO56. Specific ETo value maps at the AP scale were generated considering the spatial variation of the meteorological parameters that drive ETo: daily average, maximum, minimum and dewpoint temperatures, net solar radiation and wind speed at 2 meters. Calculations were downscaled using an interpolation technique based on linear regression from daily weather predictions of temperatures and wind. The procedure was tested using forecasts from the Global Forecast System (GFS) of the National Centers for Environmental Prediction (NCEP) belonging to the U.S. National Oceanic and Atmospheric Administration (NOAA), for the year 2022. Raw GFS forecasts were post-processed against the ERA5 reanalysis data, available through the Copernicus Climate Change Service (CS3), with a spatial resolution of 0.25o; and against observed data from the meteorological stations of the Agroclimatic Information System for Irrigation (SIAR) of Spain. In both cases, post-processing was done using artificial intelligence (AI), in particular Fuzzy Logic. Inputs for interpolation were the geographical characteristics at each GFS location within the Jucar river basin: longitude, latitude, distance to the Mediterranean Sea, mean solar radiation, mean solar radiation at a distance of 2.5, 5 and 25km from each GFS location, elevation, elevation at a distance of 2.5, 5 and 10km from each GFS location, slope, and orientation with respect to the north. Solar radiation is obtained using the Area Solar Radiation module of ArcGIS. Once the forecasts and solar radiation maps were generated, the difference between the interpolated and the predicted values was calculated. This difference generated a cloud of points which, which together with a Digital Elevation Model, allowed for surface interpolation (SI) using the Splines with the Tension methodology integrated in Grass (QGIS). These SI are subtracted from the forecast’s maps obtained by interpolation, already having corrected forecasts with which the ETo is determined using the Penman-Monteith methodology described in the FAO56. The difference between the interpolated ETo and the predicted ETo is also calculated by subtracting this SI from the obtained ETo, generating a corrected ETo. Furthermore, post-processed forecasts and ETo was compared with 41 meteorological stations and evaluated using the Mean Absolute Error (MAE). Acknowledgements:This study has received funding from the European Union’s Horizon Europe research and innovation programme under the SOS-WATER project (GA no. 101059264); and from the subvencions del Programa per a la promoció de la investigación científica, el desenvolupament tecnològic i la innovació a la Comunitat Valenciana (PROMETEO) under the WATER4CAST project.

Forecast-informed decision-making has been proven to improve water management. However, the practical implementation of such systems need to account for a wide range of processes and variables with the proper spatiotemporal resolution at the regional and local levels (meteorological, hydrological, agronomic, reservoir management and ecosystems). Furthermore, forecasts need to cover all the relevant temporal scales, from short-term to subseasonal to seasonal, to ensure an integrated approach including from quick emergency responses to strategic operational decisions. In this regard, the project "Integrated Water and Environmental Forecasting System (WATER4CAST)" develops an innovative visual decision support system (VDSS) to enable forecast-informed decision-making in the Jucar River Basin (Spain) covering the above processes (https://water4cast-app.upv.es/). The VDSS offers short-term (15 days), subseasonal (8 weeks) and seasonal (6-7 months) forecasts. It includes meteorological (temperature, precipitation, solar radiation, wind), hydrological (streamflow, soil moisture, reservoir inflows), agronomic (potential evapotranspiration, irrigation needs), environmental (habitat for native fish species) and water resource management variables (stored volumes, reservoir releases) and indicators (drought and fire risk). Short-term meteorological forecasts come from the NOAA GFS, while subseasonal predictions are obtained from the NOAA CFS. On the contrary, a multi-model approach is adopted to acknowledge uncertainty in seasonal forecasts, employing predictions from the Copernicus Climate Change Service (C3S). All raw forecasts are post-processed to correct biases, ensuring their fit to the local climatic patterns of the Jucar River Basin using artificial intelligence (fuzzy logic). Hydrological forecasts are provided by the fully-distributed eco-hydrological model TETIS, properly calibrated and validated for the Jucar. Agronomic forecasts rely on FAO56 agronomic models are tailored to the irrigated areas of the Jucar with the support of remote sensing. Ecosystem forecasts employ fish habitat models that relate streamflows to suitable habitat of native species. Finally, reservoir operation forecasts are provided by a water resource management model whose operating rules are defined using fuzzy rule-based systems. The VDSS consists of two parts: a public part and a private part available to specific users on request for selected variables considered sensible. The VDSS was co-developed with the users of stakeholders of the Jucar River Basin to ensure they account for their needs. Acknowledgement: This work has been carried out with funding from the project “INtegrated FORecasting System for Water and the Environment (WATER4CAST)”, funded by the Program for the promotion of scientific research, technological development and innovation in the Valencian Community for research groups of excellence, PROMETEO 2021 (ref: PROMETEO/2021/074), from the Ministry of Innovation, Universities, Science and Digital Society. Generalitat Valenciana. Recognition of the University Teacher Training (FPU) grant from the Ministry of Universities (FPU20/0749).

CONTEXT: During the last thirty years, many farmers and collective irrigation institutions have replaced their traditional gravity irrigation systems with modern drip irrigation systems, as a result of a water-saving policy promoted by numerous states and international organisations. The scientific-technical paradigm that associated water-savings with this process of technological change has collapsed in the last two decades and has led to a change in the position of international organisations. OBJECTIVE: In this research, we focus on the process of drip irrigation adoption in the Acequia Real del J & uacute;car (Vale `ncia, Spain). We analyse how the estimation and allocation of the expected water savings have changed in the different water planning instruments, and how it has been perceived by the different actors involved in this process. The research has also focused on the co-design and assessment of different measures to correct the impacts of this technological change, locally and on the Albufera wetland, located immediately downstream of the abovementioned irrigable area. METHOD: The research is based on a documentary review and a participatory action research. RESULTS AND CONCLUSIONS: The results show how the emerging concept of the rebound effect is permeating too slowly from academia to institutions and users, and that there is a need to stimulate innovative decisionmaking to achieve a more rigorous allocation of water and to adapt water and environmental planning. SIGNIFICANCE: The research analyse a pioneering action which is the first sign of the materialisation of a change in the efficiency paradigm.

On numerous occasions, we often have very little information or must make a decision considering qualitative aspects that are difficult to evaluate. This study focuses on obtaining objective criteria to assist in decision-making in the design phase of pressurized water pipes in collective irrigation networks. In the layout of these networks, various types of paths and roads for laying pipes can be encountered, and it is not always a simple task to obtain the least costly layout or the one with the fewest issues during construction. In order to obtain objective results, different layout alternatives are evaluated using the Analytic Hierarchy Process (AHP) Multicriteria Analysis Methodology and the Dijkstra algorithm to obtain optimal solutions. This is applied to twelve case studies where the types of available layout paths are identified as alternatives, and four criteria are established for their evaluation. Recognized experts in irrigation modernization conduct the evaluation to derive weighting coefficients for selecting the optimal layout. The coefficients or resistances obtained weigh the lengths of the pipes, allowing the selection of the most suitable alternative based on the defined criteria. The results are compared with a network designed by an expert using classical methodologies, revealing cost improvements in the design phase and a reduction in conflict points, thus leading to faster execution of the works.

Modern agriculture is underpinned by actual meteorological data registered using automated meteorological stations forming networks specifically created for advising purposes. In many cases, those data used to be accessible online by means of APIs (Application Programming Interface). One of the most common cases is the irrigation-advice weather network implemented with the aim of obtaining ETo values to be used in irrigation recommendations. However, those punctual values of ETo scattered throughout the territory do not allow to produce specific irrigation recommendations for each farm. The only way of disposing site-specific values of ETo is by compiling maps that describe its spatial variation. With this objective, a new dynamic procedure based on an existing regression-based technique of interpolation was proposed. Using the meteorological data registered at the end of each day, maximum and minimum temperature, maximum and minimum relative humidity, wind velocity, and radiation maps were interpolated and then, an ETo map was derived. The proposed procedure demonstrated a special adaptation capacity to the synoptic pattern of each day using some geographical features or others, as appropriate to explain the spatial variability of the interpolated meteorological variable. In those months where radiation plays a key role in the ETo value (growing season), ETo maps obtained were especially fine-grained in areas with significant relief. This procedure improved other contrasted methodologies they were compared with. The impact of using the nearest-weather-station ETo vs interpolated value on a daily water needs was investigated and near 10% average value of error was encountered in the case study.

The eGROUNDWATER project aims to improve sustainable, participatory groundwater management in the Mediterranean region by developing and testing Enhanced Information Systems (EIS) that integrate citizen science and information and communication technology (ICT) tools. A key component of the EIS is a mobile app that will allow farmers and other groundwater users to report groundwater levels in their wells and the amount of water used for irrigation and other purposes. At the same time, the app will provide users with information about the state of the aquifer and recommendations for sustainable water use (for example, short-term and seasonal predictions of irrigation water needs).The eGROUNDWATER app has the potential to be a valuable tool for improving the sustainable use and management of aquifers in the Mediterranean region. By gathering real-time data from a wide range of users, the app will help to create a more complete and accurate picture of groundwater conditions and usage. Policymakers and resource managers can use this information to make informed decisions about the allocation and use of water resources. It can also help to identify potential problems and areas where conservation efforts may be needed.The development of an app that meets the needs of the users required first to understand their perspectives and experiences related to the groundwater body. eGROUNDWATER has organized interviews and meetings in each case study to characterize the vision of the different agents on the groundwater bodies, and to try to build a collective framing of the current groundwater status and use in the area. On these meetings, the users identified lack of information about the aquifer as a critical issue to solve in order to advance towards a sustainable management of the resource.In addition to providing valuable data and information, the eGROUNDWATER app has the potential to engage and educate farmers and other users about the importance of sustainable water management. The app can foster a sense of ownership and responsibility for the aquifer's health among users, as it offers personalized feedback and information about the use of water and the aquifer’s health. This, in turn, could lead to more responsible water use practices and help to preserve groundwater resources for the long-term.The eGROUNDWATER project and its accompanying mobile app offer a promising approach to improving the sustainable use and management of aquifers in the Mediterranean region. The engagement of stakeholders in the development process and the collection and sharing of useful data and information through the app can help promoting education and awareness about water resource management. These efforts can help to foster a greater understanding of the importance of these resources and encourage more sustainable use of aquifers in the region, significantly contributing to the long-term sustainability of Mediterranean aquifers.Acknowledgements:This study has received funding from the eGROUNDWATER project (GA n. 1921) a project from the PRIMA programme, supported by Horizon 2020, the European Union's Framework Programme for Research and Innovation.

ABSTRACT The objective of this study was to analyze the feasibility of using thermal images to estimate the water status of melon plants (Cucumis melo L.) in tropical semi-arid climates. The study was conducted in a randomized block design with a split-plot arrangement. The plots comprised of soil cover (with and without mulching), and subplots were constructed using five irrigation regimes (120, 100, 80, 60, and 40% crop evapotranspiration), with five replicates. The following variables were evaluated: canopy temperature (Tcanopy), leaf water potential, air temperature (Tair), soil moisture, crop yield, and thermal index (ΔT), which is defined as the difference between Tcanopy and Tair. ΔT exhibited high correlations with crop yield and water consumption, indicating that thermography is an efficient tool for identifying the water status of melon plants, which could be employed for proper irrigation scheduling under tropical semi-arid scenarios. Moreover, thermal images identified the beneficial effects of soil cover on leaf water status and crop yield, primarily under moderate deficit irrigation. These results demonstrate that mulching is essential for increasing melon yield and water productivity in tropical regions.

With proper management, the modernization of irrigation systems makes it possible to improve the efficiency of application and use of water at the cost of an increase in pumping needs and, therefore, an increment of the energy consumed. The recent drastic price increase for energy put the viability of many farms at risk. In this context, using photovoltaic solar energy to power pumping stations has become an increasingly attractive alternative and a cheap and reliable option. The dimensioning of pumping systems powered by photovoltaic solar energy must be done considering the variability of solar radiation to take advantage of the available photovoltaic energy, especially during periods of less irradiation. By investigating a particular case, this paper studies the effect of increasing the number of pumps in parallel while maintaining the total power, as well as the relationship between the installed photovoltaic capacity and the power of the pumping system, to meet pumping requirements throughout the year. The pumped volume increased as the number of pumps installed in parallel increased for the same photovoltaic power generator. Although this increment has a limit, beyond which no greater significant rise in volume is achieved, installation costs increase. In addition, for the same pumping power installed, the required photovoltaic generator power decreases as the number of pumps in parallel increases. In the case studied, a 27% increase in the annual pumped volume was achieved by incrementing the number of pumps in parallel from one to five, thus leading to a 44.1% reduction in the size of the photovoltaic generator and a 13.3% reduction in the cost of installation compared with a system with only one pump. The procedure used to determine the most appropriate number of pumps to install in parallel when pumping water between two tanks, which minimizes the photovoltaic generator's size while guaranteeing pumping requirements, is easily generalizable for sizing isolated photovoltaic water pumping systems.

Irrigated agriculture is a major contributor to global groundwater use, and can sometimes lead to the overexploitation of aquifers. The Requena-Utiel, Campina de Faro and Ain Timguenay aquifers in Spain, Portugal and Morocco, respectively, are facing such a situation, with excessive pumping raising concerns about the aquifer's water levels and the long-term health of the groundwater body. Accurate estimation and remote monitoring of crop water needs are crucial for effectively managing the limited water resources in the region by providing farmers with accurate recommendations on water use.The eGROUNDWATER project aims to address this issue by applying a water balance method based on Vegetation Index data of croplands. The method uses the Fractional Vegetation Cover (FVC) to estimate bare soil evaporation and vegetation transpiration, agro-climatic data and optical data (CopernicusESA/EROS-USGS). Potential evapotranspiration was calculated using the FAO method. The result of this process was a model for determining the irrigation water needs of crops within the region that allows researchers to differentiate stressed and over-irrigated areas with a high degree of precision.The model was developed for the Spanish case study and was successfully applied to the Moroccan and Portuguese cases, where data scarcity at the local scale is also an issue. Remote sensing allows for more accurate detection of crop water needs, enabling the alignment of water requirements and agricultural demands. Although evapotranspiration estimates based on remote sensing may be subject to bias, these biases can be identified and corrected using reliable ground data. If daily images are not available, it is possible to upscale daily evapotranspiration estimates to seasonal or annual estimates. At the end, annual crop water needs can be modeled using a yearly map of irrigated areas, which is helpful for planning and managing water resources at the plot scale.In conclusion, this research has shown that remote sensing can be a valuable tool for accurately estimating and monitoring crop water needs and for improving water resource management in three Mediterranean regions. By using the described methods, it is possible to align water use with agricultural demands more effectively and to ensure sustainable use of the aquifer's limited resources.Acknowledgements:This study has received funding from the eGROUNDWATER project (GA n. 1921) a project from the PRIMA programme, supported by Horizon 2020, the European Union's Framework Programme for Research and Innovation.

The modernization process in irrigation has generated a higher energy demand. Due to this problem, the ongoing increase in energy tariffs, and the reduction in manufacturing costs of photovoltaic (PV) panels, there has been an increased use of renewable energies, such as PV energy, to power the pumping equipment involved in pres-surized irrigation.On direct pumping, the available solar power can be lower than that required by the pumping units. This fact can result in stoppages that can produce unwanted transient effects or even the emptying of the network.To avoid these phenomena and reduce the use of conventional energy, a methodology is proposed in this work, whereby meteorological predictions, corrected with a Kalman filter, are used to calculate the available PV power, irrigation needs, and maintaining soil moisture above desirable levels for the crop by minimizing deep perco-lation. This methodology is then compared to the traditional scheduling method that uses historical data and replaces the crop acute accent s evapotranspiration that occurs in a given time period.The methodology was applied to a real case study during an irrigation campaign, which was simulated using a weekly operative period. It was found that the use of meteorological predictions allowed PV energy consumption estimates to be improved from 68.7% to 79.3%, while the use of available photovoltaic energy in the case study increased from 11.64% to 13.37%.

Non-Contact Resonant Ultrasound Spectroscopy (NC-RUS) has emerged as a powerful tool to determine plant water status in a non-destructive, non-invasive and rapid way. In this study, ultrasonic parameters directly obtained from experimental measurements in the field using NC-RUS - such as resonant frequency (fres), velocity (v) and Q-factor - were evaluated as potential water stress indicators in Citrus plants. The experiments were carried out in two-year-old mandarin trees (Citrus clementina Hort. ex Tan. 'Clemenules') grown in pots in an open greenhouse where two different groups of plants were tested: a Control group (full irrigation) and a Drought Stress group (DS) whose irrigation was withdrawn during 7 days, followed by a 16 days recovery period. Soil water content, leaf water potential (Psi(leaf)) and the considered ultrasonic parameters were measured in the same leaves. fres detected changes between control and DS at day 7 without irrigation. Conversely, v showed differences after day 3, which were statistically significant at day 7, enabling discrimination between C and DS groups. Hence, Q-factor was the ultrasonic parameter that showed statistically significant differences between C and DS groups at days 3 and 7. Consequently, Signal Intensity in Q during the drought treatment showed a similar evolution to.leaf, although with slightly lower performance. However, Q-factor sensitivity excels Psi(leaf) at each day studied. Finally, a linear correlation (R-2 =0.57) between Psi(leaf) and Q-factor of all experimental data measured in DS group plants along the drought treatment was found. In conclusion, the ultrasonic parameters obtained using NC-RUS and in particular the Q-factor, demonstrated to be potential new water stress indicators in Citrus trees, with the novelty of being non-destructive, non-invasive and rapid. Future work should explore its suitability for its use in irrigation scheduling for Citrus trees.

Multioutlet hydrants as joint network infrastructure remain briefly addressed in the literature. Studies have always been limited to the individual treatment of the hydraulic components but not as a whole element. This study presents the main problems in the field of multioutlet hydrants within hydraulic infrastructure for pressure irrigation networks in Mediterranean agriculture. First, a field study with interviews was carried out in 30 water users associations (WUAs) between 2010 and 2018. Following this study, a laboratory test methodology was proposed to characterize this type of hydrant. Subsequently, four laboratory tests were performed on 12 multioutlet hydrants with different and common configurations found in irrigation networks: (i) head losses produced, (ii) global measurement precision in the multioutlet hydrant, (iii) blockage analysis in meters in vertical orientation, and (iv) hydrant behavior in response to hydraulic transients. The tests show that a horizontal configuration of the measuring elements with fewer than ten outlets and a suitable dimensioning of elements improve element maneuverability, instrument metrology, and irrigation emission uniformity. Finally, the importance of adequate design, dimensioning, and maintenance of the multioutlet hydrant devices is evidenced as a key point for the adequate management of collective pressure irrigation networks.

During the last three decades, like many other Mediterranean states, Spain has intensively promoted the modernization of irrigation, focusing mainly on the introduction of pressurized irrigation systems. Following 30 years of investment, a shift in irrigation policies is needed to solve some of the deficiencies in this modernization process and to incorporate new measures to cope with upcoming challenges generated by international markets, climate change and other social and economic processes. This paper describes and analyses the results of participatory research carried out with the water user associations in the autonomous region of Valencia, in order to define post-modernization irrigation policies. A survey and 24 local workshops involving 304 water user associations were conducted during the irrigation season of 2018 in order to form an assessment of the sector and design new irrigation policies. The results show that after 30 years of important investment, the obsolescence of the infrastructure has become the current main priority, making farmers dependent on public subsidies. New necessities have also emerged, such as renewable energies and nonconventional water resources, which farmers consider indispensable in order to reduce operating costs and guarantee water supply.

The Requena-Utiel aquifer in the Jucar River Basin (Mediterranean Spain) is mined mainly for the irrigation of vineyards (Denominación de Origen Utiel-Requena), and some olive and nut trees. It has been recently declared as in bad quantitative status by the Jucar River Basin Agency (Confederación Hidrográfica del Júcar, CHJ). Among the measures taken to control water abstraction, a pumping cap for the irrigation season (May-September) has been agreed between the CHJ and the groundwater user association. This limit depends on the cumulative precipitation from December to April (classifying the year in wet, normal or dry), although that irrigation amount is in any case below the crop requirements. Consequently, predicting the type of year beforehand is a piece of valuable information for the water users in order to optimally schedule groundwater pumping and foresee crop production. This study analyses the ability of seasonal meteorological forecasts from the Copernicus Climate Change Service (C3S) to anticipate the type of year in the agricultural areas of the Requena Utiel aquifer considering different periods ahead. The following seasonal forecasting services were used: ECMWF SEAS5, UKMO GloSEA5, MétéoFrance System, DWD GCFS, and CMCC SPS. Seasonal forecasts issued between November 1st and April 1st were downloaded and post-processed using a month-dependent linear scaling against historical records. Once post-processed, the skill of seasonal forecasts to predict the type of year has been evaluated for the 1995-2015 period, depending on the anticipation time. Results show that, on a broader view, the type of year cannot be safely anticipated before April 1st. However, we have identified that, for particular types of year and forecasting services, the anticipation time can be enlarged (e.g predicting wet years in December). Furthermore, we have found a direct relationship between the strength of the signal (number of ensemble members that predict the same type of year) and the forecasting skill, meaning that seasonal forecasts showing a strong signal, if properly identified, could offer valuable information months in advance to the beginning of the irrigation season. Acknowledgements: This study has received funding from the eGROUNDWATER project (GA n. 1921), part of the PRIMA programme supported by the European Union’s Horizon 2020 research and innovation programme. It has been also supported by the ADAPTAMED project (RTI2018-101483-B-I00), funded by the Ministerio de Economia y Competitividad (MINECO) of Spain and with EU FEDER funds.

Pressurised irrigation networks with a certain degree of automation allow centralized fertigation and maintenance operations such as cleaning subunits and preventing the proliferation of invasive species such as zebra mussels. Until now, there is no methodology that guarantees the total cleaning of the network of a substance in the shortest possible time. In the same way, it does not exist to guarantee reaching all consumption points with a certain concentration of a substance, injecting the minimum possible amount. For that purpose, a general novel methodology has been developed that makes use of the network’s hydraulic model and parallel multi-objective genetic algorithms to flush the network of a certain substance or to get it to all consumption points in the shortest possible time and supplying a minimum volume. This method assumes that the available pressure at the source is always over a minimum value. The arrival times to the consumption points are minimized and the injected volume is reduced to the minimum of replacement, that is, the volume of the network pipes. The methodology applied to the study case allowed the entire network to be flushed in a minimum time of 2.46 h. On a normal irrigation day, without making any changes to the irrigation schedule the time to completely flush the network is 11.76 h. Furthermore, the injected volume differs greatly from the total volume of the pipes.

Technological evolution is essential to make irrigated agriculture more effi cient in the use of water.Thus, this review article aims to contextualize irrigation in the age of agriculture 4.0 in order to address how these new technologies are impacting the rational use of water.With regard to the automation of irrigated systems, irrigation effi ciency with moisture sensors, applications using smartphone, controllers and fertilizer injectors, as well as how their operation can promote irrigation, was addressed.Regarding irrigation management, the use of remote sensing as an option to determine crop evapotranspiration was contextualized, listing the types of spectral bands and sensors used to collect images (orbital, aerial and terrestrial), in the monitoring of crop water status.The importance of data collection in the delineations of management zones for precision irrigation and what possible advances can still be achieved with regard to obtaining and analyzing data were also discussed.Finally, it is concluded that, despite the high effi ciency of automated irrigation systems, information of soil, climate and plant attributes obtained through the range of data provided by sensors will be responsible for mitigating the global impacts caused by irrigated agriculture in the near future, since this information can enhance irrigation, with maximum effi ciency, thus reducing water consumption by agriculture.

The accurate estimation of plant water needs is the first step for achieving high crop water productivity. The main objective of the work was to develop an irrigation scheduling procedure for mandarin orchards under Mediterranean conditions based on replacing the amount of consumed water using reference values of soil moisture according to different phenological periods. The proposed methodology includes a definition part where the threshold values were established relating the trees' stem water potential and the volumetric soil water content measured with Frequency Domain Reflectometry probes. A second part includes the steps for standardizing measurements from capacitance probes by using the LEACHM hydrological simulation model to take into account the sensor-to-sensor variations. Finally, an extrapolation procedure based on soil water retention curves was used for adapting critical soil water content thresholds to different soil conditions. Field evaluations were made in a citrus orchard located in eastern Spain during two seasons. Standardize critical soil water contents were: i) 24 % vol. for post-harvest, bloom - fruit set and phase III of fruit growth; ii) 27 % vol. for phase I of fruit growth, and iii) 29 % vol. for phase II of fruit growth with average daily air vapour pressure deficit values ranging between 0.2 - 0.4; 0.9-1.1 and 1.1-1.3 kPa, respectively. When implemented in the orchard, the sensor-based strategy resulted in water saving of 26 % respect to a control treatment, irrigated using the standard FAO-56 approach, without significant differences in yield and increasing the crop water productivity by 33 %. In conclusion, we suggest that the determination and use of the critical soil water content is a useful tool for scheduling irrigation. The proposed standardization and extrapolation methodology allows the irrigation strategy to be applied to other mandarin orchards under similar climatic conditions.

ABSTRACT: DIMSUB is a computer program to complement a decision support tool (DST) to effectively study different hydraulic design alternatives in microirrigation systems. We developed environments in Visual Basic for applications for Microsoft Excel® that allow specific step-by-step functions to be created for the design of irrigation subunits. Different alternatives can be considered, such as types of emitter, lateral and submain pipe sizes, different feeding points, irregular subunit shapes and topography slopes. Furthermore, specific uniformity criteria need to be considered to achieve efficient water applications and proper design systems. Lengths of run lateral and submain pipes, position of the hydrant connection, pressure head and head loss in pipes or pressure-compensating emitters can be assigned to evaluate the results and choose the best design alternative. This user-friendly tool to study hydraulic variables is expected to be a valuable aid for the decision-making process in designing irrigation systems. Some examples of practical cases under specific crop conditions to design drip irrigation subunits are given using DIMSUB.