Reference evapotranspiration (ET₀) is one important agrometeorological parameter for hydrological studies and climate risk zoning. ET₀ calculation by the FAO Penman–Monteith method requires several input data. However, the availability of climate data has been a problem in many places around the world, so the study of scenarios with different combinations of climate data has become essential. The aim of this study was to evaluate the performance of artificial neural network (ANN), random forest (RF), support vector machine (SVM), and multiple linear regression (MLR) approaches to estimate monthly mean ET₀ with different input data combinations and scenarios. Three scenarios were evaluated: at the state level, where all climatological stations were used (Scenario I–SI), and at the regional level, where the Minas Gerais state was divided according to the climatic classifications of Thornthwaite (Scenario II–SII) and Köppen (Scenario III–SIII). ANN and RF performed better in ET₀ estimation among the models evaluated in the SI, SII, and SIII scenarios with the following data combinations: (i) latitude, longitude, altitude, month, mean, maximum and minimum temperature, and relative humidity and (ii) latitude, longitude, altitude, month, mean temperature, and relative humidity. SVM and MLR models are recommended for all scenarios in situations with limited climatic data where only air temperature and relative humidity data are available. The results and information presented in this study are important for the agricultural chain and water resources in Minas Gerais state.

Pumping systems are the largest energy consumers in center pivot irrigation systems. One action to reduce energy consumption is to adjust the pumping pressure to that which is strictly needed by using variable speed drives (VSDs). The objective of this study was to determine the feasibility of including VSDs in pumping systems that feed center pivot systems operating in an area with variable topography. The VSPM (Variable Speed Pivot Model) was developed to perform hydraulic and energy analyses of center pivot systems using the EPANET hydraulics engine. This tool is able to determine the elevation of each tower for each position of the center pivot using any type of digital elevation model. It is also capable of simulating, in an accurate manner, the performance of the center pivot controlled with a VSD. The tool was applied to a real case study, located in Albacete, Spain. The results show a reduction in energy consumption of 12.2%, with specific energy consumptions of 0.214 and 0.244 kWh m⁻³ of distributed water obtained for the variable speed and fixed speed of the pumping station, respectively. The results also show that for an irrigation season, to meet the water requirements of the maize crop in the region of the study (627 mm), an average annual savings of 14,107.35 kWh was obtained, which resulted in an economic savings of 2821.47€.

This study aimed to evaluate the energy efficiency of a center pivot irrigation system operating in a terrain of variable topography. Values of Pumping Energy Efficiency (PEE), Supply Energy Efficiency (SEE), Global Energy Efficiency (GEE) and Specific Energy (Es in kWh m^-3) computed at 18 different angular positions of the lateral line were used as energy efficiency indicators. An ultrasonic flow meter, digital pressure transducers and a power quality analyzer were used in order to evaluate hydraulic (total system flow-Q and total dynamic head-TDH) and electrical parameters (active electrical power - AEP) of the center pivot pumping unit that were required for evaluating the selected energy efficiency indictors. Topographic elevations of the water source, the pumping unit and of the center lateral line were also determined. For the center pivot lateral line, it was necessary to determine, at the 18 angular positions considered, the altitude of the track of each center pivot support tower. Results indicated that currently, even after more than 10000h of use, the center pivot system operates with satisfactory energy efficiency, as indicated by an average GEE value equal to 42.5%, that is classified as “good”. Statistical analysis indicated that the topographic disposition of the center pivot lateral line, as characterized by a uphill or downhill disposition, resulted on different PEE, SEE and GEE values, while the average Es value (0.42 kWh m^-3) was not affected by the lateral line disposition.

Viticulture began growing in Brazil in recent years, and this growth is due to the introduction of new techniques and improvements used in vine planting, especially the use of plastic covering in the vineyard. Thus, this study aimed to evaluate the economic viability of plastic covering installation, as well as the quality of grapes produced by two cultivars, in order to compare these results with those obtained by a conventional cultivation system. The experiment was performed at an experimental farm producing grapes in southern Brazil. The grape cultivars Niagara Branca and Niagara Rosada were studied and cultivated with and without plastic covering. Data related to the costs of vineyard planting, establishment, and seasonal management, in addition to the grape revenue, were assessed. Additionally, the grape yield and quality were evaluated. The analysis of return indicators showed that the net present value was higher for the plastic-covered system, which indicates greater profitability and consequent viability of the investment. Moreover, the grape quality varied according to the cultivar and production system. In this context, it is recommended to use the cultivar Niagara Rosada for production in a plastic covering system.

The analysis of friction head-loss spatial distribution along center pivot lateral lines represents an important step when evaluating energy-use efficiency of center pivot irrigation systems. This work compares head-loss spatial distribution along center pivot lateral lines computed with the hydraulic simulator EPANET 2.0 with head-loss spatial distribution predicted by four different analytical models. For the different center pivot lateral line configurations considered in this study, two different sets of friction head-loss values were analyzed. These two sets represent head-loss estimates obtained with different values of the flow rate exponent ($\alpha$ ) in two main friction head-loss equations: Darcy–Weisbach ($\alpha =2$ ) and Hazen–Williams ($\alpha =1.852$ ). On both sets, the four analytical solutions assessed in the current work estimated head-loss values similar to those computed by the hydraulic simulator EPANET 2.0. These results show that the detailed description of flow rate distribution along the center pivot lateral line required by the numerical method did not improve the accuracy of the calculated head-loss distribution. On the data set of values produced by using the Hazen–Williams head-loss equation, the analytical solution associated with the most complex mathematical expression provided the lowest deviation in relation to head-loss values computed by EPANET 2.0. On the data set of values produced by using the Darcy–Weisbach head-loss equation, assuming a fully turbulent flow regime, the four analytical models presented the same deviation in relation to the values computed by EPANET 2.0.