Irregular Rainfall Distribution Research Articles

Spatiotemporal trends and variability of rainfall across agro-ecologies in East Guji Zone, Southeast Ethiopia

Distribution and trends of rainfall reveal spatial and temporal variability that have a paramount effect on the life and livelihood of small-holder farmers. This study aimed to analyze spatial variability and temporal trends of rainfall distribution across the three Agro-Ecological Zones (AEZs) of East Guji. Time series gridded daily rainfall data (1990–2020) were collected from the Ethiopian Meteorological Institution. Different descriptive statistics, trend tests: Man Kendal and Sen’s slope estimator, Inverse Distance Weighted Index and Precipitation Concentration Index (PCI) was used in the study. The finding demonstrated that altitude and rainfall decrease as one advances from the western (highland) to the eastern (lowland) direction in the study area where the highest rainfall was recorded in Solemo (highland) and the least in Negele (lowland).The study showed that as altitude increases annual rainfall also increases and rainfall variability decreases. Similarly the mean length of the growing season declines as one advance from the highlands to the lowlands. The PCI of the lowlands, midlands, and highlands AEZs was 19%, 17%, and 12% respectively. The PCI showed that those highlands had moderately concentrated rainfall but both lowlands, and midlands, had an irregular distribution of rainfall. The Coefficient of Variation (CV) indicated that highland areas had moderate variability in rainfall in all seasons except winter. In contrast, the low and midlands had shown high variability of rainfall (>30%) in all seasons. From a seasonal perspective, both CV and PCI revealed that the winter season showed more variability than others. Moreover, a significant increasing trend of annual rainfall was observed in the highlands AEZs (Bore 15.3mm/year and Solemo14.6mm/year), lowland AEZs (Chembe 10.9mm/year, Dawa 8mm/year and Bitata 7.8mm/year) as well as midland AEZs (Kercha 14.5mm/year) at a significant level of 5%. Therefore, strategies should be designed to use additional water resources for irrigation; and provide short-cycle grown and drought-resistant crops in the rest of the midlands and lowlands AEZs.

Efeitos de farinha de osso e hidrogel nos teores foliares de cajueiro anão

ABSTRACT In semi-arid regions, where seasonal drought or irregular rainfall distribution are common occurrences, agricultural management techniques or strategies, such as the use of bone meal and/or hydrogel, can mitigate adverse conditions and ensure crop production. This study aimed to evaluate the efects of bone meal doses (0, 250, 500, 750 and 1,000 g pit−1), in association or not with hydrogel (0 and 5 g pit−1, respectively), on the leaf nutrient content of the dwarf cashew cultivar BRS 226. The leaf nutrient contents were evaluated during two growing seasons. For being a good source of macronutrients, the bone meal increased the levels of N, P, Ca, K and Mg in the dwarf cashew leaves. The leaf contents of the micronutrients Zn, Fe and Mn decreased with increasing bone meal doses. The nutrient accumulation in the leaves of the dwarf cashew planted in pits with bone meal and hydrogel has the following order: N > K > Ca > Mg > P > Mn > Fe > Zn > Cu. The application of bone meal at levels close to 600 g pit−1, mainly with the use of hydrogel, is a viable fertilizer alternative for dwarf cashew.

Potentiality of Sustainable Maize Production under Rainfed Conditions in the Tropics by Triggering Agro-Physio-Biochemical Traits Ascertained from a Greenhouse.

A major portion of maize is produced under rainfed conditions in the tropics with relatively poor yield because of the unpredictable and irregular distribution of seasonal rainfall, as well as a decline in pre-rainy season rainfall due to climate change, so identification of sustainable production options is utmost needed. Thus, the present studies were conducted in a greenhouse (GH) to ascertain the water stress-tolerant traits of maize and at the field level in the tropical environment of Thailand to see the stimulating possibility of the ascertained traits in a locally popular cultivar using ethephon. Depending on tolerance level, three maize genotypes (Suwan 2301 > Suwan 4452 > S 7328) were tested under different water conditions-well-watered, short-term, and long-term water stress-in the GH. At the field level, the locally popular maize cultivar Suwan 5819 was examined with six ethephon levels (doses in g a.i. ha-1 of ethephon, i.e., T1, 281 at V6 stage; T2, 281 at V6 + 281 at V10 stage; T3, 281 at V10 stage; T4, 562 at V6 stage; T5, 562 at V6 + 562 at V10 stage; T6, 562 at V10 stage) against no ethephon application (T0) under rainfed conditions. Maize suffered from the scarcity of sufficient rainfall during 26-39 days after planting (DAP) and 43-63 DAP in the field. The yield index (YI) was identified from biplot analysis as one of the suitable standards for drought tolerance checks for maize at GH as well as at field level in the tropics. The YI value of observed agro-physio-biochemical traits of maize in GH showed that relative water content (RWC, 1.23), stem base diameter (SBD, 1.21), total soluble sugar (TSS, 1.15), proline (Pr, 1.13), aboveground plant biomass (APB, 1.13), root weight (RW, 1.13), relative growth rate (RGR, 1.15), specific leaf weight (SLW, 1.12), and net assimilation rate (NAR, 1.08) were the most desirable. Efforts were made to stimulate these traits under water stress at the field level. Ethephon application as T1 helped to gain higher kernel yield (KY) (5.26 t ha-1) with the support of higher RWC (90.38%), proline (24.79 µmol g-1 FW), TSS (1629 mg g-1 FW), SBD (24.49 mm), APB (271.34 g plant-1), SLW (51.71 g m-2), RGR (25.26 mg plant-1 day-1), and NAR (0.91 mg cm-2 day-1) compared to others, especially no ethephon application. Furthermore, the attributes SLW, SBD, Pr, heat utilization efficiency (HUE), 100-kernel weight, TSS, electrolyte leakage, and lodging percentage showed a substantial direct effect and significant correlation with KY. Aside from higher KY, ethephon application as T1 tactics resulted in higher values of energy efficiency (1.66), HUE (2.99 kg ha-1 °C days-1), gross margin (682.02 USD ha-1), MBCR (3.32), and C absorption (6.19 t C ha-1), indicating that this practice may be a good option for maize sustainable production under rainfed conditions.

Spatiotemporal Variability of Rainfall as an Evidence of Changing Climate over the Nigerian Niger Delta

This study assesses the spatial and temporal variability of rainfall over the Niger Delta area (Benin, Calabar, Port Harcourt and Uyo) in Nigeria between 1990 and 2020. The daily rainfall data used for this study were obtained through secondary source from NASA’s POWER (Prediction of Worldwide Energy Resources). Coefficient of variation, standardized anomaly index (SAI), precipitation concentration index (PCI) and seasonality index (SI) were used to evaluate rainfall variability and seasonality. The results of temporal analysis of annual rainfall indicated that Benin had the highest annual rainfall amount in 2000 and lowest in 1999 while Calabar and Port Harcourt had their highest rainfall amount in 2007 with the lowest occurring in 1991 and 2014 respectively. Uyo had the highest in 2000 and lowest in 2014. SAI also witnessed the presence of interannual variability of rainfall with negative and positive anomalies in 59.46% and 40.54% of the analyzed years, respectively. PCI and SI results implied that the Niger Delta area had strong irregular rainfall distribution. The results confirm the meteorological sensitivity to locations and provide support for the implementation of station and regional meteorological hazards prevention and to support the mitigation of hazards and improve the management practices of environment system in Niger Delta area.

The effects of climate change-induced flooding on harvest failure in Burkina Faso: case study.

Climate change leads to more frequent and severe extreme weather events including floods, heatwaves, heavy rainfalls, and droughts. In contrast to the majority of research on weather extremes in sub-Saharan Africa, which focus primarily on how a lack of rainfall causes droughts, this paper aims to elucidate the effect of flooding on harvest failure in rural Burkina Faso. We conducted a case study in north-western Nouna, Burkina Faso, between August and December 2021 covering a study population of n = 180 participants. The study comprised four components: (i) interviews with farmers (n = 180) on whether any of their fields had been inundated and if so, on harvest loss on these fields; (ii) determining the feasibility of using Sentinel-2 satellite images to validate study participants reports of floods; (iii) characterizing short-term weather including frequency and duration, of extreme rainfall events within the study area, as well as comparing cumulative rainfall (long-term) over the past 50 years; and (v), estimating both the food energy and economic loss of harvest failure due to flooding. 49% of interviewed farmers (n = 88) reported that floods had damaged at least one of their fields. Some fields (n = 13, 7%) had no harvest due to flooding, while some farmers (n = 14, 8%) had lost part of their harvest. Images from the Sentinel-2-Satellite indicated that reported and remotely observed flooding were consistent. According to time series of data from the local weather station, there has been an increase irregular rainfall distribution and at the same time of cumulative annual rainfall in Nouna. Furthermore, a first illustrative calculation allowed us to estimate the amount of energy lost when one hectare of a common crop is flooded. This case study demonstrated that flood-related harvest failures leading to crop losses in sub-Saharan Africa, exemplified by Burkina Faso, are likely to be substantial. This study serves as a proof-of-principle for flooding effects on food security. This could provide more detail for agricultural adaptation and mitigation strategies. Inundation-vulnerable fields need alternative and novel management practices, which may only be effectively implemented if agricultural institutions and national policy-making bodies receive evidence of flooding e.g., from remote sensing.

Regional Weather Variations and Yields Achieved in Soybean Crops

Monitoring weather conditions during soybean cultivation is essential in agricultural planning. The variation of these conditions, such as temperature, precipitation, relative humidity and soil moisture directly influence the productive performance of crop.With this, the objective of the work was to verify the effects of weather conditions on the soybean yield, carrying out the survey of the minimum, maximum and average temperature and the total precipitation during the cultivation of the soybean and collecting the data of productivity reached in the agricultural harvests of 2017/2018, 2018/2019 and 2019/2020 of soybeans in a commercial area with 15.5 ha, located in the Céu Azul City, Paraná State, Brazil. Regarding the results for the three soybean harvests, the air temperature remained adequate for the development of the crop in most of the cycle. And the values observed for precipitation indicated the occurrence of well-distributed rainfall in the 2019/2020 harvest, and in the 2017/2018 harvest there was irregular rainfall distribution, however there were no periods without precipitation. However, the large precipitation deficit occurred in the 2018/2019 harvest, where the lack of rain occurred in 28 days, between 12/03/2018 and 12/30/2018, indicating a drought in this period. The soybean yield obtained in the area in the 2019/2020 harvest was 3.727 t ha-1, higher than the other two soybean harvests, being that 2018/2019 harvest reaching the lowest value, 2.394 t ha-1, indicating the influence of the weather in the soyben yield achieved.

Calcium pyruvate in the attenuation of the water deficit on the agro-industrial quality of ratoon sugarcane.

Sugarcane is one of the largest agricultural commodities when considering the export volume and the number of jobs generated. Sugarcane production in the Brazilian Northeast region is generally low due to several factors, including the irregular rainfall distribution, which highlights the importance of studies aimed at mitigating the deleterious effects of water stress. In this scenario, this study aimed to evaluate calcium pyruvate as a water deficit attenuator on the agro-industrial quality of sugarcane in the second cycle of cultivation. The experiment was conducted out under greenhouse conditions of the Federal University of Campina Grande, where five sugarcane commercial genotypes tested (G1- RB863129, G2- RB92579, G3- RB962962, G4- RB021754, and G5- RB041443) and three irrigation management strategies (E1- full irrigation, E2- water deficit with application of 30 mM of calcium pyruvate, and E3- water deficit without calcium pyruvate application), distributed in randomized blocks in 5 × 3 factorial arrangement with three replications. The RB021754 genotype under water deficit and without foliar application of calcium pyruvate increased the fiber content (13.2%) and the sugarcane moist cake weight (143.5 g). The effects of water deficit in sugarcane genotypes are attenuated by the exogenous application of 30 mM of calcium pyruvate, with benefits on the polarized sucrose content, apparent sucrose content of the juice, soluble solids content, purity, corrected cane POL, total recoverable sugars, and stem mass in relation to plants under water deficit without calcium pyruvate application.

Application of the Analysis Time Series and Multispectral Images for the Estimation of the Conditions of the Vegetation Covers of the Natural Areas of Southern Spain

It has been scientifically proven that climate change is a reality. In subarid Mediterranean limates, this fact is observed in the irregular distribution of rainfall, resulting in alternating periods of more or less prolonged drought with episodes of torrential rains concentrated in short periods of time. We have selected 11 natural areas in southern Spain, where we will observe these circumstances and where a series of ecosystems composed of vegetation covers of a high ecological value are found. We start from the question of whether these climatic circumstances are really deteriorating them. For this study, we propose a method that combines three analysis techniques: the design of the time series, the application of vegetation indices, and the use of techniques analysis of changes in land use. From the combination of these techniques in the period from 1997 to 2021, we have observed that there have been a dynamic of changes in land use that has maintained its original characteristics by more than 70%, so it is possible to affirm that the adaptation of ecosystems to climatic conditions has occurred satisfactorily. However, this general statement shows some particularities which are those that we will show in this work.

Climate fluctuation impacts in Astronium urundeuva (M. Allemão) Engl. silvicultural characters in the Brazilian Cerrado

Currently, mankind is responsible for changing our planet’s conditions. These changes are usually catastrophic, and yet, mankind does not develop preventative strategies to reduce their impacts. However, a species present in the Brazilian Cerrado, Astronium urundeuva, can be very economically logged and has a known landscape distribution, but lacks information regarding the impacts of climate change on its silviculture. This research aimed to verify A. urundeuva’s silvicultural behavior under current environmental conditions. Progenies from three populations (Cerrado and Atlantic Forest/Cerrado transition) were measured for silvicultural characters: height (HT) and diameter at breast height (DBH), in 2019. Climatic data (temperature, precipitation, evapotranspiration and soil available water, averages and accumulated) were also measured between 1996 and 2018. Descriptive and sequential water balance analysis, descriptive statistics, collinearity tests and a multiple linear regression were performed. There was water deficit in all years (−12.7 mm) researched, which showed an irregular rainfall distribution in Selvíria-MS, concentrated mostly in summer. Average HT ranged from 8.02 m to 10.69 m, while average DBH ranged from 0.10 m to 0.12 m, with high variability (CVs between 21.99% and 34.77%). There was significant correlation between HT, DBH, , and and between , and , which highlighted the importance of water availability . Multiple linear regression showed has a direct and negative relationship with silvicultural characters, implying productivity losses while evapotranspiration increases. Even though it is not a typical Cerrado species, A. urundeuva may have adapted to phytogeographic domain conditions, with slow growth due to water deficit for its survival, considering that, in Brazil, climate change has resulted from annual variations.

Spatio-Temporal Rainfall Variability and Concentration over Sri Lanka

Changes in precipitation patterns significantly affect flood and drought hazard management and water resources at local to regional scales. Therefore, the main motivation behind this paper is to examine the spatial and temporal rainfall variability over Sri Lanka by Standardized Rainfall Anomaly Index (SRAI) and Precipitation Concentration Index (PCI) from 1990 to 2019. The Mann–Kendall (MK) trend test and Sen’s slope (SS) were utilized to assess the trend in the precipitation concentration based on PCI. The Inverse Distance Weighting (IDW) interpolation method was incorporated to measure spatial distribution. Precipitation variability analysis showed that seasonal variations are more than those of annual variations. In addition, wet, normal, and dry years were identified over Sri Lanka using SRAI. The maximum SRAI (2.27) was observed for the year 2014 for the last 30 years (1990–2019), which shows the extremely wet year of Sri Lanka. The annual and seasonal PCI analysis showed moderate to irregular rainfall distribution except for the Jaffna and Ratnapura areas (annual scale-positive changes in Katugastota for 21.39% and Wellawaya for 17.6%; seasonal scale-Vavuniya for 33.64%, Trincomalee for 31.26%, and Batticaloa for 18.79% in SWMS). The MK test, SS-test, and percent change analyses reveal that rainfall distribution and concentration change do not show a significant positive or negative change in rainfall pattern in Sri Lanka, despite a few areas which experienced significant positive changes. Therefore, this study suggests that the rainfall in Sri Lanka follows the normal trend of precipitation with variations observed both annually and seasonally.

Cutworms (Lepidoptera: Noctuidae) in central Brazil Savanna: temporal distribution and association of species abundance with climatic and meteorological factors

AbstractPopulation dynamics studies make it possible to predict the response of species to seasonal and inter‐annual climatic phenomena in hypothetical scenarios of climatic abnormality. However, long‐term studies on the temporal distribution and abundances of species are still scarce in the literature, including for species of agricultural importance. The present study aimed to bridge this gap through monthly collection events of species of cutworms (species of Agrotis and Feltia) across eight crop seasons (from July 2012 to June 2020) in the Brazilian Savanna (Cerrado). This biome is characterised by an irregular distribution of rainfall during a normal year, including two well‐defined periods of dry and rainy seasons. Only five species of cutworms were recorded: Agrotis ipsilon, Agrotis canities, Feltia repleta, Feltia submontana and Feltia subterranea, all widely distributed across South America. Except for F. submontana, occurring only in the autumn, other species occurred nearly year‐round, with distinct peaks of abundance in the dry season (April to October), supporting the hypothesis that species of Agrotina are well adapted to dry environments. The association of cutworms with dry environments was recovered for multivoltine, abundant species, such as A. ipsilon and F. subterranea, as for univoltine species, such as F. submontana. Across eight crop seasons, the abundance of all species decreased, coinciding with a high intensity El Niño effect. However, the effect itself was not found to be significant to predict the temporal distribution and abundances of cutworms and the causes of population decrease from 2014 to 2015 crop season remain to be explained. After the temporal autocorrelation effects were removed, it was revealed that the abundance of cutworms tends to be larger in crop seasons with less precipitation. Thus, this variable can be used to predict outbreaks of cutworms in the Cerrado. Some species of cutworms deserve special concern due to their frequency, seasonality and higher abundances in the Cerrado during the dry season. Their adaptability to adverse conditions may increase their spatio‐temporal distribution in Brazil and the frequency of outbreaks in a scenario of climate change, with the continuing reduction of rainfall in central and southeastern Brazil.

Optimising maize sowing under irregular rainfall distribution in northern Thailand: A model approach for improved decision-making

Rainfed maize production in northern Thailand is strongly affected by high rainfall variability and recent apparent shifts of the onset of the rainy season. Hence, decision-making on maize sowing time has become extremely difficult for farmers. This study thus aimed at (i) evaluating the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model for predicting maize performance under rainfed conditions, (ii) assessing maize yield performance under five sowing date options, and (iii) identifying the best sowing option under irregular rainfall. A 2-yr-data set with various maize sowing dates from a field experiment in northern Thailand was used to calibrate and validate the model. WaNuLCAS was able to predict maize yield well (goodness-of-fit statistics: R²=0.83; modelling efficiency: −0.61; root mean square error: 0.14 kg m −2 ; maximum error: 0.16 kg m −2 ; coefficient of residual mass: 0.02; coefficient of determination: 0.56). An analysis of rainfall data (1970–2018) of the Phitsanulok province, Thailand, showed strong interannual variations: 27.1% of the years corresponded with the long-term mean and were moderately dry or moderately wet, while the remaining years were either very wet (10.4%) or very dry (8.3%). The standardized precipitation index indicated both, an earlier rain onset and frequent dry spells towards the end of the rainy season in recent years. Therefore, sowing earlier can be seen as a valuable coping strategy. Simulated sowing date options were: farmers’ practice (FP), 15, 30, and 45 days before FP, and a combination of them (staggered planting). Simulations revealed that under current rainfall conditions water was the most limiting factor for growth and yield of maize, while nutrient limitations had little impact under the current fertilization regime. Maize water uptake was significantly correlated with yield (R²=0.45). The simulation results suggest that sowing maize 30 days before FP or staggered planting are potent alternatives under irregular rainfall, the later particularly when distinct weather forecasts are not possible. Both options reduced the risk of crop failure while maintaining yields under these conditions. Simulations further suggested, under climate scenarios (RCP 4.5) for northern Thailand and the 21st century even earlier sowing seems plausible. • Validation of a model approach to improve decision-making in maize sowing. • Analysis of past precipitation patterns to understand the impact of rainfall variability on maize growth and yield • Testing coping strategies to better adapt to climate change effects on maize cropping. • Early sowing or staggered planting of maize are potent alternatives to cope with climate change projections for northern Thailand.

Rainfall variability analysis using Precipitation Concentration Index: a case study of the western agro-climatic zone of Punjab, India

Due to climate change, the rainfall pattern has changed, which ultimately either cause flood or drought in any region of the world. Hence, a rainfall variability analysis helps to manage the water resources better. Rainfall variability analysis of a long term at particular area reveals vital information about past and future climate. The study's objective was to analyse the rainfall variability and intensity of long term monthly rainfall data (1982–2018) using the Precipitation Concentration Index (PCI). Data was collected from Punjab Agricultural University, Regional Research Station, located at Bathinda, India. The PCI was calculated for the annual, winter, pre-monsoon, monsoon, post-monsoon season, and decadal scale. Results have outlined that PCIAnnual ranges from the lowest of 14.96 in 2006 to the highest of 43.82 in 2000, and the average of 37 years is 23.22. About ≈59.5% of the year PCIAnnual was characterised by Strong Irregularity of Precipitation Distribution (SIPD, PCIAnnual> 20), an indication of SIPD within the 37 years. While ≈2.7% of the year recorded annual value within the moderate irregular range (10<PCIAnuual<15), which indicates an irregular rainfall distribution (MIPD) and concentration across the months. Similarly, the precipitation concentration in China was also found strongly irregular in the western and northern parts of the northwest and the northern region of the Tibetan Plateau. The study recommends that the Bathinda Development Authority (BDA) may use and adopt these results and redevelop the existing groundwater recharge structures (pond) and artificial recharge structures.

Estimation of dry events duration in Northern Tunisia – Analysis of extremes trends

Abstract. Modeling of extremes dry spells in Northern Tunisia, in order to detect the severity of the phenomenon, is carried out. Dry events are considered as a sequence of dry days (below a threshold) separated by rainfall events from each other. The maximum dry event duration follows the Generalized Extreme Value distribution. The data series adherence to the probability distribution was verified by the Anderson-Darling test. The positive trend and non-stationarity of dry spells was verified respectively by the Mann–Kendall test and Dickey–Fuller and augmented Dickey–Fuller tests. The irregular distribution of rainfall in the growing season for Sidi Abdelbasset station has increased the number of dry spells. The increase of rainy days in Ghézala dam and Sidi Salem gauge stations resulted in a decrease of dry spells in this area. Regarding the return period of one year (wet season), dry events occurred from 14 to 27 d in this region constitute an agricultural potential risk. The Southern region was the most vulnerable.

Assessments of multiple gridded‐rainfall datasets for characterizing the precipitation concentration index and its trends in India

AbstractRainfall is time concentric in nature. The spatial and temporal distribution of rainfall is changing over the Earth with recent anthropogenic warming. The study explores various characteristics of annual and seasonal concentration of rainfall across India using the precipitation concentration index (PCI) and its trends during the period of 1986–2015, based on a high‐resolution gauge‐based rainfall data (0.25 × 0.25°), obtained from the India Meteorological Department (IMD). An intercomparison is made with 11 other gridded rainfall datasets to infer whether these datasets can reasonably reproduce the spatiotemporal distribution of PCI and its trends in various homogenous rainfall regions of India or not. These datasets are categorized into gauge‐based (APHRODITE, GPCC, CPC), satellite‐derived (CHIRPS, PERSIANN‐CDR), and reanalysis (JRA‐55, MERRA‐2, NCEP‐2, PGF, ERA‐Interim, ERA‐5). On annual scale, about 8.52, 24.1, and 67.38% of area of India are under moderate, irregular, and strongly irregular rainfall distribution, respectively. Spatial variation of PCI in India is influenced by geographical factors such as latitude, longitude, and elevation. Significant increasing and decreasing trends in annual PCI have been observed in the northeast, eastern, and western coasts of India, respectively. Gridded data intercomparison suggests that the gauge‐based APHRODITE, GPCC, and satellite‐derived CHIRPS datasets better perform in capturing the temporal and spatial variation of PCI across India when compared to the IMD gridded dataset, whereas the ERA‐5 performs better among the reanalysis datasets. However, the rainfall datasets exhibited marked differences with the IMD while estimating the annual and seasonal trend and its magnitude across various regions of India. The JRA‐55 overestimated areas of positive trend and its magnitude on annual and seasonal scale. These findings have practical implications for hydroclimatic studies.

Water requirement and crop coefficients of sorghum in Apodi Plateau

ABSTRACT Sorghum is of significant economic importance for Northeastern Brazil, since it exhibits high growth rates in regions with irregular rainfall distribution and high temperatures, and is an alternative to corn, which has greater water requirements. Despite being a traditional crop in the region, there are few studies on irrigation management in the Apodi plateau. The aim of this study was to determine the evapotranspiration of the crop and the crop coefficient (Kc) for the different stages of sorghum growth in two cycles, and establish the relationship between the Kc and the normalized difference vegetation index (NDVI) obtained by radiometry. Two weighing lysimeters were used to estimate crop evapotranspiration (ETc). Reference evapotranspiration (ETo) was estimated by the Penman-Monteith method (FAO) and the crop coefficient determined using two methodologies: simple Kc and dual Kc. Total crop evapotranspiration in the two cycles was 452 and 557 mm. The ETc value was 23% higher in the second cycle compared to the first. The maximum Kc values for the first and second cycles were 1.21 and 1.35, respectively, using the dual Kc methodology. The linear relationship found between the Kc values and the NDVI allows monitoring and estimating the water requirements of the crop.

Climate variables on the hydrographic basin of Uruçuí Preto River – Piauí, Brazil subsidies for the management of water and agricultural resources

The knowledge of the climatic characteristics of the hydrographic basins, especially regarding the temporal and spatial distribution of rainfall, the relative humidity of the air and the maximum, minimum and average temperatures of the air, which offer important subsidies to the management of water resources and agriculture. The irregular distribution of rainfall indicates instability in the entry of water into the hydrological system, exercising control over water availability in time and space, the relative humidity of the air influences animal and plant behaviors and the amount of water available in the atmosphere. The temperature, on the other hand, influences the evapotranspiration rates, indicating the energy availability of the environment and, consequently, the environmental water demand. The work presents characteristics of the hydrographic basin of the Uruçuí Preto River (BHRUP), in terms of rainfall, relative humidity, temperature, climatological water balance and climatic regimes. The graphs of annual behavior and seasonal regimes elaborated for 25 pluviometric stations distributed in the interior and around the basin, most of them in operation since the 1960s, followed by the elaboration of average isoietas charts and the one of the rainiest semester, relative humidity of the air, isotherms of the maximum, minimum and average temperatures, and of the letters of potential evapotranspiration, real evaporation and water deficit. The climatic types were appreciated due to the influence of the habitual behavior of the atmosphere on the potential and real environmental demand for water and also on the anthropic demand. The Thornthwaite (1948, 1953) climate system was used, based on the comparison between potential evapotranspiration and rainfall.

Entropy analysis and pattern recognition in rainfall data, north Algeria

Algerian climate is characterized by the transition between the subtropical climate in the north and the hot Saharan climate in the south. Understanding the spatiotemporal variability of rainfall patterns in such areas has significant implications for water resources management. To account for the spatial variation in the rainfall pattern of north Algeria, Tsallis entropy analysis, pattern recognition, and Precipitation Concentration Index (PCI) have been analyzed over a period of 33 years (1980–2013). The rainfall trend is identified by analyzing the results of the structural break test and Mann-Kendall (MK) trend tests. The Tsallis entropy produced spatial patterns for a better understanding of rainfall characteristics and the results show that entropy values were higher for higher rainfall values. The magnitude of rainfall change indicates that a large amount of rainfall occurs over the northern country boundary compared with the central part of Algeria. The rainfall record shows a structural break in the year 1992 during the selected time period. The MK trend analysis revealed a significant decreasing trend over the central and no trend in north and south of the study area. The PCI indicates a moderate rainfall concentration across the northern border region compared with a significant irregular rainfall distribution over the central region. The Wavelet Coherence Analysis (WCA) between El Nino Modoki (EMI) and Southern Oscillation Index (SOI) events on monthly rainfall data were also investigated to find a possible influence of global climatic indicators on the rainfall events. The results show a significant correlation of EMI and SOI with the rainfall pattern of north Algeria.

TECHNICAL AND ECONOMIC FEASIBILITY OF USING A VARIABLE-FREQUENCY DRIVE IN MICRO-IRRIGATION SYSTEMS

Irrigation is essential for the development of crops in regions with scarcity or irregular rainfall distribution, enabling high productivity. However, the use of water resources and electrical energy leads to a concern with irrigation efficiency. Pressure demand varies during the operations of irrigation systems and the appropriate pressure can be regulated by variable-frequency drives for the power supply of the motor-pump set. This study aimed to analyze the technical and economic feasibility of using a variable-frequency drive to adjust the pressure in subunits of micro-irrigation systems. Laboratory tests were carried out to determine the electrical power consumed in each irrigated subunit for different slopes and the application or not of the variable-frequency drive. Thus, an economic analysis was carried out considering the electricity tariff for group B and rural consumer class, as well as different annual irrigation times. The results showed the potential for energy saving with the use of the variable-frequency drive. Thus, the economic analysis showed that the variable-frequency drive was a better alternative than the dissipative method.

EFICIÊNCIA DE IRRIGAÇÃO EM LAVOURAS DE CAFEEIROS CONILON NA REGIÃO CENTRO SERRANA DO ESPÍRITO SANTO

O café representa a principal fonte de renda dos produtores rurais de São Roque do Canaã, porém o município apresenta restrição hídrica ao cafeeiro devido à baixa e irregular distribuição de chuvas. Fato que implica na adoção de sistemas de irrigação para suprir as exigências hídricas do cafeeiro, onde é utilizado principalmente do tipo localizada por gotejamento. Porém, identifica-se a ausência de limpeza, manutenção e avaliações nestes sistemas de irrigação, o que reduz a eficiência e uniformidade de aplicação de água. Diante do exposto, objetivou-se com a realização deste trabalho, avaliar o desempenho de sistemas de irrigação localizada por gotejamento no município de São Roque do Canaã, visando determinação da uniformidade e eficiência de aplicação de água. Foram avaliados sistemas de irrigação em dez propriedades no município. Com base nos resultados obtidos, foram determinados e classificados o Coeficiente de Uniformidade de Christiansen (CUC), o Coeficiente de Uniformidade de Distribuição (CUD), Coeficiente de Uniformidade Estatística (Us) e Eficiência de aplicação (Ea). Os sistemas de irrigação localizada por gotejamento apresentaram baixa uniformidade de aplicação de água, sendo necessário que algumas práticas de manutenção preventiva e corretiva sejam adotadas para que os sistemas operem com maior uniformidade, e em consequência, com maior eficiência no uso da água.