Erosive Indices of Amparo in São Francisco — Sergipe, Brazil Related to the Phenomena El Niño La Niña
Abstract
Erosion is originally from the Latin, which means to corrode and, in a comprehensive way, can be considered a set of natural processes that promote the alteration of landscapes through degradation, wear and transport from one point to another of materials on the earth'ssurface through agents erosive. The objective is to evaluate the erosive index for the municipality of Amparo de São Francisco – Sergipe, relating them to the El Niño and La Niña phenomena. The calculation of pluvial and erosive anomalies was used, generating their respective graphs for the area understudy coupled with the extreme events of large scale El Niño and La Niña to seethe erosive contributions of the studied area. Erosion calculations were performed using the formulation developed by França (2021) for the study area. The rainfall erosivity indices of anomalies in the study area, taking into account the El Niño and La Niña periods, is a relevant factor for decision makers on the most adequate soil management practices, aiming at the sustainability of exploration for projects farming and fertile soil management.
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Introduction
One of the impacts caused by water erosion is the exhaustion of soil lacking due to the loss of nutrients, organic matter, siltation and contamination of water tables, through the displacement of fertilizers and pesticides, causing direct changes in flora and fauna (BERTONI et al., 2012; PIRES et al., 2013). According to Pires et al. (2013) erosion is evaluated as a process of natural origin with the purpose of landscape formation and soil renewal.
Erosivity has been expressed as the potentiality of the erosive agent, wind and/or water, to generate erosion. As for the rainfall erosive capacity procedure, the EI30 (kinetic energy of impact of "E" drops by the maximum rainfall intensity in 30 minutes) was created and the “R” factor of the Universal Soil Loss Equation was suggested as a rainfall index (WISCHMEIER et al., 1978). FOSTER et al. (1981) dimensioned the units for the International System of Measurements, expressing in MJ.mm/hyear ago. With the help of rainfall correlation and erosivity, the rainfall erosive potential of a location with the same climate type and which does not have rainfall data records is estimated (OLIVEIRA et al., 2012; TRINDADE et al., 2016).
In the northeastern semiarid region, precipitation spreads irregularly with long periods of drought. Temperatures register higher averages causing high evaporative and evapotranspiration rates (CLEMENTE, 2021; MARENGO, 2008). Precipitation in this region is a result of atmospheric dynamics, and the influence of local and regional factors, such as relief and geographic position (MARENGO et al., 2011).
Medeiros et al. (2016a) analyzed the oscillations of El Niño and La Niña and their influence on the number of rainy days in the municipality of Bom Jesus do Piauí. For the Northeast, the periods of El Niño are associated with the scarcity of rain and La Niña, in general, with abundant rainfall, while in the South and Southeast regions conditions are observed with opposite events. The El Niño south oscillation (ENOS) considerably influences the climate in places where it operates, with long periods of drought and total rainfall above historical normal’s (ROMERO, 2013). Medeiros (2018) showed that there is alack of studies on the correlation of rainfall with large-scale climatic phenomena, such as El Niño and La Niña. The author analyzed the influence of rainfall variability and the number of rainy days in the city of Recife-PE, and their relationship with the phenomena El Niño and La Niña. According to this author in the dry four-month period, which corresponds to October, November, December, and January, there is no interference from the El Niño and La Niña episodes in the increases and decreases in the days with rain occurrences, which are directly linked to local factors such as breeze, convective movements and line of instability. The phenomena El Niño and La Niña have little influence on the days with rain occurring in Recife-PE, because in the months with the greatest intensity of these episodes, the trend curves showed no increase or decrease. Coherent results were found in the studies by Medeiros et al. (2016) for the municipality of Bom Jesus do Piauí.
França et al. (2018) calculated the climatological water balance for the municipalities of São Bento do Una and Serra Talhada and investigated the influence of the phenomena El Niño (2012, 2016) and La Niña (2008, 2011) on the distribution of rainfall through analysis of the water balance extract. They found that the El Niño episode influenced the rainfall rates of the cities studied. In the La Niña episode, the distribution of these indices was irregular, reflecting on the water balance. Medeiros (2014) analyzed the occurrences of extreme precipitation events in Campina Grande, with daily data covering the years 1970–2010. The extreme events analyzed were those with the highest daily precipitation intensity. The results showed that there was a change in the behavior of precipitation occurrences from the 70s onwards. There was an intensification in the maximum precipitation with a greater number of events with precipitation values greater than 80 mm. There was, in general, no direct relationship between the increase in precipitation and occurrences with ENSO events. Extreme events were evident between the months of the rainy season with 88% of occurrences, and 12% of evidence in the dry season. Medeiros et al, (2012), analyzing the climatology of precipitation in the city of Bananeiras-PB, in the period 1930-2011, as a contribution to Agroindustry, found that rain gauges are essential to agro-industrial sustainability even with activities from external events The objective is to evaluate the erosive index for the municipality of Amparo de São Francisco – Sergipe, relating them to the El Niño and La Niña phenomena.
Conclusion
The anomalous variability of erosion and rainfall against large-scale El Niño and La Niña phenomena did not show large isolated activities in years of their occurrence, since in isolated years both events presented equal intensities in the elements under study.
The erosivity and rainfall indices of anomalies in the study area, taking into account the El Niño and La Niña periods, is a relevant factor for decision makers on the most adequate soil management practices, aiming at the sustainability of exploration for agricultural projects and fertile soil management.
The information provided in the study should serve as a support for the area'sconservation planning, where it will be possible to follow strategies to recover and prevent damage to environmental resources and increase the property'sproductive capacity, contributing to socioeconomic development.
