Precipitation and Erosivity in Southern Portugal: Seasonal Variability and Trends (1950–2008)

Abstract

Southern Portugal experiences the lowest amounts of annual precipitation and the highest level of susceptibility to soil erosion, drought events and desertification phenomena in mainland Portugal. The first goal of this paper was to analyse spatial variability and trends in annual precipitation and erosivity in southern mainland Portugal for the period 1950/1951-2007/2008. The second objective was to evaluate seasonality in relation to precipitation distribution, erosivity and concentration over the same period and to evaluate and detect possible changes in the time trend for precipitation erosivity. In order to achieve these objectives, the annual and seasonal precipitation figures, corresponding to data from 90 rain gauges, were analysed and the Modified Fournier Index and Precipitation Concentration Index calculated for each station. The results obtained revealed distinct behaviour patterns for yearly precipitation, erosivity and concentration trends. Decreases in annual precipitation and erosivity figures accompanied by increases in precipitation concentration were found. Nevertheless, no generalised significant trends have been detected for these variables. In seasonal terms, there was a general trend towards an increase in amount, concentration and precipitation erosivity in autumn and summer, and a significantly reducing in winter. The increase in precipitation erosivity, particularly in the autumn, the most water-erosive season, suggests a rising in potential soil erosion risk in southern Portugal.

Mapping monthly rainfall erosivity in Europe

“…In Algrave region, our results show similar patterns to de Santos Loureiro and de Azevedo Coutinho (2001) who have modelled the highest erosivity in October, November and December and the lowest in summer months. In Southern part of Portugal, similar to Nunes et al (2016), we have estimated the highest erosivity the 3-months October–December followed by erosivity the erosivity during January–March while the lowest erosivity is during summer. Similar to our results, In South-eastern Portugal (Alqueva Dam Watershed) Ferreira and Panagopoulos (2014) have modelled the highest erosivity during autumn (c.a.…”

“…Rainfall erosivity shows different patterns among the wet and dry seasons both in terms of magnitude and in relationship to rainfall amount (named erosivity density) (Hoyos et al, 2005, Meusburger et al, 2012, Borrelli et al, 2016, Panagos et al, 2016a). Monthly erosivity has been studied in some regions in Europe such Portugal (Ferreira and Panagopoulos, 2014, Nunes et al, 2016), Sicily (D'Asaro et al, 2007) and Calabria (Terranova and Gariano, 2015) in Italy, Ebro Catchment in Spain (Angulo-Martínez and Beguería, 2009), western Slovenia (Ceglar et al, 2008), north-eastern Austria (Klik and Konecny, 2013) and Czech Republic (Janeček et al, 2013). Nevertheless an assessment of monthly erosivity over Europe is still missing.…”

Soil erosion in sloping vineyards assessed by using botanical indicators and sediment collectors in the Ruwer-Mosel valley

“…Furthermore, there is a natural seasonal behaviour in soil erosion processes in climates such as the Mediterranean as the summer drought increases the infiltration capacity of the soils (Cerdà, 1999) that results in changes in the soil loss rates during the year (Cerdà, 1998(Cerdà, , 2002. In the Mediterranean these changes in erosivity are mostly based on changes in the rainfall erosivity and not in the state of the soil (Alexandridis et al, 2015;Nunes et al, 2016). However, in the Ruwer-Mosel valley the seasonal changes in rainfall are low and therefore, the differences in erosion are due the state of the soil surface that in Germany is highly influenced by human management as a consequence of the tillage, trafficking, and trampling (Rodrigo Comino et al, 2015a,b).…”

Comparing Beerkan infiltration tests with rainfall simulation experiments for hydraulic characterization of a sandy‐loam soil

“…Rainfall simulation experiments are not only more realistic and accurate but also more sophisticated and costly (Cerdà, 1997). Rainfall simulation is often used to measure the infiltration process (e.g., Bhardwaj & Singh, 1992;Iserloh, Ries, Arnáez, et al, 2013;Liu et al, 2011;Tricker, 1979), and it has become an important method for studying soil erosion and other soil hydrological processes (Iserloh, Ries, Arnáez, et al, 2013;Keesstra et al, 2016;Lassu, Seeger, Peters, & Keesstra, 2015), improving our understanding of the role of the rainfall properties and erosivity on soil hydrology (Diodato, Verstraeten, & Bellocchi, 2014;Nunes, Lourenço, Vieira, & Bento-Gonçalves, 2016). Rainfall simulation allows a specific and reproducible assessment of the meaning and the impact of several factors on the process of interest, such as slope, soil type, initial soil moisture, splash of raindrops, surface soil structure, vegetation cover, and vegetation structure (Bowyer-Bower & Burt, 1989).…”