Investigating trends in rainfall in a small island: The case of Madeira Island, Portugal

Studying climate variability, hydrological extreme events, trends in hydrological variables, along with their prediction, from global to regional and local scales, are of primary importance for agricultural, forestry and water management activities. These activities are scheduled or designed mainly in accordance to rainfall seasonality and spatiotemporal distribution (Villafuerte II et al. 2014). However, assessing climate variability and the mechanisms that cause changes and their related impacts is rather difficult. In recent years, these non-evenly distributed changes have led to an increased temporal variability mostly of precipitation, streamflow and evaporation patterns. For the purpose of understanding the climate change effects, trend analysis and change-point detection in time series of climate variables, such as temperature and precipitation, have been the focus of research worldwide. Hence, precipitation trend analyses are crucial in water planning and management (Rao et al. 2015). The features of the small islands, such as the reduced areas of their catchments and the limited, and often low, surface and groundwater storage capacity, make their hydrology and water resources development and management issues very distinct from those on larger islands or continental areas. Thus, in the former islands understanding the behaviour of the climate variables and being able of detecting their trends are fundamental issues (Falkland et al. 1991). The aim of this paper is to provide a suitable understating about the variations in rainfall and of the recent dynamics of change in rainfall over a small island environment as is the case of Madeira Island – a Portuguese island which has suffered from sustained below-average rainfall conditions in recent years (Liberato et al. 2017), located in the North Atlantic (NA), in the European part of Macaronesia.