PATTERNS OF PRECIPITATION INTERMITTENCY IN SOUTHERN PORTUGAL: IMPLICATION FOR THE CONSERVATION AND MANAGEMENT OF MEDITERRANEAN INTERMITTENT RIVERS

Abstract

Southern Portugal is a semi-arid region, characterized by an irregular spatio-temporal distribution of the precipitation that directly influences the superficial runoff. This variability, together with the occurrence of more or less extended periods of drought, often leads to situations of water stress, negatively affecting freshwater ecosystems. Human activities, particularly those associated with land use, have further aggravated this situation. Medium- small temporary streams are especially affected, as these systems are reduced to isolated pools during dry periods, where the aquatic biota persists until the following wet season. Moreover, the effect of dryness can be seriously amplified in the future, considering the foreseen climate change scenarios. Therefore, the main goal of this study was to define regions of hydroclimatic intermittence in southern Portugal based on the pattern of precipitation intermittency. Long time series of precipitation data were collected from 9 meteorological stations covering the south of Portugal region. Data analysis involved the selection of metrics and the development of intermittence indices, based on the precipitation patterns for control and future periods. Regions of hydroclimatic intermittence were displayed in a GIS environment, allowing the evaluation/classification of the persistence level of southern Portuguese streams and rivers for present and future periods. The relationships between the persistence level of streams and the long term viability of freshwater biota are discussed. The definition of regions of hydroclimatic intermittence can be a useful tool for water management in Mediterranean intermittent rivers.