Trend detection in river runoff across Mediterranean river basins: evaluation of results from Moroccan case study

Ons Oueslati (1, 2) , Anna Maria de Girolamo (1) , Antonio Lo Porto (1) , Aziz Abouabdillah (1, 3)

1 Water Research Institute
2 Environmental Engineering and Physics Department [Potenza]
3 Università degli studi della Tuscia [Viterbo]

The Mediterranean basin is considered among the ecosystems to be especially affected by climate change due to the net decline in precipitations during the last century. This study aims to identify trend in river discharges using a set of graphical and statistical procedures. Annual and monthly continuous streamflow time series from six Mediterranean flow gages in Morocco were checked for possible trend. The rescaled cumulative departure plots of monthly mean flows exhibit a net decreasing trend from 1980 until 1987 at all sites. The LOWESS-smoothed monthly mean flows have a generally decreasing trend which is more obvious from early 1970s. Standard statistical testing were applied to confirm the trends. Among these tests the non parametric Mann-Kendall test, which is widely used to detect trends in hydrologic data, was applied to detect trends in annual runoff. The results of this test showed that all the stations present negative trends indicating the decrease in runoff at 95 and 99 percent significant level.

Mots clés: Trend analysis; streamflow; Mann-Kendall; LOWESS; Morocco

Domaines: Environnement et Société

Ons Oueslati, Anna Maria de Girolamo, Antonio Lo Porto, Aziz Abouabdillah. Trend detection in river runoff across Mediterranean river basins: evaluation of results from Moroccan case study. 8th World Wide Workshop for Young Environmental Scientists WWW-YES 2009: Urban waters: resource or risks?, Jun 2009, Arcueil, France. ⟨hal-00593080⟩