Details

Autor(en) / Beteiligte

• Sadani, M
• Ouazzani, N
• Mandi, L

Titel

The effect of dryness on water quality of lake Mansour Eddahbi (Ouarzazate, Morocco)

Ist Teil von

• Revue des sciences de l'eau, 2004-01, Vol.17 (1), p.69-90

Erscheinungsjahr

2004

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Eutrophication is one of the most important water quality problems in lakes. Due to the effects of excessive external inputs of nutrients (phosphorus and nitrogen), compounded with unfavorable climatic and hydrologic conditions, the lake undergoes major changes that involve both the physical-chemical properties of water and the aquatic communities living there. There have been many studies on lake ecosystems and their evolution. These studies relate especially to the role of nutrients (nitrogen and phosphorus mainly) in the evolution of lakes. The influence of climatic and hydrologic conditions on the structure and dynamics of these ecosystems has been often underestimated. Indeed, there are few studies on the relationship between climatic conditions and the trophic status of aquatic ecosystems. The aim of this paper is to study the behavior of the physical-chemical qualities of water in lake Mansour Eddahbi (Ouarzazate, Morocco) and its trophic status under severe climatic conditions, especially during the very dry hydrological year 1998/99. The Ouarzazate region is characterized by an arid continental climate with very hot summers and cold winters. Due to both great evaporation and increasing demand for water for irrigation, the water levels of the reservoir has been reduced by 14 m and its storage capacity has been considerably reduced. The approach used was to assess water quality in a station at the deepest area of the lake during the hydrological year 1998/99. Sampling was undertaken monthly and different parameters were analyzed including temperature, pH, total suspended solids (TSS), salinity, dissolved oxygen (DO), chlorophyll a, phosphorus and nitrogen.Original Abstract: L'objectif de ce travail est d'etudier l'impact d'une annee hydrologique tres seche (98/99) sur la qualite physico-chimique et l'evolution de l'etat trophique du lac Mansour Eddahbi. Ce lac est situe dans la region de Ouarzazate, au sud du Maroc, caracterisee par un climat aride continental, avec des ecarts thermiques hiver-ete importants, des precipitations tres faibles et une forte evaporation. Ceci induit une reduction considerable du volume total du lac et par suite une baisse de 14 m de son niveau. A la lumiere des valeurs de temperatures enregistrees au niveau de la colonne d'eau, le lac peut etre classe dans la categorie des lacs monomictiques avec une seule periode de melange hivernale. Le pH est legerement alcalin. La reduction du volume d'eau au niveau du lac a engendre une augmentation de la salinite des eaux. Les conditions climatiques severes qui ont sevi durant l'annee hydrologique 98/99 ont contribue a une evolution acceleree de l'etat trophique du lac.