Assessment of physico-chemical parameters of freshwater in the Sidi Abderrahmane reservoir, Safi, Morocco

Abstract

The purpose of the study was to assess the water quality in the Sidi Abderrahmane freshwater reservoir (Safi, Morocco). The monitoring data used in the study included physical, chemical, and biological characteristics. The spatial and temporal characteristics of these parameters was evaluated by collecting water samples fortnightly from May 2011 to December 2012 in three stations chosen to represent different parts of the reservoir. Ten parameters considered as indicators of water properties were analysed: temperature, dissolved oxygen, pH, electric conductivity, transparency, orthophosphorus, ammonium, nitrites, nitrates, and chlorophyll a. The results show that nutrient concentrations were among the highest (mean concentrations: PO₄ ³⁻ = 0.64 mg l⁻¹, NH⁴⁺ = 1.08 mg l⁻¹) recorded for Moroccan freshwater reservoirs. Our data indicated that the Sidi  Abderrahmane is a destratified reservoir that it is relatively warm (mean temperature: 22.42 ± 4.88 °C); a polymictic reservoir in a semi-arid climate. Fertilisers applied in the surrounding orchards affect significantly affect nutrient levels in the waterbody, particularly PO₄ ³⁻ and NH⁴⁺ in autumn. The water column is seasonally homogeneous, as a result of wind-induced mixing, and our tests showed no anoxia throughout the study period. With suitable hydraulic conditions (short residence time, short outflow/inflow ratio, good oxygenation, and homogeneity), the Sidi Abderrahmane  water body could reduce the stratification time and improve water quality.

Keywords: Oum Er-Rabia Basin, physicochemical, Safi region, water quality, waterway