Ecological studies of three West Algerian rivers : the River Tafna and its tributary the River Remshy

الملخص EN

Limnological studies of Tafna Watershed were carried out on aquatic bodies of the coastal north-west Algeria.

Tafna Watershed near the Morrocan boarder was chosen, two sampling sites were appointed out in this investigation, on Beni-Saf, the River Tafna, a river of 110Km long and one of its tributaries, on Telemssan, the River Remshy.

Samples were taken monthly during 2 years (1986-1988), during which the phisco-chemical were studied.

The lowest air (15°C) and water temperatures (10°C) were recorded in January and the highest (30°C) in September for both air and water temperatures.

The hydrogen ion concentration investigation samples were slightly alkaline lying between (pH7.5 and 8.6).

Electrical conductivity (EC) values ranged between 56 and 4,960 μS cm-2; being higher in the River Tafna than in the River Remshy.

Dissolved oxygen (DO) values showed that the River Tafna and River Remshy were both well oxygenated (7.5-13.6mg l-1).

The minimum biological oxygen demand (BOD) value was recorded (2mg l-1) in September and maximum (7.8mg l-1) in May.

Dissolved Organic Matter (DOM) values ranged from 5.09 mg l-1 in July and 11.78 mg l-1 in March.

Suspended solids (SS) were high during the warm months and low in the cold months with a negative correlation with water turbidity WT.

Average values of total residue (TR), fixed total residue (FTR), volatile matter (VM), total hardness (TH), calcium hardness (CaH) and silica (SiO3-Si) were higher at the River Tafna than at the Tributary River Remshy.

While the average values current velocity (CV), water turbidity (WT), dissolved oxygen (DO), oxygen percentage saturation (OPS), biochemical demand (BOD), magnesium hardness (MgH), chloride, inorganic nitrogen contents and phosphorus were more at the tributary than at the river.

Increase the chloride was coincided with increase of EC and DO at River Tafna.

Total, calcium and magnesium hardness had a negative correlation with TR, FTR and VM.

The contents of the three later parameters, DO, OPS, BOD, SS, and DOM were high during the cold months and low during the hot months at the study period.

Fluctuations were likely to be more at river rather than at the tributary.