ENVIRONMENTAL CONDITIONS OF THE WATERS OF THE MANZANARES RIVER, CUMANA-SUCRE, VENEZUELA

The Manzanares River is one of the more important rivers of Venezuela inasmuch as it is used to supply drinking
water to a large part of the northeastern zone of Venezuela. For this reason a study was undertaken of the surface waters of the estuarine zone of the river, following the saline gradient from zero to salinities greater than 30. The following properties were measured: river volume flow, rainfall, pH, temperature, suspended materials, dissolved oxygen and ammonium, and heavy metals (Fe, Mn, Cu, Zn, Ni, Cr, Pb and Cd) in particulate and dissolved phases. River volume flow varied with seasonal rainfall throughout the year, as expected, while temperature varied between 24.5 and30.4 oC and pH ranged from 6.65 and 8.9. From the dry to the wet season, suspended material increased from 23 to 880 mg/l at low salinity, and always decreased progressively as salinity increased. Concentrations of total ammonium, 14.5 to 14.3 mmol/l, were high, while those of dissolved oxygen, 3.57 to 5.27 ml/l, were low, and these levels were even more accentuated at salinities under 5 during the dry season. The highest concentrations found for heavy metals were: Fe 406.02; Mn 5.57; Zn 2.18; Cu 0.72; Cr 0.19; Ni 0.72; Pb 0.12; Cd 0.03 mmol/l. These surpass Venezuelan legal limits or water intended for human consumption as well as for waters to be discharged in coastal areas. Concentrations decreased at increased salinity because of the dilution effect, flocculation and/or precipitation in the form of oxyhydroxides. The results obtained in this study reveal a serious deterioration of the state of the waters of the lower Manzanares river.