USE OF PHYSICOCHEMICAL PARAMETERS OF RIVE R WATER AS INDICATORS OF NATURAL AND ANTHROPIC INFLUENCES

The measurement of pH, temperature, conductivity and dissolved oxygen that were conducted ''in situ'' in the Tuy river watershed from 1979 t o 1990 were averaged for the dry and wet season and compared with prev ious results of other watersheds located as well in North Venezuela. T he results found in this study indicated that there are no significant differences between the dry and wet periods in the pristine areas, wh ich is contrary to what was found for the highly intervined areas. Con ductivity was found to be a function of lithology; however in the suba reas only the chemical composition of the water discriminates between lithologies. In fact, in the pristine area of the Tuy watershed, the s ubarea with high runoff and tropical jungle vegetation showed values o f conductivities lower than the low runoff and savanna area. Human act ivities have quadruplicated the values of conductivity and reduced the dissolved oxygen content to values equivalent to 50% of saturation. T hese human influences are strongly noted during the dry period. The se lf-purification capacity of the system has been considered relatively high, and attributed to dilution processes, cation exchanges and acid- base reactions that occur along the river main channel. Based on envir onmental similarities and the results found for the parameters studied , the Tuy river basin was considered as representative of the Venezuel an Caribbean Sea Watershed.