WATER QUALITY LIMITATION FOR TURBIDITY BASED SEDIMENT MEASUREMENT IN RIVERS

Abstract

The concentration and size ofsediment particles are mainly affected flow and climate conditions, soilproperties, topography, and plant cover properties. The direct water samplingmethod has many difficulties to represent continuous monitoring of sedimenttransport, especially during extreme flow conditions Turbidity based estimating of suspended sediment is widely used forriver studies due to its simply and cheap using.The strong relationship between turbidity and suspended sediment concentrationshas led to the use of turbidimetry to estimate sediment concentration. The useof turbidity values for SSC is an indirect method and based on to determine thestatistical relationship between these values; the relationship could belinear, non-linear or polynomial. But this relation is affected by waterpollution, colloids and plankton units, air bubbles and other suspendedmaterials in the water sample rather than mineral suspended particles. In this study, Seapoint Turbidity Meter sensor was used to provideaccurate, reliable, automated and continuous time series of suspended-sedimentconcentrations under different water quality conditions in river. The study wasconducted at river conditions, and two different water qualities wereconsidered depend on electrical conductivity and turbidity values. The firstsampling point was chosen close the source of river for obtaining clear waterand second one was chosen at polluted point by waste water of city. Theregression analyses were applied between the sediment concentrations with theturbidity values to observe of different water quality effects and wereevaluated using determination coefficient (R2) and regressionequation. Sediment concentration values were varied between 0.02 and 1.12 g/lduring sampling season depend on rainfall and river discharge but these valuesand water quality parameters were found extremely high and unstable due topollution of waste water pollution of city. Fairly high R2 value (0.971) was obtained for first stationwater which has relatively clear, but week relationship (0.273) was obtained ofbetween the sediment concentrations and the turbidity values for second stationdue to water pollution. This problem is important limitation for turbiditybased sediment measurement, and it should be considered to more accurately estimate sediment concentrationwith turbidity values