The Potential of Field Turbidity Measurements for the Computation of Total Phosphorus and Suspended Solids Loads

The computation of loads of material transported in streams is generally based on relationships between river discharge and concentration for particular sites. These correlations are often poor and are frequently based on samples which are unrepresentative of the range of flows occuring in the stream. These problems result in considerable uncertainty in the subsequent load estimates. Turbidity is a property that is simple to measure and can be cheaply collected continuously using an electronic data logger. It is proposed that (i) field turbidity measurements are well correlated with the concentration of some transported material, in particular total suspended solids and total phosphorus and (ii) that these correlations can be used along with logged flow and turbidity data to compute load estimates which are less uncertain than using traditional methods. Data for turbidity versus total suspended solids concentration and turbidity versus total phosphorus concentration are presented for samples taken throughout a 5000 km 2catchment under a full range of flow conditions.