EVALUATION AND COMPARISON OF TOTAL SUSPENDED SOLIDS IN A SMALL WATERSHED USING TURBIDITY METERS AND GROUND-BASED HYPERSPECTRAL IMAGING

The measurement of pollutants like dissolved solids and suspended solids in small watersheds has traditionally been done through taking on-site samples of water: however, this method means that sampling sites are non-random, since some places are simply not accessible within a watershed. Previous work has been done to measure suspended sediments through spectral data: however, this work has only been done in optically deep locations. In this study, a ground hyperspectral imaging machine, the FieldSpec 3, was used to measure points within a small watershed in Iowa named Dry Run Creek to assess if spectral data could be used to measure suspended solids in shallow water. Dissolved solids, velocity, and nitrates were also measured over an 8 week period.

Measurements were taken two ways: in the field within the natural stream environment, and within the lab under fluorescent lighting. The reflectance values from the field were scattered and inconsistent, showing little to no correlation with the amount of suspended solids (measured using a turbidity meter). The lab reflectance values showed a linear regression with increased solids in the water. The lack of correlation of field reflectance values showed that the FieldSpec 3 and spectral imaging in general are not a good method of measuring suspended solids in the field at this moment in time. This is likely due to variations in stream bottom composition and velocity. The linear regression of the lab values indicates that there is a component in the suspended solids that is absorbing light instead of reflecting it: this is a possible direction for further research. While hyperspectral imaging does not seem to be an effective method of hydrologic measurements in a small stream, point-based spectral data can be used to investigate the composition of suspended solids in a watershed. This use for spectral data can hopefully be used in the future to compare and contrast suspended solids in different watersheds.