Estimating suspended sediment concentrations from turbidity measurements and the calibration problem

Abstract

Abstract:In situ turbidity meters are being increasingly used to generate continuous records of suspended sediment concentration in rivers. However, the usefulness of the information obtained depends heavily on the existence of a close relationship between fluctuations in suspended sediment concentration and turbidity and the calibration procedure that relates suspended sediment concentration to the turbidity meter's signal. This study assesses the relationship between suspended sediment concentration and turbidity for a small (1Ð19 km 2 ) rural catchment in southern Brazil and evaluates two calibration methods by comparing the estimates of suspended sediment concentration obtained from the calibrated turbidity readings with direct measurements obtained using a USDH 48 suspended sediment sampler. With the first calibration method, the calibration relationship is derived by relating the turbidity readings to simultaneous measurements of concentration obtained from suspended sediment samples collected from the vicinity of the turbidity probe during flood events. With the second method, the calibration is based on the readings obtained from the turbidity meter when the probe immersed in samples of known concentration prepared using soils collected from the catchment. Overall, there was a close link between fluctuations in suspended sediment concentration and turbidity in the stream at the outlet of the catchment, and the estimates of sediment concentration obtained using the first calibration method corresponded closely with the conventionally measured sediment concentrations. However, use of the second calibration method introduced appreciable errors. When the estimated sediment concentrations were compared with the measured values, the mean errors were š122 mg l 1 and C601 mg l 1 for the first and second calibration procedures respectively.

Flow and nutrient transport in intermittent rivers: a modelling case-study on the Vène River using SWAT 2005

“…For instance, in a context such as the Vène River, in which the suspended load contains particles of various origins (organic matter, algae, micro-organisms, etc. ), the use of turbidimeters to assess suspended solid concentration does not always give reliable results (Gippel, 1995;Minella et al, 2008). Hence, one has to resort to grab data, which, regardless of its sampling frequency, will never provide the same information as continuous data.…”

Prediction of suspended sediment concentration from water quality variables

“…Hence, researchers have looked for alternative options for sediment predictions. One of these options is to do the predictions using other parameters, such as discharge [9], precipitation [3], turbidity [1,10], and water quality [11].…”

“…Minella et al [10] assessed the relationship between SSC and turbidity for a small (1.19 km 2 ) rural catchment in southern Brazil, and evaluated two calibration methods by comparing the estimates of SSC obtained from the calibrated turbidity readings with direct measurements obtained using a suspended sediment sampler. Meral et al [11] used two practical and relatively cheap alternative methods (namely turbidity sensor and Imhoff cone method) to estimate SSC.…”

Quantificação da produção de lodo de estações de tratamento de água de ciclo completo: uma análise crítica.

“…O padrão que emerge desses trabalhos indica que a correlação entre SST e turbidez é altamente local: estudos focados em corpos d'água específicos (FRANCO, 2009;JASTRAM et al, 2010;JONES et al, 2011;LEWIS et al, 2002;MINELLA et al, 2008;LENHART et al, 2010;TEIXIERA;SENHORELO, 2000;TOMAZONI et al, 2005;STUBBLEFIELD et al, 2007;SUSFALK et al, 2008;ULRICH;BRAGG, 2003;WASS et al, 1997;WILLIAMSON;CRAWFORD, 2011) têm maior chance de chegar em correlações significativas do que estudos nos quais o conjunto de dados, apesar de grande, seja composto por uma miscelânea de poucas medições em muitos corpos d'água (LEWIS et al, 2002;SPEAR et al, 2008;HUI et al, 2011;WILLIAMSON;CRAWFORD, 2011 …”

“…SST AF -concentração de sólidos em suspensão em mg/L na água filtrada; JASTRAM et al, 2010;JONES et al, 2011;LEWIS et al, 2002;MINELLA et al, 2008;LENHART et al, 2010;TEIXIERA;SENHORELO, 2000;TOMAZONI et al, 2005;SANTOS, 2009;STUBBLEFIELD et al, 2007;SUSFALK et al, 2008;ULRICH;BRAGG, 2003;WASS et al, 1997;WILLIAMSON;CRAWFORD, 2011), é difícil determinar a partir da literatura se a baixa incidência de altos níveis …”