# A Novel Suspended-Sediment Sampling Method: Depth-Integrated Grab (DIG)
## 3 Results  
A total of 9 rivers were sampled in 2018 and 2019 (Table 1). The sampling campaign resulted in 48 pairs of EWDI-SSC and DIG-SSC with all but 2 of those pairs having Grab-TSS being collected at nearly the same time (sequential). The rivers' sizes ranged from 12-126 m in width and 1-10 m in depth (Table S1; Supplemental Materials). The 9 rivers' streamflows ranged from 3-1823 cubic meters per second during sample collection (Table S1; Supplemental Materials). The range of EWDI-SSC measured was 4-1690 milligrams per liter (mg/L). The percentage of suspended sand in the EWDI-SSC samples ranged from 0-56 percent. The range of EWDI-Fines concentrations ranged from 2-1487 while the EWDI-Sands concentrations ranged from 0-278 mg/L (Table 2). EWDI-SSC, EWDI-Sands, and EWDI-Fines were considered the representative measures of suspended sediment and were the primary samples to which the other methods were compared. Sediment sample distributions by sampling methods are shown in Figure 4. Sediment sample distributions and median concentrations of SSC, TSS, Fines, and Sands varied among rivers and the 3 sampling methods, EWDI, DIG, and grab (Figure 4). The \begin{table}
\begin{tabular}{l l l l l l l l l} \hline  & **SWDI-SSC** & **DIG-SSC** & **EWDI-Sands** & **DIG-Sands** & **EWDI-Fines** & **DIG-Fines** & **Grab-TSS** & **Water** & **Stream** & **Q** \\  & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/L)** & **Depth** & **Width** & **(cms)** \\ \hline Min. & 4 & 3 & 0 & 0 & 2 & 2 & 3 & 1 & 12 & 3 \\ Max. & 1690 & 1690 & 278 & 629 & 1487 & 1572 & 1600 & 10 & 126 & 1823 \\ Mean & 267 & 279 & 52 & 60 & 215 & 219 & 221 & 3 & 49 & 277 \\ Med. & 90 & 80 & 13 & 15 & 65 & 52 & 76 & 2 & 37 & 16 \\ SD & 362 & 400 & 71 & 113 & 307 & 320 & 317 & 3 & 39 & 517 \\ \hline \end{tabular} Abbreviations: Min., minimum; Max., maximum; Med., median; SD, standard deviation; EWDI, equal-width or -discharge increment; SSC, suspended-sediment concentration; mg/L, milligrams per liter; DIG, depth-integrated grab; TSS, total suspended solids; m, meters; Q, streamflow; cms, cubic meters per second.  
\end{table} 
Table 2: Summary statistics for sampling and laboratory methods and river conditions. highest measured EWDI-SSC, -Fines, and -Sands were in the southwestern and southeastern sediment regions of Minnesota at the Blue Earth River at Mankato (05321995), the Cottonwood River near New Ulm (0531700), and the Zumbro River at Kellogg (05374900). The northeastern sediment region site East Fork Rapid River near Clemenston (05135000) and middle sediment region site the Nokasippi River near Fort Ripley (05261520) had the lowest median SSC, Fines, and Sands values, regardless of sampling method. The Grab-TSS concentrations were lower than those obtained by EWDI and DIG methods at most of the sites (Figure 4). Visual inspection of the SSC data showed close agreement between EWDI and DIG sampling methods (Figure 5). Most of the data plotted near or on the 1:1 line. The paired data from site 0531700 which deviated the furthest from the 1:1 line was at 1070 mg/L on the x-axis (EWDI-SSC) and 1430 mg/L on the y-axis (DIG-SSC). This paired data had the  
Figure 4: Bootstrapped median values (horizontal line) and the 2.5 th and 97.5 percentiles (vertical line), and measured values (open circle) for sampling (equal-width or -discharge increment [EWDI], depth-integrated grab [DIG], and Grab) and laboratory methods at each of the 9 sampling sites: (**a**) Suspended-sediment concentration (SSC) and total-suspended solids (TSS) laboratory methods; (**b**) Suspended-fines concentration (Fines) laboratory method; (**c**) Suspended-sands concentration (Sands) laboratory method. greatest discrepancy due to there being much higher Sands in the DIG sample (629 mg/L) than the EWDI sample (278 mg/L) when compared to the whole dataset. These paired samples had the highest measured Sands observed during the study.