# Remote Sensing of the Water Quality Parameters for a Shallow Dam Reservoir
## 2 Data, Methods, and Techniques
### Remote Sensing Methods for a Chlorophyll Content
\begin{table}
\begin{tabular}{c c} \hline
**Formula** & **Source** \\ \hline C\({}_{\text{chl-a}}\)=(23.09 \(\pm\) 0.98) + (117.42 \(\pm\) 2.49)\(\cdot\)(R\({}^{-1}\)\({}_{660-670}\) \(-\) R\({}^{-1}\)\({}_{700-730}\))\(\cdot\)R\({}_{740-760}\) & ([PERSON] et al., 2006) [21] \\ C\({}_{\text{chl-a}}\) = (-16.2 \(\pm\) 1.8) + (136.3 \(\pm\) 3.2)\(\cdot\)(R\({}^{-1}\)\({}_{662-672}\) \(\cdot\)R\({}_{745-753}\)) & ([PERSON] et al., 2006) [21] \\ \hline C\({}_{\text{chl-a}}\) = (0.74\(\cdot\)R\({}_{681}\) + ([681 nm \(-\) 665 nm)/(681 nm \(-\) 620 nm)]\(\cdot\)(R\({}_{620}\) \(-\) R\({}_{681}\)) - R\({}_{665}\) & ([PERSON] et al., 2010) [22] \\ \hline log\({}_{10}\)(C\({}_{\text{chl-a}}\)) = (0.32978 \(+\) 2.6465X + 1.9988X\({}^{2}\) + 0.5708X\({}^{3}\) + 3.033X\({}^{4}\)) & \\ X = log\({}_{10}\)(Max(R\({}_{443 nm}\), R\({}_{486 nm}\))/R\({}_{551 nm}\)) & ([PERSON] et al., 2020) [23] \\ \hline C\({}_{\text{chl-a}}\) [mg/L] = 1.67 + 299 R\({}_{438}\) - 33.1 R\({}_{675}\) - 7217 R\({}_{438}\)R\({}_{675}\) - 14022 R\({}_{438}^{2}\) - 973 & \\ R\({}^{2}\)\({}_{675}\) + 37302 R\({}^{2}\)\({}_{438}\)R\({}_{675}\) + 112440 R\({}_{438}\)R\({}^{2}\)\({}_{675}\) - 3317051 R\({}_{438}^{2}\)R\({}^{2}\)\({}_{675}\) & \\ C\({}_{\text{chl-a}}\) [mg/L] = 3.45 + 66.2 R\({}_{438}\) - 100 R\({}_{550}\) - 3.9 R\({}_{675}\) + 5349 R\({}_{438}\)R\({}_{850}\) - 16643 & ([PERSON] et al., 2018) [20] \\ R\({}_{550}\)R\({}_{675}\) - 12682 R\({}_{438}\)R\({}_{675}\) + 3077 R\({}^{2}\)\({}_{438}\) + 5209 R\({}^{2}\)\({}_{550}\) + 15992 R\({}^{2}\)\({}_{675}\) & \\ \hline log\({}_{10}\)(C\({}_{\text{chl-a}}\)) = (0.366 \(-\) 3.067X + 1.930X\({}^{2}\) + 6.049X\({}^{3}\) - 1.532 X\({}^{4}\)) & GlobColour ([PERSON] et al., 2013) [25] \\ X = log\({}_{10}\)(Max(R\({}_{443 nm}\)/R\({}_{555 nm}\), R\({}_{490 nm}\)/R\({}_{555 nm}\), R\({}_{510 nm}\)/R\({}_{555 nm}\))) & ([PERSON] et al., 2018) [24] \\ \hline log\({}_{10}\)(C\({}_{\text{chl-a}}\)) = (0.6994 \(-\) 2.0384X + 0.4656 RX\({}^{2}\) + 0.4337X\({}^{3}\)) & \\ X = log\({}_{10}\)(Max(R\({}_{\text{rs}(4435/555)}\), R\({}_{\text{rs}(490-555)}\)) & Modis-Aqua ([PERSON] et al., 2013) [24] \\ C\({}_{\text{chl-a}}\) = [mg/m\({}^{3}\)] & \\ \hline \end{tabular}
\end{table} 
Table 1: Typical mathematical formulas to calculate chlorophyll a concentrations. Figure 4: Reflectance for water with a dusty suspension [g/m\({}^{3}\)]. Reprinted with permission from [18]. the value 0.96, with an error for RMSE chlorophyll a content of 0.07 mg chl/m\({}^{3}\), determined on the basis of a few data covering 5 days of composite images for the year 2014 [24]. Empirical models that are focused on determining the chlorophyll a concentration take into account the variability of the aquatic environment in terms of the content of other substances in a very limited way, which may affect the accuracy of the results obtained. A possible solution to this problem in the case of inland waters may be the construction of seasonal models (used for imaging registered at specific seasons of the year) [26]. Another more widely used technique is the use of bioptic methods based on the modeling of light-water interaction, such as Hydrolight [27], or the newer 2 SeaColor [28], adapted to water with high turbidity. In the case of the second model, the determination indicator was equal 0.71, and model error RMSE was 6.23 mg chl/m\({}^{3}\)[28]. Such models may include bottom reflectance [29; 30], which is extremely important for shallow tanks, as pointed out by [PERSON] et al. 2013 [31]. In the works ([PERSON] et al., 2017, 2018) [32; 33], a semi-analytical method for colored dissolved organic matter (CDOM) was presented. This method includes bottom effect and is accurate (RMSE = 0.17 mg chl/m\({}^{3}\) and R\({}^{2}\) = 0.87); it also uses multispectral data. The extremely promising result for turbid water research was the model developed by [PERSON] et al. [21].