Local Settling Rate of Algae

The local settling rate of algae represents the net removal of algae due to settling. The user defines the local settling rate of algae at 20$\degree$C. The settling rate is adjusted to the local water temperature using the relationship:

$\sigma_1=\sigma_{1,20}*1.024^{(T_{water}-20)}$ 7:3.1.18

where $\sigma_1$ is the local settling rate of algae (m/day or m/hr), $\sigma_{1,20}$ is the local algal settling rate at 20$\degree$C (m/day or m/hr), and $T_{water}$ is the average water temperature for the day or hour ($\degree$C).

Table 7:3-1: SWAT+ input variables used in algae calculations.

Variable Name	Definition	File Name
AI0	$\alpha_0$: Ratio of chlorophyll a to algal biomass ($\mu g$ chla/mg alg)	.wwq
IGROPT	Algal specific growth rate option	.wwq
MUMAX	$\mu_{max}$: Maximum specific algal growth rate (day$^{-1}$)	.wwq
K_L	$K_L$: Half-saturation coefficient for light (MJ/m$^2$-hr)	.wwq
TFACT	$fr_{phosyn}$: Fraction of solar radiation that is photosynthetically active	.wwq
LAMBDA0	$k_{l,0}$: Non-algal portion of the light extinction coefficient (m$^{-1}$)	.wwq
LAMBDA1	$k_{l,1}$: Linear algal self shading coefficient (m$^{-1}$ ($\mu g$-chla/L)$^{-1}$)	.wwq
LAMBDA2	$k_{l,2}$: Nonlinear algal self shading coefficient (m$^{-1}$($\mu g$-chla/L)$^{-2/3}$)	.wwq
K_N	$K_N$: Michaelis-Menton half-saturation constant for nitrogen (mg N/L)	.wwq
K_P	$K_P$ : Michaelis-Menton half-saturation constant for phosphorus (mg P/L)	.wwq
RHOQ	$\rho_{a,20}$ : Local algal respiration rate at 20$\degree$C (day$^{-1}$)	.wwq
RS1	$\sigma_{1,20}$: Local algal settling rate at 20$\degree$C (m/day)	.swq