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ben_disp

Benthic source rate for dissolved P in the channel at 20ºC

If routing is performed on an hourly time step, the units of ben_disp are converted to mg P/m2*hr by the model.

name (nutrients.cha)

Name of the channel nutrient record

The name of the channel nutrient record is a primary key referenced by in .

nut
channel-lte.cha

plt_p

Channel organic P concentration

nutrients.cha

This file controls the channel nutrient properties.

Field
Description
Type
Unit
Default
Range

Name of the channel nutrient record

string

n/a

n/a

ptln_stl

Organic N settling rate in the channel at 20ºC

If routing is performed on an hourly time step, the units of ptln_stl are converted to 1/hr by the model.

alg_stl

Local algal settling rate in the channel at 20ºC

If routing is performed on an hourly time step, the units of alg_stl are converted to m/hr by the model.

ben_nh3n

Benthic source rate for NH3-N in the channel at 20ºC

If routing is performed on an hourly time step, the units of ben_nh3n are converted to mg N/m2*hr by the model.

cst_stl

Arbitrary non-conservative constituent settling rate in the channel at 20ºC

cbn_bod_stl

Rate of loss of carbonaceous biological oxygen demand due to settling in the reach at 20 ºC

cst_decay

Decay rate for arbitrary non-conservative constituents in the channel at 20ºC

ptlp_stl

Organic P settling rate in the channel at 20ºC

If routing is performed on an hourly time step, the units of ptlp_stl are converted to 1/hr by the model.

ben_cst

Benthic source rate for arbitrary non-conservative constituents in the channel at 20ºC

cbn_bod_co

Carbonaceous biological oxygen demand deoxygenation rate in the channel at 20ºC

If routing is performed on an hourly time step, the units of cbn_bod_co are converted to 1/hr by the model.

no2n_no3n

Biological oxidation rate of NO2 to NO3 in the channel at 20ºC in well-aerated conditions

If routing is performed on an hourly time step, the units of no2n_no3n are converted to 1/hr by the model.

ptln_nh3n

Hydrolysis rate of organic N to ammonia in the channel at 20ºC

If routing is performed on an hourly time step, the units of ptln_nh3n are converted to 1/hr by the model.

air_rt

Reaeration rate in accordance with Fickian diffusion in the channel at 20ºC

If routing is performed on an hourly time step, the units of air_rt are converted to 1/hr by the model.

bact_die

Coliform die-off rate in the reach at 20ºC

ptlp_solp

Mineralization rate of organic P to dissolved P in the channel at 20ºC

If routing is performed on an hourly time step, the units of ptlp_solp are converted to 1/hr by the model.

n/a

Channel organic N concentration

real

ppm

0.0

0.0-100.0

Channel organic P concentration

real

ppm

0.0

0.0-100.0

Local algal settling rate in the channel at 20ºC

real

m/day or m/hr

1.0

0.15-1.82

Benthic source rate for dissolved P in the channel at 20ºC

real

mg P/m2*day or mg P/m2*hr

0.05

0.001-0.10

Benthic source rate for NH3-N in the channel at 20ºC

real

mg N/m2*day or mg N/m2*hr

0.50

0.0-1.0

Organic N settling rate in the channel at 20ºC

real

1/day or 1/hr

0.05

0.001-0.1

Organic P settling rate in the channel at 20ºC

real

1/day or 1/hr

0.05

0.001-0.10

Arbitrary non-conservative constituent settling rate in the channel at 20ºC

real

1/day

2.50

0.01-10.0

Benthic source rate for arbitrary non-conservative constituents in the channel at 20ºC

real

mg /m^2*day

2.50

0.01-10.0

Carbonaceous biological oxygen demand deoxygenation rate in the channel at 20ºC

real

1/day or 1/hr

1.71

0.02-3.40

Reaeration rate in accordance with Fickian diffusion in the channel at 20ºC

real

1/day or 1/hr

50.0

0.0-100.0

Rate of loss of CBOD due to settling in the channel at 20ºC

real

1/day or 1/hr

0.36

-0.36-0.36

Sediment oxygen demand rate in the channel at 20ºC

real

mg O2/m2*day or mg O2/m2*hr

2.0

0.0-100.0

Coliform die-off rate in the channel at 20ºC

real

1/day

2.0

0.05-4.0

Decay rate for arbitrary non-conservative constituents in the channel at 20ºC

real

1/day

1.71

0.0-10.0

Biological oxidation rate of NH3 to NO2 in the channel at 20ºC in well-aerated conditions

real

1/day or 1/hr

0.55

0.10-1.0

Biological oxidation rate of NO2 to NO3 in the channel at 20ºC in well-aerated conditions

real

1/day or 1/hr

1.10

0.20-2.0

Hydrolysis rate of organic N to ammonia in the channel at 20ºC

real

1/day or 1/hr

0.21

0.20-0.40

Mineralization rate of organic P to dissolved P in the channel at 20ºC

real

1/day or 1/hr

0.35

0.01-0.70

Qual2E light averaging option

integer

n/a

2

1-4

Qual2E option for calculating the local specific growth rate of algae

integer

n/a

2

1-3

Ratio of chlorophyll-a to algal biomass

real

μg chla/mg alg

50.0

10.0-100.0

Fraction of algal biomass that is N

real

mg N/mg alg

0.08

0.07-0.09

Fraction of algal biomass that is P

real

mg P/mg alg

0.02

0.01-0.02

Oxygen production rate per unit of algal photosynthesis

real

mg O2/mg alg

1.60

1.40-1.80

Oxygen uptake rate per unit of algae respiration

real

mg O2/mg alg

2.0

1.60-2.30

Oxygen uptake rate per unit of NH3-N oxidation

real

mg O2/mg N

3.50

3.00-4.00

Oxygen uptake rate per unit of NO2-N oxidation

real

mg O2/mg N

1.07

1.00-1.40

Maximum specific algal growth rate at 20ºC

real

1/day

2.0

1.00-3.00

Algal respiration rate at 20ºC

real

1/day or 1/hr

2.50

0.05-5.0

Fraction of solar radiation computed in the temperature heat balance that is photosynthetically active

real

fraction

0.30

0.0-1.0

Half-saturation coefficient for light

real

MJ/(m^2*hr)

0.75

0.223-1.135

Michaelis-Menton half-saturation constant for N

real

mg N/L

0.02

0.01-0.30

Michaelis-Menton half saturation constant for P

real

mg P/L

0.03

0.001-0.05

Non-algal portion of the light extinction coefficient

real

1/m

1.0

0.0-10.0

Linear algal self-shading coefficient

real

1/(m*ug chla/L)

0.03

0.006-0.065

Nonlinear algal self-shading coefficient

real

(1/m)(ug chla/L)^(-2/3)

0.05

0.0-1.0

Algal preference factor for ammonia

real

none

0.50

0.0-1.0

name
plt_n
plt_p
alg_stl
ben_disp
ben_nh3n
ptln_stl
ptlp_stl
cst_stl
ben_cst
cbn_bod_co
air_rt
cbn_bod_stl
ben_bod
bact_die
cst_decay
nh3n_no2n
no2n_no3n
ptln_nh3n
ptlp_solp
q2e_lt
q2e_alg
chla_alg
alg_n
alg_p
alg_o2_prod
alg_o2_resp
o2_nh3n
o2_no2n
alg_grow
alg_resp
slr_act
lt_co
const_n
const_p
lt_nonalg
alg_shd_l
alg_shd_nl
nh3_pref

o2_nh3n

Oxygen uptake rate per unit of NH3-N oxidation

alg_o2_resp

Oxygen uptake rate per unit of algae respiration

q2e_alg

Qual2E option for calculating the local specific growth rate of algae

Qual2E provides three different options for computing the algal growth rate:

  1. Multiplicative: The multiplicative option multiplies the growth factors for light, nitrogen and phosphorus together to determine their net effect on the local algal growth rate. This option has its biological basis in the multiplicative effects of enzymatic processes involved in photosynthesis.

  2. Limiting nutrient: The limiting nutrient option calculates the local algal growth rate as limited by light and either nitrogen or phosphorus. The nutrient/light effects are multiplicative, but the nutrient/nutrient effects are alternate. The algal growth rate is controlled by the nutrient with the smaller growth limitation factor. This approach mimics Liebig’s law of the minimum.

  3. Harmonic mean: The harmonic mean is mathematically analogous to the total resistance of two resistors in parallel and can be considered a compromise between the multiplicative and limiting nutrient options. The algal growth rate is controlled by a multiplicative relation between light and nutrients, while the nutrient/nutrient interactions are represented by a harmonic mean.

nh3n_no2n

Biological oxidation rate of NH3 to NO2 in the channel at 20ºC in well-aerated conditions

If routing is performed on an hourly time step, the units of nh3n_no2n are converted to 1/hr by the model.

alg_n

Fraction of algal biomass that is N

chla_alg

Ratio of chlorophyll-a to algal biomass

lt_co

Half-saturation coefficient for light

slr_act

Fraction of solar radiation computed in the temperature heat balance that is photosynthetically active

alg_o2_prod

Oxygen production rate per unit of algal photosynthesis

ben_bod

Benthic oxygen demand rate in the channel at 20ºC

If routing is performed on an hourly time step, the units of ben_bod are converted to mg/m2*hr by the model.

const_p

Michaelis-Menton half-saturation constant for P

The Michaelis-Menton half-saturation constant for P defines the concentration of phosphorus, at which algal growth is limited to 50% of the maximum growth rate.

alg_p

Fraction of algal biomass that is P

nh3_pref

Algal preference factor for ammonia

alg_grow

Maximum specific algal growth rate at 20ºC

If routing is performed on an hourly time step, alg_grow is converted to 1/hr by the model.

alg_shd_l

Linear algal self-shading coefficient

o2_no2n

Oxygen uptake rate per unit of NO2-N oxidation

plt_n

Channel organic N concentration

const_n

Michaelis-Menton half-saturation constant for N

The Michaelis-Menton half-saturation constant for N defines the concentration of nitrogen, at which algal growth is limited to 50% of the maximum growth rate.

alg_resp

Algal respiration rate at 20ºC

If routing is performed on an hourly time step, alg_resp is converted to 1/hr by the model.

lt_nonalg

Non-algal portion of the light extinction coefficient

alg_shd_nl

Nonlinear algal self-shading coefficient

q2e_lt

Qual2E light averaging option

Qual2E defines four light averaging options:

  1. Depth-averaged algal growth attenuation factor for light (FL) is computed from one daylight average solar radiation value calculated in the steady state temperature heat balance.

  2. FL is computed from one daylight average solar radiation value supplied by the user.

FL is obtained by averaging the hourly daylight values of FL computed from the hourly daylight values of solar radiation calculated in the steady state temperature heat balance.
  • FL is obtained by averaging the hourly daylight values of FL computed from the hourly daylight values of solar radiation calculated from a single value of total daily, photosynthetically active, solar radiation and an assumed cosine function.

  • The only option currently active in SWAT+ is 2.