k_prior: Generate prior distributions for k using stream geometry

In mtalluto/NSmetabolism: N-Station Stream Metabolism Modelling

Description

Generate prior distributions for k using stream geometry

Usage

k_prior(slope, velocity, depth = NA, discharge = NA, eqn = 1:7, nsim = 5000)

Arguments

slope	Stream slope (unitless; meters of height/meters of length)
velocity	In meters/second
depth	In meters
discharge	In m^3/sec
eqn	Which equation(s) to use
nsim	Number of simulations used for the standard deviation

Details

Generates means and standard deviations for half-normal priors for k600. This function uses the 7 equations from Raymond et al 2012. Which equation to use is a user choice, though there are some recommendations from Raymond to guide the choice (see below, and see Raymond et al 2012).

Rayment et al provide standard deviations for the parameters, but do NOT provide information on correlations among parameters; therefore this function treats them as independent (which will generally produce larger prior standard deviations). The standard deviation is chosen by simulating across independent parameter combinations.

Slope and velocity are required for all equations. Discharge and depth are required for equations 6 & 7 (discharge) and 1, 2, and 7 (depth); for equations 3-5 they can safely be left set to NA.

Guidelines for k: Best for small streams: includes depth, more preditive, but less general, not in accordance with theory eq 1, 2

More general (includes only slope & velocity), but maybe less precise eq 3-5

Equation 6 also includes discharge, predictability is lower, an alt to 3-5 Equation 7 includes depth and discharge; theoretically problematic, but prediction might be better for small streams

Value

If a single equations is given, a 2-column matrix giving the mean and standard deviation for k for each value in slope, velocity, etc. Otherwise a list of such matrices, one for each equation in eqn. Units for k are meters/day

References

Raymond, P.A. et al. (2012). Scaling the gas transfer velocity and hydraulic geometry in streams and small rivers. Limnol. Oceanogr., 2, 41–53.

Examples

sl = 0.05
v = 0.5
q = 1
d = 0.5
eq1 = k_prior(sl, v, q, d, eqn = 1, nsim=3) ## normally run thousands of sims

mtalluto/NSmetabolism documentation built on May 3, 2021, 7:51 p.m.