Oklahoma-BATHTUB

okBATHTUB

Empirical reservoir eutrophication modelling in R.

okBATHTUB implements steady-state water quality predictions for reservoirs using the Walker BATHTUB Model 1 (second-order available-phosphorus sedimentation) as the default retention model, with the simpler Vollenweider (1976) / Larsen-Mercier (1976) form available as an alternative. The package predicts in-lake total phosphorus, total nitrogen, chlorophyll-a, and Secchi depth from tributary nutrient and hydraulic loading inputs, and computes Carlson (1977) Trophic State Indices.

Optional Oklahoma-specific chlorophyll-a and Secchi regression coefficients are bundled, calibrated from publicly available state lake monitoring data, but the package is fully usable for reservoirs anywhere.

okBATHTUB is designed to complement watershed loading models such as SWAT and HAWQS in a two-model nutrient management workflow.

Installation

# install.packages("remotes")
remotes::install_github("0011235813/Oklahoma-BATHTUB", subdir = "okBATHTUB")

Documentation site: https://0011235813.github.io/Oklahoma-BATHTUB/

Quick start

library(okBATHTUB)

result <- ok_load(
    inflow_m3yr   = 45e6,      # tributary inflow
    tp_inflow_ugl = 120,       # flow-weighted mean TP
    tn_inflow_ugl = 1800       # flow-weighted mean TN
  ) |>
  ok_hydraulics(
    surface_area_ha = 890,     # normal pool surface area
    mean_depth_m    = 4.2      # mean depth at normal pool
  ) |>
  ok_retention() |>            # Walker BATHTUB Model 1
  ok_inlake()    |>            # Mass balance + Chl-a + Secchi
  ok_tsi()                     # Carlson Trophic State Index

summary(result)

Three retention model families

Set	Retention	Chl-a / Secchi
`"walker"` (default)	Walker BATHTUB Model 1	Walker (1985) national
`"vollenweider"`	Vollenweider/Larsen-Mercier (= BATHTUB Model 5)	Walker (1985) national
`"oklahoma"`	Walker BATHTUB Model 1	Oklahoma ecoregion-specific

The default is Walker Model 1 because it is the canonical default of the BATHTUB program and is calibrated to U.S. Army Corps of Engineers reservoir data, which matches the management context for most U.S. reservoirs. Vollenweider / Larsen-Mercier is provided for users who want a parsimonious single-parameter retention model when ortho-P / total-P partitioning is unknown.

Pipeline functions

Function	Purpose
`ok_load()`	Assemble tributary load inputs
`ok_load_multi()`	Aggregate multiple tributaries automatically
`ok_hydraulics()`	Add reservoir morphometry; compute residence time
`ok_retention()`	TP / TN retention coefficients
`ok_inlake()`	Mass balance, chlorophyll-a, Secchi depth
`ok_tsi()`	Carlson Trophic State Indices
`ok_segment()` /	Multi-segment reservoir modelling
`ok_segment_chain()`
`ok_scenario()` /	Load reduction scenario analysis
`ok_scenario_sweep()`
`ok_reservoir()` /	Look up Oklahoma reservoir morphometry
`ok_reservoirs`	Bundled dataset (40 reservoirs, 7 ecoregions)
`ok_lake_ecoregion()` /	Look up an Oklahoma lake’s EPA L3 ecoregion
`ok_lake_ecoregions`	Bundled dataset (214 lakes, ecoregion + monitoring)
`ok_plot_response()` /	Visualizations (require `ggplot2`)
`ok_plot_scenario()` /
`ok_plot_segments()` /
`ok_plot_tsi()`

Vignettes

vignette("getting-started", package = "okBATHTUB")
vignette("oklahoma-workflow", package = "okBATHTUB")
vignette("hawqs-linkage", package = "okBATHTUB")

Caveats

All predictions are steady-state. Inputs should represent long-term annual or seasonal averages, not single-event values.
The bundled ok_reservoirs dataset is a compilation of public-domain morphometric data; for decision-relevant applications, verify against the most current authoritative source for the specific reservoir.
The Oklahoma chlorophyll-a and Secchi regressions are empirical and show substantial residual scatter (typical $R^2$ values of 0.35-0.60). Treat point predictions as central estimates within a $\pm$ factor-of-2 uncertainty range.

Origin and independence

okBATHTUB was developed independently by Jordon Henderson on personal time and personal equipment. It is released under the MIT license as personal-capacity open-source research software. It is not a product of, sponsored by, or affiliated with any employer or government agency, and does not represent or imply endorsement by any agency. All data used to calibrate the bundled Oklahoma coefficients are publicly available state monitoring data.

References

Carlson, R.E. (1977). A trophic state index for lakes. Limnology and Oceanography, 22(2), 361-369.
Larsen, D.P. & Mercier, H.T. (1976). Phosphorus retention capacity of lakes. Journal of the Fisheries Research Board of Canada, 33(8), 1742-1750.
Vollenweider, R.A. (1976). Advances in defining critical loading levels for phosphorus in lake eutrophication. Memorie dell’Istituto Italiano di Idrobiologia, 33, 53-83.
Walker, W.W. (1985). Empirical methods for predicting eutrophication in impoundments; Report 3, Phase III: Model refinements. Technical Report E-81-9, U.S. Army Engineer Waterways Experiment Station.
Walker, W.W. (1996). Simplified Procedures for Eutrophication Assessment and Prediction: User Manual. Instruction Report W-96-2, U.S. Army Engineer Waterways Experiment Station.