Modeling lake data

Numerous lakes are monitored each year through the MPCA’s lake monitoring activities, and those of its partners (county government, watershed districts, lake associations, soil and water conservation districts, nonprofits, and tribal entities) and citizen volunteers. Water quality studies typically include modeling to interpret monitoring data and predict changes in water quality based on various characteristics of the lake and its watershed.  

This web page provides access to two models commonly used in lake water quality studies at the MPCA:

  • MINLEAP is a screening tool used to model individual lakes when minimal data are available.
  • BATHTUB is used on more complex projects involving reservoirs, chains of lakes or situations where pollutant loading information is available. 

The Minnesota Lake Eutrophication Analysis Procedure (MINLEAP) was developed by MPCA staff based on an analysis of data collected from minimally-impacted lakes within each of Minnesota’s four ecoregions.  The program is used as a starting point for lake water quality studies and is intended primarily as a screening tool for estimating lake conditions with minimal input data and for identifying "problem" lakes.

The program formulates water and phosphorus balances and uses a network of empirical (regression equations) models to predict lake phosphorus, chlorophyll-a, and transparency (Secchi) values based upon lake surface area, mean depth, watershed area and the ecoregion in which the lake is located.

Program output includes:

  • statistical comparisons of observed and predicted phosphorus, chlorophyll-a, and transparency values
  • uncertainty estimates
  • estimates of chlorophyll-a interval frequencies (nuisance frequencies) for observed and predicted conditions.

The model should be used to approximate lake water quality expectations, acknowledging that individual lakes may deviate greatly from regionally defined patterns.

This model was developed by Bruce Wilson (MPCA) and Dr. William Walker, Jr. in 1988, and was converted to a Windows format in 1997 by Wade Gillingham (MPCA). It is described in greater detail in Wilson, C. B. and W.W. Walker Jr. 1989.

Development of lake assessment methods based upon the aquatic ecoregion concept. Lake and Reservoir Management. 5(2): 11-22. The current version of MINLEAP (1.xx) is a 16-bit program developed on Windows 95 and Beta tested on Windows 3.1. This version should be compatible with both operating systems and newer versions of Windows as well. MINLEAP is distributed as a self-extracting executable file:


  • Create a new directory from File Manager or Explorer, or from the DOS command line by typing MD [directory name]
  • Copy the file to the new directory.
  • Execute the program by double clicking SETUP.EXE from Explorer or File Manager, or type SETUP.EXE from the DOS command line.

The file should self-extract into four files:

  • MNLPXXXX.EXE — the program file; XXXX stands for the current version number.
  • MINHELP.HLP — the program help file
  • EAGLE.MNL — a test case
  • UPGRADES.TXT — a list of upgrades made to the original version


To run the program, simply double click MNLPXXXX.EXE from Explorer or File Manager, or create a new program icon: 

Windows 3.1

  1. create a new group by clicking [File] [New], or open an existing group.
  2. open the file manager
  3. position the windows so both the program group and file manager can be seen.
  4. drag the MNLPXXXX.EXE file to the new program group.

Windows 95

  1. open Microsoft Explorer
  2. drag MNLPXXXX.EXE to the wallpaper


MINLEAP is intended for research and not for business application.

MINLEAP is provided "AS IS" without warranty of any kind, either express or implied, including fitness for a particular purpose. In no event shall the authors of this software be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.

MINLEAP is routinely used in MPCA’s lake water quality studies as a starting point for modeling efforts. For more complex projects, that may include observed data from several adjoining lake basins, chains of lakes, and/or where tributary loading data are available, a more complex tool like the BATHTUB model is recommended.  

HTML icon Water quality models and tools: BATHTUB

BATHTUB is an empirical lake eutrophication model developed by Dr. William Walker, Jr. for the USACE in the 1980s based on data from USACE reservoirs. As such, it is a good tool for modeling reservoirs, chains of lakes, lakes with multiple inlets or situations where more detailed nutrient and water budgets are required. BATHTUB is used routinely in developing nutrient-based Total Maximum Daily Load studies. A related data-reduction tool entitled FLUX is routinely used for reducing tributary flow and concentration data and making unbiased estimates of pollutant loading.

BATHTUB has undergone several updates since it was first developed. Dr. David Soballe, of the USACE, provides training, maintains the model, and distributes current versions of FLUX and BATHTUB.

  • MINLEAP application or program problems: Wade Gillingham, MPCA, 800-657-3864 (Greater Minn.), 651-296-6300 (Twin Cities Metro Area)
  • BATHTUB application or training opportunities: Dr. David Soballe, USACE,