Okeechobee Update to EAMMOD

Funded by South Florida Water Management District

Introduction

The Everglades Agricultural Area MODel (EAAMOD) was specifically developed for high water table, multi-layered soils.  Soils likes the coastal plain flatwoods and the flat organic soils (Histosols) found in the Everglades Agricultural Area are well represented by the model.  The model simulates nitrogen and phosphorus species in both surface and subsurface discharge. 

Computer simulation can be a cost-effective way to assess water quality impacts over a wide range of temporal and spatial variables like weather, land use, soil, and management.  Water quality simulation models attempt to model both the water and nutrient movement, and while not always accurate, are an excellent tool in evaluating the marginal effect of Best Management Practices (BMPs).

Project Objective

The overall objective was to make EAAMOD a useful management tool for assessing the water quality (phosphorus is a primary focus) for farming conditions found in the Okeechobee basin.  The specific objectives of this study were:

• Expand the model user interface and databases for the soils and crops (pasture grasses, vegetables, and citrus) found for the Okeechobee basin.
• Add a surface applied organic pool to the model to better represent the manure from grazing animals and bio-solids applications.
• Link EAAMOD-field submodel to the Watershed Assessment Model (WAM) in order to simulate farm-scale accumulative water impacts.

Model Structure

The EAAMOD-FIELD model is a two-dimensional model that predicts flow, N, and P losses from a field.  The hydraulic flow model divides the field into four vertical layers within the soil profile and numerous horizontal cells across the field.  These zones can vary in both hydraulic conductivity, P retention, and oxidative state.  Any one or two of the cells can be a ditch with a variety of discharge structures such as flashboard riser, culverts, weirs, and pumps.  Note an automatic board control algorithm is available for the flashboard riser control.  The vertical impeding layer can be used to represent the Spodosols (organic hardpan) soils very well. 

The P model tracks the size of the mineral and organic N and P pools, including adsorbed and soluble/labile P.   Modeled P processes include mineralization and sorption-desorption while inputs of P can be from fertilizer, rainfall, and irrigation water.  Further details of the model can be found in Bottcher et al. (1998).   Full documentation of EAAMOD and the existing model is available for download off this website (see download option below).

Model Interface

EAAMOD-FIELD is a complex model that uses input files to change the parameters for the model.  These files allow the model to be used over a wide range of farming practices encountered in the EAA, but they are difficult for the casual user to change.  When the files are manipulated manually, an engineer or scientist experienced in modeling is required to use the model effectively and appropriately.

A user-friendly Windows-based interface that was upgraded for this project is shown below.  The interface is designed to make the model useable by farmers, agricultural technical advisors, and governmental personnel.  It provides access to pre-defined EAA farming scenarios and the ability to manipulate the soils, phosphorous, and management parameters.  Farming scenarios include a number of soils, crops, water management options, and a large record of weather data.  Each farm/crop/soils option can be further customized by the use of a management calendar that allows day by day or minute by minute refinement of management activities.  Output is presented graphically or in tables and extensive on-line help is available.  Examples of some of the interface screens are given below.

Main Screen

Sugar Cane Management Screen

Output Screen

References

A.B. Bottcher, N.B. Pickering, and A.B. Cooper, 1998.  EAAMOD-FIELD: A flow and phosphorus model for high water tables.  Paper prepared for the 7th International Drainage Symposium, Orlando, Florida, March 8-11.