STATEMENT OF WORK
REVIEW OF AGRICULTURAL WATER USE IN THE EAST CENTRAL FLORIDA TRANSIENT GROUNDWATER
FLOW MODEL (ECFT MODEL)
I.
INTRODUCTION/BACKGROUND
The St. Johns River, South Florida and Southwest Florida water management districts (WMDs) have
concluded that sustainable quantities of groundwater in central Florida are insufficient to meet all future
public water supply demands and that there is an immediate need to develop and implement supplemental
water supply projects.
The area of concern has been designated as the Central Florida Coordination Area (CFCA) and includes
Seminole, Orange and Osceola counties and south Lake County within the St. Johns River Water
Management District; Orange, Osceola and Polk counties within the South Florida Water Management
District (SFWMD); and Polk County within the Southwest Florida Water Management District.
To address these issues, the three WMDs developed an action plan for formal coordination and
communication in the CFCA where the boundaries of the three districts come together and where
permitting actions in one district can impact water resources and water users throughout the area. The
Action Plan addresses three areas of coordination — regulation, planning, and computer modeling and
predictive tools.
The primary planning tool to implement the Action Plan was the development and calibration of the
necessary hydrologic models to determine the sustainability of the groundwater supplies. Because of the
complexity of the effort and the desire for consensus among the stakeholders, including the WMDs, the
effort to implement the Action Plan is being modified to incorporate a more collaborative approach to
resolving the technical issues.
One of hydrologic modeling tools developed to evaluate the environmental impacts to the CFWI is the
East Central Florida Transient (ECFT) Model a numerical groundwater model developed under contract
with the USGS. The model is a finite difference model created with MODFLOW that uses many of the
commonly available packages to simulate the unsaturated and saturated flow components of the
hydrologic cycle in this region. In order to simulate groundwater and consider some aspects of surface
water processes in the model, a preprocessor was developed to calculate runoff and infiltration component
of the water budget using the Green and AMPT equations. This preprocessor incorporates rainfall and
irrigation applied to the land throughout the area.
The focus of this contract is on the agricultural withdrawals used for irrigation in the region that are
estimated for the purpose of inclusion in the groundwater model and the Green and AMPT preprocessor.
The SJRWMD developed a modified version of the AFSIRS code to estimate the irrigation demand for
the crops that were grown in the region during the calibration period (1995 to 2006) of the model.
AFISRS is an agricultural field scale model that requires basic information to estimate the agricultural
plant water needs. This model uses the following data that the SJRWMD put together for this purpose:
crop type, irrigation method, soils, rainfall, and evapotranspiration. SJRWMD has developed a GIS
database of agricultural irrigation locations and has field surveyed these locations for crop type and
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irrigation method. Soils information was taken directly from the SURRGO soils database. SJRWMD
incorporated a radar rainfall and GOES ET climate database which is a departure from the basic climate
data available in the AFSIRS program.
Irrigation amounts calculated using AFSIRS were further adjusted irrigation amounts were more
consistent with available metering data obtained through the Benchmark Farms (BMF) program at the
SJRMWD. The AFSIRS and BMF process has been the subject of discussion, as it returns results not
entirely consistent with the available literature values that represent average irrigation quantities under
long-term rainfall conditions versus irrigation quantities for specific years and rainfall conditions.
The Florida Department of Agriculture (FDAC) as part of the CFWI Hydrologic Assessment Team
(HAT) has determined that a review of the methods and results of this process is in order. The goal is to
develop confidence in the data being applied in the calibration of the ECFT groundwater model and to
insure its appropriateness and represents reasonable values for this category of water use in the region.
II.
OBJECTIVE(S)
The objective of this agreement is for the CONTRACTOR to provide a review of the approach used to
develop a data set of agricultural water use for input to the USGS East-central Florida Transient
Groundwater Flow model for the calibration period from 1995 to 2006, in support of the CFWI effort..
III.
SCOPE OF WORK
The CONTACTOR will review the available documents and data used in the development of the AFSIRS
process as well as the resulting output. The review will assess the appropriateness of the process and
output for representing the water requirements of the commodity crops in the region (???? Something
seems missing here) give the data availability for purpose of estimating this agricultural water use.
IV.
TASK IDENTIFICATION
TASK 1:
The CONTRACTOR will meet with District staff to discuss methods used and available data sources of
agricultural water use information within the CFCA. Staff will make available to the CONTRACTOR all
available information in electronic format for evaluation.
Task 2:
The CONTRACTOR will review the methodologies used to develop the data set utilized by the
Agricultural Field Scale Irrigation Requirements (AFSIRS) process that generates monthly irrigation
demands for various crops identified within the CFWI for the period 1995-2006.
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Task 3:
The CONTRACTOR will review the methodology used to adjust the AFSIRS based irrigation demands
as compared to SJRWMD Benchmark Farms data and SWFWMD meter data. In addition, the Contractor
will review the BMF and SWFMD metered data to determine if the BMF adjustment process is warranted
for the purposes of developing an agricultural water use data set for the ECFT groundwater flow model
for the period 1995-2006. The review will include evaluation of annual irrigation rates for the major
commodity crops as wells as the monthly distribution of irrigation as it relates to the output of AFSIRS.
Climatic variation during the calibration period should be considered to determine if irrigations rates are
consistent with know agricultural practices during this period.
Task 4:
The CONTRACTOR will prepare a draft memorandum summarizing the findings of the review and make
it available to staff for comment. The CONTRACTOR will meet with staff to discuss comments and
clarify any points of concern.
Task 5:
The CONTRACTOR will prepare a final memorandum summarizing the findings of the review and make
recommendations for alternative procedures to develop monthly water use data for agricultural crops
spatially within the CFCA on a monthly basis for the period 1995-2006.
V.
TIME FRAMES/DELIVERABLES
The expiration date of this AGREEMENT is September 30, 2012
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