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Water Quality/Quantity

BMPs for Indian River

Area Citrus Groves

i May, 2000

Water Quality/Quantity BMPs

for Indian River Area Citrus Groves

Edited by B. Boman, C. Wilson, and J. Hebb

May 2000

The Indian River Citrus League led the initiative to produce this BMP document. Represen- tatives of the following organizations participated in the document’s development and provided

valuable input, discussion, feedback, and review as part of the process.

• Florida Citrus Mutual
• Florida Department of Agriculture and Consumer Services
• Florida Department of Environmental Protection
• Florida Farm Bureau
• Florida Fruit and Vegetable Association
• Indian River Citrus League
• Indian River Soil and Water Conservation District
• South Florida Water Management District
• St. John’s River Water Management District
• St. Lucie River Initiative
• St. Lucie Soil and Water Conservation District
• University of Florida, Indian River Research and Education Center
• Univ.of Florida, Indian River County Cooperative Extension Service
• University of Florida, St. Lucie County Cooperative Extension Service
• USDA Natural Resource Conservation Service

ii May, 2000

REGISTRATION

This document is a collection of Best Management Practices that are directed at enhancing and protecting the water resources of the Indian River Lagoon and St. Lucie Estuary Watersheds. It is recognized by all the groups that participated in the development of this document that this collection of BMPs will need to be revisited, reviewed, and modified over time as new scientific data becomes available. Therefore, all users are encouraged to register their copy of this manual. Registered users will be mailed all addendums and revisions as they become available. A registration form is included in the front of this document. If missing, contact the Indian River Citrus BMP Steering Committee at the address below to register.

The Indian River Citrus BMP Steering Committee will meet periodically to act on suggestions for addendums and/or revisions to the document. Any changes to the docu- ment will be announced at the annual Indian River Citrus Seminar. To provide input or to obtain the latest addendums to the Water Quality/Quantity BMPs for Indian River Area Citrus Groves document, contact:

Indian River Citrus BMP Steering Committee c/o Indian River Research and Education Center 2199 South Rock Road Fort Pierce, FL 34945- 561-468-

DISCLAIMER

Mention of a specific product or company is for information purposes only and does not constitute an endorsement or criticism of that product or company.

This publication was funded in part by a Section 319 Nonpoint Source Management Program Grant funded by the United States Environmental Protection Agency.

May 2000

iii May, 2000

ACKNOWLEDGMENTS

This document is the product of many, many hours of effort by numerous people. Doug Bournique and Michael Minton are recognized for outlining the importance of developing BMPs and getting the citrus industry to be at the forefront of the efforts to improve water quality in the St. Lucie Estuary and the Indian River Lagoon. Stan Carter, representing the Indian River Citrus League Production Committee has guided the process since inception and kept the committees focused and productive. Rich Budell, Ken Kuhl, John Folks, and Jane Foos from FDACS provided the background and enthusiasm to get the process rolling. John D’Albora, Stan Carter, Paul Driscoll, Lex Krumhout, Phil Strazzulla, Talmage Rogers and Mike Ziegler, were instrumental in developing the initial BMP listings.

Thanks is extended to the following individuals who assisted in the development, proof- reading, and assembly of this document: Liberta Scotto, Mike Ziegler, Jane Foos, Donna Smith. Paul Whalen and Boyd Gunsalus developed the initial sections for the final docu- ment. Sandra Phares and Audrey Beany are thanked for their efforts in preparing the manuscript for publication.

Special thanks is extended to the BMP subcommittee chairs: Stan Carter, John D’Albora, Paul Driscoll, Travis Murphy, and Mike Ziegler for their tireless efforts to guide the BMP development process. The process could not have been completed without the dedicated efforts of the many participants of the subcommittees who attended the meet- ings and provided written and verbal discussions of the proposed BMPs. Dr. Mike Thomas from FDEP secured the funding required for printing the document, performed final editing and formatting on the manuscript, and coordinated the printing and distribution of the document.

SUB-COMMITTEE PARTICIPANTS

Water Volume Chair: Travis Murphy, River Country Citrus Brian Boman, UF-IFAS Doug Bournique, IR Citrus League Hugo Carter, Martin County Paul Driscoll, Driscol Citrus Service, Inc. Boyd Gunsales, SFWMD Jack Hebb, UF-IFAS Dick Hellstrom, LBFH Don Loving, SFWMD Linda McCarthy, FDACS Victor McDaniel, SJRWMD Esa Ontermaa, A. Duda and Sons Tom Stopyra, Diamond R Gene Swearingen, Consolidated Citrus Ed Weinberg, St. Lucie River Initiative Paul Whalen, SFWMD

Sediment Chair: Paul Driscoll, Driscoll Citrus Service Brian Boman, UF, IFAS Jim Collins, St. Lucie River Initiative Boyd Gunsalus, SFWMD Jack Hebb, UF, IFAS Esa Ontermaa, A. Duda and Sons, Inc. Liberta Scotto, UF, IFAS Donna Smith, USDA-NRCS Pete Spyke, Arapaho Citrus Bob Ulevich, SFWMD Don West, St. Lucie County Paul Whalen, SFWMD Chris Wilson, UF, IFAS

Chris Wilson, UF-IFAS Mike Ziegler, Ag. Resource Mgmt.

iv May, 2000

Pesticides Chair: Stan Carter, McAuthur Groves Calvin Arnold, UF-IFAS Brian Boman, UF, IFAS Paul Driscoll, Driscoll Citrus Service, Inc. Jane Foos, FDACS Greg Graves, FDEP Mary Ann Gosa, Florida Farm Bureau Boyd Gunsalus, SFWMD Jack Hebb, UF-IFAS Extension Tom Hill, Florida Farm Bureau Carol Johnson, FDACS Victor McDaniel, SJRWMD Esa Ontermaa, A. Duda and Sons Richard Pfeuffer, SFWMD Ron Polumbo, FMC, Inc. Max Quackenbos, St. Lucie River Initiative Gary Roderick, FDEP Dominick Scotto, D.L. Scotto Co., Inc. Liberta Scotto, UF, IFAS Patti Sime, SFWMD Donna Smith, USDA-NRCS Tom Stopyra, Diamond R Fertilizer, Inc. Ed Stover, UF-IFAS IRREC Paul Whalen, SFWMD Chris Wilson, UF-IFAS Mike Ziegler, Ag Resources Mgmt.

Nutrients Chair: Mike Ziegler, Ag. Resource Mgmt. Robert Adair, Kerr Center Calvin Arnold, UF-IFAS Brian Boman, UF-IFAS Doug Bournique, IR Citrus League David Calvert, UF-IFAS Paul Driscoll, Driscoll Citrus Service Al Goldstein, SFWMD Greg Graves, FDEP

Boyd Gunsalus, SFWMD Kevin Henderson, St. Lucie River Initiative Tom Hill, Florida Farm Bureau Charles Holtzhower, Tampa Farm Service Carol Johnson, FDACS Greg Knecht, FDEP Lex Kromhout, IR Citrus League Victor McDaniel, SJRWMD Esa Ontermaa, A. Duda and Sons, Inc. Gary Roderick, FDEP Liberta Scotto, UF-IFAS Kim Shugar, FDEP Peter Spyke, Arapaho Citrus Ruth Stanbridge, Indian River Co. Comm. Tom Stopyra, Diamond R Gene Swearingen, Consolidated Citrus Winston Tooke, USDA-NRCS Marc Von Canal, SJRWMD Paul Whalen, SFWMD Chris Wilson, UF-IFAS Mike Ziegler, Ag Resources Management

Aquatic Weeds Chair: John D’Albora, J. D’Albora Co Michael Adams, Adams Ranch Calvin Arnold, UF-IFAS Brian Boman, UF-IFAS Boyd Gunsalus, SFWMD Jack Hebb, UF-IFAS Johnny Moose, Citrus Grower Esa Ontermaa, A. Duda & Sons Talmage Rogers, Rogers Bros. Vernon Vandiver, UF-IFAS Paul Whalen, SFWMD Chris Wilson, UF-0FAS Michael Ziegler, Ag. Resources Mgmt

v May, 2000

TABLE OF CONTENTS

Page

AGENCY PARTICIPANTS ......................................................................................... i

ACKNOWLEDGMENTS ............................................................................................ iii

SUB-COMMITTEE PARTICIPANTS ......................................................................... iii

INTRODUCTION ....................................................................................................... 1

BMP Development .................................................................................................. 1 Steering Committee ................................................................................................. 3 Background ............................................................................................................. 3 St. Lucie Estuary Watershed .................................................................................... 3 Citrus Production in the Indian River Watershed ....................................................... 6 Environmental Concerns in the SLE and IRL ............................................................ 7 Regional Attenuation Facilities .................................................................................. 8 Requirements for BMP Development ....................................................................... 8 Implementation of BMPs ......................................................................................... 9 BMP Reference Documents ..................................................................................... 10

CHAPTER

A. WATER VOLUME ......................................................................................... A-#

Purpose ........................................................................................................ 1 Brief Description of BMPs ............................................................................ 3 Expanded Description of BMPs Water Table Monitoring ....................................................................... 6 Irrigation Water Requirements .............................................................. 9 Drainage ............................................................................................ 13 Mobile Irrigation Lab ......................................................................... 16 Soil Moisture Measurement ............................................................... 18 Conservation Plan .............................................................................. 21

B. SEDIMENT TRANSPORT ............................................................................. B-#

Purpose ....................................................................................................... 1 Brief Description of BMPs ........................................................................... 2 Expanded Description of BMPs Riser-Board Water Control Structures ................................................... 5 Settling Basins (Collector Ditches) .......................................................... 6 Ditch Construction ................................................................................. 8 Stabilize Bare Soils ................................................................................ 9 Ditch Bank Vegetation Maintenance ....................................................... 10

C. PESTICIDES ................................................................................................... C-#

 - vi May, 

• Ditch Cleaning Program
• Ditch-Bank Contours
• Protect Ditch Banks
• Vegetative Stabilization (water furrows)
• Herbicide Applications (water furrows)
• Settling Basins (water furrows)
• Purpose
• Brief Description of BMPs
  • Reduce Spray Drift Expanded Description of BMPs
  • Turn Sprayer Nozzles Off at Row Ends
  • Equipment Calibration and Maintenance
  • Integrated Pest Management
  • Pesticide Spill Management
  • Precision Application
  • Maintain Soil pH
  • Read and Understand the Label
  • Pesticide Application Equipment Washwater
  • Mixing and Loading Activities (Permanent Location)
  • Field Mixing and Nurse Tanks
  • Portable Mixing Centers
  • Pesticide Container Management
  • Pesticide Selection
  • Pesticide Record Keeping
  • Pesticide Storage
  • Pesticide Waste Management (Summary)
• Purpose D. NUTRIENTS D-#
• Brief Description of BMPs
  • Nutrient Management Expanded Description of BMPs
  • Nutrient Management-Utilization of Waste Resources
  • Tissue and Soil Analysis
  • Use Appropriate Application Equipment
  • Apply Materials to Target Sites
  • Fertilizer Storage
  • Spilled Fertilizers
  • Use Caution when Loading Near Ditches, Canals, and Wells
  • Use Backflow Prevention Devices
  • Incorporate Organic Materials
  • Well Protection
  • Use Appropriate Sources and Formulations

vii May, 2000

E. AQUATIC PLANTS .............................................................................................. E-#

Purpose ....................................................................................................... 1 Brief Description of BMPs ........................................................................... 2 Expanded Description of BMPs Debris Baffle ......................................................................................... 3 Ribbon Barriers ..................................................................................... 4 Hyacinth Barrier .................................................................................... 5 Mechanical Aquatic Weed Removal ....................................................... 6 Post Pump Settling Basin (PPSB) ........................................................... 7 Biological Control-Triploid Grass Carp .................................................. 8 Biological Control-General ..................................................................... 10 Herbicide Applications to Control Aquatic Weeds .................................. 11 Aquatic Weeds ...................................................................................... 13 Aquatic Herbicide Toxicity ..................................................................... 20 Aquatic Herbicides ................................................................................ 21

Appendix 1. References Appendix 2. Important Telephone Numbers (Emergency Reporting) Appendix 3. Non-Emergency Numbers Appendix 4. Spill Reporting Requirements

Page 1 May, 2000

Water Quality/Quantity BMPs

for Indian River Area Citrus Groves

INTRODUCTION:

BMP Development The development of best management practices (BMPs) for citrus production in the Indian River Area originated from a June 1998 letter from the South Florida Water Management District’s executive management to the Commissioner of the Florida Department of Agriculture and Consumer Services (FDACS). This letter initiated a process to develop acceptable and effective BMPs aimed at improving the quality, quantity, and timing of water draining into the St. Lucie Estuary (SLE) and the Indian River Lagoon (IRL).

During December 1998, the Production Committee of the Indian River Citrus League in con- junction with FDACS and UF-IFAS took the initiative to begin the development of BMPs for Indian River Area citrus groves. The objective was to develop BMPs that have the potential to improve water quality and reduce the quantity of runoff water draining into the SLE and the IRL. The initial product of these efforts was a draft BMP listing dated January 29, 1999. This draft BMP document was presented to interested groups and agencies in a meeting on March 26, 1999, at the Indian River Research and Education Center.

Following the March meeting, five subcommittees were appointed by the Steering Committee and charged to further develop and refine the BMPs. The subcommittees began meeting in August 1999, with most of the subcommittees meeting several times throughout the fall of 1999. A draft document dated December 6, 1999, was the product of discussions and consensus reached at these meetings. This revised draft BMP document was circulated to all subcommit- tee participants for critical review. Each subcommittee met during the second week of January 2000 to further refine and finalize the document for presentation and adoption by the Steering Committee.

This document should be viewed as a living document. The development and implemen- tation of BMPs is an ongoing process to identify and develop improved, science-based BMPs to enhance and protect the Indian River Lagoon and St. Lucie Estuary Resources. It is recognized by all the groups that participated in the development of this document that this collection of BMPs will need to be revisited, reviewed, and modified over time and as new information becomes available.

Steering Committee In January 1999, a steering committee was established to guide the development of the BMPs for Indian River Area citrus. The Steering Committee consisted of representatives from the following organizations:

• Florida Department of Agriculture and Consumer Services
• Florida Department of Environmental Protection

Page 2 May, 2000

• Florida Farm Bureau
• South Florida Water Management District
• Indian River Citrus League
• U. S. Department of Agriculture - Natural Resources Conservation Service
• University of Florida, IFAS - Indian River Research and Education Center

Steering Committee Members

Co-Chairs: Chuck Aller, FDACS Calvin Arnold, UF-IFAS

Members: Brian Boman, UF-IFAS Mary Ann Gosa, Florida Farm Bureau Doug Bournique, IR Citrus League Ken Kuhl, FDACS Jerry Brooks, FDEP Linda McCarthy, FDACS Rich Budell, FDACS Michael Minton, SFWMD Stan Carter, IR Citrus League Donna Smith, USDA-NRCS John Folks, FDACS Mike Ziegler, Ag Resource Management

The Steering Committee established immediate and long-term goals directed at improving water quality and reducing water quantity impacts for the SLE and IRL. The goals are to:

Immediate Goal: Identify, evaluate, develop and implement BMPs based on the best information available, that will protect and enhance the Indian River Lagoon and St. Lucie Estuary’s Resources, while maintaining an economically viable citrus industry.

Long-Term Goal: Implement an ongoing process to identify and develop improved, science-based BMPs to enhance and protect the Indian River Lagoon and St. Lucie Estuary’s Resources.

Consistent with the goals set forth by the Steering Committee, this document outlines a variety of BMPs which have the potential to improve water quality, reduce the quantity of fresh water discharges, and manage the timing of surface water discharges into the SLE and the IRL.

In addition to the BMP subcommittees, a Monitoring Subcommittee was appointed by the Steering Committee to evaluate data that have been collected in the past related to the BMP objectives. An additional objective of the Monitoring Committee is to develop a list of further research that is necessary to characterize the impacts of citrus production in the IRL and SLE basins, evaluate effectiveness of BMPs presented in this document, and to identify research that should be conducted to scientifically evaluate other potential BMPs.

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Background Many activities such as urban development, agriculture, industry, and regional water manage- ment have all impacted the waters of the IRL and SLE. Over the years, several projects have been initiated to address environmental impacts in the IRL and SLE. Numerous efforts and activities have been initiated and are currently underway to improve surface water discharges to the SLE and IRL. There is no single project or effort that will eliminate all human impacts to the estuary and lagoon. Improvements will come through incremental program achievements, projects, and efforts that reduce the volume of water and loadings of constituents that degrade water quality.

These incremental achievements and activities cover all land uses from agriculture to urban, and include a variety of efforts such as education, water conservation programs, mobile irrigation labs, surface water permit design criteria, regional reservoirs, urban stormwater retrofit projects, and BMPs. The BMPs that have been developed in this document are for the entire Indian River Citrus Area. However, since the development of these BMPs was initiated by concerns in the SLE, a brief history of the watershed and the process of development is in- cluded.

St. Lucie Estuary Watershed The St. Lucie Estuary watershed covers approximately 288,000 acres which are ultimately tributary to the Indian River Lagoon (Fig. 1). Approximately 300,000 people reside within the watershed. The general land use area within the watershed is approximately 82% agriculture and 18% urban (Table 1 and Fig. 2).

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Figure 1. Sub-basins within the St. Lucie Estuary watershed.

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Figure 2. Land uses in the St. Lucie Estuary Basin.

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Table 1. Distribution of land uses in the St. Lucie Estuary watershed (288, total acres).

Area type Acres Percent of total area Citrus 120,000 42 Pasture 100,000 35 Urban 53,000 18 Row Crops 15,000 5

Citrus Production in The Indian River Watershed The sub-tropical nature of the Indian River region requires intense agricultural management to ensure that the citrus produced has the quality to succeed in an increasingly competitive global market. As a result, production costs in the Indian River Area are among the highest of any citrus producing area in the world. Through research and innovation, Indian River growers have over- come the limitations of poor quality soils, excess rainfall, high water tables, saline irrigation waters, annual drought periods, and unique bacterial and fungal diseases and insect pests, to produce the world’s best grapefruit.

Historically, most of the land in the region was submerged during the rainy season. In the early 1900s, several drainage districts were formed under Chapter 298 of the Florida Statutes. Under this law, the districts could only spend money on drainage projects. Beginning in the 1940s, structures were constructed in district canals to control water. One of the benefits of this effort was to retain ground water and prevent salt water intrusion.

As the Indian River citrus industry expanded from the naturally well- drained locations to the poorly drained soils further west (Fig. 3), it became

Figure 3. Location of the 215,000 acres of citrus (95% of Indian River area total) located in Martin, St. Lucie, and Indian River counties.

Page 7 May, 2000

necessary to construct beds in order for the trees to develop a rooting depth sufficient to support commercial production levels. Initially the beds were constructed with an open end to allow drainage into adjoining ditches. The rapid drainage of excess rainfall resulted in erosion and runoff that was not beneficial to the grove or the environment. As a result, the USDA- NRCS encouraged growers to install tiles or pipes at the end of water furrows to slow drainage rates and limit soil erosion. The water furrow pipe, together with a well-maintained cover crop, have been innovations that reduced many of the soil erosion problems in citrus groves.

One of the most significant examples of the environmental benefits derived from research has been the massive conversion from flood irrigation to microirrigation systems. About 85% of the 225,000 acres of citrus in the Indian River Area have been retrofitted (old groves) or developed (new groves) with microirrigation systems. The benefits of reduced water requirements have enhanced citrus production and provided conservation benefits for other agricultural and non- agricultural water users in the region. All of the Indian River Area groves planted in the last decade have been developed with on-site retention, which limits both the rate and volume of surface water discharged. This practice requires large land areas plus additional investment for construction and maintenance of ditches, pumps, dikes, control structures, and access roads.

Environmental Concerns in The SLE and IRL Recent concerns with the health and sustainability of plant and animal species in the Indian River Lagoon (IRL) and associated tributaries have highlighted the need for all users (agriculture, urban, golf courses, industrial, and public lands) to minimize the adverse environmental effects of their operations. The most pressing concerns identified as injurious to the Indian River Lagoon’s long-term health are listed in Table 2. Off-site reductions in the rates and volumes of each of these constituents of concern should benefit the waters of the Indian River Lagoon and the St. Lucie Estuary.

Table 2. Major BMP groups and objectives.

BMP Group Objective

Water Volume Minimize off-site discharges after excessive rainfall

Sediment Transport Minimize the movement of sediments off-site

Pesticides Minimize the off-site transport of pesticides and metals

Nutrients Minimize the movement of nutrients off-site

Aquatic Plants Minimize the proliferation of aquatic plants in waterways

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At an August 2, 1999 meeting of the Pesticide Sub-committee, the following were identified as parameters of concern in the waters of the IRL and SLE. The BMPs listed in this document were developed with these in mind. Although all of the parameters of concern require BMP activities, some parameters can not be addressed in this document since the products are not used in citrus management.

Total Nitrogen (TN) Atrazine Total Phosphorus (TP) Diazinon Total Suspended Solids (TSS) Ethion Arsenic (As) Endosulfan Copper (Cu) Simazine

In addition, the FDEP has identified the following parameters of concern for waters in the St. Lucie Basin. The development of Total Maximum Daily Loads (TMDLs) will begin in 2002. Parameters of concern for which TMDLs will be developed are:

St. Lucie Estuary - Nutrients South Fork, St Lucie River - Dissolved Oxygen (DO), Nutrients, Total suspended Solids (TSS), Biological Oxygen Demand (BOD), Coliforms North Fork, St. Lucie River - DO, Coliforms, Nutrients, Mercury

Regional Attenuation Facilities Proposed Regional Attenuation Facilities (RAFs) in St. Lucie and Martin counties will be a major factor for achieving the necessary adjustments in water quantity to improve the Indian River and St. Lucie River systems. The successes of the St. John’s River Water Management District’s Upper Basin project have demonstrated the tremendous environmental benefits that are possible when state, federal, public, and private interests cooperate to solve water-related problems. Comparable benefits can be achieved in agriculture, outdoor recreation, and tourism through similar efforts in the St. Lucie Estuary watershed.

Requirements For BMP Development Best Management Practices (BMPs) are production systems and management strategies that have been scientifically shown to minimize adverse impacts of agricultural production. BMPs can be defined as those on-farm operational procedures that are designed to achieve greatest agronomic efficiency in food and fiber production, while limiting the off-site effects of agricultural operations and simultaneously maintaining an economically viable farming operation for the grower. In cases where the economic cost of implementing certain BMPs puts an excessive financial burden on the grower, such practices can only be considered BMPs if external funds are available.

There are significant benefits that can occur with adoption of the BMPs in this document. The intent of these BMPs is to ensure that water quantity and quality in the IRL and SLE are pre- served to the benefit of all interests. Not all BMPs are applicable to any particular citrus opera- tion. Therefore, the “big” picture for each citrus operation should be considered prior to adop- tion of any BMP to ensure that each one adopted achieves its proper objective.

Page 9 May, 2000

All BMPs must be environmentally protective and economically viable. Recommendations must be based on factual information and science, and must be focused on real problems and solu- tions that work. However in some cases, there is no definitive research that applies to a particular BMP. In other cases, available research cannot predict the effectiveness of a BMP. In situations like these, BMPs presented in this document are based upon a combi- nation of available research, best professional judgment, and practical experience. Best professional judgement allows modification of a particular practice to the field conditions in a specific grove to achieve water quality and quantity objectives. BMPs should be consistent, while providing reasonable flexibility to accommodate local needs and site specific conditions. Most of all, BMPs should not be a barrier to incentive-based programs or to technical innova- tion.

Implementation of BMPs These BMP measures are not regulatory or enforcement-based. Landowners are requested to maintain records and provide documentation regarding the implementation of all BMPs. Ad- equate records are very important for documentation of BMP implementation. These records are an integral part of the non-regulatory, incentive-based initiative of the BMP program.

The priorities for BMP implementation are:

1. To correct existing water quality/quantity problems.
2. To minimize water quality/quantity problems resulting from land use.
3. To improve effectiveness of applied BMPs.
4. To seek additional improvement of BMPs based on new information.

All growers are encouraged to perform an environmental assessment of their crop production operations. This resource allocation assessment process is a tool that will aid in identifying which BMPs should be considered to achieve the greatest economic and environmental benefit. Among the incentives for adoption of BMPs are:

• Improved crop yield
• Improved crop quality
• Improved worker safety
• Efficient allocation of resources
• Reduced environmental impacts
• Opportunity to receive cost-sharing incentives
• Reduced new regulatory requirements
• Opportunity for industry self-regulation.

It is recognized that additional research is required to establish the effectiveness of some BMPs in the Indian River Area. Education is a key factor to ensure success of the BMP programs. Training programs are needed to ensure that BMPs are applied and implemented properly. Public participation is needed to provide input into the selection and designation of BMPs. Monitoring programs are needed to show that BMPs are effective in protecting water quality/quantity and to provide data for BMP revisions. Economic incentive programs are needed when a proposed BMP results in adverse economic impact.

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BMP Reference Documents

There are several sources of research that have been used to develop BMPs for citrus in the Indian River Area. Primary sources include the USDA-NRCS, University of Florida-IFAS, EPA, FDEP, and FDACS. This document cites pertinent documentation from these sources that may guide implementation, evaluation and verification of BMPs.

A-1 May, 2000

CHAPTER A: WATER VOLUME

Purpose The drainage infrastructure that has been developed in the Indian River Area to make productive agricultural and urban land has significantly increased drainage frequency, discharge volumes, and the velocity of water discharged from structures within the watershed. Excess rainfall from high intensity thunderstorms, tropical storms, and hurri- canes (Fig. A-1) must be drained off in order to protect agricultural and urban areas from flooding. The resulting discharges to the SLE and IRL from these events (Fig. A-2) can cause significant environmental impacts. Under natural conditions, the salinity levels in the SLE and IRL fluctuate in response to freshwater runoff in the watershed. Many organisms have adapted to transient low salinity conditions that occur in the inner estuary, but can not tolerate exposure to freshwater for extended periods. Therefore, target salin- ity envelopes have been proposed that encompass the salinity ranges that can maintain the viability of several aquatic species.

Figure A-1. Satellite view of the “Parade of Storms” taken August 30, 1995 by the GOES-8 satellite in geosynchronous orbit 22,300 miles above earth.

More stable and lower flow rates will improve water quality in the SLE and IRL and will help restore desired submerged aquatic vegetation. Reduced discharges to the estuary following heavy rainfall periods will also help maintain water quality within the appropriate salinity

A-2 May, 2000

envelope required for a healthy aquatic system.

Estuarine water quality is directly affected by nutrients, pesticides, and sediment present in freshwater inflows and by tidal dilution with ocean water. Typically, seasonal variation in water quality in the estuary is driven by incoming freshwater flows from within the watershed. There is also a correlation between inputs to the watershed and the development of algae in the estuary. Therefore, management strategies need to address both freshwater quantity and quality.

All types of land uses within the watershed contribute surface water runoff and pollutant loads to the estuary. Since citrus is the largest land use type in the SLE watershed, the activities associated with citrus production are an important consideration in the overall health of the estuary. All activities in groves can affect the water resources of the water- shed. Wherever feasible, citrus growers should consider implementing surface water management strategies that can provide additional storage and reduce the impacts associ- ated with excessive freshwater discharges. These surface water management strategies can range from improved ditch maintenance and water table management to additional on-site canal storage or the construction of detention reservoirs for holding excess rain- fall. It is important to conduct site-specific evaluations to determine if additional storage can be provided on-site and to plan long-term water management strategies that will minimize off-site discharges during periods of intense rainfall.

Figure 2-A. Agricultural drainage water being released from 298 district canal following a heavy rainfall event.

A-3 May, 2000

Brief Description of BMPs to Minimize Off-Site Discharges After Excessive Rainfall

A1. Water Table Management Water table control can be managed more efficiently by: having sufficient hydrau- lic capacity in the ditch/canal system, using water control structures on culverts, laser land leveling where appropriate, constructing and maintaining a properly designed drainage system, and actively monitoring the water table.

See Section A-1 for additional information.

References: • BUL251 Water Table Monitoring

• BUL731 Manual Monitoring of Farm Water Tables
• CIR769 Water Budgeting For High Water Table Soils
• CIR1188 Simple Water Level Indicator for Seepage Irrigation
• Obreza and Boman, 1992.
• Obreza and Admire, 1985.

A2. Scheduling Irrigation and Drainage Drainage and irrigation schedules should focus on optimal crop production that encour- ages deep rooting by maintaining a water table that minimizes water quantity and quality impacts. During intense rainfall periods, when drainage rates are insufficient to prevent upward fluctuations of the water table, root pruning can occur. Therefore, irrigation and drainage practices should be focused on maintain- ing a well-defined root zone that can be managed during both drought and wet periods.

See Sections A-2a, A-2b and A-2c for additional information.

References: • BUL208 Trickle Irrigation Scheduling For Florida Citrus

• FC81 Mgmt of Microirrigation Systems For Florida Citrus
• HS166 Irrigation Scheduling Tables For FL Citrus
• Circ. 444 Citrus Irrigation Management
• Boman, 1994
• Boman, 1996
• Boman et al., 1999
• Graser and Allen, 1987
• Rogers et al., 1983
• Smajstrla et al., 1985

A3. Moderate Discharge Rate Adjust the rate of discharge proportionate to the rate of lateral movement of water through soils. This can lessen the turbulence, reduce sediment movement, reduce erosion, and moderate the impacts on the receiving water body.

A-4 May, 2000

A4. Water Furrow Maintenance Maintain a consistent bottom slope on water furrows between beds to achieve uniform drainage. Avoid rutting and sloughing of water furrow areas.

A5. Monitor Soil Moisture Use tensiometers and water table observation wells for irrigation and drainage management to avoid excess soil moisture depletion and minimize water volume requirements during irrigation cycles.

See Section A-5 for additional information.

References: • Bul 319 Tensiometer Service, Testing and Calibration

• CIR487 Tensiometers for Soil Moisture Mea- surement and Irrigation Scheduling Calibration
• CIR532 Measurement Of Soil Water For Irriga- tion Management

A6. Drainage Management Plan Implement and maintain a written drainage management plan that provides specific responses to various types and levels of rainfall. The goal of the plan should be a reduction in volume of off-site discharge while maintaining a healthy environment for citrus production. The plan should include target water table levels and pump or drainage structure operating procedures that will be used for typical and extreme rainfall events. Consideration should be given to the use of existing canals and ditches for temporary water storage.

See Section A-6 for additional information.

Reference: • USDA-NRCS Conservation Plans can be used to help develop drainage management plans.

A7. Drainage Rate and Volume Drainage rates and the volume of water released or discharged following intense rainfall events should provide an adequately drained root zone while minimizing off-site impacts. When the water table approaches the target level, off-site discharges should be moderated. Depending on the grove design, this may require reducing pump rpm, adjusting the discharge structure, or pulse drainage (discharging for short periods of time and then allowing for recharge in the ditches). If adequate drainage in one portion of a grove results in water tables that are below target levels in another area, ditch cleaning, drainage system redesign, or auxiliary pumps may be needed to achieve more uniform drainage.

A-5 May, 2000

References: • Circ. 661 A guide for plastic drain tile in Florida citrus groves.

• Reitz and Long, 1955.

A8. Discharge Structures Structures and/or pumps that regulate off-site water discharge should be ad- equately designed, constructed, and maintained so that target water table levels within the grove can be achieved. If safety or operational concerns prevent structures from being adjusted to regulate discharges during storm drainage events, they should be rehabilitated or replaced. (i.e. modifying riser-board structures to allow easier water level control).

A9. Detention Where possible, on-site detention should be provided to reduce both the rate and volume of off-site discharges following heavy rains. Detention areas allow all or a portion of the drainage water to be temporarily stored on-site. The excess water can be stored for use or released later at low flow rates.

A-6 May, 2000

Water Table Monitoring A-1

Effective water management under Flatwoods soil conditions requires monitoring the water table elevation with enough precision to minimize pumping for irrigation and drainage. Knowl- edge of the water table level is essential to ensure that adequate drainage can be provided. Since a significant portion of the tree water requirements can come from upward flux from the water table, water table monitoring should be an essential component of irrigation decisions.

Upflux The movement of water upward within the soil profile from the water table is called “upflux”. As water is removed from the soil by the tree roots and by evaporation at the ground surface, water content of the soil decreases. By capillary action, water moves from the water table into the drier soil above. Water tends to adhere to soil particles. Smaller soil particles have smaller inter- particle voids. The smaller particles provided greater surface areas upon which water can adhere. In addition, the smaller voids allow water to be retained at higher surface tensions. As a consequence, soils with smaller particles have the ability to move water greater distances by capil- lary action than coarser soils (Figs. A-1a-1 and A-1a-2). As a result, the upflux process can move water into the root zone from a much deeper water table in clay soils than it can in sandy soils. Excess water drains by gravity into the shallow water table after a saturating rain or irrigation cycle. The removal of soil water by evaporation

Figure A-1a-1. Typical upflux rates by water table depths for EauGallie, Myakka, Pineda, and Riviera series soils (data from Obreza and Boman, 1992).

Figure A-1a-2. Typical upflux rates by water table depths for Felda, Immokalee, Wabasso, and Winder series soils (data from Obreza and Boman, 1992).

A-7 May, 2000

Fig. A-1a-3. Schematic of completed observation well.

and transpiration results in water move- ment upwards (upflux) by capillary action to replace some of the water in the root zone. The deeper the water table is, the farther the water has to travel upwards into the root zone. Therefore, the effectiveness of the water table for providing moisture to the roots decreases as the water table level drops. If the level is allowed to drop too low, capillarity is broken and upflux action ceases until another saturating rain or irrigation cycle refills the soil profile.

Water Table Observation Wells A water table observation well allows the ground water level to rise and fall inside it as the water level naturally changes. The changing water level moves an inserted float with an attached measuring rod (Fig. A-1a-3). The float assembly provides a quick visual indication of water table depth. With more precise inspections of the observation well, the information required for more detailed water management can be obtained.

Calibration Calibration is required to determine water table levels that are optimum for tree response, and to determine when to apply irrigation water to maintain water table levels. The measuring rod can be marked with divisions painted at appropriate intervals for the desired maximum and minimum water table depths (Fig. A-1a-4).

The measuring rod in a water table obser- vation has marks that indicate critical water table levels relative to ET rates. When the water table drops lower than these marks, the soil will not provide suffi- cient moisture to meet tree demands. If a very slowly permeable spodic and/or argillic horizon is present, it may be necessary to use the depth to the restrictive layer as the lower depth limit.

Fig. A-1a-4. Observation well installed in citrus grove.