Performing A Greenhouse Performing A Greenhouse Water AuditWater Audit

By Paul Thomas, and Forrest Stegelin, The University Of Georgia

Cooperative Extension Service

Adverse Water Use Legislation Is Inevitable

1). 27 counties in Georgia currently have year-round water restrictions in place that limit landscape watering.

2) Birmingham, Alabama landscapers, greenhouse and nursery owners are desperately trying to prevent city officials fromshutting down nursery’s and landscapers….again.

3). Most of Florida is in a Stage 2 drought. Water tables are dropping and water use legislation is popping up everywhere.

4). California, Texas, Oregon, Washington and most other western states have new and more extensive water use legislation. You do not own water in these states…you pay for the right to extract it.

Adverse Water Use Laws Are Preventable

The drought is forcing legislators to take action. They are in a tough spot! They cannot control the weather, and yet answer to the citizens. They need facts to make the best decisions.

The question is not “if” restrictive legislation is to be proposed at the local level, it already has been and will be again!

If things don’t improve, it’s only a matter of time before national legislation is proposed that will limit water use for all farmers and growers.

Doing nothing will result in legislators justified in their beliefs that they must act given what facts are known and what they see.

Why Do A Water Why Do A Water Audit?Audit?

The large volumes of irrigation water used, and the high visibility of our industry, puts our industry at risk of losing control over our water resources.

Worse, our industry is being viewed as a major water waster!

Legislators want to know how much water we use, so they can assess if steps need to be taken…but we have no clue! Our lack of interest greatly concerns the people who regulate water usage in our state. We must become pro-active.

Our Image? What Can We Do?

Will A Greenhouse Audit Really Help?

Yes, The greenhouse industry is probably the most efficient wateruser group of all commodities in agriculture. The greenhouse industry is efficient compared to car washes and industrial firms.

The trouble is, we don’t have the proof.

What proof? Facts! Figures, Ratios, Comparisons!

Water conservation documentation – Drip tubes, etc. Gallons of water per dollar of tax revenue generate.Gallons of water per square foot / acre / year.Gallons of water per dollar wholesale “farm-gate” value.

We need to get this information soon!

Water Audit Water Audit ProceduresProcedures

Carefully audit (measure), review and then document commercial water use in your operation.

Identify potential problem areas, and then explore methods to improve water use efficiency.

Develop short and long term management tactics to reduce water use.

Water Audit ProcedureWater Audit Procedure

The following are some important questions you should ask.

Once answered, develop a summation of your findings, and document all the improvements you made.

This information will help you explain your water use policy and use history to legislators.

What’s In A Water What’s In A Water Audit? Audit?

Audit Information:

Current “Best Management Practices” (BMP’s).

Crop inventory organized by water need.

Pesticide and chemical inventory.

Expansion, storage and recycling options.

Water conservation technology implemented.

Goals Of A Water AuditGoals Of A Water Audit

Reduce luxury water consumption!Reduce luxury water consumption!

Eliminate non-target water use Eliminate non-target water use (waste).(waste).

Reduce current fertilizer and pesticide Reduce current fertilizer and pesticide usage. usage.

Minimize legislative problems through Minimize legislative problems through consistent education efforts.consistent education efforts.

Restore legislator’s confidence in our Restore legislator’s confidence in our water use policies, and our industry.water use policies, and our industry.

Greenhouse Water Use Is Different Than Field Agriculture

The Audit

Part 1. Water Source Assessment ________________________________

Do you have multiple sources of water?

Do you store water for emergencies?  Do you have a “manditory water restriction” plan?

How long can your operation do without water?

What would be the financial loss if water was cut off?

Is Your Water Source and/or Pump Capacity Up To The Challenge?

If your pump provides only 30 gallons per minute (GPM), you can easily see that it will not be capable of irrigating a large field of perennials and eight greenhouses at the same time.

You would likely have to water one house or one zone at a time. A member of your crew would likely be watering all day, most days. Your pump would run all day, every day.

Hot weather labor costs would skyrocket!

If you had that one day’s supply of water stored in a 30,000 gallon storage tank….

with a distribution pump, and a capability to deliver several hundred gallons per minute…

and you automated the delivery system…..

and used efficient drip irrigation or ebb and flow benching….

…..you could water your entire facility in a few hours for just pennies in labor !!!

What If Things Were Different? ?

The Solution: Water Storage!

YES! You can! At 30 GPM, would you have enough water replaced in the storage tank each day to allow full watering schedules? If we assume the pump cycles on 45 minutes per hour, then 45 x 24 hours in a day = 1080 minutes. At 30 gallons per minute, we would have 32,400 gallons of water pumped per day.

If watering was automated, you’d save the labor cost, and complete all your watering in a few hours. If you had a three day supply, you’d never have a direct use shortage, and you may use less electricity as the tank would rarely be drawn down and require a full day of pump activation.

The labor savings would be significant!

Part II. Water Use Assessment and Storage

Do you know your greenhouse operation’s maximum daily water demand in summer?

Do you know your greenhouse operation’s maximum daily water demand?

Do you know your greenhouse operation’s maximum weekly, monthly or yearly water usage – in cubic feet or gallons?

Do you know which crops have maximum daily water demand? Which have the least?

Part II. Water Use Assessment and Storage

1. Endpoint Flow Rate

2. Volumetric Calculations

3. Flow Meter Reading

There are three basic methods to determine water usage over time!

Flow Meters Are Your Best Choice!

Accuracy

Continuous Measurement

Data Acceptability Is Good

Low Maintenance / Permanent

Low Long-term Cost

Simple To Install

An In-Line Flow Meter

And easy to read:

 Are your employees watering efficiently?

Do you periodically observe your employees watering skills?

Do you know how much the application of water is

costing you per hour?

Part III. Water Use Labor Cost Assessment

On what basis do you decide to water? Need? Schedule?

Do you have a daily time period set to water within?

Part III. Water Use Assessment

Do you record daily, weekly or monthly water use?

Do you test your water quality on a monthly basis?

Do you keep theresults of your watertests to show theabsence or presenceof ground-water contamination

You can save up to 70% of water used for pot crops and 35% for bedding plant production by updating your watering system to include drip irrigation, ebb and flow benching or flood floor systems.

The estimated labor savings is significant. If you pay theaverage of $8.40 / hour, you can save just over $7300.00per Quonset house or large bay per year.

Knowing True Costs Can Generate Significant Savings

Automation would savehundreds of hours / month.

Part IV. Application Technology Do you know if your pressure is correct for that particular

system component?  Do you have particle filters and properly calibrated injectors

or proportioners? When did you last test the system?  What percentage of your total crop “variable cost” does watering take up?  

Back-Flow Prevention Selection:

Back-flow prevention is the law in Georgia!

  Are you connected to a municipal water source controlled by a water authority? Pumping from a well? Pumping from a stream?

Do you or any neighbors live within a mile of the greenhouse?  How are you applying the water? Using drip irrigation? Injecting fertilizer, pesticides or chemicals? If so, you are required to have a back-flow prevention system  

 

However, if you are connected to a local water authority (LWA), their rules supersede all others.

If the State requires only a single stage check valve and the water LWA requires a double check reduced pressure device, you must go with the more expensive LWA requirements.

The most effective and cheapest back-flow prevention measure is a 12” air-gap between the top of a storage tank and the incoming water line. Water can’t jump up-hill in open air!

Consult with the Local, State, County or on some cases the Federal agency that may monitor water quality and safety. They have specific guidelines as to the type of back-flow prevention needed.

Back-Flow Prevention Guidelines:

 

 REDUCED PRESSURE ZONE BACKFLOW PREVENTERS

 

PROS: 

   Two IN-LINE INDEPENDENT CHECK VALVES with intermediate relief valve .

    For use in hazardous CROSS-CONNECTION situations.

    If both check valves fail, BACK SIPHONAGE IS DIVERTED TO THE ATMOSPHERE.

CONS:

   Expensive in the SHORT RUN

    Must be installed one foot above the ground.

REDUCED PRESSURE ZONE BACKFLOW PREVENTERS

    They have low pressure drains incorporated into their design.

    Test port cocks are provided for testing back siphonage.

    Can be installed below irrigation sprinkler head,.

Part V. Water Recycling  

Do you recycle any portion of the water used in your growing operation?  Can you accurately measure the amount of recycled water?  Could you report with some accuracy how much water

you saved per year by recycling?

Have you attended a water recycling lecture or meetingin the last year to update your understanding of the new technology, standards and methods being used?

There are many ways to recycle water, but all systems require you toplan on how you will Collect and reuse or of the water.

Cisterns, and ponds aresuitable for large or smalloperations. Getting thewater to that holdingare can be a challenge.

Water Collection

Drainage Channels

Holding Ponds

Storage Tanks and Cisterns

Table 4.0 – Rainfall In Georgia

Month Average Rainfall

January 4.0

February 4.0

March 5.0

April 3.0

May 4.0

June 3.0

July 3.0

August 3.0

September 2.0

October 2.0

November 3.0

December 4.0

Potential Rainfall

Table 1.0 Greenhouse Rainfall Recapture PotentialIf you collect rainwater as a supplemental source, the gallons add up to significant savings.

Roof Size in Square Feet Rainfall in Inches 

0.25 0.50 0.75 1.00 2.00 3.00 4.00 5.00 6.00

1000 140 281 421 562 1124 1685 2247 2809 3371

1100 154 309 463 618 1236 1854 2472 3090 3708

1200 169 337 506 674 1348 2022 2697 3371 4045

1300 183 365 548 730 1461 2191 2921 3652 4382

1400 197 393 590 787 1573 2360 3146 3933 4719

1500 211 421 632 843 1685 2528 3371 4214 5056

1600 225 449 674 899 1798 2697 3596 4494 5393

1700 239 478 716 955 1910 2865 3820 4775 5730

1800 253 506 758 1011 2022 3034 4045 0566 067

1900 267 534 801 1067 2135 3202 4270 5337 6405

2000 281 562 843 1124 2247 3371 4494 5618 6742

2100 295 590 885 1180 2360 3539 4719 5899 7079

Capacities of Various Sized Cisterns

 Diameter of Round Type

DEPTH 6 8 10 12 14 16 18

6 1266 2256 3522 5076 6906 9018 11412

8 1688 3008 4696 6768 9208 12024 15216

10 2110 3760 5870 8460 11510 15030 19020

12 2532 4512 7044 8532 13812 18036 22824

14 2954 5264 8218 11844 16114 21042 26628

Part VI. Water Release - Pollution Prevention 

Do you know how much water you are releasing from your operation?

Do you have a bio-remediation site (a catch-pond with established plants such as cattails) to reduce free nutrients and act a s a bio-filter prior to releasing the water.

Do you have a scouting or evaluation program to monitor water release quality and quantity

Do you know the acceptable limits for nitrate or phosphorus release in your local community or waterdistrict?

Part VII. Monitoring water use legislation and local water use regulations  

Do you know if your county or city has a commercial water use ordinance?

Are there water use restrictions in effect in your community?  Is your region currently in a drought or low-water supply situation? 

 Have any operations near you been asked to conserve or cease watering use due to a municipality shortage?

Do you have a site-specific water use fact sheet for local legislators or regulatory personnel to inspect upon demand?

Is your growing facility within 5 miles of a subdivision or city?

Are you familiar with your state regulations regarding water release, well contamination and groundwater contamination?

Part VIII. Planning For Future Expansion

Part VIII. Planning For Future Expansion

 

Is your current water supply sufficient for your potential expansion needs over the next ten years?  What are the impediments to expanding your water supply?  

Could conservation and new technology negate the need for a new well or expanded usage?

 

Would you consider changing crops grown to include more drought tolerant plants.

 

Would changing over to a water efficient application method pay for the new well or additional water source costs in the next five years?

Part VIII. Planning For Future Expansion

Automating Your Irrigation System Is a Great Investment!

Automating your irrigation system proves to be a very good investment.

Payback (breaks even) for $4778.00 is under 1 ½ years with 79% return on investment; @ 6% interest over 10 yrs, this is greater than a $22,000 net present value, or a 65% internal rate of return with a benefit cost ratio of 5.8. That is a fantastic benefit ratio.

Net labor savings is over $3,712 per house over the next 10 years !!!!!

.

Non-monetary tangible benefits:

More uniform plant growth, Scarce labor now freed up Labor for planting or loading trucks,Hire less staffMore management time for planning!

Don’t forget the real conservation benefit of using between 30% and 70% less water ….and the public relations benefit gained by being efficient and aware!

Automating Your Irrigation System Is A Great Investment!

Read Your Greenhouse Water Audit Handout

If you have questions, The University of Georgia has faculty that specialize in Irrigation Technology, Crop Production, Agricultural Economics, Regulatory Compliance and Environmental Assessment.

See your county agent to access these resources.

Acknowledgments:

The author would like to thank Ben Bradshaw, Progress Growers Inc, Dr. Don Wilkerson, Texas A&M University, Dr. Maryann Rose, formerly at The Ohio State University, and Dr. Tom Yeager, University of Florida for the use of their previously published materials, tables and figures.