Payback Period from High Tunnel Rainwater Catchment for Vegetable Crops in Urban Farming

Commodities

Practices

• Crop Production: high tunnels or hoop houses, water management
• Farm Business Management: budgets/cost and returns
• Sustainable Communities: urban agriculture

Being at the lowest end of the value chain, farmers need to be very careful in choosing their investment. Any information that can reduce the uncertainty will help farmers in making investment decisions. Sourcing of irrigation water is one of the crucial decisions made by farmers. Irrigation water availability is a big challenge in urban vegetable farming under high tunnels. The outcomes from the proposed study in terms of a tool kit, and accompanying data on investment plus payback period for rainwater catchment from high tunnel will certainly provide crucial information to high tunnel farmers so that they can make an objective decision and have a peace of mind. This tool kit and payback period information will help a small urban farmer like us, who have a low level of risk tolerance due to limited farm income and resources. Any support from state and federal government to lower the risk of an investment decision will greatly enhance the quality of life of a farmer. Therefore, proposed project and the consequent solution have value for being funded by SSARE grant.

Our hypothesis is that the rainwater catchment from high tunnel will payback the farmer in less than 3 years, and will be
profitable for a small urban vegetable farmer. Currently, we have a 16’x100’ high tunnel on one of the three plots of the farm. The high tunnel does not have rainwater catchment. The approach is to install gutters on both sides of the high tunnel, capture the rain water from gutters into rain barrels placed at the end of the tunnels, pump the captured water to drip irrigation in the high tunnel with a solar pump, quantify the amount of water used throughout the year. In parallel, keep record of all the materials, methods and expenses incurred in installing the rainwater catchment. Using two years’ data, estimate how long will it take for the rainwater catchment to payback investment to the farmer. The study will also document the items required and the method of installing the rainwater catchment on high tunnels.

1. Install gutters on both sides (lengthwise) of 16’x100’ high tunnel.
2. Put one 1000 gallon water storage tank on each side of the high tunnel to capture the water from the gutters. If two tanks are used on each side, connect the tanks with a pipe so that overflow from one fills the other tank.
3. Connect a water meter to the outlet of the water storage tank supplying water to the drip system. This water meter will record the gallons of water used in watering the high tunnel.
4. To increase water pressure in the drip tapes, install a solar pump and connect it to the water storage tank pipe supplying to the drip irrigation. A pressure regulator will also be installed to maintain the water pressure in drip tapes.
5. Water the crops inside the high tunnel as needed using the water collected in the storage tanks.
6. Estimate the total water used in gallons in the year (April 15^th to April 14^th) for two years, 2024 and 2025.
7. Average the total water used in gallons over two years to calculate average annual gallons of water used.
8. Estimate the value of water used from the collection tanks. The 2024 irrigation rate for Town of Cary is $15.05 per 1000 gallons of water used. Therefore, the value of used water can be calculated as: Average annual value of water used= (average annual gallons of water used x $15.05)/1000= $...
9. Calculate the total expenses in installing the rainwater catchment on the high tunnel in 2024. Total expense= cost of all materials + installation labor= $...
10. Payback period (years)= total expense/average annual value of water used
11. As an example, if rainwater catchment over my high tunnel provided me 120,000 gallons of water to irrigate my crops in 2024 and 140,000 gallons in 2025,
    1. Average annual value of water used= [(120,000+140,000)/2]
       x $15.05)/1000= $1956.50
    2. Let’s assume, total expense= $5,000
    3. Payback period (years)= 5000/1128.75= 2.56
12. Details of all materials used and the procedures to install the rainwater catchment will be documented. Based on this
    detailed documentation, a tool kit report will be prepared for use by other farmers, researchers and academics.