Payback period from high tunnel rainwater catchment for vegetable crops in urban farming

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2024: $10,000.00
Projected End Date: 03/31/2026
Grant Recipient: Natural & Local LLC
Region: Southern
State: North Carolina
Principal Investigator:
Dr. Dasharath Lohar
Natural & Local LLC


No commodities identified


No practices identified

Proposal summary:

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.

Project objectives from proposal:

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
  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
    15th to April 14th) for two years, 2024 and
  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.
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.