Final report for FS24-360
Project Information
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. This project was implemented between 04-01-2024 and 03-31-2026 to study the feasibility of rainwater catchment from high tunnel for use in irrigating vegetable crops in urban farming. The rainwater catchment tool installed for the project included gutters on each side of the tunnel, two 550-gallon water tanks, a solar pump, a solar rechargeable battery and a solar panel. Two water filters were installed to prevent dirt getting into the drip system used to irrigate the high tunnel. A water meter measured the gallons of water used. The tool was robust and functioned well except a minor challenge that gutters buckled under snow weight in 2025, which was fixed with minimum effort. The tool cost $4970 including the materials and labor. The single largest cost was for water tanks, $2,279.70. During the project period, a total of 86600 gallons of rainwater was collected and used for irrigating the high tunnel crops. The collected rainwater would save the farmer $1303 during the project period. Thus, the calculated payback period for the tool was 7.6 years. This payback period could be reduced if the farmer can self-install the tool, saving $1000 of labor. This could bring down the payback period to 6 years. We found this rainwater collection tool very robust and long lasting without the need for any significant repair. More than 225 visitors observed the tool during the project period, and they were impressed by the sustainable nature of it. A class was also taken for students in Horticulture Department at NC State University on this topic and they also visited the project site. In conclusion, we recommend the rainwater catchment from high tunnel using this tool wherever appropriate.
Our hypothesis was that the rainwater catchment from high tunnel would payback the farmer in less than 3 years, and would 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 was to install gutters on both sides of a 16'x100' 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, record was kept of all the materials, methods and expenses incurred in installing the rainwater catchment. Using two years’ data, payback period was calculated to understand the payback investment to the farmer.
- Installed gutters on both sides (lengthwise) of 16’x100’ high tunnel.
- Put one 550 gallon water storage tank on each side of the high tunnel to capture the water from the gutters. Tanks were connected to each other with a pipe.
- Connected a water meter to the outlet of the water storage tank supplying water to the drip system. This water meter would record the gallons of water used in watering the high tunnel.
- To increase water pressure in the drip tapes, installed a solar pump and connected it to the water storage tank pipe supplying to the drip irrigation. A pressure regulator was also installed but later found to be not necessary.
- Watered the crops inside the high tunnel as needed using the water collected in the storage tanks.
- Estimated the total water used in gallons in each year of the project period. This water was 86600 gallons
- Averaged the total water used in gallons over two years to calculate average annual gallons of water used, which was 43300 gallons.
- Estimated the value of water used from the collection tanks. The 2024 irrigation rate for Town of Cary was $15.05 per 1000 gallons of water used. Therefore, the value of used water could be calculated as: Average annual value of water used= (43300x $15.05)/1000= $651.5
- Calculated the total expenses in installing the rainwater catchment on the high tunnel in 2024. Total expense= cost of all materials + installation labor= $3970+$1000= $4970
- Payback period (years)= $4970 (total expense)/$651.5= 7.6 years
- Details of all materials used is documented in this report. Based on this detailed documentation, the rainwater catchment tool could be easily installed by a farmer.
Cooperators
- (Educator and Researcher)
- - Producer
Research
We chose various materials based on the effectiveness and the cost. A contract worker was hired to complete the work. The material list is provided below. Two 550 gallon capacity water tanks were purchased from Tank Depot (tank-depo.com) for a total sum of $2279.70, which was the single largest item cost for the project other than the installation labor. The project is easy to implement/install provided the farmer has time. Total material cost was $3970. Labor to install everything was $3700. However, most of the labor charge was for installing the plastic on the high tunnel. The actual cost to install the rainwater catchment would be only $1000.
Materials:
32’x130 6mil greenhouse plastic $430
200ft vinyl gutters, end caps, support brackets, and connectors $320
45PSI 4.0 GPM Self-priming 115V AC Diaphragm Pump $85
300W Portable Power Station with Foldable 60W Solar Panel $300
3/4" Hose ThreadIPX6 Waterproof, flow meter $20
¾” brass threaded hose fittings, splitter, and teflon tape $75
4” Greenhouse tape to cover wiggle wire channel (2 rolls) $50
Spigot fittings and silicon for each tank $30
¾” Garden hose and splitter to connect tanks $25
¾” hose threaded water filter $15
200 board feet baseboard and hip board lumber $360
3" exterior wood screws $40
1 1/4" exterior wood screws $20
Conduit strap brackets for baseboards x60 $100
5/16” x 2 ½ " bolts and nuts for hip boards x100 $120
T-posts x2 $5
Window screens x 2 $5
Below is result of the first two years of the project. A water meter was installed in the water line from the storage tanks to the drip system irrigating the high tunnel. The project expenditure was in line with the budget. The project saved 47500 gallons of water from the town's water distribution system from May 2024 to March 2025 due to the high tunnel irrigation from the harvested rainwater. In the second year of the project, the rainwater harvest provided 39100 gallons of water (April 2025 to March 2026). The rainwater harvest system saved the farmer $714 in the first year and $589 in the second year of the project. Since the water pumping to the drip used a solar pump, there was no energy cost to the farmer. It sustained the high tunnel for irrigation throughout the year. More than 225 visited observed the rainwater catchment tool on site. A guest lecture was given at North Carolina State University for students in Horticulture Department (a class of about 13 students) on this topic on April 3rd 2025. The students were also taken to to tour the project site after the talk on April 7th 2025.
- Actual cost to install the rainwater catchment (excluding plastic installation): $4970 (Labor $1000 and materials $3970)
- Total water used from the catchment during the project period: 86600 gallons
- Monetary value of water used: $1303
- Average annual value of used water: $651.50
- Payback period: 7.6 years
Educational & Outreach Activities
Participation summary:
There was one CFSA Farm Tour in 2024. The CFSA tour of 2025 did not occur. There were five Harvest Fests, one Farm-to-Fork dinner, and many farm tours including during farm volunteer days throughout 2024 and 2025. A group of faculty and students from Horticulture Department at NC State University (total 13) also observed the research project in 2025. A total of more than 225 visitors visited to project and learned about it. In addition to on-farm events, we also had a lecture containing the outcome of the study for undergraduate students in Horticulture Department at NC State University on April 3rd 2025. A social media post on FaceBook (www.facebook.com/naturalnlocal) and Instagram (
https://www.instagram.com/p/DW0Bua9ju96/) was made on the successful completion of the grant project.
Learning Outcomes
About SARE grants and sustainability of rainwater harvesting
Use of high tunnels for growing Asian vegetables
Project Outcomes
The project has been successful in saving 86600 gallons of drinking water for the town, and concurrently saving farmer the cost of this water in irrigation. Both rainwater and the solar power used in rainwater catchment and pumping water are renewable resources. Therefore, this project proved to be a sustainable approach to irrigate high tunnel crops in urban farming. Visitors to the site were impressed by the simple and robust design of the tool and sustainability components used. They were thankful that SSARE funded this project in the town that could save drinking water. Since the rainwater from the high tunnel was directed to the water storage tanks, it prevented the water run-off and consequent erosion on the farm. The current NRCS grant for the rainwater catchment from high tunnels only funds in-ground water storage tanks without gutters. USDA-NRCS personnel also visited the project site, and liked the water catchment design from this SSARE project. Based on the success of this grant project, they considered funding high tunnel rainwater catchment modeled after this SSARE grant project tool. Therefore, we consider this grant project as a success with a very positive outcome for, 1) the participant farmer, 2) academics and students at NCSU, 3) town residents, 4) other farmers, 5) USDA-NRCS grantors.
We at Natural & Local are thankful to SSARE for funding this project. Grants like this encourage farmers to test innovative ideas on farm such as this one. We recommend that such grants should continue. We also recommend that farmers with a similar situation as us can easily install the rainwater catchment tool that we developed through this grant project.