My farming operation has involved growing produce using sustainable methods for the past 9 years on multiple lots across the Twin Cities, including 2 seasons on a certified organic farm in North Branch. I use companion planting practices, crop rotation, and intensive approaches including succession planting, relay planting, and high tunnel growing to extend the growing season and maximize production on a small amount of land.
I have marketed produce through Farmers Markets including Mill City, Linden Hills, Market on the Bluff, directly to restaurants, and through a small CSA for a couple of years. I have been at the forefront of innovation in urban agriculture in both Minneapolis and St Paul, building the first permitted high tunnel and deer fence at sites in the Hamline Midway and North End neighborhoods in St Paul.
I have been developing a number of value added products over the past few years including Salsa Verde, Herb infused vinegar, and zucchini bread morsels. I have just received a mini-grant to further develop the Salsa Verde.
I have always used sustainable practices including crop rotation, no chemical pesticides or herbicides, adding organic matter for better water absorption and optimum pH so the plants are better able to take up the nutrients available in the soil.
GOALS: The project goals were to:
- Research a water capture system for a high tunnel and install it to
- Reduce erosion caused by the large volume of water shedding off the high tunnel
- Reduce the amount of water introduced into the city waste water management system
- Redirect the collected water for use inside the high tunnel
- Employ an alternative energy source to power a pump to increase water pressure so the water collected from the roof could be used inside the high tunnel
- Reduce use of municipal water, both to reduce the cost and so the produce grown can benefit from the trace minerals available in rainwater while avoiding chemicals like Chlorine and Fluoride which are found in city water
- Share the process with other interested parties
I researched other projects where a water collection system was used on a high tunnel and found that the project that was most similar to what I planned to do was done by Iowa State University.
In the end, I elected to follow their model for the most part with some modifications. To begin with, since I didn’t have a ribbon board I tried a freestanding approach which I later redesigned to mimic the method for attaching the gutters used by the University of Iowa in their project. Instead of using 2 large volume water tanks, I selected (12) attractive, residential style 49 gallon rain barrels to better suit the urban residential site.
I originally planned to put the rain barrels on the north and south sides of the high tunnel, but found that the system would work better if all of the rain barrels were located together with short hoses between rather than a long hose connecting sets of 6 rain barrels located on opposite sides. In addition, because there was already a fence on the west end of the high tunnel, the west side was selected for the rain barrel location since the fence was already shading that side, and since the biggest concern in terms of shading the planting beds inside the tunnel is from the south in the winter.
- I installed a row of pine 2×4’s between the hoops just below the newly installed ribbon (hip) board (higher than the rain barrel height) the length of the high tunnel on both curved sides (north and south).
- Just below the channel and wiggle wire at the ribbon board, I installed the gutter mounting brackets and gutters at a slope of about 2-3” over the 30’ length of the high tunnel using a string to mark the slope to indicate where to position the gutter brackets.
- At the northwest and southwest corners of the high tunnel, I added a downspout and extension to direct rainwater into 2 rain barrels which were then connected to another 10 rain barrels for a total capacity of 588 gallons. I used the short hoses supplied with the rain barrels attached to open splitters at the base opening of each rain barrel. I used this approach so that the rain barrels would fill and drain in unison rather than one at a time.
- Into the southwest corner rain barrel, I installed a small pump attached to a short hose.
- The hose was connected to a water meter, a timer, a backflow preventer, pressure regulator, a filter, a tubing adapter, drip tubing (capped at the far end), emitters, drip tape capped by folding each end and covering it with a short section of drip tape. Each 24” wide bed has (2) strips of drip tape at 8-10” apart, and a wider bed at the edge has (4) strips at about 8” apart.
- For solar power, I selected the Wagan Tech Solar e Cube 1500 watt AC inverter which I purchased from Costco. This product is compact and it also has 12 volt DC outlets and 2.1 Amp USB power ports supported by a 55 AH hybrid battery. Specifications can be found at http://www.wagan.com/index.php/products/solar-innovations/solar-industrial/2546-solar-e-power-cube-1500.html This product is expandable, so it seemed like a good choice since there may be a need for more power for other functions in the high tunnel at some point.
Urban Farmer, Tim Page, helped to install and manage the system. Capital Region Watershed District reviewed the plan and provided matching funds to cover the portion of the materials cost which was not covered by the SARE grant. Ramsey County Master Gardeners nominated the site for the Blooming St Paul award and came for a tour of the project. Betsy Wieland, from U of MN Extension, supported the project.
The results achieved include the successful installation of a water capture system that has the ability to divert approximately 600 gallons for every inch of rain from the municipal storm water system. If rainfall would arrive at a constant rate, the average total number of gallons diverted per year would be 19,644 based on average rainfall of 32.74” per year. During 2014 the total rainfall was 30.92”, so the maximum amount of water available to collect off of the high tunnel was 18,552 gallons. There were only 4 rain events (or a series of back to back days of rain fall) that exceeded the nearly 600 gallon capacity of the system.
The gutter and rain barrel layout that I originally developed was abandoned in favor of the approach used by the University of Iowa which meant removing the original equipment layout and installing it to the revised plan which meant using city water to irrigate the high tunnel crops for part of the 2014 season. Therefore, I was not able to collect a full season of actual water usage from the water meter. The calculations above reflect the expected outcome.
Because water is relatively inexpensive for this size of operation, cost savings on water alone would not be enough of a reason to employ a water capture system like the one I installed. The value of the other advantages of this type of system are more difficult to measure. The Capital Region Watershed District felt that the project made enough of a contribution as an example of a way to reduce pressure on the municipal storm sewer system to fund 50% of the materials/equipment cost of the project. The ability to use rain water rather than municipal water has the advantage of adding Nitrogen the plants need while avoiding introducing the Chlorine and Fluoride found in city water. Erosion in the area around the high tunnel was effectively mitigated and can be used for vining crops that are started inside the high tunnel and later need more space to spread out.
I was thrilled with the attendance at our field day of a large group of Master Gardeners. I feel that we missed an opportunity to present findings at the High Tunnel Conference as we had hoped because we didn’t have a full season of data on water collection. I continue to share information about this project with everyone I educated on the various topics of urban agriculture including many youth from across the Twin Cities.
What I learned from this grant is the importance of water management to the operation, to the city, and to the environment. While I am fortunate to have access to city water, I believe this project shows how it may be possible to use a system like this in an area where there is no access to city water supply. The volume of water available to be collected (19,644 gallons), even taking into consideration the fact that not all of the rain that hits the high tunnel will be collected or retained, seems to exceed the University of Iowa estimate of the average water requirement for high tunnel grown tomatoes which is .625 gallons per square foot per week which equals about 13.5 gallons/sf needed over the 21.66 week growing period from last frost to first frost. In a 960 sf high tunnel, the total needed would be 12,996 gallons. Even so, it is important to note that the University of Iowa recommends this type of water catchment system as supplementary to a more consistent source of supply.
The advantages of implementing a project like this one are reduced erosion, reduced pressure on water sewer system, use of rainwater rather than city water on plants, and use of alternative energy to reduce use of fossil fuel and other sources of energy that have a negative impact on the environment.
Disadvantages are the having more equipment to monitor and maintain. Some of the gutter brackets were damaged over the winter and will need to be replaced. It’s also tricky timing when to put out and take down watering equipment so it doesn’t get damaged by freezing temperatures.
There were a few issues with the Solar e Cube. It was recommended to first charge the Solar e Cube from an AC source, but there wasn’t a cord for that, so I ordered one. I also realized in reading the directions that it was not recommended for the Solar e Cube to be located in a space where the temperature would fall below 32 degrees Fahrenheit, which would be typical of the high tunnel in the winter since I am not using a heating source. While the rolling feature is helpful, at 84 pounds, it is pretty heavy to haul anywhere like into the basement for storage. I think this product would have been better suited to a heated greenhouse. One other consideration is that keeping it inside the high tunnel to protect it from theft or vandalism means that it is collecting through plastic that has about 91% transmission.
In August 2014, during our field day, I was fortunate to present the project to 58 Ramsey County Master Gardeners who were invited to visit the site, including a tour of the high tunnel and especially the distinctive water capture system. The Master Gardeners in attendance were impressed by the multiple benefits of the system including removing water from the municipal storm sewer system, reducing erosion, use of rain water rather than city water being beneficial for the plants with only upfront cost rather than an ongoing cost per gallon. Because the mission of Master Gardeners is to educate, news of this installation has been spread far and wide via word of mouth as Master Gardeners engage in the hundreds of volunteer hours of education they provide each year.
Capital Region Watershed District personnel visited the project a couple of times and shared information about the project with others interested in ways to manage storm water.
A group of professors from the University of Minnesota was also invited to see the project as they work on a grant proposal that may include a high tunnel.
Minnesota Conservation Corps youth workers (6) and (2) leaders learned about the high tunnel water capture system during their visit in 2014.
Photos of the project have been shared one on one with a number of people who are active in urban agriculture in the Twin Cities and beyond, and many individuals have visited and learned about the project.
I am in the process of updating my website and I plan to include information about the project.
Water conservation is one of the benefits of our plan to capture and redirect water flow from the hoop house into the drip irrigation system for use inside. Drip irrigation puts the water directly at the root of the plant and minimizes water loss through evaporation in the air while also reducing the potential for diseases associated with wet leaves inside the moist enclosed environment.