The "Rou Dalagurr Food Sovereignty Lab Rainwater Catchment System Retrofit" is an ENGR 205 design project created to help provide the Food Sovereignty Lab at Cal Poly Humboldt with accessible and sufficient rainwater. Designed and constructed in the fall semester of 2026, a group of ENGR 205 engineers (Team QOAD), wanted to make it possible for the FSL to have consistent, accessible water to use at the Wiyot Plaza. After the design and construction was completed, the FSL now has access to ~ 500 gallons of rainwater to use to water the various garden plots around the Wiyot Plaza.

The Rou Dalagurr Food Sovereignty Lab is dedicated to revitalizing Indigenous food systems and fostering community-based food sovereignty through hands-on learning, research, and collaboration.

In the Wiyot Plaza on the Cal Poly Humboldt campus, there is a rainwater catchment system that was constructed years ago, however a lot of the system has broken parts that need to be replaced. The system includes a solar panel that is connected to a water pump that transfers collected rainwater up to two different storage tanks as well as a small irrigation system that drip irrigates small plots in the plaza.

The goal of the team’s project is to retrofit this current system and then improve it to where it is easy to operate and will last for years to come.

Before any prototyping or designing of the system could occur Team QOAD had to do research on many of the pieces and materials that go into a water catchment and irrigation system.

This section will summarize all of the research and reading completed to deliver the most important and impactful information surrounding the project.

Client Information

The Rou Dalagurr Food Sovereignty Lab is dedicated to revitalizing Indigenous food systems and fostering community-based food sovereignty through hands-on learning, research, and collaboration. This project works to help them create an educational, renewable, and functional system of irrigating the Wiyot Plaza.

Pentair Pump

The pump that was used during this project's original creation was the Pentair Shurflo Revolution 4008-101-E65. After testing, the pump was found to be working and running at its recommended 10 volts. The pump runs automatically whenever given a current without an on or off switch, but has thermal, voltage, and pressure cut-offs as seen in Figure 1. (130 degrees F, anything over 12V, and past 40 PSI.)

[pentair pump specs sheet]

The pump is compact, only needing a clearance of ~ 4.9” x 4.4” x 8.1” as seen in Figure 2, which was clearly chosen on purpose as the pump sits in a small box to protect it from the outdoor conditions. This small design allows for it to be easily moved for any convenience needs and would allow us to move it wherever needed for the continuation of this project.

[pentair pump dimensional sheet/tech drawing]

PVC Applications and Lifespan

Polyvinyl Chloride (PVC) is the most prominently used polymer in the construction of consumer products and goods, see Figure 3, and is what was used in the original construction of the irrigation system we are working on.

[pvc global consumption metrics]

PVC can come in many forms and has many different applications. For example, the PVC used to create our irrigation lines is flexible PVC which means it has a plasticizer added to it, like polyesters or citrates, but on the other hand PVC can have fillers added to it like talc or carbon based compounds to give it bulk and create it more sturdy allowing it to be used in the construction of buildings and automotive products. PVC can generally be used in any application so long as it has the right mix of ingredients as seen in Figure 4.

[types of pvc additives]

Irrigation Systems and Their Benefits

Proper and efficient water use was, and continues to be, a major requirement and expectation of this project, which is the main reason an irrigation system was originally used. However there are multiple types of irrigation systems that can be used and that need to be considered when remodelling the system. Currently, the system uses one of the two major types of irrigation, human-managed localized irrigation, a type of irrigation in which a low-pressure piped network dispenses water in a set pattern to keep plants and the surrounding area watered, which could still work efficiently. The second major type of irrigation is used in areas with water abundance, like Humboldt with considerable amounts of rain, and is called flood irrigation. It’s a type of irrigation in which a large amount of water is collected before being directed over crop fields, and could be used.

To assist the crops' growth rates, we could also add a fertigation system that runs on the same pump over different piping, which would dispense nutrients to plants whenever they require and allow for their growth to almost require zero human labor outside of simply switching systems on and off or checking and maintaining the health of irrigation lines.

Gravity Fed Irrigation Systems

Gravity-fed drip irrigation systems operate using only gravity and pressure to move water from storage tanks to the irrigation output. Gravity-fed systems do not require a power source to distribute water from its storage source to its output. Gravity-fed irrigation systems are applicable to conditions where the geography can allow the installation of water-sources that can be placed at a higher elevation than the soil and plant-life that would receive the water. These systems are also applicable to situations where power sources are limited or not available.

Part of the original project done for CCAT was executed by a group from the ENGR 305 class and included a gravity-fed irrigation system, which supplied water to multiple garden beds. For their system, they used the rain water runoff from the roof of a shed which was then collected in a storage tank. From the storage tank next to the shed, the water was then pumped uphill to another tank at a higher elevation, the pump was powered via Solar Panel.

[ccat food forest]

Another important note for gravity-fed irrigation systems is the geography of the environment to be irrigated. The optimization of gravity-fed irrigation systems to have the maximum amount of controlled discharge is directly proportional to the elevation of the head of the tank and the lateral distance the water travels. A study featured in the International Journal of Agriculture Extension and Social Development sought to find an applicable mathematical model to predict the outflow of water from the different output elevations and lateral distances. The study concluded that the most optimal model for gravity-fed irrigation is to have the head at the highest elevation and the lateral distance be as short as possible.

[lateral vs emitter discharge graphs]

For the case of our project, this means when deciding the placement of our tank, it should be at the highest elevation possible while being as close to the garden needing irrigation as possible as well. Further research and mathematical analysis will be done to consider the best possible position to implement the most efficient system.

Overview of Photovoltaic Technology

Solar panels, or Photovoltaic (PV) cells, turn sunlight directly into electricity. They do this when photons strike a semiconductor material, typically silicon, electrons become excited and move around. When we put two semiconductors next to each other, one with a slight positive charge and one with a negative charge, we can cause a “flow” of electrons through an external circuit, generating direct current (DC) electricity (Grafman, 2021).  Solar panels are then composed of many interconnected PV cells encapsulated within protective layers of glass, polymer backing, and aluminum framing.

[construction of silicon cell]

Small off-grid irrigation systems commonly use low-voltage configurations, such as 12V or 24V arrays, which are directly compatible with DC pumps. Direct coupling between a PV module and a DC motor reduces system complexity because no inverter is required. Eliminating the inverter avoids conversion losses typically ranging from 5% to 15% (Khare 2015). For small-scale rainwater transfer applications, direct DC systems are frequently used due to their simplicity and reduced initial cost.

Photovoltaic systems used for pumping water are typically sized based on daily water demand, pump efficiency, and total dynamic head (TDH). One useful way to measure performance is to compare how much electricity the pump uses with how much water it actually moves (Khare 2015). The performance of the PV array must therefore be considered in relation to pump characteristics and seasonal water demand.

Solar Panel Efficiency

A potential issue with the current rainwater catchment system could be inefficient sunlight to power the pump that delivers water to the storage tanks. The current solar panel that is powering the pump is in a location that may be getting blocked by tree cover, so a way to increase the efficiency of the system could be moving the solar panel to a position where it will receive a greater amount of total sunlight. Without a sufficient amount of power being supplied to the pump, it could limit the performance of the whole system and prevent the irrigation system from working correctly.

Another important performance factor is panel orientation and tilt. In the Northern Hemisphere, solar panels usually work best when they face south and are tilted at an angle close to the local latitude, which typically maximizes annual energy production.

Advantages of Photovoltaic Integration in Irrigation Systems

Photovoltaic systems offer several advantages when integrated into decentralized irrigation infrastructure. First, PV systems provide renewable, low-carbon footprint energy. Once installed, they generate electricity without fuel consumption or direct greenhouse gas emissions (Grafman, 2021). Second, PV-powered irrigation systems have low operating costs. Unlike diesel-driven pumps, solar systems do not require fuel purchases or transport. Maintenance requirements are generally limited to periodic cleaning of module surfaces and inspection of electrical connections (Khare 2015). Over time, avoided fuel and grid electricity costs may offset higher initial capital expenditures.

Third, solar irrigation systems often align well with agricultural water demand cycles. Irrigation demand tends to peak during warm, sunny periods when solar irradiance is highest (Khare 2015). This natural synchronization reduces the need for energy storage in many small-scale systems. In rainwater-based irrigation systems, solar-powered transfer pumping can occur during

[solar irradiance in arcata]

Fourth, PV systems are modular and scalable. Additional modules can be added to increase pumping capacity or compensate for future system degradation. This modularity makes photovoltaic systems suitable for renovation projects where incremental improvements may be implemented over time.

Finally, photovoltaic systems enhance resilience. For educational institutions, visible solar infrastructure also serves an educational function, demonstrating renewable energy applications in real-world settings.

Limitations and Challenges of Photovoltaic Systems

Despite these advantages, photovoltaic systems present several limitations that must be considered in small-scale irrigation applications. The biggest limitation of solar power is that it isn’t constant. Cloud cover, shading, and seasonal changes can reduce available power (Adaramola, 2014). In coastal environments with frequent fog or overcast conditions, energy yield may fluctuate considerably.

Another limitation is initial capital cost. PV modules, mounting hardware, wiring, and associated control equipment require upfront investment. Although costs have decreased significantly in recent decades, capital expense remains higher than simple grid-powered alternatives in some contexts (Grafman, 2021). If the solar panels and pump are not properly matched, the system may not run efficiently. In changing sunlight conditions, this can reduce water output (Khare 2015).

Material degradation over time represents another challenge. PV modules typically experience performance degradation rates of approximately 0.5% to 1% per year. Regular inspection and maintenance are therefore necessary to ensure sustained system performance.

Finally, photovoltaic systems require careful integration with hydraulic components. Because power availability varies throughout the day, water storage capacity becomes an essential buffer. In irrigation systems that rely on gravity-fed distribution from elevated tanks, sufficient transfer pumping must occur during daylight hours to maintain the supply.

Photovoltaic Systems in Integrated Rainwater Irrigation Applications

Integrated photovoltaic and rainwater harvesting systems have been studied as sustainable water-energy solutions for small farms and institutional landscapes (Grafman, 2021). In such systems, PV modules power transfer pumps that move collected rainwater from primary storage tanks to elevated distribution tanks. The stored water is then delivered via gravity to drip irrigation networks.

Research indicates that coupling renewable energy with rainwater harvesting reduces dependence on municipal water supplies while lowering operational emissions (Grafman, 2021). However, successful integration depends on appropriate sizing of both electrical and hydraulic components. Oversized PV arrays increase capital cost, whereas undersized arrays may fail to meet daily pumping requirements.

In renovation contexts, evaluation of existing PV capacity, pump specifications, and control components is essential for determining system performance limitations. Literature on decentralized solar pumping emphasizes the importance of wire-to-water efficiency and component compatibility (Khare 2015). Control systems, including float switches, play a critical role in preventing pump damage and ensuring reliable operation.

Overall, photovoltaic cells serve as the foundational energy component of decentralized solar irrigation systems. Their effectiveness depends on proper integration with pumps, storage tanks, and control mechanisms. Literature consistently identifies system matching, environmental conditions, and long-term maintenance as primary determinants of performance.

The objective of this project is to iterate on and design a new rainwater catchment system for the Rou Dalagurr Food Sovereignty Lab, as well as implement an appropriate form of irrigation into the system.

Criteria is necessary for any engineering design project to create outlines and give those working on it a proper direction. For Team QOAD it was no different, and much thought went into weighing all of possible factors.

Criteria	Description	Weight (1-10)
Accessibility	Easy to Operate / Maintain	9
Cost	Budget of $250	8
Footprint	Minimizing Land Use	7
Irrigation	Supplies Crops with Sufficient Water	7
Aesthetic	System is Hidded for the Most Part	6

Much of the prototyping for this project weren't tangible physical pieces due to the scale of the project. Most of the prototyping work was research into materials, testing individual components, and doing mathematical equations.

The solutions that were used in the final product of this project consisted of a Durable Pipe and Flexible PVC System, Integrated Solar Pump Box, Maintenance and Infrastructure Improvements, and Educational Signage and Tank Design. The team believes that the best route for restoring the rainwater catchment system is to get the connection from the solar panel to the water pump working again as well as enhancing the irrigation system with a durable PVC pipe system to prevent the irrigation lines from getting damaged, which is one of the main problems of the current system. Along with making the pump more accessible, the team will make it straightforward for the client to maintain the system with educational signs showing how the system works and how to keep it functioning well. Going with this combined solution, the team believes that a system can be built that costs less than $250 and can be finished within the project’s allotted time frame. The finished system will be durable, have a small geographic footprint, store sufficient water for irrigation, and be simple to maintain.

The final design we settled on uses both flexible and rigid PVC for its piping, with the flexible PVC being reused from the old system whenever possible to keep waste low. We also created a new pump box as to replace the existing one that was poorly located and made it almost impossible to access or test the pump without disassembly. Alongside the pump box we added a controller to the system to ensure longevity of all the electrical components.

The first step in constructing the new rainwater catchment system was to move the storage tanks both to the top of the hill so the system has the greatest elevation head possible. This means that the system will be able to gravity feed the plots down the hill from the storage tanks.

The next step in constructing this project was to choose the path for the new PVC that was being installed. When choosing this path you want to make sure there is the least amount of bends/turns as possible because with each turn, it decreases the ability for water to be pumped up the hill.

Once the path for the PVC is chosen, trenches around 1ft need to be dug and then the PVC can be laid and buried.

After the PVC is laid, the piping can be connected to the storage tanks and water pump.

After the pump and storage tanks are all connected to the piping, the pump can be connected to the solar panel.

After the pump and storage tanks are all connected to the piping, the pump can be connected to the solar panel.

Most of our material cost went to the PVC piping and connections, while being the cheapest piping option for this project still went over our initial budget of 250$.

Item	Amount	Cost per unit	Total
3/4 PVC 20ft — 240ft total	1	USD 176.15	USD 176.15
Arrowhead 1/2 or 3/4 in. FIP Hose Brass Garden Valve	3	USD 23.99	USD 71.97
Cantex 3/4 in. D PVC Male Terminal Adapter For Rigid	3	USD 0.99	USD 2.97
Charlotte Pipe Schedule 40 2 in. Slip X 3/4 in. D Slip PVC Reducing Bushing	2	USD 6.59	USD 13.18
Fernco Schedule 40 2 in. Hub each X 2 in. D Hub PVC Flexible Coupling	2	USD 9.47	USD 18.94
Charlotte Pipe Schedule 40 3/4 in. Slip X 3/4 in. D Slip PVC Elbow (45 degree)	6	USD 1.75	USD 10.50
Charlotte Pipe Schedule 40 3/4 in. Slip X 3/4 in. D Slip PVC Elbow (90 degree)	11	USD 1.79	USD 19.69
Charlotte Pipe FlowGuard 3/4 in. Slip X 3/4 in. D Slip CPVC Tee	3	USD 1.39	USD 4.17
Charlotte Pipe Schedule 40 1 in. Slip X 3/4 in. D FPT PVC Pipe Adapter	1	USD 2.39	USD 2.39
Charlotte Pipe Schedule 40 1 in. FPT X 1 in. D FPT PVC Coupling	2	USD 2.39	USD 4.78
Charlotte Pipe Schedule 40 3/4 in. Slip X 3/4 in. D FPT PVC Pipe Adapter (female)	2	USD 2.59	USD 5.18
Charlotte Pipe Schedule 40 3/4 in. Slip X 3/4 in. D MPT PVC Pipe Adapter (male)	2	USD 0.99	USD 1.98
Oatey Handy Pack Clear Primer and Cement For PVC 2 pk	1	USD 13.99	USD 13.99
Float Switch for Sump Pump - 10-Foot Water Level Sensor with Honeywell Microswitch and Adjustable Tether Length for Ground Water Bilge Pump and Water Tank – Non-Corrosive PP Casing, Rated to 13 Amps	1	USD 26.17	USD 26.17
Solar Pump Controller, LCB 10A,DC Pump Controller,Linear Current Boosters used in solar direct pumping applications;Compatible Models: 12V or 24 VDC pumps; Input Voltage: 16 - 50 DC volts PV Array.	1	USD 81.68	USD 81.68
SHURFLO 4008-101-A65 New 3.0 GPM RV Water Pump Revolution, 12V	1	USD 73.50	USD 73.50
Water storage tanks — re-used from CCAT system	3	USD 0.00	USD 0.00
Solar Panel, 12 volt, 10 amp, 130 watt — re-used from CCAT system	1	USD 0.00	USD 0.00
Solar mc4 connectors and extra pv wire — graciously donated and attached by John Davis of Solar Projects Unlimited	1	USD 0.00	USD 0.00
Grand total			USD 527.24EUR 453.43 <br />GBP 384.89 <br />CAD 653.78 <br />MXN 10,992.95 <br />INR 39,463.91 <br />

Fortunately for our team we were able to re-use the storage tanks and solar panel from the previous system, which would have increased our material cost by nearly double.

With ideal conditions our system will function without the need of direct operation. At the top of the hill are two storage tanks, these tanks are filled with water from the storage tank at the bottom of the hill. There are valves on each of the storage tanks, these should be left open at all times in order to ensure that water is flowing through the whole system.

Our system has 3 standing spigots placed adjacent to the garden beds. These three spigots are all connected to the same line of pvc coming from the top of the tanks. Due to this, only one spigot should be used at a time, as opening another valve will cause the pressure to drop, reducing the flow of water at each spigot.

Listed below is the maintenance schedule that should be followed for the system.

Daily

• Day to day maintenance for this system will be minimal, but checking to see if the pump is running when it should be daily is key to catching issues before they become bigger.

Weekly

• Weekly and monthly maintenance should look like checking to make sure the solar panel surface is clean to ensure maximum power, and clearing the gutter of the rainwater catchment of any debris.

Yearly

• Test water pressure annually, compare the pressure reading to average pressure. Any drop in pressure is a sign of potential leaks.

Describe the testing results.

Discuss the testing results.

Discuss lessons were learned during this project and what you would do different next time.

At the moment, the current steps we have in mind for improving efficiency within this system is to trim/ remove branches and foliage that block sunlight from hitting the solar panel. If this can be done, water will be pumped more often, and more efficiently.

When should water be pumping?	Water should be pumping consistently during the afternoon of clear skies on sunny days, around 10 AM - 3 PM. With these ideal conditions, the rainwater catchment tank water should be pumped to the top two tanks in no more than 3-4 days.	-	Why is water not being pumped?	Our system is set up to automatically pump water uphill, so if water is not being pumped during a day with ideal weather and a full tank at the bottom of the hill, then it will likely be a failure of the pump due to age.	-	Where are PVC lines buried?	The PVC lines are buried mostly out of the way but some are buried underground along the pathway. Below are images taken during construction that show exactly where lines are buried. Rock markers have also been placed alongside certain parts of the buried PVC.

Introduce team and semester in the following format:

• Quinlan Sauter
• Owen Miranda-Hupp
• Antonio Rubio
• Dalton Sullivan

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