Design of Gravity-Fed Drip System for MacLeish Field Station Alexandria Julius ’14, Brittany Bennett ’15, Malia Charter ’15, Linnette Figueroa ’15

Introduction Design Development Future Implementation An apple orchard is being planted at the Ada and Archibald MacLeish Field Station in West Initial Design Requirements Hydraulics of Pipe Flow Modeling in SolidWorks - The irrigation system is integral to the success of the Whately, MA. Our team set out to design the To avoid using an external power source, gravity must provide enough force to transport from the tank to the furthest Modeling the tank in SolidWorks would apple orchard but will not be needed for more than hydraulic aspects of the irrigation system to end of the irrigation tubing. The flow must also be controlled to prevent water from moving too quickly and bypassing the drip provide a static mechanics analysis to asses if support the young orchard for its first few approximately three years. the tank is designed safely. For the purpose of - During its use, the irrigation is expected to supply emitters closest to the water tank. To address both extremes, water will flow from the highest elevation possible for the water years. The project included designing the approximately 300 gallons of water per week. tank, but tubing will then the contours of the land, normal to the downward slope. this project, it is appropriate to approximate tubing and aerator configuration, identifying - Since the design must also conform to the Field Sta- The drip emitters should face the roots. It is assumed that there is no pressure variation due to elevation within any given the water tank in SolidWorks as a cylindrical the water source, routing the water, and se- tion’s focus on sustainability, all processes and materi- row. Orienting the piping along one side of each row of trees requires that the holes in the piping be angled toward the trees. tank and not a barrel of rectangular planks. lecting physical equipment. als should be have little to no environmental impact. We assumed no variation due to pressure based on elevation in a given row. Target rate of water mission is half a gallon per The material properties of the Black lotus was - Material and costs should be minimized where pos- hour and a flow rate of 5 feet per second through the gate valve. Precipitation rate can then be calculated using Equation 4. based on Oak but modified with the dimen- sible. Precipitation rate from an emitter (the gmp) is found to be 3 inches per hour per tree. Operating time can then be found using sions listed isted in Table 5. - The orchard will be planted on a slope, allowing the Equation 5: irrigation to be gravity fed. The design will thus not PR = (96.3 x gpm)/(L x S) (Eqn 4) require an electric pump, photovoltaic power input, OT = (I x 60)/(PR x DA) (Eqn 5 ) or electrical housing from the design. where PR is precipitation rate, gmp is the total global precipitation measurement, S is the spacing between emitters, and L is the spacing between rows of tubing, OT is operating time, I is the system irrigation requirement in inches per week, and DA is days available for irrigation per week. If the trees were to be watered three times per week, the irrigation system would have Figure 2: This photo was taken looking up the slope which will be used to employ a gravity fed irrigation system. System Components to run for approximately ten minutes per day. - manual water valve will direct water into piping at highest elevation, above the tree line - High Density Polyethylene tubing containing intentionally The Site placed holes as drip emitters The site allocated for the apple orchard lies - various valves throughout system to control water flow - gate valve, characterized by having the largest valve diame- Construction of the Water Tank on the northwest side of the field station, ter, controls water flow from the water tank Tubing Layout Options Mechanical Properties The wood should be purchased with a thick- approximately 190 feet from the northeast- Option 1. A line of tubing can lay behind the trees, The dimensions of the water tank are restricted by ness of 2 inches cut parallel to the grain for ern corner of the Bechtel Environmental parallel to the alignment of the trees. The parallel the mechanical properties of Black Locust wood be- greater compressive strength. The length of Classroom (Figure 1). The Northampton lines of tubing will avoid opposing gravity, result- cause the force exerted by the water on the sides of each plank is determined by the number of Reservoir is located to the west of the apple Tank Volume Requirements ing in a smooth flow of water One possible disad- the tank cannot exceed the yield stress by a reasonable planks needed to construct the tank. This final orchard site, providing a potential water To assess how much of the irrigation could be vantage is the drip emitters do not encircle the dimension should be found with the help of privided by rainfall, the group used rainfall data root system of each tree, causing a potentially factor of safety. The maximum allowable pressure can source for the irrigation system. The site is the machine shop. Furthermore, one should collected by the environmental monitoring station at harmful uneven water supply. be found using the Equation 2. From there, he maxi- surrounded by trees on the north and west. MacLeish. Even anticipating that the actual mum safe depth of water can be used using the hydro- purchase three metal bands to hold the water Additionally, the site is downward sloping distribution of water over the time is sporadic, tank together, measuring 3.05 meters in Option 2. Another option is to wrap the tubing static pressure formula, Equationσ 3: toward the northwest, making it ideal for a analysis concluded that natural rainfall will be able to around each tree trunk so that water is emitted t/r (Eqn 2) radius -- the inner radius with error. P = γ gravity fed irrigation system. The slope of provide the majority of the orchard’s irrigation uniformly around the entire trunk, requiring more P = h (Eqn 3) requirements. A sufficiently large storage tank would the land ranges from fifteen to twenty de- tubing. While providing water to the tree trunks Where P is the hydrostatic pressure, σ is the yield be able to irrigate the orchard during dry weeks or grees (Figure 2). The total area of the site is uniformly, the emitters may provide the tree with strain, t is the thickness of the tank wall, r is the Cost Analysis draughts. Additionally, a valve could be implemented γ approximately 8000 square feet. There will to provide more control over the irrigation, which too much water and might not reach all the trees. radius of the tank, is the specific gravity of water, From the final irrigation layout design, an be three forty by forty square plots where will be especially useful when the orchard is new- This design is less likely to provide a steady flow and h is the depth of water in the tank. initial budget was generated to estimate the the rows of trees will be planted. Each ploplott ly-planted and water must be monitored carefully. rate of water based without an additional pump With a radius of 3 meters, P becomes 2.523 MPa cost of the project. Currently, the supplies we powered by an external power source. wiwillll havehave threethree rows withwith fivefive trees each,each, forfor after dividingσ = 366 psi by five as a safety precau- will be using for the project will be the same a totatotall ofof forty-fiveforty-five trees. tion. The maximum height is then 4.35 meters (14.27 as those used for the Chestnut orchard at Ma- ft) and maximum volume storage is 122 cubic meters cLeish. Paul Wetzel, Environmental Re- Water Storage Tank Material of water (32,480 gallons), which is well above the re- search Coordinator for CEEDS at Smith The initial material suggested for a wooden quirements for the system. Since the tank will hold College, provided the specifications of the water storage tank was R. pseudoacacia (Black needed materials, accounting for repairs or Locust). Black Locust wood is local and easi- more than enough water, cost becomes the most im- portant factor in determining the dimensions of the any replacements of parts will be simpler. The ly-purchased. It is also more sustainable than cost of the water tank cannot be determined tank. and has advantageous material proper- without a unit cost for the Black Locust ties. The radius remains 3 m because a large exposed wood. Once determined, total project cost A common practice for gauging the surface area is needed to collect enough rainwater. can be easily calculated based on the decided strength of wood is assessing its specific gravi- The other changable dimension is the height. The dimensions. The valve for the water tank will ty. While the average specific gravity for North minimum height that could be used is 0.25 m, but a cost anywhere between eight and 15 dollars American hardwoods is 0.51, the specific 0.25 meter high tank with a 3 meter radius is dispro- (Home Depot). Using the higher approxima- Figure 1: The apple orchard (yellow star) will be planted West of the gravity of Black locust 0.68. The wood is also Bechtel Classroom. The North direction increases in height. The portional; 1 meter is preferable. Because tank is shal- tion, The total cost of the project that can be large body of water is the Northampton Reservoir. Orchard location resistant to decay, which extends the life cycle was added to the map of development limits created by Professor Figure 4: AutoCAD drawing of irrigation pipe and water col- low, it may require a platform to assist in the gravi- estimated at this point is $444.25. Reid Berton-Johnson. of the water tank and reduces total lifetime lection system layout (yellow) with regard to contours and costs. the three square plots of trees (green). ty-powered irrigation.

Acknowledgments: Reed Burtone-Johnson and Professor McKahn for their help and collaboration on this project