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Nursery Automated Irrigation for Optimizing Water Efficiency: A Case Study in Cataño Puerto Rico
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Soil Erosion Research Under a Changing Climate, January 8-13, 2023, Aguadilla, Puerto Rico, USA .(doi:10.13031/soil.23535)Authors: Yiyang Chen, Gian L Gerena, Roger A Leyba, Daniela M Markazi
Keywords: Rainwater harvesting, Remote sensing, Hurricane, Watershed models.
Abstract
In 2017, Hurricane Maria caused severe damage to Puerto Rico, with immense costs that fractured the island‘s food, water, and energy systems. The increasing frequency of severe weather events, with Hurricane Fiona being the latest, threatens many habitats. The need to increase disaster resilience in high-vulnerability areas arises from these unpredictable events. This project highlights a collaboration between the University of Illinois Urbana-Champaign, the University of Puerto Rico, Mayagüez Campus, and the non-governmental organization Caras con Causa. Caras con Causa aims to promote sustainable community development through ecology, education, and economic progress focused on communities in Guaynabo and Cataño, Puerto Rico. One of the organization‘s main projects is centered on a charter school, Escuela Rosalina Caraballo de Martínez, that seeks to eradicate poverty while promoting education and the environment. The Rosalina school has an existing small-scale nursery where the plant species propagated are constantly rotated. The nursery is about 30 ft by 40 ft. This location presents the opportunity to use solar energy and rainwater to create a highly resilient, self-sufficient nursery that could create a reliable source of food, energy, and water that the students can benefit from personally and academically. Historically, the system has been watered by hand with a hose, which can take up to 90 minutes. This presents an inefficient use of time and water. In this project, we seek to automate the process using solar energy and rainwater to decrease water use and reliance on the municipal water supply, thereby increasing the nursery‘s resilience.
In this project, we designed and built an irrigation system capable of automatically irrigating the entire nursery through a main pipe which splits off into 8 branching pipes, each branch with its own row of tables. These branches are paired up into 4 tarps. This was done by relating the 40 inch width of the tables at the nursery to the minimum radius of the wetted area from each nozzle necessary to irrigate the tables without leaving dry spots between adjacent nozzle areas. To calculate the water application efficiency (WAE), we utilized the ratio of the wetted area that falls off the sides of the table to the total wetted area of each nozzle. We found the WAE to be 92% in this way.
The system aims to supply plants with water equal to the evapotranspiration depth each day, allowing for flexibility that accounts for the range of species and pot sizes under constant rotation. Evapotranspiration on-site is calculated following FAO-56 report guidelines based on the Penman-Monteith equation (Allen et al., 1998) and parting from data collected by an on-site weather station. Given the climate crisis, we highlight how water efficiency should always be considered in an agricultural environment, but it becomes even more critical when irrigating a sizable area using a limited rainwater supply. Using evapotranspiration to calculate water requirement functions as a one size fits all approach that works around the range of needs in the nursery due to the different species. From this project, we produced a proof of concept for a custom fit automated irrigation system which is self-sufficient. The nursery's current system can now function as a model for the local community to base designs for their own systems. Over time, increasing the number of resilient systems such as the one described here will help make the island more resilient to a natural disaster.
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