Current and Future Water Quality Challenges on a Local Urban Farm and its Value as a Local Food Source

Abstract

Food sustainability has been an ongoing concern throughout the Hawaiian islands, necessitating further research into potential threats to local food sources. Water resources, both water quantity and quality, are an important limiting factor for agriculture. At the same time, farms surrounded by urbanized land face potential water quality challenges due to runoff and nearby wastewater infrastructure. Sumida Farm is the largest watercress producer on the island of Oʻahu and is located in a highly urbanized area in ʻAiea, Oʻahu. The first objective of this study was to assess the presence and temporal dynamics of potential wastewater runoff to Sumida Farm by analyzing water samples for two wastewater tracers, caffeine and carbamazepine, and by correlating results with E. coli enumeration. The second objective of this study was to assess the environmental impact of local and imported watercress by comparing carbon emission data between Sumida Farm and a mainland watercress farm. Results showed that caffeine and carbamazepine are currently rare or nonexistent at Sumida Farm and thus, it was concluded that E. coli present at the farm was not correlated with wastewater. It was not possible to establish whether precipitation influenced the presence of caffeine, carbamazepine, and E. coli concentrations during the study period. Finally, it was found that the total greenhouse gas emissions associated with imported watercress is over 50 times the emissions of local watercress. This multi-part study illustrates the importance of local agriculture and provides a baseline analysis of current threats to the farm that may change in the future.