Potential Threats To Water Quality At Sumida Farm Caused By Wastewater, Urbanization, And Climate Variability

Abstract

Wastewater infrastructure on the island of Oʻahu is expected to become increasingly vulnerable due to climate change, potentially increasing risks to agricultural areas surrounded by urbanized land by causing wastewater overflow in subsurface and surface runoff. Sumida Farm is the largest watercress producer on the island of Oʻahu and is located in a highly urbanized area in ʻAiea, Oʻahu. The farm is subject to stressors from the surrounding urban setting including runoff that can potentially contain wastewater. By analyzing the water at the farm for the presence of two pharmaceutical substances, caffeine and carbamazepine, that are consumed and excreted by humans and are thus commonly used as wastewater tracers, this project focuses on assessing the presence and temporal dynamics of wastewater runoff to the farm and in the watershed. Results were analyzed under various detection limits to determine, with increased confidence, whether caffeine and carbamazepine were present or absent in each sample. Overall, results indicate that caffeine and carbamazepine are rare or nonexistent at Sumida Farm. Due to the minimal presence of caffeine and carbamazepine at the farm and few precipitation events before sample collection dates, it could not be definitively determined whether there was a correlation between precipitation, caffeine, and carbamazepine during the study period. The results of this project will contribute to further understanding of potential threats to local agriculture and food sustainability on Oʻahu while also providing farm managers an overview of the current status of water quality at the farm, which may change in the future due to climate change.