Effects of Reclaimed Water on Two Golf Courses Located Over a Potable Aquifer in Central Oahu

Abstract

This study set out to evaluate the biological, chemical and agronomic effects of reclaimed water for irrigation on two golf courses (KGC and LGC) located over a potable aquifer in Central Oahu. Percolate water and grass samples were collected on two soils at background sited (potable water irrigation) and pilot-scale test plots (reclaimed water irrigation) at both golf courses with different managements during the two-year pilot-scale study. The variations in chemical characteristics of percolate samples and the relationships of these changes to soil characteristics (pH, CEC, clay content, etc) and the golf course managements were determined in a general way based on the results of this study. Great differences in soil water content were observed between the soil at LGC (wet) and the soil at KGC (dry), and between the two years of the pilot-test. Fecal contamination will be caused due to reclaimed water irrigation is still in doubt after this study. Significant percolate chloride and sodium concentration increases were found at the LGC test plot but not at the KGC test plot. Nitrate leaching was found to mainly relate to fertilization, irrigation method (amount and schedule), and soil pH. All the percolate samples with nitrate concentrations higher 20 mg/l were found at background sites with high pH. High and constant irrigation rates caused a similar degree leaching at the LGC test plot using reclaimed water as that at the background sites with fertilization and historic irrigation methods. TDS in percolates is not expected to increase significantly with the reclaimed water using the irrigation method applied at the test plots of both golf courses in this study. However, whether or not harmful agronomic effects will occur cannot be determined in this study without samples from the dry season and at the soil surface layer. Suction lysimeters are good for monitoring most of chemical parameters measured and work best at high soil water content, but are not suitable for bacteria monitoring.