Water quality changes in golf course irrigation ponds transitioning to reuse

Irrigation ponds on nine golf courses in southern Nevada were monitored for water quality over a 1600-day period. Three of the golf courses were fresh water courses, three were courses scheduled to transition to reuse water during the study period and three were long term users of reuse water. Salinity [electrical conductivity (EC)], NO3 (-)-N, PO4-P, pH, algal chlorophyll concentration, clarity, temperature, oxygen, and all major cations and anions were analyzed on a monthly basis. A selected fairway on each course was equipped with water meters to assess irrigation volumes on a bimonthly basis. Estimates of salt and NO 3 --N loading on fairways were made by weighting irrigation volumes with concentrations of salt (assuming 700 mg-L-1 per dS-m(-1)) and NO3--N measured in the irrigation ponds. Pond spectral reflectance measurements were obtained on a single monitoring day and correlated with water quality parameters. EC, temperature, NO3--N, PO4-P,algal chlorophyll concentration and clarity all demonstrated significant changes in all irrigation ponds that transitioned to reuse water (p < 0.05). Multiple regression analysis revealed that as much as 75% of the variability in pH in some irrigation ponds could be accounted for based on water quality parameters measured, with higher R-2 values associated with elevated HCO-(3), concentrations. Spectral reflectance (individual wave bands and spectral indices) was shown to be correlated with pH, clarity and algal chlorophyll concentration (R-2 = 0.66** to 0.82***) with a well defined threshold relationship between clarity and the spectral index R705/R670. Average yearly NO3- -N loads on fairways averaged 8.5 kg-ha(-1)-yr(-1) on fresh water courses, 86.5 kg-ha(-1)-yr(-1) on transition courses and 209.8 kg-ha(-1)-yr(-1) on long term reuse courses (all significantly different at p = 0.05). Average yearly salt loads on fairways averaged 11,959 kg-ha(-1)-yr(-1) on fresh water courses, 14,675 kg-ha(-1)-yr(-1) on transition courses and 27,445 kg-ha(-1)-yr(-1) on long term reuse courses (long term significantly different atp = 0.05). Such results indicate that significant attention must be given to irrigation strategies used on reuse irrigated golf courses to properly manage for higher nitrogen and salt loads.