‘L-93'creeping bentgrass, ‘Tiger II' colonial bentgrass, and ‘Greenwich' velvet bentgrass were examined at two different mowing heights (1/4” and 3/8”) to compare species variation in irrigation frequency requirements and Crop Water Stress Index (CWSI) values. Treatments included irrigation at four intervals: 1) three times per week (Monday, Wednesday, Friday); 2) two times per week (Monday and Friday); 3) once per week (Friday); and 4) biweekly (every other Monday). This field project was conducted in a fully automated, mobile rainout shelter (35' x 60') at Rutgers University Horticultural Farm II, allowing for strict control of irrigation frequency and amount. Our results demonstrate that irrigating at 100% ET, three times a week may not be necessary to sustain plant growth and physiological processes, and that this depended on species and time of year. Generally, irrigating twice a week and replacing 100% of ET was adequate to maintain acceptable turf quality during summer months for all species of grasses tested. The data also suggest that both early and late in the season, watering once a week is sufficient to maintain adequate quality in both colonial and velvet bentgrass. Maintaining turf at a lower cutting height produced higher water demands when irrigated 3 times a week. Lysimeter readings consistently show that creeping bentgrass watered three times a week and maintained at ¼” lost more water than turf cut at 3/8”. Both creeping and colonial bentgrass had significantly lower carbon fixation rates and lower Water Use Efficiency (WUE) when watered once a week or less. Velvet bentgrass was much better adapted to maintaining high levels of both parameters, even when irrigation was limited.