ET rates, or the amount of water lost, are a function of sun, wind, temperature and relative humidity.
Water is important to maintaining a quality turf and minimizing pest problems, including weeds.
When turfgrasses do not have access to sufficient water they begin to turn bluish green. If allowed to wilt for too long a period, the leaves will die. Even if only the leaves die, weeds may gain a foothold in the turf and increase in population. ET rates can be estimated using weather stations which track environmental variables including rainfall. Although these are too expensive for most schools, ET can be estimated by measuring the amount of water lost from a large pan placed in the open.