There is no rule of thumb for how often to test irrigation water quality. Depending on the source of irrigation water at your golf facility, water quality can change throughout the year. One example for testing irrigation water several times annually is if salt is used to control ice on roads during winter months in your area. If your source of water is a deep well, then your water quality would not likely be affected but if your primary source of irrigation water is lakes or ponds that receive surface water runoff from surrounding areas, especially in urban landscapes, then salt concentrations may spike in the spring following snowmelt. Another example prompting testing irrigation water is during a drought. Without the diluting effect of rainfall, water supplies may experience dramatic increases in salts and bicarbonates.
If using poor-quality water or recycled water, then regular analysis of water quality is essential. There are other reasons irrigation water quality may change throughout the year, so routine testing several times per year is always wise so as to establish baseline information, identify trends and monitor changes so that sound agronomic decisions can be made and future problems on the golf course can be avoided