In delivering workshops on irrigation (and drought) management, there are always a few questions on how to estimate canopy coverage without the use of special equipment. Not being content with the typical answer of “Use your best guess,” I began to review the research, and found that an estimate of photosynthetically active radiation (PAR) (also known as mid-day light interception) can be calculated from orchard yields. This question was asked because in a water short year, the available water needs to be spread out evenly as the respective % of evapotranspiration. This following will help determine how much water your trees are using.