Dam Monitoring monitors vegetation vigor (greeness) and moisture using an unspecified index that measures change. Vegetation moisture and vigor should correlate with each other and with seasonal changes in weather. As part of the retrospective analysis, we look at vegetation vigor and moisture over 3 years to identify what is normal for that dam. We then use a threshold to identify when vegetation is behaving outside our expectations of normal e.g. if there is higher than normal moisture in the soil that seems to inhibit vegetation vigor. It is abnormalities like this that we use as a indicator for potential seepage.