- The Water Year is defined as the period between
October 1st of one year and September 30th of the next. This interval is
often used by hydrologists because hydrological systems are
typically at their lowest levels near October 1.
- Total Precipitation maps depict the Water Year precipitation
totals in inches.
- Departure from Normal maps depict the difference between the Water Year
precipitation totals and the "normal", a 30 year average. The units are in inches.
- Historical ranking maps depict Water Year precipitation totals
as they rank when compared to Water Year totals over the modern record. The values presented are
percentiles. A ranking near zero indicates the year was drier than any found during the period of
record. A ranking near 100 designates that the year was wetter than any found on record. A ranking
of 50 is equivalent to the "median", a measure of central tendency.
