Water levels in rivers typically follow rainfall patterns, rising and falling during periods of wet weather and drought. By examining seasonal and year-to-year data, one can get a picture of how recent flood or drought events compare to historical patterns.
- Latest Value is the most recent data available for the water body.
- The Historic Norm for the Month is the average (mean) of all values for this water body for the current month over the entire period of record of the data.
- Historic Range is generated by reporting the minimum and maximum values for this water body over the entire period of record.
- FEMA Values may include NHWE Flood and/or FEMA 100-year Flood values, whichever are available:
- NHWE stands for "Normal High Water Elevation" and refers to the customary high-level water level of a water body. It is usually defined by the public works department of local government and is defined as the landward edge of a water body during normal hydrological conditions. It is usually determined by examining vegetation patterns and high-water marks on trees.
- The FEMA 100-year Flood elevation is defined by the Federal Emergency Management Administration as the water level which has a one percent chance of being reached or exceed in any single year.