Stevens Creek Datum Change

Service Change Notice

On December 1st, 2023 the zero datum for the USGS river gage on Stevens Creek near Lincoln will be lowered by 10 feet. This is being done due to significant scouring of the river channel over the past few years. In addition, the NWS will be raising the flood stages and previous records by 10 feet. This is being done to allow for past and future gage heights to be comparable and to maintain a smooth record of past and future floods.  The other tabs on this website go into more detail about this change.  Below is a table describing how the numbers will change on December 1st. Please contact the National Weather Service before December 1st with any questions.

The concept of zero datum can be tricky to understand. The graphic below attempts to describe this concept. Consider a generic river channel as shown below. The "ruler" in the water is the river gage. Note how the "ruler" actually goes below the bottom of the river. This is on purpose and allows readings to continue even during a drought.  Over time, scouring of the channel bottom can cause the "zero" to be above the streambed and lead to negative readings. When this happens, the gage owner may lower the zero datum.

Lowering the zero datum has a major impact on the data related to a particular river gage. Flood stage increases because lowering the zero datum causes the gage height to be higher. There isn't more water in the river, it's just that the reference point, the zero datum, has changed. The graphic below shows how when the zero datum is lowered, the gage height increases. Other gage height related data increases too, like flooding records and impact statements.