There are over 140 stream-gaging stations in the Delaware River Basin. Overall, the total number of basin gages has not declined. However, as new gages have been added at different locations within the basin, many gages with long periods of streamflow record have been discontinued due to lack of funding.

When a gage that has collected data for many years is permanently or even temporarily discontinued, a history of streamflow is now fragmented and a valuable hydrological tool lost. This is a troubling circumstance as gages with long periods of streamflow information are vital to the effectiveness of the USGS stream-gaging program. While there are many uses for short-term (less than 20 years of record) streamflow data, some applications of data require long-term, consistent records to achieve accuracy. One example of such an application is trend analysis and the study of the greenhouse gases. Due to concerns about the effects of greenhouse gas concentrations in the atmosphere on the earth's hydrology and climate, scientists have used actual streamflow records to determine whether streamflows are beginning to change as a result of human activities or global warming. For such studies, streamflow record lengths of 50 or more years were essential for detecting trends in streamflow variability.

As of 1998, the Delaware River Basin had approximately 51 stream-gaging stations with periods-of-record of 50 or more years. The longest period of record in the basin, 94 years of continuous streamflow data, belongs to the gaging station on the Delaware River at Port Jervis, New York. Three other gaging stations in the basin have records of 90 or more years: Bush Kill at Shoemakers, Pennsylvania (90 continuous years), the Delaware River at Riegelsville, New Jersey (92 continuous years), and the Lehigh River at Bethlehem, Pennsylvania (92 years, 4 years of missing data).