The NRP had its beginnings in the late 1950's. Since that time, the program has grown to encompass a broad spectrum of scientific investigations. The sciences of hydrology, mathematics, chemistry, physics, ecology, biology, geology, and engineering are used to gain a fundamental understanding of the processes that affect the availability, movement, and quality of the Nation's water resources. Results of NRP's long-term research investigations often lead to the development of new concepts, techniques, and approaches that are applicable not only to the solution of current water problems, but also to future issues that may affect the Nation's water resources. Basic tools of hydrology that have been developed by the NRP include ground water modeling, geochemical modeling, and regional flood frequency analysis. These and other tools developed by the NRP are in common use today throughout the USGS, in other agencies, and in the private sector. Additional information about the NRP is provided by a fact sheet published in 2005, The National Research Program in the Hydrological Sciences (also available in pdf format, 1.6 MB). U.S. Geological Survey Circular 1195 (pdf format, 9 MB) provides some indication of the scope of research problems that were being addressed in 2000, when it was published.