For scientific study of water resources, which is known as hydrology, GIS has been of immense use. As water is one of the most important resources its management requires detailed studies to understand how climate change could affect water availability. The demand for water by growing populations has been of great import, necessitating professional studies of the patterns of water availability, waste water management, etc.
Water flows as a result of hydrological cycles, necessitate the need to understand, and GIS helps in pin pointing information. We can understand changing patterns of water resources with the help of GIS. Earlier GIS systems were of static nature, but in recent times they have become very dynamic, helping us to understand water resources in the light of present realities and analyze the patterns with historical data.
GIS helps us to understand availability of water not only by the present stream flows but also with its historicity, through interconnected systems. Monitoring sites, measuring locations etc., are all part of GIS information systems. GIS can also include remote sensing data, as well. It helps hydrologists to know where the precipitation will eventually drain, by analyzing the runoff points of water sources.
GIS can point to the snowpack stations on the ground, so that when snow melts, its coverage can be properly calculated, and with this the hydrologists will also be able to ascertain how much of water will be finally available for use to cities and for agriculture.
GIS plays an important role in case of precipitations, which pose a challenge to hydrologists. Precipitation is ascertained by using information from point locations, but there is the difficulty of extrapolating information and applying them to areas. This is done through construction of Theissen Polygons to calculate distances, for finding out the precise locations to give them precipitation values. Thus GIS application in hydrology holds great importance.