They allow you to enter layers of data and conduct spatial analysis of that data. They can vary from simple systems r un on personal computers to sophisticated and very powerful systems that run on large mainframes. You can also locate your sites on a topographic map that can be digitized on to an electronic map of the watershed. Once these points have been established, you can link your database to the points on the map, query your data base, and create graphic displays of the data. Powerful GIS applications typically require expensive hardware, software, and technical training.
Many people are capable of writing their own programs to manipulate and display data.
Also, most commercial programs are developed to easily import and export data in standard formats. This feature is important because if you want to share data with other programs or organizations all you need are compatible software programs. A specific set of quality control measures will be required for any data entered into the system to aid in data sharing.