Since streams are a critical link in the trophic interactions and biogeochemical cycles of the McMurdo Dry Valleys, streams located throughout the area were chosen for the long-term ecological research (LTER) study. To monitor stream hydrology, an extensive network of gauging stations was set up to continuously measure streamflow throughout the austral summers. Some streams are intermittently gauged to monitor water quality and quantity. While the researchers are in the field to collect hydrology data, stream water samples to be used for chemical analysis are also gathered. Sample locations for hydrology data thus coincides with those for stream chemistry samples. Locations also remain consistent from season to season. The coordinates (latitude, longitude and elevation) for many of these sites were measured with a GPS (global positioning system) gauge. Records based on the 1996-97 GPS measurements are accurate to about a meter. (They contain a value of "GPS96-97.DOC" for the 'file name' field). Other records may not have coordinates as precise as this. Most of them were obtained from a locations table created by Harry House (U.S Geological Survey). However, it is unknown what was initially used to measure these latitudes, longitudes and elevations. From time to time, samples are taken from sites that are not regularly monitored. When that occurs, the field team uses a GPS gauge, accurate to about 10 meters, to obtain the coordinates for the sample. The coordinates are then added to this dataset.