The USGS National Water Information System (NWIS) provides access to millions of sites measuring streamflow, groundwater levels, and water quality. This web service provides methods for retrieving data from NWIS. For more information about NWIS, see the NWIS home page at <a href='http://waterdata.usgs.gov/nwis' target='_blank'>http://waterdata.usgs.gov/nwis</a> This function returns a string formatted as XML containing a list of all streamflow sites within the NWIS system. The site code for each site is provided within &lt;SiteCode> tags in the XML. This function returns a string formatted as XML containing a list of sites than have been updated in the past x minutes. Input the number of minutes as an integer in the Minutes argument of the method. Given a USGS station number, this method returns a string (formatted as XML) with the station's metadata. Given a USGS variable code, this method returns a string (formatted as XML) of the variable's name, units, and description. Given a USGS station number, a variable code, a start date, and an end date, this method returns a time series in XML format. Given a USGS station number, a variable code, a start date, and an end date , this method returns the url for a graph image of the pvariable for that station. Given a lat/long box, a begin date, an end date, a USGS parameter code, and a minimum count, this method returns a string where each record is a new line, and each record contains (1) the USGS station number, (2) the number of observations, (3) the date of the first observation, and (4) the date of the last observation of the given parameter, for that station. Given a USGS station number, a USGS parameter code, a start date, and an end date, this method returns a string with the water quality time series date/times and values. Given a USGS station number, a start date, and an end date, this method returns a string with the daily averaged discharge time series date/times and values. Given a USGS station number, this method returns an array with (1) the number of discharge observations, (2) the date/time of the first discharge observtion, and (3) the date/time of the last discharge observation for that station. Given a USGS well number, a start date, and an end date, this method returns a string with the groundwater level time series (date/times and values). Given a USGS parameter code, this method returns the parameter's measurement units. Creates a KML file that can be used to view stations in Google Earth. The USGS National Water Information System (NWIS) provides access to millions of sites measuring streamflow, groundwater levels, and water quality. This web service provides methods for retrieving data from NWIS. For more information about NWIS, see the NWIS home page at <a href='http://waterdata.usgs.gov/nwis' target='_blank'>http://waterdata.usgs.gov/nwis</a>