CE 394K.2 Hydrology

University of Texas at Austin


Introduction to NWIS Analyst


By David R. Maidment

Center for Research in Water Resources

University of Texas at Austin


January 25, 2007




1. Introduction

2. Plotting Daily Streamflow Using NWIS Analyst

3. Plotting Unit Value and Instantaneous Irreglar Data


1. Introduction


NWIS Analyst http://water.usu.edu/nwisanalyst/  is a graphing application for data from the National Water Information System developed by Jeff Horsburgh at Utah State University.  It assumes that you know a USGS station number, an NWIS parameter code, and a period of record from begin date to end date, and it enables you to plot time series and probability graphs with the data.  Information about available periods of record for NWIS stations can be found from the USGS NWIS web site to which links are given on the NWIS Analyst page.  The observational data are extracted from NWIS through CUAHSI web services http://www.cuahsi.org/his/webservices.html .   


2.  Plotting Daily Streamflow Using NWIS Analyst


Open an Internet Explorer web browser and go to the URL http://water.usu.edu/nwisanalyst/  



In this case, we’ll access daily value data for streamflow (variable 00060) for the Neuse River near Clayton, North Carolina (station 02087500).  The record begins in 1 August 1927 and continues to the present.  Lets check out the flow data for this year.  Fill in the Station, Variable, Start Date and End Date fields as shown, and hit Plot Graph.  



And after a few seconds while the web services go off to acquire the data, you’ll get a graph that shows as follows, along with quite a few descriptive statistics of the data on the right hand side.



Now, if you want to see all the record from the Neuse River at this location, put in 01/01/1900 as the start date on the application.  You’ll see that it takes quite a bit longer to extract all the data from NWIS for this plot – you are pulling 80 years of daily data, so that’s nearly 30,000 numbers!  Here is the plot and statistics that you get:



Your can see the cumulative frequency curve of these data by hitting the Probability Tab at the top of the graph:

with the result:



And the frequency histogram by hitting the Histogram tab



And, finally the Box and Whisker plot of daily flow statistics in each month of the year:



In this case, the symbology on the graph corresponds to the statistics on the right hand table: the green line goes through the median values for each month, the box around that represents the difference between the 25% and 75% values of the data, and the black hatch marks on the line represent the 10% and 90% values of the data.  Individual values higher than 90% are shown as dots on the lines.    This is a very nice way of seeing seasonal trends in the statistics of these data.


If you want to download the data rather than just plotting it, go to the top of the graph tabs and hit Data Export



And you’ll get a nice message to download a compressed Excel file


Pretty neat!


3.  Plotting Unit Values and Instantaneous Irregular Data


NWIS maintains three kinds of data: Daily Values, which are summary statistics over a day for a variable, Unit Values which are the instantaneously recorded values of the variable within the day (e.g. each 15 minutes for streamflow), and Instantaneous Irregular Values which are sampled data at a particular instant of time, such as water quality samples.  In the case of Unit Value data, at present only the last 31 days are accessible, which can be obtained for the Neuse river by selecting Unit Value Data as the NWIS Database, as shown below, and leaving all the other displays the same:



You can see the graph is a bit dense with dots, so if you use the Plot Options on the right hand side, you can just plot a line:



Pretty neat!


For instantaneous irregular data, you need to know the Variable Code for the parameter that you want.  The parameter 00300 is Dissolved Oxygen, so if we put in that, and look at the period of record, we get:



And so on.  You have direct access to tens of thousands of stations all over the country.  Enjoy!  To figure out the parameter codes, you can check out the NWIS web site at http://nwis.waterdata.usgs.gov/usa/nwis/pmcodes