**CE 394K.2 Hydrology**

**University**** of Texas at **

**Introduction to NWIS Analyst **

By David R. Maidment

Center for Research in Water Resources

January 25, 2007

**Contents**

2. Plotting Daily Streamflow Using NWIS Analyst

3. Plotting Unit Value and Instantaneous Irreglar Data

NWIS Analyst http://water.usu.edu/nwisanalyst/
is a graphing application for data from
the National Water Information System developed by Jeff Horsburgh at

**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 **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 ** 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 **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