TITLE: Mesonet Arizona Maricopa County ALERT Streamflow Network Data
     
CONTACTS:

Flood Control District of Maricopa County
sdw@mail.maricopa.gov
(602) 506-8701
http://www.fcd.maricopa.gov/alert/alert.htm


1.0  DATA SET OVERVIEW
     

This data set contains streamflow data from the Maricopa County ALERT 
streamflow network.  There are a total of 134 stations included in the 
data set.  The temporal resolution and parameters measured vary by
station.  The stations are located throughout Maricopa County in Arizona.
This data set covers the period from 1 June to 30 September 2004.  The data 
are in columnar ASCII format.


2.0  INSTRUMENT DESCRIPTION

2.1  Instrumentation Information

At the time of this writing (25 March 2005) instrumentation information
is not available.  It is expected that by April or May of 2005 the
Maricopa County  Flood Control District web page:
http://www.fcd.maricopa.gov/alert/alert.htm
will have detailed information on the instrumentation at each station.
Also included will be site descriptions, obstructions and photographs
around each station.


2.2  Station Locations

Station locations are included in the comma delimited file
stream_sites.txt that is included with your data order.


3.0  DATA COLLECTION AND PROCESSING


Information on the collection and processing of these data can be
found at the Maricopa County network page:
http://www.fcd.maricopa.gov/Services/ALERT/default.asp

UCAR/JOSS conducted no processing or quality control on these data.


4.0  DATA FORMAT AND FILE NAMING


4.1  Data Format
 
There are individual files for each station.

These data are in columnar ASCII format. 

Each file contains some header records, e.g.

FCDMC ALERT System Streamflow Data Display
Note: Depth (feet) shown is arbitrary and may or may not represent the
actual
depth of water at the gage.
However, the Discharge (cfs) is the true total flow with depth / datum
differences taken into account.
5163 Tiger Wash Pressure Transducer
Date       Time        feet      cfs


These provide the sensor id (5163) the station name (Tiger Wash),
the instrumentation (Pressure Transducer in this case) and then the 
data column headers with the Date and Time (in Mountain Standard Time) 
and the units (feet and cubic feet per second (cfs) in this case).


4.2  File Naming conventions

StationName_SensorID.txt
e.g.
TigerWash_5163.txt

5.0  DATA REMARKS

Q: How do the streamgages work?
A: The majority of our streamgages use a sensor called a "pressure
transducer". This device senses the pressure exerted by water (or any
fluid) above it. Only the density of the fluid need be known to calculate
the depth of the fluid above. Once the depth is known, the flow rate
(usually cubic feet per second, or cfs, also known as discharge) can be
calculated by application of a rating curve.

Q: OK, so what is a rating curve?
A: A rating curve is a graph of depth (usually in feet) versus discharge
(usually cfs). It is created through application of a mathematical formula
in the case of weirs and engineered channels, or through a process of
channel surveying and mathematical modeling for natural channels. In either
case, the channel slope, area and roughness determine the capability of a
channel to transmit water.

Q: Why do stream gages sometimes show a depth value but no corresponding
discharge?
A: Because frequently the instrument is not at the "bottom" or zero point
in the channel or the pool area of a dam. It is often necessary to locate
the instrument above or below this point. In these cases there will either
be some positive or negative depth displayed when discharge numbers begin
to register. In neither case will flow actually be happening at the site
unless the discharge value is non-zero.


6.0  REFERNCES


None.