Rio Grande / Rio Bravo NASQAN
1. Purpose and Objectives: Since 1995, the National Stream Quality
Accounting Network (NASQAN) of the USGS, has focused on monitoring the
water quality of some of the nation’s largest rivers, including the Rio
Grande. NASQAN operates a network of 39 stations where the concentration
of a broad range of chemicals, including pesticides and trace elements,
and stream discharge are measured. From these data, source contaminants
can be identified; contaminants can be routed through the river system
to determine gains and losses; and the amount of contaminants delivered
to receiving waters— such as estuaries and reservoirs—can be estimated.
NASQAN data provide information on the influence of large-scale environmental
processes and human activities on these rives that serve as drinking-water
supplies, navigational routes, recreational areas, and biological habitats.
Also, data from this program can be used to affect water policy in communities.
2. Funding: Since the NASQAN project involves the nation’s four
largest rivers-- Mississippi, Colorado, Rio Grande, and the Columbia—it
would be difficult to compute an estimate for a single river. However,
the network, or the NASQAN overall, gets about $5 million annually. Estimates
for the Rio Grande and Colorado Rivers were not given.
3. Partners: USGS and IBWC
4. Description and Background: NASQAN today, is markedly different
from the program that was operated before 1995. NASQAN was begun in 1973
to provide nationally comparable information on water quality. Consistent
with the design of the national streamflow-gaging network, water quality
measurements were made at stations at the downstream end of most hydrologic
accounting units; hence, the term accounting in the network name. More
than 500 stations sampled on a monthly basis for suspended sediment, major
ions (such as sulfate and chloride), trace elements (such as lead), nutrients
(such as nitrate), sanitary indicators (such as fecal coliform), and limited
biological information (such as chlorophyll-a). These data were intended
to provide general purpose information on the status and trends of water
quality.
5. Methodology of Sampling: NASQAN stations are sampled frequently
enough to characterize variations in chemical and sediment concentrations
that occur during a year, particularly the variation that occurs between
low and high lows, during different seasons of the year, and during different
hydrologic regimes—such as periods when snowmelt dominates river discharge.
By sampling a river under these different conditions, the amount of material
that passes a station, known as the mass-flux of a constituent (expressed
as tons per day), can be reliably determined by multiplying the concentration
of a constituent by the stream discharge. Constituent mass fluxes can be
compared among stations and across spatial scales. For example, yields
of contaminants (in tons per sq. mi.) can be compared between stations;
gains or losses in a river reach can be determined between any two stations;
and amounts of materials delivered to a reservoir or estuary can be calculated.
The ability to determine these three values—source, transport, and delivery
of constituents—enables a broad range of scientific and policy issues to
be addressed.
6.) Status: The program is ongoing.
7.) U.S. Contacts: Chuck Heywood, USGS, (505) 262-5351; Fax:
(505) 262-5298 Albuquerque, NM Yusef Farran, IBWC, (915) 534-6704; Fax:
(915) 534-6680 El Paso, TX
For more complete information, please see NASQAN website at: http://water.usgs.gov/public/nasqan