USGS Continuous Nutrient Monitoring in the Mississippi River Basin

USGS Continuous Nutrient Monitoring in the Mississippi River Basin


USGS Continuous Nutrient Monitoring in the
Mississippi River Basin video The Mississippi River is the fourth largest
river in the world and with its tributaries, the Mississippi drains all or part of 31 States
or about 41% of the continental United States. This central artery of the US connects the
Great Lakes to the Heartland to the Gulf. The U.S. Geological Survey is working with
water, industrial, and agricultural groups, as well as cities, States, Federal and non-governmental
organizations to better understand the river and monitoring data. One such collaboration is with mayors of the
Mississippi River Cities and Towns Initiative. “We are actually a group of 76 mayor’s from
Minnesota to Louisiana who have come together to protect our water way and make sure that
the economies that depend on the river are more sustainable. We know in government, especially, what gets
measured, gets managed. In March of this year, the mayors signed a
memorandum of common understanding with the USGS and we are working together to deploy
a comprehensive nutrient monitoring network for the entire Mississippi River Valley. That might not sound like what would expect
for a group of Mayors and cities but we do understand that it all starts with water quality.” The USGS historically has collected both discreet
and continuous water-quality data. Both discreet and continuous data have provided
a rich foundation of information for science analyses such as determining trends in water
quality to assess the health of our Nation’s rivers and streams. Recent advances in nitrate sensors are now
providing an opportunity to measure changes in concentration many times per hour or day
and can be deployed in many types of rivers and lakes. The USGS has 3,894 real-time stream gages
in the Mississippi River basin that monitor the flow in the Mississippi and its tributaries. About 60 sites have continuous monitoring
for nitrates and about 10 sites monitor for continuous phosphate, but some are temporary
monitoring sites that are deployed for assessing site specific nutrient issues. A dedicated long-term nutrient monitoring
or “supergage” network is needed that will provide a cost effective, consistent,
unbiased regional approach to evaluate the changes in nutrient loads. Significant resources are invested by farmers,
industry, and the public to reduce nutrient pollution to the river and a long-term network
will help us assess the changes that are occurring. But, setting up and maintaining these continuous
monitoring “supergages” is complex as Elizabeth Murphy explains. A USGS “supergage” is a gauge station
with real-time, continuous measurements of streamflow, other parameters ( such as pH,
Specific Conductance, turbidity, and Dissolved Oxygen), and at least one chemical constituent
such as nitrate or phosphate. Discrete samples of nitrate and phosphate
are still collected but the continuous nutrient sensors help fill in the gaps between samples. The supergages also collect data when it isn’t
safe to collect discrete samples, such as during extreme flood events when the largest
loads of nutrients are being flushed through the basin. We are here at the USGS supergage to collect
continuous water quality. This site is on the Green River near Geneseo
Illinois where the station is housed along the edge of the river. We can see that nitrate and turbidity are
being continuously recorded at this site from instruments that are deployed in the river. Solar power allows these supergages to be
positioned in remote locations. Integrating cellular and satellite modems
into the supergage also supports remote sites and allows real-time data upload to the Web
along with remote system monitoring. (put NWIS web address at bottom of screen). The long pipes going down to the stream house
the four instruments for measuring nitrate, phosphate, turbidity, and general water quality. The USGS makes monthly maintenance trips to
most water-quality sites to clean the sensors and calibrate them against known standards. This helps insure that there has been no degradation
to the instrument and the data available on the web are accurate. Additionally, the hydrologic technicians collect
samples at the extreme flow events (high and low) to make sure the instruments are recording
accurately at the extremes. The largest loads of nutrients to the river
occur during storm and high flow events. Since the sensors are located at one point
in the river, the technicians will visit the site for periodic cross-sections of water
quality. These measurements across the river will allow
us to understand how the measurement at the instrument relates to variability across the
channel. By monitoring and analyzing the nutrient data
from a regional network of supergages we are taking the first steps in understanding how
actions by farmers, industry and governments on the landscape are changing the conditions
in the river and the actions we may need to take to preserve this vital resource for generations
to come.

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