Water Numeric Nutrient Criteria: What, Why, and the 4Rs

04th Jun 2014 4R Practices,Implement the 4Rs,Right Source,

State water quality agencies
have the major responsibility of ensuring the protection of water resources
from nutrient (N and/or P) pollution. For decades, lake, stream, and river
water quality nutrient levels have been periodically monitored by either state
agencies or federal agencies.

Historically, most states
have relied on narrative nutrient criteria that stipulate that designated uses
of water resources shall not be impaired by nutrients. Since about 2000, the
U.S. EPA has emphasized the need for more robust numeric nutrient criteria by
states, based on sampling of reference waters and human-impacted waters. The
EPA has advocated use of overlapping frequency distributions of nutrient levels
from least-impacted reference streams/rivers and monitored streams/rivers, in
selecting numeric nutrient criteria.

Last year, in its 2013
release of the 2008-2009 National Rivers and Streams Assessment Report on water
quality,
the EPA used a more narrowed statistical approach than in the past, in
interpreting stream/river quality conditions. Overall, the U.S. EPA found that
55% of the monitored rivers and streams were in poor biological condition.
Compared to the 2004 EPA wadeable stream assessment, 7% fewer stream miles were
in good biological condition and 19% fewer stream miles were in good condition
for P.

The good news was that 9%
more stream miles were in good condition for N, 17% more stream miles were in
good condition for in-stream fish habitat, and 12% more stream miles were in
good condition, as measured by riparian disturbance.

Currently, seven states have
statewide or partial N numeric criteria for rivers/streams, while 11 have
statewide or partial P numeric criteria for rivers/streams. More states are
making progress
, and the number
of states with statewide or partial numeric criteria may double by 2016. According
to a 2013 paper published in the Journal of Environmental Quality,
among the several states with site-specific nutrient criteria for streams and
rivers, only Wisconsin and Florida have statewide criteria which are
well-supported by peer-reviewed and technical papers documenting the process of
criteria development. A number of states have developed new nutrient loss
reduction strategies. Several state strategies are designed to primarily
encourage agriculture, and other nonpoint or diffuse sources of nutrient loss
from land to water resources, to become more aggressive with their best
management practice implementation and mitigation actions.

The 12 states adjacent to the
Mississippi River are under greater pressures to do even more to reduce the
losses of N and P that get transported downstream to the Gulf of Mexico, and
which aggravate the early summer development of low dissolved oxygen conditions
(hypoxia) in the northern Gulf of Mexico. Each of those 12 states is
developing, or has developed, a nutrient loss reduction strategy to further its
commitment to improved and protected water quality throughout the Mississippi
River Basin and the northern Gulf of Mexico.

More agricultural losses of N
and P from nonpoint (diffuse) sources can be curbed, through more timely and
wise implementation of 4R (right source at the right rate, time, and place)
nutrient management practices. Those 4R practices will be most effective when
skillfully combined with in-field and edge-of-field soil and water conservation
practices. There is no time like the present to keep more of our applied
nutrients in fields and out of water resources.

How will you be adjusting
your 4R nutrient management and soil and water conservation plans to be part of
the winning water quality solution?

– CSS –

For more information, contact
Dr. Clifford S. Snyder, Nitrogen Program Director, IPNI, Phone (501) 336-8110,
E-mail: [email protected]  

Abbreviations: N = nitrogen;
P = phosphorus.