How can agriculture
affect lakes and rivers?
agricultural activities may impact surface water by contributing nutrients,
pesticides, sediment, and bacteria, or by altering stream flow. Fertilizer
and pesticide use, tillage, irrigation, and tile drainage can affect
water quality and hydrology. Livestock production practices, including
riparian grazing, confined feeding operations, and manure management
can also impact water quality.
plans and Best Management Practices (BMPs) address these activities
to minimize degradation of water resources. Not all agricultural production
adversely affects water quality, but because much of the state is
agricultural land, there is a potential for impact on your local stream
or lake. Regional differences in land use and lake characteristics
will influence how susceptible your lake or river may be.
How can crop production
affect water quality and hydrology?
management can contribute nutrients from excessive use of either commercial
fertilizer or manure, improper application methods or timing, or inadequate
BMPs to minimize leaching or runoff. Nitrogen moves easily as nitrate,
dissolved in surface water runoff, drain-tile flow, or seepage to
ground water. Phosphorus is generally bound to soil particles and
may be carried to surface water through erosion or in solution. Nutrients
cause excessive plant and algae growth in lakes and streams.
Crop production may
also contribute pesticides to surface or ground water. Pesticides
include herbicides, insecticides, fungicides, and other chemicals
to control pests. Some pesticides or their breakdown products last
a long time in soil or water. Some pesticides are very soluble in
water and are more susceptible to leaching or runoff.
Thousands of acres
of agricultural land in Minnesota have been tiled and drained to improve
productivity. Drainage carries excess nutrients and pesticides and
moves water more quickly off the landscape. Rather than soaking slowly
into the ground, water moves rapidly into streams and lakes, changing
the hydrology, or flow patterns. More water ends up reaching lakes
and streams faster than it would from undeveloped landscapes. This
has implications for water quality and biological communities.
Irrigation and chemigation
(when pesticides are added directly to irrigation water) can increase
the potential for nutrient and pesticide transport to nearby surface
waters and ground water below agricultural fields. Base flow in nearby
streams, lakes, or wells may be affected by intensive irrigation that
draws down the ground water table.
can also increase the sediment load in lakes and rivers. Exposed soil
is more susceptible to wind and water erosion. Cultivation near shorelines
or on Highly Erodible Lands (HEL) can intensify erosion and sedimentation.
Increased sediment can reduce flood capacity, instream flows, habitat,
and aesthetics. Riparian filter strips, grassed waterways, crop residue,
and other conservation practices can minimize soil loss.
How can livestock production
affect water quality?
Manure contains nutrients
(nitrogen and phosphorus), fecal coliform bacteria, and, often, pharmaceuticals
used to enhance growth or improve animal health. When animals are
allowed continuous, unrestricted access to streams and lakes, manure
ends up in the water and riparian vegetation may be severely damaged.
Exposed, compacted soil is more susceptible to erosion and is more
difficult to revegetate.
Manure from livestock
operations away from the waters edge may also cause problems
if it is not properly contained and managed. When animals are confined
in feeding areas, vegetation is usually limited and manure is concentrated.
Appropriate BMPs to collect, handle, and apply manure according to
nutrient management plans have been adopted by many producers. However,
there is still much work to address feedlots and manure management,
including state and local policy development and implementation, education,
and adoption of BMPs.
What can we do about
at the watershed level, you can identify the potential influence of
nearby or upstream agriculture on your lake or river. At the same
time you should characterize other sources of nutrients or pollution,
including on-site sewage treatment systems or municipal wastewater
plants, lawn care practices, impervious surfaces, highway maintenance,
construction, industrial sources, in-lake processes, and atmospheric
By identifying all
potential sources and adopting strategies to manage or minimize impacts,
you may be able to avoid conflict and work together to protect your
lake or river. There are also incentive programs to assist farmers
with adopting BMPs. As a last resort, enforcement may be necessary.
Talk with your local Feedlot Officer, SWCD, or Planning and Zoning
office for enforcement options.
Who can I call if I
have a question or problem related to agriculture near water?
Check your local telephone
listing, the Who to Contact
section of the Minnesota Shoreland Management Resource Guide Web site,
or the Web sites listed below for:
What are some additional
resources related to agriculture near water?
Voluntary Best Management Practices That Help Control Pests. 1998.
Minnesota Department of Agriculture, U of MN Extension Service, Natural
Resources Conservation Service
- BMPs for Water
Quality. 1995. Conservation Technology Information Center
- The Minnesota
Pesticide Management Plan. 1996. Minnesota Department of Agriculture
- Whole Farm Planning.
1997. Land Stewardship Project, U of MN Extension Service, Minnesota
Department of Agriculture