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Rivers don't
just flow
through a watershed, they
drain
it. Rivers are fed by smaller-order creeks and streams. As
water runs off land into creeks, streams and rivers, it carries with it
suspended sediments, minerals, nutrients and pollution. As
such, land use directly and indirectly affects natural
systems. Changes in land use alter soil properties, nutrient
inputs, the
distribution of plant communities, and available habitats for animals.
Land use also affects the amount and composition of stream water,
nutrient loads, water temperatures, and water quality, all of which
impact
aquatic ecosystems. The figure to
the right shows the
distribution of land within the Portneuf River basin based on land
ownership. Although the upland areas are under Federal
jurisdiction, the lowlands and valleys are privately owned. The
majority of the privately-owned land is used for agriculture.
Agriculture relies on diversions of the river for irrigation and,
through application of fertilizer, increases nutrient inputs to the
river, a process called eutrophication.
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| Cattle can have
serious negative effects on streams when allowed to graze in riparian
areas. |
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In addition to
agricultural land, the
Portneuf River passes through towns and cities, including Pocatello, on
its way to the Snake River. These urban areas are another
contributor of point and nonpoint source pollution. Point sources
include the Pocatello Water Treatment Plant, urban runoff (including
motor oil and gasoline) and industrial discharges from FMC and
Simplot. Nonpoint sources include agricultural and range lands,
construction activities, and hydrelectric power.
To
maintain water quality in the face of these inputs, the Clean
Water Act
establishes the water quality standards
and Total Maximum Daily Load (TMDL)
for pollutants. |
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A TMDL is the
sum of the allowable loads of a single pollutant from all
contributing point and nonpoint sources. The City of Pocatello's
TMDL implementation plan can be found at http://www.ci.pocatello.id.us/Envirodiv/tmdl/tmdl.htm
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Because
of the
important effects land use
can have on a river, a variety of research into the effects of
land use on
the Portneuf has been conducted by undergraduate and graduate students
and several faculty at Idaho State University. In addition, water
quality monitoring
programs
help to determine sources of pollution and track compliance with water
quality standards. Monitoring parameters include sediment load,
nutrients, bacteria,
oil, flow,
dissolved oxygen concentration, and water temperature.
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