Geology Reference
In-Depth Information
constructed) on the Osage river is the Lake of the
Ozarks impounded by the Bagnell Dam, originally
constructed in 1931 to provide hydropower to
much of eastern Missouri - mainly St. Louis.
Reducing sediment loads to these rivers and reser-
voirs will ensure a sustainable water resource for
these multiple purposes for generations to come.
To help ensure that sustainability, the potential
impact of global warming should be evaluated.
An additional problem for the entire Midwest
agricultural area of the US is the contribution to
the annual creation of an area of hypoxia in the
Gulf of Mexico. The hypoxia area is partially
caused by soil erosion and the ensuing delivery of
nutrients to the Gulf of Mexico. One way of reduc-
ing the delivery of nutrients is to reduce soil ero-
sion and sediment delivery, and this may well be
required to reduce the hypoxia area in the Gulf; in
fact, nutrient reduction goals for a number of states
are already under discussion (UMRSHNC, 2005).
It is also important in selecting farming prac-
tices to evaluate the long-term implications of
global climate change on sediment lost from this
watershed. While the exact nature of the climate
change in particular regions is still unknown,
tools are already being developed and some are in
place (Southwest Watershed Research Center,
2008) to estimate the impact of climate change
when this change is known.
The problem is to select for this small watershed
a suitable, sustainable land-management system
that will reduce soil erosion, runoff volume, and
sediment and nutrient delivery, and allow for
intense use of this land in an area with a soil that is
suitable for row crops, small grains and permanent
grass production. The watershed layout as it will be
modelled is shown in Fig. 9.3. While sustainability
can be defined in a number of ways, in this case the
focus will be on soil erosion and sediment delivery.
(1) an average annual soil loss and sediment
delivery estimate for an extended period;
(2) sediment characteristics;
(3) return period estimates for single storms for
design purposes, and for estimation of onsite and
offsite damages from rare storms;
(4) an identification of areas on the watershed
hillslopes or channels where remedial measures
might be needed; and
(5) an estimate of the impact of global climate
change on soil erosion and sediment delivery.
The annual soil loss and sediment delivery esti-
mates, as well as sediment characteristics, are
important for the long-term viability of the
streams and lakes in the Osage river watershed.
Return period estimates for single storms are
more related to the design of nearby structures
and water conveyance systems, perhaps for zon-
ing to minimize damage to high-value real estate
and to minimize danger to humans and livestock.
Siting and design of roadways, waterways,
impoundments and conservation practices could
be based on the results from such an analysis.
Global climate change estimates are being
made, and these estimates could be included in
such an evaluation. While there are many
unknowns, there seems reasonable consensus that
rainfall intensities and amounts will increase
(Nearing et al ., 2005). With easily used tools avail-
able to develop scenarios for climate change, it
seems prudent to use models and data that could at
least give some reasonable estimate of the poten-
tial impact of global change. Such information
could result in improved selection and design of
systems, and in lowered future costs and damages.
9.3
Models that Might be Applicable
There are several models that could potentially
be used (http://soilerosion.net/doc/models_menu.
html). Not all have all the abilities needed to pro-
vide the information necessary to meet the crite-
ria above. Several widely used models include:
RUSLE (http://fargo.nserl.purdue.edu/rusle2_
dataweb/RUSLE2_Index.htm)
9.2 Model Criteria
The factors needed to evaluate for this watershed
the impact of land management on sediment
yield and water quality, and to design facilities
that could mitigate damages, are:
SWAT (http://www.brc.tamus.edu/swat/)
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