watervulnerability

Ouachita National Forest Watershed Vulnerability Assessment, Southern Region (R8)
ASSESSMENT OBJECTIVE
The assessment objective, using the Aquatic Cumulative Effects (ACE) model, is to determine changes in
risk level for aquatic biota for each subwatershed for two climate scenarios (B1 and A1B) for the near
term (year 2050) and long term (year 2080).
SCALES OF ANALYSIS
There are 13 fourth-level
cataloging units on the forest
and 50 fifth-level watersheds.
Within those fifth-level units,
190 sixth-level subwatersheds
have some NFS ownership. The
area assessed included all NFS
ownerships under the
management of the Ouachita
National Forests. Subwatersheds
are also referred to as sixth-level
watersheds or 12 digit
hydrologic units. They are
typically 10,000 to 40,000 acres
in size.
CONNECTIONS TO OTHER ASSESSMENTS, PLANS AND EFFORTS
This analysis has several connections within the Forest and across the Region. The Forest has participated
in a number of assessments at various scales. The first and largest assessment was the Ozark Ouachita
Highlands Assessment (OOHA) Aquatic Condition report (USDA Forest Service, 1999). This assessment
addressed water quality and management concerns across a three state area at the fourth-level cataloging
units (eight digit hydrologic units).
From 1999 through 2001, the Region (including the Ouachita) completed a series of forest-level
assessments using the East-wide Watershed Assessment Protocol (EWAP, 2000). This assessment
occurred at the fifth-level watershed scale. It addressed a number of conditions and vulnerabilities for
each watershed and applied a ranking system for condition, vulnerability, and overall watershed health
among the fifth level watersheds on the forest.
From that exercise, watershed condition was determined for many forest-level plan revisions across the
region. The Ouachita was one of the forests that took the information from the assessments and developed
a disturbance (based on sediment) model to address cumulative effects. The value of the model was that it
provided a correlation of disturbance to fish guild communities. For the first time, this allows a numerical
assessment of the effect of management actions on fish communities. Again this exercise was at the fifthlevel
watershed. To date, this process has been applied on 10 of 16 forests in the Southern Region.
The Ouachita NF developed a project level analysis using the same protocols found in the forest plan.
This model is referred to as the Aquatic Cumulative Effects (ACE) model. This forest level model was
modified to address the short and long term risks of climate change for two different climate scenarios.
228 Assessing the Vulnerability of Watersheds to Climate Change