JAWRA - Ag Conservation

• Project Type: General OWC
• Title: Designing Impact Assessments for Evaluating Ecological Effects of Agricultural Conservation Practices on Streams
• Date: 12/15/2009
• Water Conservation - Doc Type: Reports

SMILEY, SHIELDS, AND KNIGHT
have too slow of a water flow for effective surber sam-
pling. A dipnet sample consists of a 1 m long dipnet
sweep that samples macroinvertebrates in the ben -
thos and water column. Three surber samples are col-
lected from riffles and shallow runs.
Preliminary Results
Differences in selected response variables from the
first year of the study (2006) were examined with sin-
gle factor ANOVA (riparian habitat and geomorphol-
ogy) or two factor repeated measures ANOVA
(instream habitat, water chemistry, and fish commu-
nity response variables). Preliminary results confirm
the site selection criteria as the minimally impacted
streams had greater (p < 0.05) riparian widths, can-
opy cover, woody vegetation density, and sinuosity
than the ditches with and without herbaceous ripar-
ian buffers (Table 3). Additionally, drainage ditches
with and without herbaceous riparian buffers had
greater (p < 0.05) thalweg depths and top bank
widths than the minimally impacted streams
(Table 3). Water velocity was greater (p < 0.05) in the
minimally impacted streams than ditches with and
without herbaceous riparian buffers (Table 3). No dif-
ferences (p > 0.05) in other instream habitat, water
chemistry, or fish community response variables were
observed (Table 3). However, general trends in
water chemistry and fish community variables among
treatments were as expected. Water temperature,
turbidity, and percent omnivores (percent of fishes
that eat plants and animals) were greater in the
drainage ditches with and without herbaceous ripar-
ian buffers than the minimally impacted streams
(Table 3). Fish species richness and Percidae abun-
dance (number of darters) were the greater in the
minimally impacted streams than drainage ditches
(Table 3). The high variability in water chemistry
and fish community response variables likely hin-
dered detection of significant differences among
means in this preliminary analysis. Future analyses
using five years of data will have greater sample
sizes that will improve the ability to detect differ-
ences among treatments. These preliminary results
represent the starting point in this evaluation of her-
baceous riparian buffers and future analyses will
examine how the habitat and biota within the treat-
ments change over time.
CONCLUSIONS
Guidelines for designing impact assessments to
assess the ecological responses of streams to conser-
vation practices have been developed based on our
experiences and others. The guidelines were intended
to provide guidance for others investigating the influ-
ence of restoration and other anthropogenic habitat
alterations with impact assessments in small to
TABLE 3. Mean (SD) Riparian Habitat, Geomorphology, Instream Habitat, and Fish Community Response Variables Among
Drainage Ditches Without Herbaceous Buffers (control), Drainage Ditches with Herbaceous Buffers (buffer treatment), and
Unchannelized Streams With Forested Riparian Buffers (minimally impacted) Within the Upper Big Walnut Creek, Ohio, 2006
Note: Different letters within a row indicate a significant (p < 0.05) difference among treatments
JAWRA
876 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
Control
Buffer Treatment
Minimally Impacted
Riparian habitat
Riparian width (m)
8.2 (2.4) C
49.0 (28.5) B
99.4 (14.9) A
Canopy cover ( %)
6.7 (6.5) B
6.9 (10.1) B
71.6 (19.5) A
Woody vegetation density ( # /m
0.2 (0.2) B
0.2 (I).1) B
0.9 (0.1) A
Geomorphology
Thalweg depth (m)
1.8 (0.2) A
1.6 (0.4) A
0.8 (0.1) B
Top bank width (m)
9.0 (1.2) A
8.9 (1.1) A
4.8 (0.0) B
Sinousity
1.0 (0.0) B
1.0 (0.1) B
1.6 (0.2) A
Instream habitat
Water depth (m)
0.12 (0.04) A
0.13 (0.09) A
0.13 (0.02) A
Water velocity (m/s)
0.03 (0.05) B
0.01 (0.02) B
0.09 (0.02) A
Wet width (m)
2.00 (0.48) A
1.74 (1.00) A
2.40 (0.30) A
Water chemistry
Water temperature ( °C)
18.8 (7.2) A
17.2 (6.4) A
14.5 (6.3) A
Dissolved oxygen (mg 11)
8.4 (3.2) A
8.8 (3.8) A
9.8 (1.9) A
Turbidity (NTU)
69.7 (50.4) A
52.2 (47.3) A
31.0 (28.7) A
Fish community
Species richness
7.9 (3.8) A
7.0 (5.4) A
8.7 (1.2) A
Percent omnivores
28.4 (27.6) A
32.4 (33.4) A
4.9 (4.3) A
Percidae abundance
27.4 (26.7) A
24.2 (21.5) A
95.5 (44.2) A
Note: Different letters within a row indicate a significant (p < 0.05) difference among treatments
JAWRA
876 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION