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How Big of an Effect Do Small Dams Have? Using Geomorphological Footprints to Quantify Spatial Impact of Low-Head Dams and Identify Patterns of Across-Dam Variation.

Fencl JS, Mather ME, Costigan KH, Daniels MD - PLoS ONE (2015)

Bottom Line: Dams are significant disruptions to streams.Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network.For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams.

View Article: PubMed Central - PubMed

Affiliation: Kansas Cooperative Fish and Wildlife Research Unit, Division of Biology, Kansas State University, Manhattan, Kansas, United States of America.

ABSTRACT
Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0-15.3 km) or 287 wetted widths (136-437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams.

No MeSH data available.


Related in: MedlinePlus

Evaluation of Substrate Selection among Individuals.Comparison of (A) mean substrate size picked by four individuals at three randomly chosen points along a transect with ten replicates for each point and (B) average D50 of three Wolman pebble counts of one riffle. NS indicates no significant difference between individuals. Statistics are the result of a Kruskal-Wallis test of sampler effect using (A) a Bonferroni corrected α = 0.016 (0.05 divided by 3 (for each location)) (B) α = 0.05.
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pone.0141210.g003: Evaluation of Substrate Selection among Individuals.Comparison of (A) mean substrate size picked by four individuals at three randomly chosen points along a transect with ten replicates for each point and (B) average D50 of three Wolman pebble counts of one riffle. NS indicates no significant difference between individuals. Statistics are the result of a Kruskal-Wallis test of sampler effect using (A) a Bonferroni corrected α = 0.016 (0.05 divided by 3 (for each location)) (B) α = 0.05.

Mentions: Substrate sizes were characterized in the field following a careful evaluation of potential individual sampler bias in substrate size selection (sensu [42]). First, we tested if substrate size selection by four different individuals was more variable than repeated selection of substrate by a single individual (10 replicates) at the same location along a transect using a randomized block design. Substrate was measured along the intermediate axis with a gravel template (gravelometer, 2–362 mm). All individual samplers selected similar-sized substrates (+/- one size class of the gravelometer) at three predetermined locations along a transect (location 1 (chi-sq = 0.72, df = 3, P = 0.87), location 2 (chi-sq = 1.31, df = 3, P = 0.73), location 3 (chi-sq = 7.25, df = 3, P = 0.06); Kruskal-Wallis test, α = 0.016 with Bonferroni correction; Fig 3A). Second, we tested if D50 (the median substrate size, e.g., [19]) from a standard Wolman pebble count on a riffle [43] was more variable among individuals than repeated counts by a single individual (three replicates) for the same riffle. In the second evaluation of individual sampler effects, D50 was not different among the four individuals (Kruskal-Wallis test: chi-sq = 6.55, df = 3, P = 0.09, α = 0.05; Fig 3B).


How Big of an Effect Do Small Dams Have? Using Geomorphological Footprints to Quantify Spatial Impact of Low-Head Dams and Identify Patterns of Across-Dam Variation.

Fencl JS, Mather ME, Costigan KH, Daniels MD - PLoS ONE (2015)

Evaluation of Substrate Selection among Individuals.Comparison of (A) mean substrate size picked by four individuals at three randomly chosen points along a transect with ten replicates for each point and (B) average D50 of three Wolman pebble counts of one riffle. NS indicates no significant difference between individuals. Statistics are the result of a Kruskal-Wallis test of sampler effect using (A) a Bonferroni corrected α = 0.016 (0.05 divided by 3 (for each location)) (B) α = 0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4634923&req=5

pone.0141210.g003: Evaluation of Substrate Selection among Individuals.Comparison of (A) mean substrate size picked by four individuals at three randomly chosen points along a transect with ten replicates for each point and (B) average D50 of three Wolman pebble counts of one riffle. NS indicates no significant difference between individuals. Statistics are the result of a Kruskal-Wallis test of sampler effect using (A) a Bonferroni corrected α = 0.016 (0.05 divided by 3 (for each location)) (B) α = 0.05.
Mentions: Substrate sizes were characterized in the field following a careful evaluation of potential individual sampler bias in substrate size selection (sensu [42]). First, we tested if substrate size selection by four different individuals was more variable than repeated selection of substrate by a single individual (10 replicates) at the same location along a transect using a randomized block design. Substrate was measured along the intermediate axis with a gravel template (gravelometer, 2–362 mm). All individual samplers selected similar-sized substrates (+/- one size class of the gravelometer) at three predetermined locations along a transect (location 1 (chi-sq = 0.72, df = 3, P = 0.87), location 2 (chi-sq = 1.31, df = 3, P = 0.73), location 3 (chi-sq = 7.25, df = 3, P = 0.06); Kruskal-Wallis test, α = 0.016 with Bonferroni correction; Fig 3A). Second, we tested if D50 (the median substrate size, e.g., [19]) from a standard Wolman pebble count on a riffle [43] was more variable among individuals than repeated counts by a single individual (three replicates) for the same riffle. In the second evaluation of individual sampler effects, D50 was not different among the four individuals (Kruskal-Wallis test: chi-sq = 6.55, df = 3, P = 0.09, α = 0.05; Fig 3B).

Bottom Line: Dams are significant disruptions to streams.Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network.For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams.

View Article: PubMed Central - PubMed

Affiliation: Kansas Cooperative Fish and Wildlife Research Unit, Division of Biology, Kansas State University, Manhattan, Kansas, United States of America.

ABSTRACT
Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0-15.3 km) or 287 wetted widths (136-437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams.

No MeSH data available.


Related in: MedlinePlus