Data from: 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

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.

纵向连通性是河流的基本特征，可被自然及人为过程（anthropogenic processes）破坏。水坝是对溪流的重大干扰因素。超过200万座低水头水坝（low-head dams，高度<7.6米）分割了美国的河流。尽管这些普遍存在的干扰可能带来不利影响，但低水头水坝对地貌学（geomorphology）和生态学的空间影响在很大程度上仍未得到验证。由于不了解低水头水坝影响的程度，研究与保护工作的进展受到阻碍。基于地貌学文献，我们改进了一种方法，可量化低水头水坝影响的空间范围（本文中称为坝足迹，dam footprint），评估河网内不同低水头水坝坝足迹的变化，并确定该变化背景的特定方面。我们测量了美国堪萨斯州上尼欧肖河（Upper Neosho River）内六座低水头水坝上下游的湿宽、深度及底物粒径分布。总坝足迹平均为7.9公里（范围3.0-15.3公里）或287个湿宽（范围136-437个湿宽）。估算结果包括上游（平均值：6.7公里或243个湿宽）和下游坝足迹（平均值：1.2公里或44个湿宽）。这六座低水头水坝总共影响了该河网主河道47.3公里（约17%）的范围。尽管在年龄、大小、位置及主要功能上存在差异，但上尼欧肖河网内单个低水头水坝的地貌足迹大小相对相似。上游水坝的数量及与上游水坝的距离会影响坝足迹的空间范围，但水坝高度无此影响。综上所述，普遍存在的低水头水坝无论个体还是累积作用，均改变了流水生态系统（lotic ecosystems）。单个水坝的特征及相邻水坝的背景均会影响河网内低水头水坝的作用效果。因此，低水头水坝的研究与管理需要采用与大型水坝不同的、更具整合性的方法，而非目前针对大型水坝的个体化方法。