了解大坝大小与其生态效应之间的关系对于基于大坝拆除的河流恢复工作的优先级很重要。尽管人们对大型存储水坝的影响了解很多,这些信息可能不适用于小型水坝,这代表了绝大多数正在考虑拆除的大坝。为了更好地了解大坝的影响如何随大小而变化,我们进行了一项多学科研究,研究了大坝对一系列生态特征的下游影响,包括地貌,水化学,附生植物,河岸植被,底栖大型无脊椎动物,和鱼。我们将大坝大小变量与大西洋中部地区16座大坝的实测生态特征的下游-上游分数差异相关联,高范围为0.9至57m,水力停留时间(HRT)从30分钟到1.5年。对于一系列物理属性,更大的水坝有更大的影响。例如,大坝下方的水面宽度在大型大坝下方更大。相比之下,大坝大小对沉积物粒度没有影响,尽管细粒床料的比例低于大坝,但与大坝大小无关。更大的水坝往往会更多地降低水质,下游溶解氧减少,温度升高。较大的水坝减少了无机养分(N,P,Si),但增加了颗粒营养素(N,P)在下游。水生生物倾向于在较大水坝(对于鱼类和附生植物)以下的物种组成上具有更大的差异,较低的分类多样性(对于大型无脊椎动物),和更高的污染耐受性(对附生和大型无脊椎动物)。植物在大水坝和小水坝下的反应不同,大型水坝下的入侵物种较少,但更多的是在小水坝下面。总的来说,这些结果表明,更大的水坝对我们测量的生态系统组件有更大的影响,因此,它们的移除对恢复河流生态系统具有最大的潜力。
Understanding the relationship between a dam\'s size and its ecological effects is important for prioritization of river restoration efforts based on dam removal. Although much is known about the effects of large storage dams, this information may not be applicable to small dams, which represent the vast majority of dams being considered for removal. To better understand how dam effects vary with size, we conducted a multidisciplinary study of the downstream effect of dams on a range of ecological characteristics including geomorphology, water chemistry, periphyton, riparian vegetation, benthic macroinvertebrates, and fish. We related dam size variables to the downstream-upstream fractional difference in measured ecological characteristics for 16 dams in the mid-Atlantic region ranging from 0.9 to 57 m high, with hydraulic residence times (HRTs) ranging from 30 min to 1.5 years. For a range of physical attributes, larger dams had larger effects. For example, the water surface width below dams was greater below large dams. By contrast, there was no effect of dam size on sediment grain size, though the fraction of fine-grained bed material was lower below dams independently of dam size. Larger dams tended to reduce water quality more, with decreased downstream dissolved oxygen and increased temperature. Larger dams decreased inorganic nutrients (N, P, Si), but increased particulate nutrients (N, P) in downstream reaches. Aquatic organisms tended to have greater dissimilarity in species composition below larger dams (for fish and periphyton), lower taxonomic diversity (for macroinvertebrates), and greater pollution tolerance (for periphyton and macroinvertebrates). Plants responded differently below large and small dams, with fewer invasive species below large dams, but more below small dams. Overall, these results demonstrate that larger dams have much greater impact on the ecosystem components we measured, and hence their removal has the greatest potential for restoring river ecosystems.