Effects of Dams on Rivers

by

Andrew Wilcox

• LAST REVIEWED: 24 May 2017
• LAST MODIFIED: 24 May 2017
• DOI: 10.1093/obo/9780199363445-0068

Introduction

The focus of this annotated bibliography is on the physical and Ecological Effects of dams on rivers. Thousands of papers have been published on the topics addressed here; this bibliography therefore only provides an introduction to the literature and identifies some key papers, although many important works beyond those annotated here have been published. The bibliography is divided into the following subsections: General Overviews, Special Issues, Geomorphic Effects, Sediment Issues, Hydrologic Effects, Ecological Effects, Riparian Vegetation effects, US Case Studies, International Studies, environmental flows, and Other Dam Effects Topics. Many of the papers included here could fit under more than one subheading; for example, studies of dam effects typically consider hydrologic effects and some combination of associated geomorphic and/or ecological effects. The following topics are, for the most part, not addressed here, although some of the individual papers may address some of these issues as part of broader studies of dam effects: social effects, human health, economics, river response to dam removal, and effects of beaver dams.

General Overviews

The papers in this section provide overviews of dam effects, including linkages among multiple types of dam effects (e.g., hydrologic and geomorphic). These papers are based on reviews of multiple studies (Collier, et al. 2000) and data sets with large temporal and/or spatial scales (Graf 1999, Graf 2006); provide general syntheses (Rosenberg, et al. 1997; Poff and Hart 2002; Gregory 2006); and present metrics for assessing effects of dams (Schmidt and Wilcock 2008). Williams and Wolman 1984 is a classic and comprehensive work that documents dam-induced changes on rivers in the United States.

• Collier, M., R. H. Webb, and J. C. Schmidt. 2000. Dams and rivers: A primer on the downstream effects of dams. US Geological Survey Circular 1126. Tucson, AZ: US Geological Survey.

  Reviews changes to rivers downstream of dams, including changes to the morphology of riverbeds and banks, as well as to biota and riparian habitats. Linkages are drawn between dam management strategies and the types of downstream changes that occur. Dam effects on a set of US rivers are discussed, including the Rio Grande and the Upper Salt, Snake, Chattahoochee, Platte, Green, and Colorado Rivers. Issues such as fish passage, water quality, sediment budgets, and habitat maintenance flows are discussed.

• Graf, W. L. 1999. Dam nation: A geographic census of American dams and their large‐scale hydrologic impacts. Water Resources Research 35.4: 1305–1311.

  DOI: 10.1029/1999WR900016

  Describes dam-induced fragmentation of rivers and impacts on flow regimes in the continental United States, including geographic variation. Impacts are described in terms of the number of years of runoff stored by dams (greater than three years in some western and plains rivers; as low as 25 percent of annual runoff in northeast and northwest rivers); drainage area per dam (lowest in New England, highest in the lower Colorado basin); storage volumes; and storage volumes compared to mean annual runoff.

• Graf, W. L. 2006. Downstream hydrologic and geomorphic effects of large dams on American rivers. Geomorphology 79.3–4: 336–360.

  DOI: 10.1016/j.geomorph.2006.06.022

  Hydrologic Effects of very large dams (dams that store 1.2 km³ [10⁶ acre feet] of water or more) on various flow metrics are documented, using stream gauge analysis from thirty-six paired reaches upstream and downstream of dams and including assessment of regional variation. Geomorphic Effects are described in terms of dam-induced effects on the size of low- and high-flow channels; the amount of active versus inactive floodplain area; and geomorphic complexity, defined as the number of separate functional surfaces per unit channel length. Overall, dam-affected reaches have shrunken channels with simplified morphology.

• Gregory, K. J. 2006. The human role in changing river channels. Geomorphology 79.3–4: 172–191.

  DOI: 10.1016/j.geomorph.2006.06.018

  Reviews both direct (e.g., from engineering works such as dams) and indirect (e.g., from land use) effects of human activities on rivers, including numerous references to foundational literature on these topics. Causes (various types of human activities) and effects (e.g., scour, aggradation, other types of channel change) are discussed. Challenges in considering human effects on rivers are identified, including modeling, feedbacks, climate change, channel design, and cultural issues.

• Poff, N. L., and D. D. Hart. 2002. How dams vary and why it matters for the emerging science of dam removal. BioScience 52.8: 659.

  DOI: 10.1641/0006-3568(2002)052[0659:HDVAWI]2.0.CO;2

  Reviews how dams impair river ecosystems, including changes to flow, sediment transport, biogeochemical fluxes, water quality, and connectivity. Describes variation in dams and the scientific limitations of some criteria used to characterize dams. Calls for an ecological classification of dams and outlines a framework for developing such a classification. Discusses how these topics can inform dam removal decisions.

• Rosenberg, D. M., F. Berkes, R. A. Bodaly, R. E. Hecky, C. A. Kelly, and J. W. M. Rudd. 1997. Large-scale impacts of hydroelectric development. Environmental Reviews 5.1: 27–54.

  DOI: 10.1139/a97-001

  Reviews environmental and social effects of biogeochemical and hydrological effects of dams and reservoirs, including methylmercury bioaccumulation in the food web, greenhouse gas emissions from reservoirs, downstream effects of hydrologic alteration, and biodiversity impacts. The unique spatial and temporal scales of these effects are discussed, ranging from the small spatial and temporal scales at which methylmercury bioaccumulation operates to the larger-scale effects of flow changes, greenhouse gas emissions, and losses of biodiversity.

• Schmidt, J. C., and P. R. Wilcock. 2008. Metrics for assessing the downstream effects of dams. Water Resources Research 44.4: W04404.

  DOI: 10.1029/2006wr005092

  Three metrics for assessing the downstream effects of dams on hydrogeomorphic processes are described: (1) the balance between changes in supply and transport capacity, (2) the Shields number, (3) the ratio of post-dam to pre-dam discharge, for a specified recurrence interval. Calculation of sediment-balance conditions can be used to evaluate how to reverse undesired deficit or surplus conditions. The metrics are evaluated for 4000 km of dammed rivers in the western U.S.: 67 percent are in sediment deficit, 4 percent in sediment surplus, and the rest are indeterminate.

• Williams, G. P., and M. G. Wolman. 1984. Downstream effects of dams on alluvial rivers. United States Geological Survey Professional Paper 1286. Washington, DC: US Government Printing Office.

  Largely relying on data from twenty-one US rivers with alluvial beds and monumented cross sections, many semiarid, shows that dams consistently reduced flood peaks but had more variable effects on other elements of the flow regime. Sediment loads were consistently lower downstream of dams than pre-dam, with effects persisting for up to hundreds of kilometers. Degradation of the channel bed was observed at many of the sites and usually occurred 10–20 years after dam construction. Channel width changes downstream of dams included widening, narrowing (e.g., in association with Riparian Vegetation expansion), and no change.