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D A M R E M O V A L. Panacea or Pandora for Rivers. Joseph C. Greene Research Biologist Greene Environmental Services May 2006. Original background illustration from: Gregory Stewart, Ph.D. http://www.collbett.org/greg/. Some Facts.
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D A M R E M O V A L Panacea or Pandora for Rivers Joseph C. Greene Research Biologist Greene Environmental Services May 2006 Original background illustration from: Gregory Stewart, Ph.D. http://www.collbett.org/greg/
Some Facts • Hydropower is the most plentiful and efficient renewable energy resource. It contributes more than 90 percent of all renewable electric energy produced in the U.S.; • If all the energy produced by hydropower was produced by coal instead, pollutants from coal would increase by 16 percent; • A third of countries depend on hydropower for over half their electricity, and over a third of irrigated land depends on dams; and, • much of the world's food is subsidized by cheap irrigation water provided by dams.
The Argument Against Dams The reservoir or lake created by a dam may cover many thousands of acres of forest that once served as habitat for wild animals and plants. Large dams have contributed to: • the extinction of many fish and other aquatic species; • the disappearance of birds in floodplains; • huge losses of forest, wetland, and farmland; and, • the erosion of coastal deltas.
Dam Removal Panacea or Pandora for Rivers The debate is playing out against a backdrop of power crises, cycles of flood and drought, endangered ecosystems, and changing societal expectations and demands for water. The idea that dams are not necessarily permanent features of the landscape, but can and should be removed, has emerged as a rallying cry, political lightning rod, and unparalleled scientific opportunity for understanding the behavior of rivers Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
Why is dam removalemerging as an issue? • Increased hazard of aging dams; • Open policy window because of the large number up for re-licensing; • Response to concerns about physical fragmentation of river systems;
Why is dam removal emerging as an issue? • Response to concerns about threatened and endangered fish species; • Response to calls for the return to a more “natural” hydrologic regime to restore ecological and geomorphic (surface configuration )function; and, • Finally, dam removal has great symbolic value in terms of representing our good intentions toward our environment. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
Dam Removal A striking conclusion from a number of recent workshops was ……………… “We actually know very little about the biological and physical consequences of removing dams”. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
The response to dam removal is intrinsically complex! Because of the longevity of dams, channels typically adjust to the altered hydrologic and sediment transport regimes that dams impose; consequently, Dam removal itself represents a land surface re-configuration disturbance to a quasi-adjusted river system. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
“We know that this disturbance tends to propagate both upstream and downstream through cascades of erosional and depositional processes that are coupled in time and space.” “Typically, the upstream response drives the downstream response.” Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
Stewart, G, S. Hayes, G. Grant, and C. Bromley, 2003, Where did all the dam sediment go, Predicting the effects of dam removal on channel morphology and ecology.
From: Gregory Stewart, Ph.D. http://www.collbett.org/greg/
From: Gregory Stewart, Ph.D. http://www.collbett.org/greg/
Key upstream unknowns are: The rate and mechanisms of removal of sediment from the upstream reservoir in relation to ….. • Flow regime; • Grain size; • Channel and deposit geometry; • Method of dam removal. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
Downstream of the Dam: Sediment will be transported through a channel system already altered by the presence of the dam. A complex array of storage features and associated residence times limits our ability to accurately predict how long it will take for sediment to be routed downstream. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
Downstream of the Dam: Even more challenging to predict are the interactions among … • Sediment transport and deposition; • Vegetation establishment; • Responses to aquatic ecosystems to elevated sediment loads; and, • Transformed channel morphology. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
Needs: We need coordinated retrospective laboratory and field studies …. • On how dams function in the landscape; • On impacts and consequences of past removals, including analysis of dam removal analogues, such as natural and artificial dam failures; and, • Studies that are rigorous pre- and post-removal monitoring schemes for those dams slated for removal. The studies should be targeted at resolving key uncertainties. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
From Past Work on the Effects of Dams on Rivers “We know that all dams are not created equal!” Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
The Same May Be True For Dam Removal • Some will stimulate dramatic effects on river and ecosystem processes; • Others will have no effects; • Some may open Pandora’s boxes of new problems. Grant, G., 2001, Dam Removal: Panacea or Pandora for Rivers?, Hydrological Processes 15, 1531-152.
The National Academies' National Research Council committee estimated that the research, monitoring, andremediation outlined in its report, on the Klamath River Basin, would cost about $25 million to $35 million over the next five years …. excluding costs for major projects SUCH AS DAM REMOVAL! National Research Council, 2003, News Release, Broader Approach Needed for Protection And Recovery of Fish in Klamath River Basin, http://national-academies.org
Savage Rapids Dam Rogue River, Oregon The design for the removal of Savage Rapids dam is proceeding, slowly. The completion date isn't moving up, but the cost sure is. The Bureau of Reclamation estimates a cost of $30 million to remove part of Savage Rapids Dam and install pumps Grants Pass Daily Courier, "Savage Rapids Total: $30 Million."
Klamath River Dam Removal Investigation • J. C. Boyle Dam • Copco 1 Dam • Copco 2 Dam • Iron Gate Dam G&G Associates developed a report for American Rivers, Trout Unlimited, California Trout, Friends of the River, and the Klamath River Intertribal Fish and Water Commission. G&G Associates, 2003, Investigation of Removal of Four Lower Klamath River Dams, J. C. Boyle Dam, Copco 1 Dam, Copco 2 Dam and Iron Gate Dam
The scope of this investigation is feasibility level only. Specific information regarding volume, location, and size of trapped sediment, specific dimensions of structures, nature and extent of water use downstream of the dams, and location of spoils sites was either not available or developing such information was beyond the scope of this report. Numerous issues require more investigation before final costs estimates can be completed. The objective of this report is to determine whether removal of the four lower Klamath River dams is feasible from a construction and cost perspective. G&G Associates, 2003, Investigation of Removal of Four Lower Klamath River Dams, J. C. Boyle Dam, Copco 1 Dam, Copco 2 Dam and Iron Gate Dam
Studies conducted as part of the hydropower re-licensing proceeding indicate that cumulatively, all four dams trap approximately 14.4 million cubic yards of sediment, of which approximately 87% is silt and clay and 13% is sand or larger material. G&G Associates, 2003, Investigation of Removal of Four Lower Klamath River Dams, J. C. Boyle Dam, Copco 1 Dam, Copco 2 Dam and Iron Gate Dam
Cost estimates developed for this study are based on the assumption that sediment trapped behind the dams would be naturally eroded downstream. Information regarding the volume of sediment trapped appears to be well developed but information regarding grain size distribution of trapped sediment appears to be insufficient to determine how quickly the eroded sediment would move through and out of the river system. G&G Associates, 2003, Investigation of Removal of Four Lower Klamath River Dams, J. C. Boyle Dam, Copco 1 Dam, Copco 2 Dam and Iron Gate Dam
Review of available information regarding the dams, trapped sediment, and river characteristics indicates that removing the dams is feasible and that the cost would be approximately$40 million. Based on assumptions stated in this report, the cost for removal would be $19.2, $1.9, $8.5, and $6.2 million respectively for Iron Gate, Copco 2, Copco 1, and J.C. Boyle dams. G&G Associates, 2003, Investigation of Removal of Four Lower Klamath River Dams, J. C. Boyle Dam, Copco 1 Dam, Copco 2 Dam and Iron Gate Dam
Effects of removal of a small dam on downstream macroinvertebrate and algal assemblages in a Pennsylvania stream There is little empirical data on which to base predictions about ecological responses to dam removal. Less than 5% (~20) of all dam removals in the United States have been accompanied by published ecological studies. Most of the dams removed to date were relatively small structures (usually <15 ft. high). Thomson, 2005, Effects of removal of a small dam on downstream macroinvertebrate and algal, J. N. Am. Benthol. Soc., 2005, 24(1):192–207
Effects of removal of a small dam on downstream macroinvertebrate and algal assemblages in a Pennsylvania stream The authors examined the responses of benthic macroinvertebrate and algal assemblages in downstream reaches to the removal of a small, run-of-river dam on Manatawny Creek, Pennsylvania. Benthic macroinvertebrates, algae, and habitat characteristics were monitored upstream and downstream of the dam for 4 months before removal, 3 months after partial removal (i.e., when the impoundment was largely eliminated but sediment remained trapped behind the remaining structure), and 12 months after complete dam removal. Thomson, 2005, Effects of removal of a small dam on downstream macroinvertebrate and algal, J. N. Am. Benthol. Soc., 2005, 24(1):192–207
Effects of removal of a small dam on downstream macroinvertebrate and algal assemblages in a Pennsylvania stream Macroinvertebrate density, algal biomass, and diatom species richness declined significantly downstream of the dam following complete dam removal. Downstream impacts occurred only after the dam structure had been completely removed and sediments had been transported downstream from the former impoundment by high flows. Thomson, 2005, Effects of removal of a small dam on downstream macroinvertebrate and algal, J. N. Am. Benthol. Soc., 2005, 24(1):192–207
Effects of removal of a small dam on downstream macroinvertebrate and algal assemblages in a Pennsylvania stream Biotic impacts persisted for the duration of the study (12 months after complete removal). Our results and other studies of dam removal suggest that downstream sedimentation following dam removal can reduce densities of macroinvertebrates and benthic algae and may reduce benthic diversity, but for small dams such impacts may be relatively minor and will usually be temporary.
