Januchowski-Hartley, S.R., P.B. McIntyre, M. Diebel, P.J. Doran, D.M. Infante, C. Joseph, and J.D. Allan, 2013: “Restoring aquatic ecosystem connectivity requires expanding inventories of both dams and road crossings.” Frontiers in Ecology and the Environment, v. 11, pp. 211-217, doi: 10.1890/120168.
A key challenge in aquatic restoration efforts is documenting locations where ecological connectivity is disrupted in water bodies that are dammed or crossed by roads (road crossings). To prioritize actions aimed at restoring connectivity, we argue that there is a need for systematic inventories of these potential barriers at regional and national scales. Here, we address this limitation for the North American Great Lakes basin by compiling the best available spatial data on the locations of dams and road crossings. Our spatial database documents 38 times as many road crossings as dams in the Great Lakes basin, and case studies indicate that, on average, only 36% of road crossings in the area are fully passable to fish. It is therefore essential that decision makers account for both road crossings and dams when attempting to restore aquatic ecosystem connectivity. Given that road crossing structures are commonly upgraded as part of road maintenance, many opportunities exist to restore connections within aquatic ecosystems at minimal added cost by ensuring upgrade designs permit water flow and the passage of fish and other organisms. Our findings highlight the necessity for improved dam and road crossing inventories that traverse political boundaries to facilitate the restoration of aquatic ecosystem connectivity from local to global scales.
Powers, S.M., J. Julian, M. Doyle, and E.H. Stanley, 2013: “Retention and transport of nutrients in a mature agricultural impoundment.” Journal of Geophysical Research, v. 118, doi: 10.1029/2012JG002148.
Small impoundments intended for irrigation, livestock watering, and hydropower are numerous in agricultural regions of the world. Many of these artificial water bodies are well positioned to intercept fertilizer runoff and pollutants but could be vulnerable to long-term sedimentation, management intervention, or failure. We examined solute retention in a mature, sediment-filled, run-of-river impoundment created by a small, >100 year old dam in agricultural Wisconsin, United States. To do so, we measured instantaneous net fluxes of inorganic and organic solutes through the system, which contained wetlands. The impoundment was a persistent net sink for sulfate and, during the warm season only, a net sink for nitrate, ammonium, and soluble reactive phosphorus. There was also a negative relationship between nitrate and sulfate retention, suggestive of nitrate-stimulated sulfate production. Impoundment hydraulics were then altered by a management manipulation (dam removal) that caused mean water travel time to decrease by approximately 40%. Following manipulation, autoregressive modeling of solute time series indicated a decrease in mean net retention of nitrate, sulfate, ammonium, and soluble reactive phosphorus. There was also a decrease in the variability (coefficient of variation) of instantaneous net exports of dissolved organic nitrogen and dissolved organic phosphorus. These biogeochemical changes were consistent with predictions based on hydraulics (reduced water travel time), with the exception of ammonium release immediately following reservoir dewatering. Our results emphasize the biogeochemical importance of reservoir-wetland ecosystems, which are expanding with impoundment sedimentation but are threatened by infrastructure aging. We suggest that reservoir wetlands be considered in the management of dams and surface water pollution.
Wang, P., J.P. Lassoie, S. Dong, and S.J. Morreale, 2013: “A framework for social impact analysis of large dams: A case study of cascading dams on the Upper-Mekong River, China.” Journal of Environmental Management, v. 117, pp. 131-140, doi: 10.1016/j.jenvman.2012.12.045.
Construction of large dams on the Upper-Mekong River, China, has significant social impacts on local communities. To analyze the social impacts, we identified three classes of wealth for the affected people, material, embodied, and relational, and comprehensively compared the loss and compensation in each type of wealth. Then we examined the effects on gap of wealth at household and community levels. Lastly, an insider–outsider analysis was conducted to understand the differences in the perceptions of wealth loss between local villagers and policy makers, and recommendations for more reasonable compensation policies were provided.
Jørgensen, D., and B.M. Renöfält, 2013: “Damned if you do, dammed if you don’t: Debates on dam removal in the Swedish media.” Ecology and Society, v. 18, doi: 10.5751/ES-05364-180118.
Dam removal is an increasingly common practice. Dams are removed for various reasons, with safety, economics, and ecosystem restoration being the most common. However, dam removals often cause controversy. Riparian land owners and local communities often have a negative view of removal, and their reasons vary. It may be the loss of recreational benefits such as swimming and boating, loss of cultural and historical context tied to the dam, or fear that removal may have a negative effect on aesthetic values. Because controversies are often picked up by local media, and media in itself is an important channel to build support around a cause, the way in which dam removals are reported and discussed in the media is likely to influence the debate. Here, we examine the ways in which proponents and opponents of dam removal frame the services provided by two contrasting ecosystems, i.e., an existing dam and the potential stream without a dam, by performing a media discourse analysis of the reasons given for removal and the reasons presented for the dam to remain in place. Our source material includes Internet-based newspaper articles and their associated public comments in four dam removal controversies in Sweden. Our analysis indicates that public opposition is not based on knowledge deficiency, where more information will lead to better ecological decision-making, as is sometimes argued in dam removal science; it is instead a case of different understandings and valuation of the environment and the functions it provides.
Landry, R., A.A. Assani, S. Biron, and J.-F. Quessy, 2013: “The management modes of seasonal floods and their impact on the relationship between climate and streamflow downstream from dams in Quebec (Canada).” River Research and Applications, doi: 10.1002/rra.2644.
The goal of the study was to compare the modes of management of seasonal floods for different dams and to constrain their impact on the relationship between climate variables and streamflow downstream from the dams. At the Rawdon dam, downstream from which the Ouareau River is characterized by a natural-type regulated flow regime, a ‘type A’ flood management mode prevails, in which the same rainfall and/or snowmelt events account for seasonal floods both in the unregulated (natural) stretch of river upstream from the dam and in the river downstream from the dam. As a result, seasonal floods in the natural setting and downstream from the dam are nearly synchronous. In contrast, downstream from the Matawin dam (Matawin River), which produces an inversion-type regulated flow regime, the prevalent flood management modes are of types B and D, whereby seasonal floods observed upstream and downstream from the dam are not caused by the same rainfall and/or snowmelt events and, as a result, are not synchronous. This difference in seasonal flood management modes affects the interannual variability of the magnitude of seasonal daily maximum flows related to the seasonal floods. Thus, the interannual variability of these flows downstream from the Matawin dam differs significantly from that of flows upstream. No correlation is observed between climate variables and streamflow downstream from the Matawin dam. This absence of correlation disappears gradually at the annual scale, at which streamflow is correlated with rainfall, as is observed upstream from the dam.
Luo, X.X., S.L. Yang, and J. Zhang, 2012: “The impact of the Three Gorges Dam on the downstream distribution and texture of sediments along the middle and lower Yangtze River (Changjiang) and its estuary, and subsequent sediment dispersal in the East China Sea.” Geomorphology, v. 179, pp. 126-140, doi: 10.1016/j.geomorph.2012.05.034.
The grain size of river sediments changes systematically downstream from source to sink, and is influenced by catchment lithology, geomorphology, hydrology, oceanography and, in modern settings, anthropogenic impacts. Compared with small, gravel-bedded river systems, less is known about large, sandy‐bed rivers, particularly from the river source to marine sink. In the present study, we examine longitudinal changes in sediment grain size along the middle and lower Yangtze River, downstream of the Three Gorges Dam (TGD), and along the major sediment dispersal pathway into the East China Sea, over a total length of 2100 km. We also examine the spatial patterns of seabed sediment grain size in the East China Sea adjacent to the Yangtze Estuary (70,000 km2 in area). In particular, we consider the impact of the TGD on the grain size of the riverbed and seabed sediments. Before the construction of the TGD, the relationship between median grain size and distance along the sandy bed of the middle and lower Yangtze showed a downstream fining trend that was exponential in form. After the TGD was built, erosion caused an abrupt gravel–sand transition to develop in the section immediately downstream of the TGD. In the Yangtze Estuary, flocculation and subsequent deposition of suspended riverine mud during the slack water period between flood and ebb tides led to the formation of an abrupt sand–mud transition. Muddy deposits along the major longshore sediment dispersal route also show an exponential fining trend. However, towards the open East China Sea, the modern riverine muds are replaced seawards by older sands. The mud margin there was found to have retreated landward significantly over the post-TGD period due to erosion driven by the significant decrease in sediment supply from the Yangtze River. We expect that the impact of the TGD on the grain size of bed sediments in the Yangtze River and the East China Sea will continue for some time, and the change in the grain size of bed sediments there will become more pronounced.
Castello, L., D.G. McGrath, L.L. Hess, M.T. Coe, P.A. Lefebvre, P. Petry, M.N. Macedo, V.F. Renó, and C.C. Arantes, 2012: “The vulnerability of Amazon freshwater ecosystems.” Conservation Letters, doi: 10.1111/conl.12008.
The hydrological connectivity of freshwater ecosystems in the Amazon basin makes them highly sensitive to a broad range of anthropogenic activities occurring in aquatic and terrestrial systems at local and distant locations. Amazon freshwater ecosystems are suffering escalating impacts caused by expansions in deforestation, pollution, construction of dams and waterways, and overharvesting of animal and plant species. The natural functions of these ecosystems are changing, and their capacity to provide historically important goods and services is declining. Existing management policies—including national water resources legislation, community-based natural resource management schemes, and the protected area network that now epitomizes the Amazon conservation paradigm—cannot adequately curb most impacts. Such management strategies are intended to conserve terrestrial ecosystems, have design and implementation deficiencies, or fail to account for the hydrologic connectivity of freshwater ecosystems. There is an urgent need to shift the Amazon conservation paradigm, broadening its current forest-centric focus to encompass the freshwater ecosystems that are vital components of the basin. This is possible by developing a river catchment-based conservation framework for the whole basin that protects both aquatic and terrestrial ecosystems.
Pearse-Smith, S.W.D., 2012: “‘Water war’ in the Mekong Basin?” Asia Pacific Viewpoint, v. 53, pp. 147–162, doi: 10.1111/j.1467-8373.2012.01484.x.
The Mekong River system provides a crucial source of natural resources for riparian nations. However, the increasingly rapid pace of hydro-development in the Mekong Basin is threatening the integrity of the river system, posing a real concern for Lower Basin states, which are particularly dependent on the basin. This scenario has led to warnings of armed conflict, or even ‘water war,’ between riparian states. Certainly, the expanding scale of hydro-development can be expected to continue increasing interstate tensions in the Mekong region; but are these tensions really likely to escalate to armed conflict? This paper explores this question by drawing on the water and conflict theory of Aaron Wolf. Ultimately, this paper concludes that interstate tensions over Mekong hydro-development are unlikely to generate armed conflict. This is in part due to the strategic impracticality of such a conflict as well as the presence of a river basin management institution. Most compellingly, though, armed conflict is unlikely because the economic imperative shared by Mekong states is better served by cooperation – or at least non-interference – than conflict, over regional hydro-development. In closing, the paper urges that the study of water and conflict in the Mekong Basin be refocused at the intrastate level.
Pal, I., U. Lall, A.W. Robertson, M.A. Cane, and R. Bansal, 2013: “Diagnostics of Western Himalayan Satluj River flow: Warm season (MAM/JJAS) inflow into Bhakra dam in India.” Journal of Hydrology, v. 478, pp. 132-147, 10.1016/j.jhydrol.2012.11.053.
Here we analyze the variability of MAM (March–April–May) and JJAS (June–July–August–September) seasonal Satluj River flow into the Bhakra dam in India through Pearson anomaly correlation and composite analyses with antecedent and concurrent seasonal climatic and atmospheric circulation patterns. The MAM seasonal inflow of Bhakra dam is significantly correlated with winter (DJF/FM) precipitation and temperature of the Satluj basin while the correlation with FM was more prominent for precipitation (snow = +0.72, rainfall = +0.60), and temperature (diurnal temperature range (DTR) = −0.76 and maximum temperature (Tmax) = −0.57). The JJAS inflow was also positively correlated with DJF/FM as well as JJAS precipitation of the Satluj basin while the correlation with basin average FM was the largest (+0.54). These suggested that both MAM and JJAS inflow anomalies are linked with DJF/FM climate over the Western Himalayas and adjoining north and central Indian plains, which were also found to be linked with the fluctuation of equatorial concurrent Sea Surface Temperature anomalies over the western Indian Ocean (max anomaly correlation was > +0.70) and mean sea level pressure over western pole of the Southern Oscillation sea-saw region (max Pearson anomaly correlation was ∼ +0.60). Low (high) MAM inflow was found to be associated with negative (positive) precipitation anomalies over the basin and north India in DJF and FM while FM precipitation anomaly is more concentrated over the Western Himalayas. In addition, low (high) JJAS inflow is also associated with negative (positive) precipitation anomalies over the basin and north India in DJF and over the Western Himalaya in FM and JJAS. Negative geopotential height anomaly at 500 hPa (Z500) over Siberia and northwestern pacific in DJF, and positive Z500 anomaly over the northwest India in FM were noticed in low MAM inflow years. Whereas high inflow in MAM was linked with a negative Z500 anomaly between two positive Z500 anomaly regions – one over eastern Siberia stretched up to northern Pacific and second over the Eastern Europe in DJF, which gets stronger in FM. We also found southwesterly (northeasterly) wind vectors at 850 hPa pressure level (uv850) bringing more (less) moisture to the Western Himalayas in DJF and FM in high (low) MAM/JJAS flow years.
Brown, J., K.E. Limburg, J.R. Waldman, K. Stephenson, E.P. Glenn, F. Juanes, and A. Jordaan, 2013: “Fish and hydropower on the U.S. Atlantic coast: Failed fisheries policies from half-way technologies.” Conservation Letters, doi: 10.1111/conl.12000.
Globally, diadromous species are at risk from fragmentation by damming of rivers, and a host of other anthropogenic factors. On the United States Atlantic Coast, where diadromous fish populations have undergone dramatic declines, restoration programs based on fishway construction and hatcheries have sustained remnant populations, but large-scale restoration has not been achieved. We examine anadromous fish restoration programs on three large Atlantic Coast rivers, the Susquehanna, Connecticut, and Merrimack with multiple mainstem hydropower dams, most with relatively low generating capacity. Mean passage efficiencies through fishways on these rivers from the first dam to the spawning grounds for American shad are less than 3%. The result is that only small fractions of targeted fish species are able to complete migrations. It may be time to admit failure of fish passage and hatchery-based restoration programs and acknowledge that significant diadromous species restoration is not possible without dam removals. The approach being employed on the Penobscot River, where dams are being removed or provided the opportunity to increase power generation within a plan to provide increased access to habitat, offers a good model for restoration. Dammed Atlantic Coastal rivers offer a cautionary tale for developing nations intent on hydropower development, suggesting that lasting ecosystem-wide impacts cannot be compensated for through fish passage and hatchery technology.