Individual Dams Research Articles

Meconium microbiota in naturally delivered canine puppies

BackgroundMicrobial colonization during early life has a pivotal impact on the host health, shaping immune and metabolic functions, but little is known about timing and features of this process in dogs. The objectives of this study were to characterize the first step of intestinal microbiota development in naturally delivered canine puppies and to investigate its relationship with the maternal bacterial flora, using traditional culture and molecular analyses. Sixty puppies of two breeds, Appenzeller Cattle Dog (n = 3 dams) and Lagotto Romagnolo (n = 6), housed in the same breeding kennel, were included in the study. Swabs were collected in duplicate (for culture and for molecular analysis) from the dams’ vagina and rectum at the end of parturition, from puppies’ rectum, before maternal care, and from the environment (floor of the nursery and parturition box).Results93.3% meconium samples showed bacterial growth, limited to a few colonies in 57.0% of cases. High growth was detected for Enterococcus faecalis, which was the most frequently isolated bacterium. The genus Enterococcus was one of the most represented in the dams’ rectum and vagina (88.9% and 55.6%, respectively). The genera Staphylococcus, Enterococcus, Escherichia and Proteus were also often isolated in meconium but were usually present in maternal samples as well, together with ubiquitous bacteria (Acinetobacter, Psychrobacter). In the environmental samples, just a few bacterial species were found, all with low microbial load. Additionally, bacteria of the phyla Proteobacteria, Firmicutes, and Actinobacteria were identified in meconium through molecular analysis, confirming the culture results and the early colonization of the newborn gut. Maternal, meconium and environmental samples had similar alpha diversity, while beta-diversity showed differences among families (i.e. a dam and her litter), and association indexes revealed a significant correlation between family members and between sample origin, suggesting a strong contribution of the maternal flora to the initial seeding of the canine neonatal gut and a strong individual dam imprint.ConclusionThis study showed that the meconium of vaginally delivered puppies has its own microbiota immediately after birth, and that it is shaped by the dam, which gives a specific imprint to her litter.

Geomorphic Response to the Removal of the Ward's Mill Dam on the Watauga River, North Carolina

abstract: Though economic situations of individual dams vary, current dam removal studies largely indicate that ecological benefits of river re-connectivity may outweigh the costs of maintaining aging infrastructure. However, there is a lack of comprehensive studies in certain regions of the United States, including Southern Appalachia. We used the removal of the 6-meter-high Ward's Mill Dam on the Watauga River in North Carolina to conduct a before-after/control-impact study to monitor geomorphic impacts to such removals in this understudied region with the objective of identifying changes in channel form, analyzing bed sediment characteristics, and quantifying rates of volumetric evacuation and deposition. To capture geomorphic change repeated pre- and post-removal cross-sectional surveys, longitudinal profiles, and in-situ particle size sampling was conducted in upstream and downstream reaches. Field collections the day after removal show significant deposition of gravel sized particles immediately downstream of the dam (≤200 m). Channel bed texture remains significantly finer across the 2 km downstream study reach 506 days following removal. Erosion rates of the impoundment during the deconstruction period were on average ~860 m3/day and decreased to 75.5 m3/day by day 74. Below average mean daily flows during this period were able to exhume ~62.9 percent of impounded sediment.

Tailings dams’ classification based on risk using data from SIGBM

The Brumadinho and Mariana tailings dam failures in Brazil tragically highlighted the critical need for robust risk management in the mining sector. Tailings dams, by their very nature, pose significant risks to downstream communities and the environment in the event of failure. To mitigate these risks, a comprehensive risk classification system is essential. This abstract emphasizes the real-world impact of dam failures and strengthens the importance of risk classification. Risk analysis plays a central role in identifying, quantifying, and ultimately mitigating the potential consequences of tailings dam failure. The classification process considers various factors that influence dam stability and safety, including dam geometry and construction methods — the design and construction techniques employed significantly impact a dam's stability; tailings characteristics — the physical and chemical properties of the stored tailings can influence factors like liquefaction potential; operating conditions — factors like the rate of tailings deposition and the presence of seismic activity need evaluation; drainage system effectiveness — a well-functioning drainage system is crucial for managing pore pressures within the dam. By analyzing these elements, risk classification aims to categorize tailings dams into distinct risk levels, typically ranging from low to very high. This categorization allows for targeted risk mitigation strategies to be implemented based on the specific vulnerabilities of each dam. This paper proposes a methodology for risk classification of tailings dams utilizing data from the Brazilian National Mining Agency's (ANM) Integrated Mining Dam Management System (SIGBM). The study focuses on 203 dams situated in Minas Gerais, a Brazilian state with a history of dam failures. Data was extracted from SIGBM in February 2023. This research not only presents a general risk classification for the assessed dams but also delves deeper, offering a quantitative measure of vulnerability, risk potential, and potential consequences of a failure event for each individual dam.

Geomorphic Response to the Removal of the Ward’s Mill Dam on the Watauga River, North Carolina

Though economic situations of individual dams vary, current dam removal studies largely indicate that ecological benefits of river re-connectivity may outweigh the costs of maintaining aging infrastructure. However, there is a lack of comprehensive studies in certain regions of the United States, including Southern Appalachia. We used the removal of the 6 m high Ward’s Mill Dam on the Watauga River in North Carolina to conduct a before-after/control-impact study to monitor geomorphic impacts to such removals in this understudied region with the objective of identifying changes in channel form, analyzing bed sediment characteristics, and quantifying rates of volumetric evacuation and deposition. To capture geomorphic change repeated pre- and post-removal cross- sectional surveys, longitudinal profiles, and in-situ particle size sampling was conducted in upstream and downstream reaches. Field collections the day after removal show significant deposition of gravel sized particles immediately downstream of the dam (≤200 m). Channel bed texture remains significantly finer across the 2 km downstream study reach 506 days following removal. Erosion rates of the impoundment during the deconstruction period were on average ~860 m3/day and decreased to 75.5 m3/day by day 74. Below average mean daily flows during this period were able to exhume ~62.9 percent of impounded sediment.

Total and pathogen-specific serum Immunoglobulin G concentrations in neonatal beef calves, Part 2: Associations with health and growth.

The association of poor transfer of passive immunity (TPI) with negative health outcomes is extensively researched in dairy calves. However, few field studies have examined the effect of total and particularly pathogen-specific Immunoglobulin G (IgG) concentrations on pre-weaning health and growth of beef calves. Hence, the objective of this study was to determine the association of total and pathogen-specific IgG concentrations against selected pathogens associated with neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) and the odds of pre-weaning treatments, mortality, and the growth of newborn beef calves. A total of 420 serum samples from 1- to 7-day old beef calves born on 6 farms in Alberta, Canada, were available for this observational study. Serum samples were analyzed by radial immunodiffusion for total IgG concentration and by enzyme-linked immunosorbent assays for pathogen-specific IgG concentrations against Escherichia coli (E. coli), bovine Rotavirus (BRoV), Cryptosporidium parvum (C. parvum), Bovine Viral Diarrhea Virus (BVDV), Parainfluenza Virus Type 3 (PI-3), Bovine Respiratory Syncytial Virus (BRSV), and Bovine Herpesvirus Type 1 (BHV-1). Data about the individual dam- and calf-level risk factors, calf treatments, mortality, and birth and weaning weights were collected. Multivariable multilevel logistic and linear regression models were built to evaluate the association of total and pathogen-specific IgG concentrations with the odds of mortality and average daily gain (ADG), respectively, while their association with the odds of pre-weaning treatment was established by univariable logistic regression analysis. The odds of calves with IgG concentrations <10g/L of getting treated (OR 7.9, 95 % CI 2.7-23.7) and dying (OR: 18.5, 95 % CI: 3.7-93.4) were higher than for their counterparts (P<0.0001). Calves with IgG concentrations <24g/L also had higher odds of dying (OR: 10.1, 95 % CI: 2.6-40.2) and had lower ADG (-0.09kg, SE: 0.03, P<0.002) than calves with IgG concentrations ≥24g/L. Higher BVDV-specific IgG concentration was protective against mortality (OR: 0.97, 95 % CI: 0.96-0.99, P<0.001). This study highlights the negative association of inadequate TPI with health and growth of beef calves and thus, the need to refine protocols for dam vaccination and colostrum intervention in cow-calf operations to meet these higher IgG targets.

Stochastic Day-ahead operation of cascaded hydropower systems with Bayesian neural network-based scenario generation: A Portland general electric system study

Coordinating water usage of cascaded dams along a river to serve electric power generation and other non-power needs is challenging, due to the volatile and time-variate streamflow, the tight hydrologic couplings between the dams, and the strict regulation of individual dams. With this, cascaded hydropower system (CHS) operators, such as Portland General Electric (PGE), usually adopt empirical strategies to sidestep these difficulties, but at the expense of water usage inefficiency and economic losses. Motived by this, a stochastic optimization-based day-ahead operation model of CHSs is developed to determine scenario-independent hourly forebay levels of individual dams, which could assist operators in effectively utilizing available water resources against inflow uncertainties and maximizing the profit of hydropower. A common penstock effect model is also integrated to accurately capture the physical operating characteristics of CHSs. Moreover, a data-driven Bayesian neural network (BNN)-based scenario generation model is seamlessly connected to the stochastic day-ahead operation model for preparing water inflow scenarios of the impending operating day. Leveraging actual operation data of the PGE’s Round Butte-Pelton CHS, numerical simulations demonstrate that the day-ahead operation schedules out of the proposed approach could deliver more efficient water usage and higher economic benefits than the PGE’s current practice.

Effects of limited bedding and nesting on postpartum mood state in rats.

This study examined the effect of limited bedding and nesting (LBN) stress on postpartum anhedonia, maternal behaviors, anxiety-like behaviors, and neuroendocrine and neuroimmune function as a potential model of postpartum depression. Dams underwent sucrose preference tests prior to breeding, during gestation and again postpartum, to examine the potential onset of anhedonia. On embryonic day 19, dams were placed into either a LBN or control housing condition. Contrary to our predictions, LBN stress had no effect on postpartum sucrose preference. We also found no effect of LBN condition on fecal estradiol or corticosterone levels, both of which increased at birth and decreased postpartum. Regardless of housing conditions, approximately 40% of new mothers exhibited a decrease in sucrose preference, while others show no change, suggesting an individual susceptibility to postpartum anhedonia. In a separate cohort of LBN and control dams, we measured pup retrieval, hoarding behavior, elevated plus maze (EPM), and marble burying. LBN dams exhibited increased anxiety, associated with decreased time spent in the open arms of the EPM. We also measured a significant increase in IL-6 expression in the dorsal hippocampus and medial prefrontal cortex of postpartum dams compared to nonpregnant dams. These findings suggest that while LBN stress has effects on anxiety and maternal care, it does not induce postpartum anhedonia. Rather, there are inherent differences in susceptibility to anhedonia in individual dams, and future studies should be conducted to better understand individual vulnerability and resilience to postpartum anhedonia.

Modeling the impacts of fully-filled check dams on flood processes using CAESAR-lisflood model in the Shejiagou catchment of the Loess Plateau, China

Study regionThe Shejiagou catchment on the Loess Plateau, China Study focusThis study used CAESAR-lisflood to simulate the impacts on flood processes of fully-filled check dams with different numbers, silt land areas and connection modes. According to the model results, the protective measures of fully-filled check dams and recommendations for promoting the construction of check dams were proposed in the study. New hydrological insights for the regionCAESAR-lisflood model in the study obtained higher accuracy with both the Nash-Sutcliff coefficient of efficiency and the coefficient of determination greater than 0.8. Our results showed the presence of fully-filled check dams made the flood process tend to balance, and reduced the flood volume by 9.56–75.52%, peak discharge by 14.25–89.74%, runoff kinetic energy by 30.21–99.75% and runoff power by 20.17–95.23% under different layout scenarios. Meanwhile, the results indicated that the impacts of fully-filled check dams in main channel mainly manifested in the energy dissipation of silt land and energy increase at the outside slope of dam body, which was aggravated by downstream channel with steep slope. The combination of fully-filled check dams could amplify the flood control efficiency of individual dam. These results provide a scientific basis for reinforcement of fully-filled check dams and optimization of check dams layout in the future on the Chinese Loess Plateau.

Impacts of changing snowfall on seasonal complementarity of hydroelectric and solar power

Abstract Complementarity of variable renewable energy sources at multiple temporal scales is important in order to ensure reliability of a decarbonizing energy system. In this study, we investigate the hypothesis that a decrease in the fraction of precipitation falling as snow (SWE/P) would increase monthly complementarity of hydro and solar power generation in the western U.S. With a focus on 123 dams responsible for 93% of generation, we found that these resources are seasonally complementary at about half of dams, as indicated by the sign of correlation coefficients (ρ). As hypothesized, average SWE/P at individual dams was generally positively correlated with ρ, but the dependence of ρ on SWE/P was non-linear and SWE/P only explained a modest portion of the variance in complementarity. At each dam, the dependence of annual ρ on interannual variations in SWE/P between 2002–2020 was assessed; these relationships were positive at 72% of dams but not statistically significant at the level of individual dams. Finally, at the system scale ρ was significantly related to SWE/P, with a stronger relationship observed than the dependence of total hydropower generation on SWE/P. Notably, the system-scale relationship between ρ and SWE/P changed dramatically in the latter part of the temporal domain (2012–2020), with a much steeper slope and greater fraction of variance explained by SWE/P. These results illustrate the historical relationship between SWE/P, monthly complementarity of hydro and solar power, complexities of these relationships due to snow and watershed hydrology and reservoir management, and a change in the observed relationship between SWE/P and hydropower generation timing. To the extent that hydro and solar power generation complementarity is responsive to SWE/P, expected declines in SWE/P may indicate greater seasonal complementarity but reduced hydropower available for load-balancing when solar power generation is highest.

The evolution of dam-litter microbial flora from birth to 60 days of age

BackgroundEarly bacterial colonization in puppies is still a poorly understood phenomenon. Although the topic is of considerable interest, a big gap in knowledge still exists on the understanding of timing and features of neonatal gut colonization. Thence, the purpose of this study was to evaluate the relationship between dam and litter microbial flora, in vaginally delivered puppies, from birth to two months of age. Bacteria were identified using MALDI-TOF, an accurate and sensitive method, and cluster analysis of data provided a new insight on the investigated topic.MethodsSix dam-litter units of two medium size breeds were enrolled in the study. Vaginal and colostrum/milk samples were collected from dams after delivery and 48h post-partum, while rectal samples were taken from dams and puppies after delivery and at day 2, 30 and 60 (T2, T30 and T60, respectively) post-partum. Bacterial isolation and identification were performed following standard techniques, then the data were analyzed using a new approach based on bacterial genus population composition obtained using a wide MALDI-TOF screening and cluster analysis.ResultsForty-eight bacteriological samples were collected from the dams and 145 from their 42 puppies. Colostrum/milk samples (n = 12) showed a bacterial growth mainly limited to few colonies. Staphylococci, Enterococci, E. coli, Proteus spp. were most frequently isolated. All vaginal swabs (n = 12) resulted in bacteria isolation (medium to high growth). Streptococci, Enterococci, E. coli were the most frequently detected. E. coli, Proteus mirabilis, Enterococcus spp., Streptococcus spp. were often obtained from dams’ and puppies’ rectal swabs. Clostridia, not isolated in any other sampling site, were rarely found (n = 3) in meconium while they were more frequently isolated at later times (T2: n = 30; T30: n = 17; T60: n = 27).Analysis of the bacterial genus pattern over time showed a statistically significant reduction (P < 0.01) in the heterogeneity of microbial composition in all time points if compared to birth for each dam-litter unit. These results were confirmed with cluster analysis and two-dimensional scaling.ConclusionThis novel data analysis suggests a fundamental role of the individual dam in seeding and shaping the microbiome of the litter. Thus, modulating the dam’s microbiota may positively impact the puppy microbiota and benefit their health.

A new index to quantify longitudinal river fragmentation: Conservation and management implications

The proliferation of river infrastructure projects has altered aquatic longitudinal connectivity, posing a growing threat to riverine biodiversity and ecosystem processes worldwide. Effective methods to quantify loss of river connectivity across spatiotemporal scales and in data-limited landscapes are important to understand and inform basin-wide conservation and development planning. Here we introduce a Catchment Area-based Fragmentation Index (CAFI) and its derivative, the Catchment Area- and Rainfall-based Fragmentation Index (CARFI) as new metrics to quantify river fragmentation. These indices use catchment area as a proxy for riverine habitat availability, avoiding the drawbacks of existing metrics that rely on river length and associated derivatives. CAFI/CARFI can be computed across spatiotemporal scales, incorporate barrier passability values, assesses the cumulative impact of multiple barriers, and be applied even in data-limited environments.We first applied CAFI and CARFI to a simulated network to illustrate their properties with respect to the number and location of barriers and compared these results to the widely applied Dendritic Connectivity Index (DCI). While all indices varied with barrier addition, CAFI and CARFI were more sensitive to both barrier number and location. Next, we illustrated the utility of CAFI and CARFI through case studies in two contrasting settings: the Klamath River in California, where dam building has ceased (and dam removals are being considered) and the Netravathi River in India, where dam building is ongoing, with 65 dams proposed for future development. Results indicate that CAFI and CARFI can effectively quantify trends in fragmentation across spatial scales and temporal scenarios of dam development (i.e. descriptive applications) and can aid the prioritization of sites for dam removal, restoration, or conservation (i.e. prescriptive applications). Overall, these indices can quantify the impacts of individual dams and assess a range of development scenarios to inform basin-wide conservation and development planning.

Influence of check dams on flood hydrology across varying stages of their lifespan in a highly erodible Catchment, Loess Plateau of China

Check dams are applied worldwide as an effective approach for soil conservation. Its effect on hydrology, however, has not been fully understood. As a critical step towards revealing the lumped effect of check dams at the regional scale, this study explored the modified flood hydrology induced by check dams in a representative highly erodible catchment in the Loess Plateau, China. A coupled hydrological and hydraulic modeling approach was applied to simulate the flooding process in different stages of deposition and topographic changes in a check dam reservoir. The results suggest a paradigm shift of the dam effect on flood attributes, which transits from a total interception in the early stage of the dam to peak reduction and flood detention, rather than a complete loss of flood control functions, when it approaches the maximum capacity of sedimentation. Under the same level of deposition, the reduction of a minor flood by a check dam was higher than that of a major flood. The topographic changes contributed to the reduction of flood peak appreciably by reducing the flow velocity and retarding the flood propagation. Noticeably, this reduction was augmented with the advancement of siltation and topographic changes, indicating the persistence of the hydrologic effects of check dams in the long run. As a result of these hydrological changes, the reduction in the flood flow velocity induced by check dams suggests substantial reductions in sediment transport and channel erosion during floods. In addition, a dam system containing multiple, cascading check dams exhibits much more significant effect in modifying both hydrologic and hydraulic properties of flood than individual dams. The current research provides a mechanistic understanding of the effects of check dams on catchment hydrology under heavy rainstorm conditions in small catchments.

Technical fishway passage structures provide high passage efficiency and effective passage for adult Pacific salmonids at eight large dams

Fishways have been widely used for upstream passage around human-built structures, but ‘success’ has varied dramatically. Evaluation of fishway success has typically been conducted at local scales using metrics such as fish passage efficiency and passage time, but evaluations are increasingly used in broader assessments of whether passage facilities meet population-specific conservation and management objectives. Over 15 years, we monitored passage effectiveness at eight dams on the Columbia and Snake rivers for 26,886 radio-tagged spring-summer and fall Chinook Salmon O. tshwaytscha, Sockeye Salmon O. nerka, and summer steelhead O. mykiss during their migrations to spawning sites. Almost all fish that entered dam tailraces eventually approached and entered fishways. Tailrace-to-forebay passage efficiency estimates at individual dams were consistently high, averaging 0.966 (SD = 0.035) across 245 run×year×dam combinations. These estimates are among the highest recorded for any migratory species, which we attribute to the scale of evaluation, salmonid life history traits (e.g., philopatry), and a sustained adaptive management approach to fishway design, maintenance, and improvement. Full-dam fish passage times were considerably more variable, with run×year×dam medians ranging from 5–65 h. Evaluation at larger scales provided evidence that fishways were biologically effective, e.g., we observed rapid migration rates (medians = 28–40 km/d) through river reaches with multiple dams and estimated fisheries-adjusted upstream migration survival of 67–69%. However, there were substantive uncertainties regarding effectiveness. Uncertainty about natal origins confounded estimation of population-specific survival and interpretation of apparent dam passage ‘failure’, while lack of post-migration reproductive data precluded analyses of delayed or cumulative effects of passing the impounded system on fish fitness. Although the technical fishways are effective for salmonids in the Columbia-Snake River system, other co-migrating species have lower passage rates, highlighting the need for species-specific design and evaluation wherever passage facilities impact fish management and conservation goals.

Strategic basin and delta planning increases the resilience of the Mekong Delta under future uncertainty

The climate resilience of river deltas is threatened by rising sea levels, accelerated land subsidence, and reduced sediment supply from contributing river basins. Yet, these uncertain and rapidly changing threats are rarely considered in conjunction. Here we provide an integrated assessment, on basin and delta scales, to identify key planning levers for increasing the climate resilience of the Mekong Delta. We find, first, that 23 to 90% of this unusually productive delta might fall below sea level by 2100, with the large uncertainty driven mainly by future management of groundwater pumping and associated land subsidence. Second, maintaining sediment supply from the basin is crucial under all scenarios for maintaining delta land and enhancing the climate resilience of the system. We then use a bottom-up approach to identify basin development scenarios that are compatible with maintaining sediment supply at current levels. This analysis highlights, third, that strategic placement of hydropower dams will be more important for maintaining sediment supply than either projected increases in sediment yields or improved sediment management at individual dams. Our results demonstrate 1) the need for integrated planning across basin and delta scales, 2) the role of river sediment management as a nature-based solution to increase delta resilience, and 3) global benefits from strategic basin management to maintain resilient deltas, especially under uncertain and changing conditions.

Callous unemotional trait-like mice and their stressed dams

The co-occurrence of excess rates of aggression, general violation of societal norms and callous-unemotional trait confers specific risk for adult psychopathy. With the aim to address experimentally a model of conduct disorder, we investigated the male offspring of individual mouse dams characterized by high basal plasma corticosterone concentration (HC trait). Notably, classification indices correlated selectively in these females with quite poor maternal care devoted to their offspring. Contrary to their HC mothers, adult male offspring exhibited an integrated profile of dampened physiological reactivity to external stressors co-occurring poor sociability/emotional contagion, impaired punishment-induced memory, and exacerbated aggression. A significant reduction of glucocorticoid and opioid mu receptors’ expression in frontal cortex of model HC offspring was also evidenced. Moreover, in the absence of changes in oxytocin receptor in behaviorally-relevant neural areas, we showed that intranasal oxytocin administration (0 or 20.0 µg/kg) selectively modulated specific components of the behavioral phenotype. Ultimately, current data support the notion that maternally-inoculated environmental stress early in development may represent a critical risk factor in disturbances characterised by abnormal aggression and excess callousness.

Prioritizing native migratory fish passage restoration while limiting the spread of invasive species: A case study in the Upper Mississippi River

Despite increasing efforts globally to remove dams and construct fish passage structures, broad-scale analyses balancing tradeoffs between cost and habitat gains from these mitigations infrequently consider invasive species. We present an optimization-based approach for prioritizing dam mitigations to restore habitat connectivity for native fish species, while limiting invasive species spread. Our methodology is tested with a case study involving 240 dams in the Upper Mississippi River, USA. We integrate six native migratory fish species distribution models, distributions of two invasive fishes, and estimated costs for dam removal and construction of fish passes. Varying budgets and post-mitigation fish passage rates are analyzed for two scenarios: ‘no invasives’ where non-selective mitigations (e.g., dam removal) are used irrespective of potential invasive species habitat gains and ‘invasives’ where a mixture of selective (e.g., lift-and-sort fish passage) and non-selective mitigations are deployed to limit invasive species range expansion. To achieve the same overall habitat connectivity gains, we find that prioritizations accounting for invasive species are 3 to 6 times more costly than those that do not. Habitat gains among native fish species were highly variable based on potential habitat overlap with invasive species and post-mitigation passabilities, ranging from 0.4–58.9% (‘invasives’) and 7.9–95.6% (‘no invasives’) for a $50M USD budget. Despite challenges associated with ongoing nonnative fish invasions, opportunities still exist to restore connectivity for native species as indicated by individual dams being frequently selected in both scenarios across varying passabilities and budgets, however increased restoration costs associated with invasive species control indicates the importance of limiting their further spread within the basin. Given tradeoffs in managing for native vs. invasive species in river systems worldwide, our approach demonstrates strategies for identifying a portfolio of candidate barriers that can be investigated further for their potential to enhance native fish habitat connectivity while concurrently limiting invasive species dispersal.

Connectivity of fish communities in a tropical floodplain river system and predicted impacts of potential new dams

Longitudinal and lateral connectivity is important for mobile aquatic species in rivers for reproductive migrations, recruitment, gene flow and access to food resources across habitat types. Water resource developments such as dams and levees may disrupt these connections, causing river fragmentation and loss of access to highly productive habitats such as floodplain wetlands. We used sulfur stable isotopes as a tracer to estimate patterns of fish movement in an unregulated river in tropical northern Australia, taking advantage of observed spatial variation in sulfur isotope values of their food resources across the catchment. We also modelled the flow and barrier related impacts of potential dam development scenarios on fish movement. Fish with isotope values significantly different from local prey values were determined to be migrants. In the ‘no dams’ scenario, movement varied among fish species (0–44% migrant fish within species where n > 5) and sites (0–40% migrant fish within sites where n > 5), and immigration was higher in more connected sites. Impacts of water resource development on fish movement varied between dam scenarios, with predictions that a dam on the main channel of the Mitchell River would have the highest impact of the three individual dam scenarios. This study provides critical information on how flow-mediated connectivity supports patterns of fish community movement in an unregulated river system. The generic quantitative approach of combining tracers of fish movement with connectivity modelling provides a powerful predictive tool. While we used sulfur stable isotopes to estimate fish movement, our approach can be used with other tracers of movement such as otoliths and acoustic telemetry, making it widely applicable to guide sustainable development in other river systems.

Quantifying Cooperation Benefits for New Dams in Transboundary Water Systems Without Formal Operating Rules

New dams impact downstream ecosystems and water infrastructure; without cooperative and adaptive management, negative impacts can manifest. In large complex transboundary river basins without well codified operating rules and extensive historical data, it can be difficult to assess the benefits of cooperating, in particular in relation to new dams. This constitutes a barrier to harmonious development of river basins and could contribute to water conflict. This study proposes a generalised framework to assess the benefits of cooperation on the management of new dams in water resource systems that do not have formal sharing arrangements. Benefits are estimated via multi-criteria comparison of historical reservoir operations (usually relatively uncooperative) vs. adopting new cooperative rules which would achieve the best results for riparian countries as evaluated by a water resources simulator and its performance metrics. The approach is applied to the Pwalugu Multipurpose Dam (PMD), which is being built in Ghana in the Volta river basin. The PMD could impact downstream ecosystems and infrastructure in Ghana and could itself be impacted by how the existing upstream Bagre Dam is managed in Burkina Faso. Results show that with cooperation Ghana and Burkina Faso could both increase energy production although some ecosystem services loss would need to be mitigated. The study confirms that cooperative rules achieve higher overall benefits compared to seeking benefits only for individual dams or countries.

Watershed Suspended Sediment Supply and Potential Impacts of Dam Removals for an Estuary

Observations and modeling are used to assess potential impacts of sediment releases due to dam removals on the Hudson River estuary. Watershed sediment loads are calculated based on sediment-discharge rating curves for gauges covering 80% of the watershed area. The annual average sediment load to the estuary is 1.2 Mt, of which about 0.6 Mt comes from side tributaries. Sediment yield varies inversely with watershed area, with regional trends that are consistent with substrate erodibility. Geophysical and sedimentological surveys in seven subwatersheds of the Lower Hudson were conducted to estimate the mass and composition of sediment trapped behind dams. Impoundments were classified as (1) active sediment traps, (2) run-of-river sites not actively trapping sediment, and (3) dammed natural lakes and spring-fed ponds. Based on this categorization and impoundment attributes from a dam inventory database, the total mass of impounded sediment in the Lower Hudson watershed is estimated as 4.9 ± 1.9 Mt. This represents about 4 years of annual watershed supply, which is small compared with some individual dam removals and is not practically available given current dam removal rates. More than half of dams impound drainage areas less than 1 km2, and play little role in downstream sediment supply. In modeling of a simulated dam removal, suspended sediment in the estuary increases modestly near the source during discharge events, but otherwise effects on suspended sediment are minimal. Fine-grained sediment deposits broadly along the estuary and coarser sediment deposits near the source, with transport distance inversely related to settling velocity.

Data‐Driven Reservoir Simulation in a Large‐Scale Hydrological and Water Resource Model

AbstractLarge‐scale hydrological and water resource models (LHMs) are used increasingly to study the vulnerability of human systems to water scarcity. These models rely on generic reservoir release schemes that often fail to capture the nuances of operations at individual dams. Here we assess whether empirically derived release‐availability functions tailored to individual dams could improve the simulation performance of an LHM. Seasonally varying, linear piecewise relations that specify water release as a function of prevailing storage levels and forecasted future inflow are compared to a common generic scheme for 36 key reservoirs of the Columbia River Basin. When forced with observed inflows, the empirical approach captures observed release decisions better than the generic scheme—including under conditions of drought. The inclusion of seasonally varying inflow forecasts used by reservoir operators adds further improvement. When exposed to biases and errors inherent in the LHM, data‐driven policies fail to offer a robust improvement; inclusion of forecasts deteriorates LHM reservoir simulation performance in some cases. We perform sensitivity analysis to explain this result, finding that the bias inherent in LHM streamflow is amplified by a reservoir model that relies on forecasts. To harness the potential of interpretable, data‐driven reservoir operating schemes, research must address LHM flow biases arising from inaccuracies in climate input, runoff generation, flow routing, and water withdrawal and consumption data.