Aging Dams Research Articles

Subsurface condition assessment of critical dam infrastructure with non-invasive geophysical sensing

Recent cases of dam failures indicate that the safe operation and proactive maintenance of critical infrastructure is of significant importance considering the growing number of ageing dams and the increase in intensity and frequency of extreme climatic events. The current procedures to assess the performance of dam infrastructure, usually based on geodetic and geotechnical instrumentation, do not provide repeatable and reliable information with regard to subsurface hazards that evolve within the body of earth-fill dams that could compromise the integrity of the structure. This increases the risk of failure with significant socio-economic impacts and long-term disruption on downstream communities. On the contrary, geophysical methods can provide advanced information about subsurface hazards and can therefore significantly assist to define the safety level of dam infrastructure. This will enable early remedial maintenance and repair actions to be carried out enhancing public safety and eventually reducing costs for asset owners. This study presents for the first time the investigation of the condition of three reservoir dams in Scotland with the application of two complementary non-invasive geophysical methods coupled with visual inspection. Electromagnetic (EM) sensing was initially employed to provide an assessment of the upper soil layers of the crest and downstream shoulder of the dam. Electrical Resistivity Tomography (ERT) arrays were then installed on the crest to assess the subsurface conditions of the dam based on the resistivity signatures. The analysis of the geophysical models identified weak zones within the body of dams associated with high-resistivity patterns associated with potential animal burrowing activity and fissuring on the crest of the dam. The electrical resistivity surveys revealed low-resistivity zones influenced by seepage conditions inside the body of dams but also provided an indication of potential internal erosion areas. Finally, the geophysical models provided an insight of the homogeneity of the fill material and determined the dam foundation characteristics. The geophysical results presented in this investigation provide important baseline measurements and key information about the current condition and on-going performance of dam infrastructure.

Copula-based reliability and sensitivity analysis of aging dams: Adaptive Kriging and polynomial chaos Kriging methods

Time-dependent reliability and sensitivity analysis, in which the nature of demand, capacity and the limit state function varies over the life cycle of the structural system, is a challenging task. Meta-models are a suitable tool to construct inexpensive-to-evaluate and accurate surrogates in analysis of modern engineering problems. The paper’s contribution is threefold: First, the superiority of polynomial chaos Kriging (PCK) meta-model in terms of efficiency and accuracy is depicted in comparison to two other state-of-the-art methods in an explicit representation of a pilot gravity dam. Second, the problem of aging dams is analytically studied. Adaptive reliability approaches which benefit from Kriging and PCK meta-models are also investigated in a comparative analysis with classical reliability methods. Third, the importance of considering nonlinear dependency between random variables by copula theory is investigated under the reliability and sensitivity concepts. The results show that PCK meta-model can be used as an effective technique in uncertainty quantification (UQ) of dams. Furthermore, Kriging and PCK-assisted reliability methods can establish fairly accurate meta-models to perform reliability analysis in structural UQ with low computational efforts. Finally, the concept of UQ is propagated to ”dam class” in which the dam shape and its age are assumed to be variable. A generalized program is developed to assist dam owners and decision-makers in approximate failure probability estimation of gravity dams. This paper paves the road for global risk assessment of dams.

Deformation early-warning index for heightened gravity dam during impoundment period

The mechanical parameters of materials in a dam body and dam foundation tend to change when dams are reinforced in aging processes. It is important to use an early-warning index to reflect the safety status of dams, particularly of heightened projects in the impoundment period. Herein, a new method for monitoring the safety status of heightened dams is proposed based on the deformation monitoring data of a dam structure, a statistical model, and finite-element numerical simulation. First, a fast optimization inversion method for estimation of dam mechanical parameters was developed, which used the water pressure component extracted from a statistical model, an improved inversion objective function, and a genetic optimization iterative algorithm. Then, a finite element model of a heightened concrete gravity dam was established, and the deformation behavior of the dam with rising water levels in the impoundment period was simulated. Subsequently, mechanical parameters of aged dam parts were calculated using the fast optimization inversion method with simulated deformation and the water pressure deformation component obtained by the statistical model under the same conditions of water pressure change. Finally, a new early-warning index of dam deformation was constructed by means of the forward-simulated deformation and other components of the statistical model. The early-warning index is useful for forecasting dam deformation under different water levels, especially high water levels.

The Socio-Economic Impacts of Aged-Dam Removal: A Review

Water storage dams worldwide are ageing, and many will reach the end of their designed lifespan by the middle of the 21st century. Some of these dams will likely need to be removed. While dam construction impacts have been widely discussed, dam removal impacts on society and the economy need to be synthesized and considered in the ageing dams’ decision-making process. This paper summarizes dam removal impacts on the local economy and industry, culture, history and heritage, property value, recreation, aesthetics, and disaster avoidance from identified studies worldwide. It demonstrates that these impacts may vary depending on geography and between developed and developing countries. It concludes that dam removal should consider the cost, environmental, and the socio-economic impacts while including all stakeholders who could be positively and negatively impacted by dam removal.

WinDAM C: Analysis Tool for Predicting Breach Erosion Processes of Embankment Dams Due to Overtopping or Internal Erosion

HighlightsThe computational models comprising the current version of WinDAM, called WinDAM C, are summarized.WinDAM C estimates the response of an earthen embankment subjected to overtopping or internal erosion.WinDAM C is a model that quantifies erosion/breach processes observed in physical embankment failure tests.Understanding the current technology and limitations provides a basis for further model development.Abstract. Internal erosion and overtopping erosion of earthen embankments are the leading causes for earthen embankment failures. Challenges like reservoir sedimentation, structural deterioration, rodent damage or tree root growth, and changing hazard classification from low to significant or high have arisen with aging dams. To address these challenges, new technology and tools for predicting the performance of homogeneous, cohesive earthen embankments during overtopping or internal erosion are needed. Windows Dam Analysis Modules (WinDAM) is a modular software application developed through collaborative efforts of the United States Department of Agriculture (USDA) Agricultural Research Service (ARS), the USDA-Natural Resources Conservation Service (NRCS), and Kansas State University (KSU) in response to this need. WinDAM uses a simple storage routing model to simulate flow through a reservoir and incorporates algorithms for predicting the progression of erosion resulting from embankment overtopping or flow through an internal discontinuity in the embankment. These algorithms are based on existing literature and data and observations from physical model experiments of homogeneous, cohesive embankments conducted by scientists at the USDA-ARS Hydraulic Engineering Research Unit in Stillwater, Oklahoma. The resulting computational model is a simplified representation of the observed process of progressive erosion that may lead to embankment breach. This paper reviews the components of the erosion/breach process and the way in which these components are quantified and integrated into the current WinDAM software, WinDAM C. The scope of application of the software, limitations, and computational assumptions are also discussed. Keywords: Breach, Dams, Erodibility, Erosion Process, Failure, Internal erosion, Model, Overtopping, Piping.

Advanced maternal age induces fetal growth restriction through decreased placental inflammatory cytokine expression and immune cell accumulation in mice.

Advanced maternal age is a risk factor for female infertility, and placental dysfunction is considered one of the causes of pregnancy complications. We investigated the effects of advanced maternal aging on pregnancy outcomes and placental senescence. Female pregnant mice were separated into three groups: young (3 months old), middle (8–9 months old), and aged (11–13 months old). Although the body weights of young and middle dams gradually increased during pregnancy, the body weight of aged dams only increased slightly. The placental weight and resorption rate were significantly higher, and live fetal weights were reduced in a maternal age-dependent manner. Although mRNA expression of senescence regulatory factors (p16 and p21) increased in the spleen of aged dams, mRNA expression of p16 did not change and that of p21 was reduced in the placenta of aged dams. Using a cytokine array of proteins extracted from placental tissues, the expression of various types of senescence-associated secretory phenotype (SASP) factors was decreased in aged dams compared with young and middle dams. The aged maternal placenta showed reduced immune cell accumulation compared with the young placenta. Our present results suggest that models using pregnant mice older than 8 months are more suitable for verifying older human pregnancies. These findings suggest that general cellular senescence programs may not be included in the placenta and that placental functions, including SASP production and immune cell accumulation, gradually decrease in a maternal age-dependent manner, resulting in a higher rate of pregnancy complications.

Risk of hydrological failure under the compound effects of instant flow and precipitation peaks under climate change: A case study of Mountain Island Dam, North Carolina

The risk of flooding as a result of infrastructure failures among aging dams in the United States continues to increase dramatically, which lead to the severe consequences in socio-economic and environmental terms. Environmental impacts regarding the failure of hydrological facilities, including the loss of sustainable habitats and clean water previously provided by reservoir, have raised concerns. In this study, the potential risks to hydrological infrastructure within the context of the 100-year joint probability of maximum rainfall and peak water stage were examined over the Mountain Island Dam (North Carolina, USA) for the period of 1950–2099. We found that nearly 92% of annual maximum extreme rainfall events were closely related to the passage of hurricanes over the dam’s watershed over the 25 years of the validation period. The results show that the projected annual maximum precipitation is likely to intensify under the RCP8.5 climate scenario and the frequency of the annual precipitation maxima exceeding 100 mm/day is projected to increase in the future. Noticeably, it is found that even weaker storm events can contribute a significant amount of rainfall at inland locations. The probability of occurrence of a hurricane like Gustav is higher than that of a 100-year storm rainfall event under the RCP8.5 climate change scenario, this type of storm rainfall will more likely occur near the Mountain Island Dam in the future. Inspectors should focus more on observing water level fluctuation and rainfall volume variation at station two under the same rainstorm - water level situations, because it is more sensitive to the once-in-a-century co-occurrence event than other stations. A HEC-RAS (The Hydrologic Engineering Center (HEC) developed the River Analysis System (RAS) to aid hydraulic engineers in channel flow analysis and floodplain determination) simulation demonstrated that the occurrence probability of hurricane Gustav induced rainfall is more than that of 100-year rainfall events and this type of storm rainfall would highly likely occur near the Mountain Island Dam again under the future warming conditions by the conditional prediction of Copula function. Insights gained suggest that it is critical to evaluate the risk of dam failures regarding either extreme weather conditions or potential environmental concerns under the climate change scenarios, especially where human lives are threatened.

A SLOT-CUTTING TECHNIQUE FOR REPAIR AND REHABILIATION OF CONCRETE DAMS AFFECTED BY ALKALI-SILICA REACTION

The combined impacts of earthquake damage and aging of concrete material on vulnerable aged dam systems have been typical causes of structural failure. The possible malfunction or loss of these vital systems and components can have serious socio-economic consequences and impacts on potable water resource availability, crop irrigation, and electric power generation. Worldwide extensive work has been done to evaluate the structural safety of aged concrete dam system components and to develop suitable remedial action and rehabilitation strategies. This paper reports a Chemo-Thermo-Mechanical Finite Element model developed by the authors which was used to demonstrate the use of the Finite Element Method (FEM) to model the behavior of a synthetic dam if the concrete is affected by Alkali-Silica Reaction (ASR), applying the slot cutting rehabilitation technique. ASR is a destructive chemical reaction between the cement paste and siliceous aggregate components in concrete materials that causes long-term expansion and degradation of concrete structures, including dams. Slot cutting is recognized as one of the promising techniques suitable to repair concrete dams suffering from ASR. The results show that the FE model could predict the stress and displacement field before and after the sawing of the slot in an assumed dam affected by ASR and demonstrate a promising capability for modeling the repair strategies in real dams suffering from ASR.

Dams are coming down, but not always by choice: the geography of Texas dams, dam failures, and dam removals

This study examines spatial and temporal trends in Texas dams, dam failures, and dam removals. Dams were examined from a state-wide perspective and within 10 major river basins that collectively account for over 80% of all dams in the state. The state-scale and basin-scale analysis revealed similar patterns of dam occurrence, however there was greater variation in the patterns observed in both the purpose of dams and the timing for when most of the storage was created in each basin. Climate factors, mainly precipitation, influenced dam location. Population was not directly measured in this study but was an obvious influence on the spatial distribution of dams and their functions. While new dams are being built in Texas to secure future water supplies, documented dam incidents/failures have occurred in 15 of the 23 major river basins in Texas, with 328 total instances occurring since 1900. As the number of newly constructed dams and dam failures continue to grow across the state, so should the number of planned dam removals. Between 1983 and 2016, 50 dams have been removed across the state. The purpose for the majority of removals was to eliminate liability concerns associated with aging dams. Future dam removals will likely continue to occur based on the number of older, smaller dams with potential liability concerns. As Texas’ dam infrastructure continues to age, dam removal is a practical management option for mitigating potential dam-related hazards and improving the connectivity and ecological function of the river systems. Citation: Dascher ED, Meitzen K. 2020. Dams are coming down, but not always by choice: the geograph of Texas dams, dam failures, and dam removals. Texas Water Journal. 11(1):89-129. Available from: https://doi.org/10.21423/twj.v11i1.7092.

Resolving Emerging Issues with Aging Dams under Climate Change Projections

AbstractConcerns about the collapse of dams due to overtopping are increasing owing to heavy rainfall and frequent typhoons associated with climate change. As a result, there has been a spike in an...

Elements for the Successful Computer Simulation of Sediment Management Strategies for Reservoirs

Computer simulation of reservoir sediment management strategies is becoming more important as worldwide water supply shrinks due to sediment deposition, while population growth continues. We identified the physical processes underlying each of the several alternatives available to transport incoming or deposited sediments downstream into receiving waters and the governing equations that describe each process. The purpose of this paper is to understand how physical characteristics of reservoir sediment management can be simulated with available computer codes. We described commonly available computer codes and their abilities to solve the appropriate equations in one, two, or three dimensions. The results revealed that one dimensional models are most appropriate for long-term simulations of the evolving reservoir bottom profile, while two or three dimensional codes are more appropriate for simulating density currents and detailed lateral movement of sediments, such as during local pressure flushing near reservoir outlets. We conclude that existing codes can successfully simulate sediment management, but because each code has limitations, they require seasoned judgment in their choice, application, and interpretation. Incorporating sediment prediction and management correctly into the planning, design, and operational phases of dam projects is essential for ensuring that the benefits of reservoir storage are sustained over the long term. The implications of our key findings are that sediment management strategies can be successfully simulated and that such simulations should be performed for our aging dams and newly proposed projects.

Exit here: strategies for dealing with aging dams and reservoirs

Aging infrastructure is prevalent throughout the world, but water control management structures, specifically dams, are of growing concern. Dams and their corresponding reservoirs have inherent, but separate, lifespans. The proportion of dams around the world that continue operation beyond their intended lifespans is growing at an alarming rate. Society will not only have to navigate the tradeoffs associated with the deterioration of services provided by reservoirs and dams, but also impending structural failures. Society is nearing a critical pinch point where we will have to decide how to deal with dams and reservoirs at scales that range from a single system to multiple systems in large watersheds. No comprehensive strategy exists to inform both the range of actions that can be applied to such infrastructure and how such actions would influence biophysical, socioeconomic, and geopolitical tradeoffs. The development of proactive exit strategies is a critical first step in ensuring controlled transitions for aging dams and reservoirs. Herein, we present an overview of actions and considerations for aging dams and reservoirs, followed by an initial framework for exit strategy development to launch a further discussion on how society could deal with this aging infrastructure.

Development of Diving Tilt Rotor UAV

In recent years, the number of the aging dam is increasing. In Japan, the total number of dams tends to increase.

On the Application of Laser Vibrometry to Perform Structural Health Monitoring in Non-Stationary Conditions of a Hydropower Dam.

This paper presents the first application of the Laser Doppler Vibrometer (LDV) in non-stationary conditions within a hydropower plant powerhouse. The aim of this research is to develop a methodology to include non-contact vibration monitoring as part of structural health monitoring of concrete dams. We have performed in-situ structural vibration measurements on the run-of-the-river Brežice dam in Slovenia during the start-up tests and regular operation. In recent decades, the rapid development of laser measurement technology has provided powerful methods for a variety of measuring tasks. Despite these recent developments, the use of lasers for measuring has been limited to sites provided with stationary conditions. This paper explains the elimination of pseudo-vibration and measurement noise inherent in the non-stationary conditions of the site. Upon removal of the noise, fatigue of the different structural elements of the powerhouse could be identified if significant changes over time are observed in the eigenfrequencies. The use of laser technology is to complement the regular monitoring activities on large dams, since observation and analysis of integrity parameters provide indispensable information for decision making and maintaining good structural health of ageing dams.

Effect of Precipitation Change on Dams Storage in Jordan

Precipitation patterns' change, rising surface temperature, extensive ice melting and increments in intensity and frequency of droughts and floods are several kinds of the reported hydrologic changes that are connected with the worldwide climate change. Therefore, climate change and its associated precipitation change are anticipated to influence the water storage as well as water supply in Jordan and impose challenges in front of the current water management policies and plans. The hydrological impacts of upcoming anticipated climate may influence the Jordanian dams' capacity and operating attributes. Accordingly, this paper tends to explore and review mainly the effect of precipitation change on dams' storage in Jordan, by providing a brief review of major types of dams and considerations that must be taken through their design and construction as well as clarifying the necessity for a national climate change policy for Jordan. The researcher concluded that climate change and precipitation variability require new management strategies for water storage infrastructures (reservoirs), including the design for new dams and rehabilitation of the infrastructure of aging dams as well as imposing new operational systems. Several advantages of dam management ought to be considered, evaluated and actualized right away in Jordan alongside with issuing of national climate change policy taking into account the effect of precipitation change. DOI : 10.7176/JEES/9-5-05 Publication date :May 31 st 2019

Effects of Sediment Released from a Check Dam on Sediment Deposits and Fish and Macroinvertebrate Communities in a Small Stream

Dam removal is typically intended for river restoration or as a countermeasure for aging dams. The influence of dam removal has mainly been studied in large rivers. This study is intended to investigate the influence of the sediment supplied after opening a check dam drain in a small steep stream to contribute to the establishment of sediment release technology form check dam by accumulating the basic knowledge about the influence of sediment release. Deposited sediment in the impoundment was rapidly discharged immediately after opening the drain outlet, and a moderate sediment discharge followed. The water course of the sediments deposited by repeated channel widening and riverbed degradation tended to stop longitudinal topographic changes from downstream. In addition, the turbidity during a flood was high in the first year and tended to decrease in the second year. As for the ecosystem response, changes in the benthic macroinvertebrate community were confirmed in downstream sites, and net-spinning species especially deceased immediately after the sediment supply began. Our monitoring results suggest that the increasing turbidity was suppressed during the flood because sediment release was conducted from the small-scale facility. As a result, a negative impact on the aquatic ecosystem seemed to be reduced.

The effects of birth rank (single or twin) and dam age on the lifetime productive performance of female dual purpose sheep (Ovis aries) offspring in New Zealand.

Greater rates of genetic gain can be achieved by selecting animals born to younger parents. However, little is known about the lifetime performance of dual purpose ewes (Ovis aries) that are born to primiparous ewe lambs (8 to 9 months old at breeding). This experiment investigated the effect of being born from either a ewe lamb or mixed age dam as either a single or twin on the lifetime performance of ewe progeny. Lifetime performance was measured in terms of the life time live weights of the ewes, the weight and number of lambs born and weaned, the efficiency of production (kilograms of lamb weaned / predicted pasture intake (kgDM) of the ewes), and ewe survival. The study followed the lifetime production of 17 single and 41 twin female lambs born to mature ewes (M1 and M2, respectively), and 28 single and 29 twin lambs born to ewe lambs (L1 and L2, respectively). Over their lifetime L2 ewes were lighter (P<0.05) but had similar body condition scores to the other three ewe groups. There was no difference in average progeny weaning weight or total progeny litter weaning weights between groups. The M1 ewes had the greatest longevity (P<0.05) of the four groups. Even though L2 ewes were lighter than the other three groups, this was insufficient to increase their lifetime efficiency of production (kg lamb weaned/predicted pasture consumption), relative to the other groups. These results suggest farmers could select replacements born to ewe lambs without sacrificing animal production.

Sex-specific effects of advanced maternal age on cardiovascular function in aged adult rat offspring.

Pregnancy at an advanced maternal age has an increased risk of complications for both the mothers and their offspring. We have previously shown that advanced maternal age in a rat model leads to poor fetal outcomes, maternal vascular dysfunction, and hypertension, concordant with findings in humans. Moreover, offspring from aged dams had sex-specific cardiovascular dysfunction in young adulthood. However, the detrimental impact of aging on the cardiovascular system of the offspring in this model is unknown. We hypothesized that offspring born to aged dams (9.5-10 mo old) would have impaired cardiovascular function at 12 mo of age. Echocardiographic data revealed signs of mild left ventricular diastolic dysfunction in only male offspring from aged dams [isovolumetric relaxation time: 34.27 ± 2.04 in the young dam group vs. 27.61 ± 0.99 ms in the aged dam group, P < 0.01; mitral annular velocity ratio ( E'/ A'): 1.08 ± 0.04 in the young dam group vs. 0.96 ± 0.02 in the aged dam group, P < 0.05]. We have previously shown that in young adulthood (4 mo of age), male, but not female, offspring born to aged dams had impaired recovery from ischemia-reperfusion injury. Aging did not alter the susceptibility of female offspring to ischemia-reperfusion injury. Interestingly, wire myography data revealed that male offspring from aged dams had enhanced vascular sensitivity to methacholine (negative log of EC50: 7.4 ± 0.08 in young dams vs. 7.9 ± 0.11 in aged dams, P = 0.007) due, in part, to increased prostaglandin-mediated vasodilation. Despite intact endothelium-dependent relaxation, female offspring from aged dams had elevated systolic blood pressure (125.3 ± 4.2 mmHg in young dams vs. 144.0 ± 6.9 mmHg in aged dams, P = 0.03). These data highlight sex-specific mechanisms underlying cardiovascular programming in offspring born to dams of advanced age. NEW & NOTEWORTHY Our study demonstrated that adult male and female offspring (12 mo old) born to aged dams had impaired cardiac diastolic function and increased blood pressure, respectively, signifying sex-specific differential cardiovascular effects of advanced maternal age.

365. Maternal and fetal consequences of preeclampsia

Vascular dysfunction in women with preeclampsia is complex. Placenta-derived circulating factors and/or the maternal response to these factors contribute to vascular endothelial cell dysfunction. Risk factors for preeclampsia include many conditions such as maternal aging, pre-existing hypertension, obesity and diabetes. The heterogeneity of this population, including the diversity of circulating factors such as oxLDL, TNF α , and advanced glycation end products, has contributed to the overall complexity of targeting a specific pathway for therapeutic prevention and/or intervention. Interestingly, these circulating factors are also among the factors known to upregulate and/or activate the lectin-like oxidized LDL receptor-1 (LOX-1). Our laboratory has shown that LOX-1 is increased in the systemic vasculature of women with preeclampsia and contributes to vascular oxidative stress. Moreover, our rat model of reduced uteroplacental perfusion (RUPP), which has preeclampsia-like signs, demonstrates increased LOX-1 expression, increased vascular oxidative stress and ultimately vascular dysfunction. Since LOX-1 has multiple ligands, it may be a point of convergence for many plasma factors known to be elevated in preeclampsia; including placental-derived microparticles; a current area of investigation. Notably, pregnancy has an important influence on both short- and long-term cardiovascular outcomes for women and their offspring. One risk factor for preeclampsia is maternal age, an important factor considering that the age at which women experience their first pregnancy has steadily increased through the decades. We use aged female rats (9.5 months; equivalent to ∼35 yr old human), to investigate the impact of maternal aging on later-life maternal and offspring cardiovascular health. Our data show that advanced maternal age worsens postpartum vascular function and that offspring born from aged dams have an altered cardiovascular risk profile that is sex-specific. These data further illustrate pregnancy as a window of opportunity to assess both maternal and offspring future cardiovascular risk.

Increased susceptibility to cardiovascular disease in offspring born from dams of advanced maternal age.

Advanced maternal age increases the risk of pregnancy complications such as fetal growth restriction, hypertension and premature birth. Offspring born from compromised pregnancies are at increased risk of cardiovascular disease as adults. However, the effect of advanced maternal age on later-onset disease in offspring has not been investigated. In adulthood, male but not female offspring born to dams of advanced maternal age showed impaired recovery from cardiac ischaemia/reperfusion injury. Endothelium-dependent relaxation was also impaired in male but not female offspring born from aged dams. Oxidative stress may play a role in the developmental programming of cardiovascular disease in this model. Given the increasing trend toward delayed parenthood, these findings have significant population and health care implications and warrant further investigation. Exposure to prenatal stressors, including hypoxia, micro- and macronutrient deficiency, and maternal stress, increases the risk of cardiovascular disease in adulthood. It is unclear whether being born from a mother of advanced maternal age (≥35years old) may also constitute a prenatal stress with cardiovascular consequences in adulthood. We previously demonstrated growth restriction in fetuses from a rat model of advanced maternal age, suggesting exposure to a compromised in utero environment. Thus, we hypothesized that male and female offspring from aged dams would exhibit impaired cardiovascular function as adults. In 4-month-old offspring, we observed impaired endothelium-dependent relaxation in male (P<0.05) but not female offspring born from aged dams. The anti-oxidant polyethylene glycol superoxide dismutase improved relaxation only in arteries from male offspring of aged dams (ΔEmax : young dam -1.63±0.80vs. aged dam 11.75±4.23, P<0.05). Furthermore, endothelium-derived hyperpolarization-dependent relaxation was reduced in male but not female offspring of aged dams (P<0.05). Interestingly, there was a significant increase in nitric oxide contribution to relaxation in females born from aged dams (ΔEmax : young dam -24.8±12.1vs. aged dam -68.7±7.7, P<0.05), which was not observed in males. Recovery of cardiac function following an ischaemia-reperfusion insult in male offspring born from aged dams was reduced by ∼57% (P<0.001), an effect that was not evident in female offspring. These data indicate that offspring born from aged dams have an altered cardiovascular risk profile that is sex-specific. Given the increasing trend toward delaying pregnancy, these findings may have significant population and health care implications and warrant further investigation.