Reducing uncertainty in stochastic streamflow generation and reservoir sizing by combining observed,reconstructed and projected streamflow     

Jason?PatskoskiEmail authorView author&#;s OrcID profile  A.?Sankarasubramanian 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):1065-1083

Reservoir sizing is one of the most important aspects of water resources engineering as the storage in a reservoir must be sufficient to supply water during extended droughts. Typically, observed streamflow is used to stochastically generate multiple realizations of streamflow to estimate the required storage based on the Sequent Peak Algorithm (SQP). The main limitation in this approach is that the parameters of the stochastic model are purely derived from the observed record (limited to less than 80 years of data) which does not have information related to prehistoric droughts. Further, reservoir sizing is typically estimated to meet future increase in water demand, and there is no guarantee that future streamflow over the planning period will be representative of past streamflow records. In this context, reconstructed streamflow records, usually estimated based on tree ring chronologies, provide better estimates of prehistoric droughts, and future streamflow records over the planning period could be obtained from general circulation models (GCMs) which provide 30 year near-term climate change projections. In this study, we developed paleo streamflow records and future streamflow records for 30 years are obtained by forcing the projected precipitation and temperature from the GCMs over a lumped watershed model. We propose combining observed, reconstructed and projected streamflows to generate synthetic streamflow records using a Bayesian framework that provides the posterior distribution of reservoir storage estimates. The performance of the Bayesian framework is compared to a traditional stochastic streamflow generation approach. Findings based on the split-sample validation show that the Bayesian approach yielded generated streamflow traces more representative of future streamflow conditions than the traditional stochastic approach thereby, reducing uncertainty on storage estimates corresponding to higher reliabilities. Potential strategies for improving future streamflow projections and its utility in reservoir sizing and capacity expansion projects are also discussed.  相似文献   

Experimental validation of seismic retrofit solutions for URM chimneys     

Marta Giaretton  Jason M. Ingham  Dmytro Dizhur 《Bulletin of Earthquake Engineering》2018,16(1):295-313

Clay-brick unreinforced masonry (URM) chimneys are a common architectural feature of vintage domestic and commercial URM and timber-framed buildings widely encountered worldwide. URM chimneys include a cantilevered appendage above the roofline that during earthquakes-induced shaking is susceptible to significant damage and collapse, which can result in fatalities, injuries, and property damage. To mitigate this risk, many vintage URM chimneys are removed, braced, or eventually replaced with modern alternatives. The earthquake performance of 15,400 URM chimneys damaged during the 2010/2011 Canterbury earthquake sequence was investigated using a photographic database and insurance claims data. The widespread damage and failure of a large proportion of retrofitted chimneys was the impetus for an experimental shake-table testing campaign that was undertaken to assess the performance of five prototypical URM chimneys in their as-built and retrofitted conditions. Cost-effective retrofit techniques with low aesthetic impact, including the use of near surface mounted carbon-fibre reinforced polymer strips and post-tensioning, were investigated. Tested chimneys were constructed to replicate the most commonly encountered geometric characteristics and construction details collected during an in-field pilot survey of 351 undamaged vintage URM chimneys.  相似文献   

The likelihood of having a household emergency plan: understanding factors in the US context     

Rivera  Jason D. 《Natural Hazards》2020,104(2):1331-1343

Natural Hazards - Individual household emergency planning is the most fundamental and can be the least expensive way to prepare for natural disasters. However, despite government and nonprofit...  相似文献   

Thresholds for post-wildfire debris flows: Insights from the Pinal Fire,Arizona, USA     

Carissa A. Raymond  Luke A. McGuire  Ann M. Youberg  Dennis M. Staley  Jason W. Kean 《地球表面变化过程与地形》2020,45(6):1349-1360

Wildfire significantly alters the hydrologic properties of a burned area, leading to increases in overland flow, erosion, and the potential for runoff-generated debris flows. The initiation of debris flows in recently burned areas is well characterized by rainfall intensity-duration (ID) thresholds. However, there is currently a paucity of data quantifying the rainfall intensities required to trigger post-wildfire debris flows, which limits our understanding of how and why rainfall ID thresholds vary in different climatic and geologic settings. In this study, we monitored debris-flow activity following the Pinal Fire in central Arizona, which differs from both a climatic and hydrogeomorphic perspective from other regions in the western United States where ID thresholds for post-wildfire debris flows are well established, namely the Transverse Ranges of southern California. Since the peak rainfall intensity within a rainstorm may exceed the rainfall intensity required to trigger a debris flow, the development of robust rainfall ID thresholds requires knowledge of the timing of debris flows within rainstorms. Existing post-wildfire debris-flow studies in Arizona only constrain the peak rainfall intensity within debris-flow-producing storms, which may far exceed the intensity that actually triggered the observed debris flow. In this study, we used pressure transducers within five burned drainage basins to constrain the timing of debris flows within rainstorms. Rainfall ID thresholds derived here from triggering rainfall intensities are, on average, 22 mm h⁻¹ lower than ID thresholds derived under the assumption that the triggering intensity is equal to the maximum rainfall intensity recorded during a rainstorm. We then use a hydrologic model to demonstrate that the magnitude of the 15-min rainfall ID threshold at the Pinal Fire site is associated with the rainfall intensity required to exceed a recently proposed dimensionless discharge threshold for debris-flow initiation. Model results further suggest that previously observed differences in regional ID thresholds between Arizona and the San Gabriel Mountains of southern California may be attributed, in large part, to differences in the hydraulic properties of burned soils. © 2019 John Wiley & Sons, Ltd.  相似文献   

The role of antecedent groundwater heads in controlling transient aquifer storage and flood peak attenuation in karst watersheds     

Patricia Spellman  Jason Gulley  Jonathan B. Martin  Jeremy Loucks 《地球表面变化过程与地形》2019,44(1):77-87

Transient storage of floodwaters in aquifers is known to attenuate peak flows in rivers and drive subsurface dissolution. Transient aquifer storage could be enhanced in watersheds overlying karst aquifers where caves facilitate surface and groundwater exchange. Few studies, however, have examined controls on, or magnitudes of, transient aquifer storage or flood peak attenuation in karstic watersheds. Here we evaluate flood peak attenuation with multiple linear regression analyses of 10 years of river and groundwater data from the Suwannee River, which flows over the karstic upper Floridan aquifer in north-central Florida and experiences frequent flooding. Regressions show antecedent river stage exerts the dominant control on magnitudes of transient aquifer storage, with recharge and time to peak having secondary controls. Specifically, low antecedent stages result in larger magnitudes of transient aquifer storage and thus greater flood attenuation than conditions of elevated antecedent stage. These findings suggest subsurface weathering, including cave formation and enlargement, caused by transient aquifer storage could occur on a more frequent basis in aquifers where groundwater table elevation is lowered due to anthropogenic or climatic influences. Our work also shows that measures of groundwater table elevation prior to an event could be used to improve predictive flood models. © 2018 John Wiley & Sons, Ltd.  相似文献   

Analysis of noble gases in water using a quadrupole mass spectrometer in static mode   总被引：1，自引：0，他引：1  

Jason C. Poole  Gavin W. McNeill  Stephen R. Langman  Frank Dennis 《Applied Geochemistry》1997,12(6):707-714

A quadrupole-based mass spectrometer used in static mode has been employed to determine noble gas concentrations of water samples by isotope dilution. Water samples are degassed and spiked with minor isotopes of each noble gas. After separation of the various gas components, the isotopic ratios are measured in the mass spectrometer. Because a spike is added to each sample, the recovery of each gas component does not have to be quantitative. Equilibration temperatures are calculated from the gas concentrations, based on noble gas solubility data. An accuracy of ±1°C, from the air equilibration temperature, is attainable for air-saturated water samples prepared under controlled conditions in the laboratory. The method has been applied to groundwaters from the London Basin Chalk aquifer. The noble-gas-derived temperatures are consistent with climatic conditions prevailing at the periods of recharge.  相似文献   

Isotopic and noble gas study of Chalk groundwater in the London Basin, England     

Frank Dennis  John N. Andrews  Andrew Parker  Jason Poole  Manfred Wolf 《Applied Geochemistry》1997,12(6):763-773

The chemical and isotopic composition of groundwater from 52 sites in the London (U.K.) area was determined as part of a project aimed at assessing the spatial variation in the age of Chalk groundwater, and in determining the relationship between fracture and matrix groundwater in this dual porosity system.Systematic changes in groundwater chemistry take place in the downgradient direction in response to several chemical processes. These processes include early concentration by evaporation and congruent dissolution of calcite followed by widespread incongruent dissolution and ion exchange in addition to local oxidation-reduction reactions, gypsum dissolution and saline intrusion. As a result of the above processes, Chalk groundwater follows an evolutionary path from Ca bicarbonate type to Na bicarbonate type.The age of Chalk groundwater was modelled using¹⁴C, δ¹³C,³H, δ²H and δ¹⁸0. There is a general increase in the groundwater age in a downgradient direction with the oldest water found in N central areas of the basin. Groundwater in the unconfined zones and in areas S of the Greenwich fault is almost entirely of unevolved, modem composition. Carbon-14 modelling suggests that Chalk groundwater in the S basin is generally less than 10000 a old while that in the north is generally between 10000 and 25000 a old. The presence of³H in concentrations of up to 7 TU in groundwater which yields ages of several 1000 a, however, indicates that mechanisms exist for the rapid introduction of recent groundwater to the confined aquifer. Results of palaeorecharge temperature determinations using δ²H, δ¹⁸0 and noble gas analytical results suggest that significant Devensian recharge did indeed occur in the aquifer.A model of the development of the Chalk recognizes that it is a classic dual porosity aquifer in which groundwater flow occurs predominantly in the fracture system. The upper 50 m of the aquifer was flushed with fresh water during the 2–3 × 10⁶ a of the Quaternary and therefore meteoric water largely replaced the Tertiary and Cretaceous marine water that previously saturated the system. Most processes which control the chemistry of the groundwater occur in the matrix where the surface area is exceptionally high. Although fracture flow dominates the flow regime, diffusion from the matrix into the fracture porosity controls the chemistry of Chalk groundwater.  相似文献   

Source Characterization and Tsunami Modeling of Submarine Landslides Along the Yucatán Shelf/Campeche Escarpment,Southern Gulf of Mexico     

Jason D. Chaytor  Eric L. Geist  Charles K. Paull  David W. Caress  Roberto Gwiazda  Jaime Urrutia Fucugauchi  Mario Rebolledo Vieyra 《Pure and Applied Geophysics》2016,173(12):4101-4116

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Very slow erosion rates and landscape preservation across the southwestern slope of the Ladakh Range,India          下载免费PDF全文

Craig Dietsch  Jason M. Dortch  Scott A. Reynhout  Lewis A. Owen  Marc W. Caffee 《地球表面变化过程与地形》2015,40(3):389-402

Erosion rates are key to quantifying the timescales over which different topographic and geomorphic domains develop in mountain landscapes. Geomorphic and terrestrial cosmogenic nuclide (TCN) methods were used to determine erosion rates of the arid, tectonically quiescent Ladakh Range, northern India. Five different geomorphic domains are identified and erosion rates are determined for three of the domains using TCN ¹⁰Be concentrations. Along the range divide between 5600 and 5700 m above sea level (asl), bedrock tors in the periglacial domain are eroding at 5.0 ± 0.5 to 13.1 ± 1.2 meters per million years (m/m.y.)., principally by frost shattering. At lower elevation in the unglaciated domain, erosion rates for tributary catchments vary between 0.8 ± 0.1 and 2.0 ± 0.3 m/m.y. Bedrock along interfluvial ridge crests between 3900 and 5100 m asl that separate these tributary catchments yield erosion rates <0.7 ± 0.1 m/m.y. and the dominant form of bedrock erosion is chemical weathering and grusification. Erosion rates are fastest where glaciers conditioned hillslopes above 5100 m asl by over‐steepening slopes and glacial debris is being evacuated by the fluvial network. For range divide tors, the long‐term duration of the erosion rate is considered to be 40–120 ky. By evaluating measured ¹⁰Be concentrations in tors along a model ¹⁰Be production curve, an average of ~24 cm is lost instantaneously every ~40 ky. Small (<4 km²) unglaciated tributary catchments and their interfluve bedrock have received very little precipitation since ~300 ka and the long‐term duration of their erosion rates is 300–750 ky and >850 ky, respectively. These results highlight the persistence of very slow erosion in different geomorphic domains across the southwestern slope of the Ladakh Range, which on the scale of the orogen records spatial changes in the locus of deformation and the development of an orogenic rain shadow north of the Greater Himalaya. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Heterogeneous distributions of CO2 may be more important for dissolution and karstification in coastal eogenetic limestone than mixing dissolution          下载免费PDF全文

Jason D. Gulley  Jonathon B. Martin  Paul J. Moore  Amy Brown  Patricia D. Spellman  John Ezell 《地球表面变化过程与地形》2015,40(8):1057-1071

Mixing dissolution, a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals, is commonly considered to form cavernous macroporosity (e.g. flank margin caves and banana holes) in eogenetic karst aquifers. On small islands, macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface, suggesting that dissolution processes are decoupled from surface hydrology. Mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pCO₂ was assumed to be homogeneously distributed within the phreatic zone. Here, we report data from two abandoned well fields in an eogenetic karst aquifer on San Salvador Island, Bahamas, that demonstrate pCO₂ in the phreatic zone is distributed heterogeneously. The pCO₂ varied from less than log ?2.0 to more than log ?1.0 atm over distances of less than 30 m, generating dissolution in the subsurface where water flows from regions of low to high pCO₂ and cementation where water flows from regions of high to low pCO_2. Using simple geochemical models, we show dissolution caused by heterogeneously distributed pCO₂ can dissolve 2.5 to 10 times more calcite than the maximum amount possible by mixing of freshwater and seawater. Dissolution resulting from spatial variability in pCO₂ forms isolated, globular chambers lacking initial entrances to the surface, a morphology that is characteristic of flank margin caves and banana holes, both of which have entrances that form by erosion or collapse after cave formation. Our results indicate that heterogeneous pCO₂, rather than mixing dissolution, may be the dominant mechanism for observed spatial distribution of dissolution, cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献