Thermal Monitoring of Natural Source Zone Depletion          下载免费PDF全文

Kayvan Karimi Askarani  Emily B. Stockwell  Keith R. Piontek  Tom C. Sale 《Ground Water Monitoring & Remediation》2018,38(3):43-52

Natural depletion of subsurface petroleum liquids releases energy in the form of heat. The rate of natural source zone depletion (NSZD) can be derived from subsurface temperature data. An energy balance is performed to resolve NSZD‐generated energy in terms of W/m². Biodegradation rates are resolved by dividing the NSZD energy by the heat of reaction in joules/mol. Required temperature data are collected using data loggers, wireless connections, and automated data storage and analysis. Continuous thermal resolution of monthly NSZD rates at a field site indicates that apparent monthly NSZD rates vary through time, ranging from 10,000 to 77,000 L/ha/year. Temporal variations in observed apparent NSZD rates are attributed to processes governing the conversion of CH₄ to CO₂, as opposed to the actual rates of NSZD. Given a year or more of continuous NSZD rate data, it is anticipated that positive and negative biases in apparent NSZD rates will average out, and averaged apparent NSZD rates will converge to true NSZD rates. An 8.4% difference between average apparent NSZD rates over a 31‐month period using the thermal monitoring method and seven rounds of CO₂ efflux measurements using CO₂ traps supports the validity of both CO₂ trap and thermal monitoring methods. A promising aspect of thermal monitoring methods is that continuous data provide a rigorous approach to resolving the true mean NSZD rates as compared to temporally sparse CO₂ trap NSZD rate measurements. Overall, a vision is advanced of real‐time sensor‐based groundwater monitoring that can provide better data at lower costs and with greater safety, security, and sustainability.  相似文献   

Changes in Projected Spatial and Seasonal Groundwater Recharge in the Upper Colorado River Basin          下载免费PDF全文

Fred D Tillman  Subhrendu Gangopadhyay  Tom Pruitt 《Ground water》2017,55(4):506-518

The Colorado River is an important source of water in the western United States, supplying the needs of more than 38 million people in the United States and Mexico. Groundwater discharge to streams has been shown to be a critical component of streamflow in the Upper Colorado River Basin (UCRB), particularly during low‐flow periods. Understanding impacts on groundwater in the basin from projected climate change will assist water managers in the region in planning for potential changes in the river and groundwater system. A previous study on changes in basin‐wide groundwater recharge in the UCRB under projected climate change found substantial increases in temperature, moderate increases in precipitation, and mostly periods of stable or slight increases in simulated groundwater recharge through 2099. This study quantifies projected spatial and seasonal changes in groundwater recharge within the UCRB from recent historical (1950 to 2015) through future (2016 to 2099) time periods, using a distributed‐parameter groundwater recharge model with downscaled climate data from 97 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections. Simulation results indicate that projected increases in basin‐wide recharge of up to 15% are not distributed uniformly within the basin or throughout the year. Northernmost subregions within the UCRB are projected an increase in groundwater recharge, while recharge in other mainly southern subregions will decline. Seasonal changes in recharge also are projected within the UCRB, with decreases of 50% or more in summer months and increases of 50% or more in winter months for all subregions, and increases of 10% or more in spring months for many subregions.  相似文献   

A physics-based earthquake simulator and its application to seismic hazard assessment in Calabria (Southern Italy) region     

Rodolfo Console  Anna Nardi  Roberto Carluccio  Maura Murru  Giuseppe Falcone  Tom Parsons 《Acta Geophysica》2017,65(1):243-257

The use of a newly developed earthquake simulator has allowed the production of catalogs lasting 100 kyr and containing more than 100,000 events of magnitudes ≥4.5. The model of the fault system upon which we applied the simulator code was obtained from the DISS 3.2.0 database, selecting all the faults that are recognized on the Calabria region, for a total of 22 fault segments. The application of our simulation algorithm provides typical features in time, space and magnitude behavior of the seismicity, which can be compared with those of the real observations. The results of the physics-based simulator algorithm were compared with those obtained by an alternative method using a slip-rate balanced technique. Finally, as an example of a possible use of synthetic catalogs, an attenuation law has been applied to all the events reported in the synthetic catalog for the production of maps showing the exceedance probability of given values of PGA on the territory under investigation.  相似文献   

Connectivity as an emergent property of geomorphic systems     

Ellen Wohl  Gary Brierley  Daniel Cadol  Tom J. Coulthard  Tim Covino  Kirstie A. Fryirs  Gordon Grant  Robert G. Hilton  Stuart N. Lane  Francis J. Magilligan  Kimberly M. Meitzen  Paola Passalacqua  Ronald E. Poeppl  Sara L. Rathburn  Leonard S. Sklar 《地球表面变化过程与地形》2019,44(1):4-26

Connectivity describes the efficiency of material transfer between geomorphic system components such as hillslopes and rivers or longitudinal segments within a river network. Representations of geomorphic systems as networks should recognize that the compartments, links, and nodes exhibit connectivity at differing scales. The historical underpinnings of connectivity in geomorphology involve management of geomorphic systems and observations linking surface processes to landform dynamics. Current work in geomorphic connectivity emphasizes hydrological, sediment, or landscape connectivity. Signatures of connectivity can be detected using diverse indicators that vary from contemporary processes to stratigraphic records or a spatial metric such as sediment yield that encompasses geomorphic processes operating over diverse time and space scales. One approach to measuring connectivity is to determine the fundamental temporal and spatial scales for the phenomenon of interest and to make measurements at a sufficiently large multiple of the fundamental scales to capture reliably a representative sample. Another approach seeks to characterize how connectivity varies with scale, by applying the same metric over a wide range of scales or using statistical measures that characterize the frequency distributions of connectivity across scales. Identifying and measuring connectivity is useful in basic and applied geomorphic research and we explore the implications of connectivity for river management. Common themes and ideas that merit further research include; increased understanding of the importance of capturing landscape heterogeneity and connectivity patterns; the potential to use graph and network theory metrics in analyzing connectivity; the need to understand which metrics best represent the physical system and its connectivity pathways, and to apply these metrics to the validation of numerical models; and the need to recognize the importance of low levels of connectivity in some situations. We emphasize the value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning. © 2018 John Wiley & Sons, Ltd.  相似文献   

The mixed-bed glacial landform imprint of the North Sea Lobe in the western North Sea     

David H. Roberts  Elena Grimoldi  Louise Callard  David J.A. Evans  Chris D. Clark  Heather A. Stewart  Dayton Dove  Margot Saher  Colm Ó Cofaigh  Richard C. Chiverrell  Mark D. Bateman  Steven G. Moreton  Tom Bradwell  Derek Fabel  Alicia Medialdea 《地球表面变化过程与地形》2019,44(6):1233-1258

During the last glacial cycle an intriguing feature of the British-Irish Ice Sheet was the North Sea Lobe (NSL); fed from the Firth of Forth and which flowed south and parallel to the English east coast. The controls on the formation and behaviour of the NSL have long been debated, but in the southern North Sea recent work suggests the NSL formed a dynamic, oscillating terrestrial margin operating over a deforming bed. Further north, however, little is known of the behaviour of the NSL or under what conditions it operated. This paper analyses new acoustic, sedimentary and geomorphic data in order to evaluate the glacial landsystem imprint and deglacial history of the NSL offshore from NE England. Subglacial tills (AF2/3) form a discontinuous mosaic interspersed with bedrock outcrops across the seafloor, with the partial excavation and advection of subglacial sediment during both advance and retreat producing mega-scale glacial lineations and grounding zone wedges. The resultant ‘mixed-bed’ glacial landsystem is the product of a dynamic switch from a terrestrial piedmont-lobe margin with a net surplus of sediment to a partially erosive, quasi-stable, marine-terminating, ice stream lobe as the NSL withdrew northwards. Glaciomarine sediments (AF4) drape the underlying subglacial mixed-bed imprint and point to a switch to tidewater conditions between 19.9 and 16.5 ka cal BP as the North Sea became inundated. The dominant controls on NSL recession during this period were changing ice flux through the Firth of Forth ice stream onset zone and water depths at the grounding line; the development of the mixed-bed landsystem being a response to grounding line instability. © 2018 John Wiley & Sons, Ltd.  相似文献   

The impact of different rainfall products on landscape modelling simulations     

Christopher J. Skinner  Nadav Peleg  Niall Quinn  Tom J. Coulthard  Peter Molnar  Jim Freer 《地球表面变化过程与地形》2020,45(11):2512-2523

Rainfall products can contain significantly different spatiotemporal estimates, depending on their underlying data and final constructed resolution. Commonly used products, such as rain gauges, rain gauge networks, and weather radar, differ in their information content regarding intensities, spatial variability, and natural climatic variability, therefore producing different estimates. Landscape evolution models (LEMs) simulate the geomorphic changes in landscapes, and current models can simulate timeframes from event level to millions of years and some use rainfall inputs to drive them. However, the impact of different rainfall products on LEM outputs has never been considered. This study uses the STREAP rainfall generator, calibrated using commonly used rainfall observation products, to produce longer rainfall records than the observations to drive the CAESAR-Lisflood LEM to examine how differences in rainfall products affect simulated landscapes. The results show that the simulation of changes to basin geomorphology is sensitive to the differences between rainfall products, with these differences expressed linearly in discharges but non-linearly in sediment yields. Furthermore, when applied over a 1500-year period, large differences in the simulated long profiles were observed, with the simulations producing greater sediment yields showing erosion extending further downstream. This suggests that the choice of rainfall product to drive LEMs has a large impact on the final simulated landscapes. The combination of rainfall generator model and LEMs represents a potentially powerful method for assessing the impacts of rainfall product differences on landscapes and their short- and long-term evolution. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

2006年ESRI开发者研讨会随笔     

James Fee  瓢虫  Tom 《地理信息世界》2006,4(2):56-56

ESRI的国际用户研讨会5月17-18日在California举行,James Fee在自己的BLOG中谈到了这次研讨会中几个非常好的Comments,并对ArcGIS家族体系中的一些新特性给予了描绘。Web ADF它毫无疑问该排第一位。仅从用户及开发人员在9.1中配置专业地图存在的困难来说,Web ADF(译者注:Appli-  相似文献