Groundwater Depletion and Agricultural Land Use Change in the High Plains: A Case Study from Wichita County,Kansas*     

Nathan Kettle  Lisa Harrington  John Harrington Jr. 《The Professional geographer》2007,59(2):221-235

Shifts in resource availability and resulting land use changes are important research themes for coupled human and natural systems and human dimensions of global environmental change. This study examines the relationship between groundwater depletion and agricultural land use change within a single county in the High Plains, where agro-economic systems and populations are dependent on access to reliable groundwater supplies. Results indicate a significant relationship between high proportionate decreases in groundwater and land being removed from irrigation. This case study strengthens the links among local, regional, and global environmental change, and contributes to a greater understanding of the High Plains in the context of regional sustainability and vulnerability concerns.  相似文献   

Vertical-axis rotation controlled by upper crustal stress based on force balance analysis: A case study of the western Transverse Ranges of California     

Nathan W. Onderdonk   《Tectonophysics》2007,436(1-4):1-8

This paper evaluates driving mechanisms of vertical-axis rotation using data from the western Transverse Ranges in southern California. Simple force balance considerations and comparison of torque applied to a rotating block indicate that shear forces applied to the base of the block are not strong enough to produce the motions and deformation observed at the surface. For the measured dimensions of the crustal blocks and crustal viscosities in southern California, stresses transmitted through the upper crust are one to three orders of magnitude stronger than forces generated in the ductile lower crust. These results suggest that the kinematics of crustal blocks in continental deformation zones are primarily controlled by forces within the upper crust rather than a flow field beneath.  相似文献   

An improved practical approach for estimating catchment-scale response functions through wavelet analysis     

Ravindra Dwivedi  Christopher Eastoe  John F. Knowles  Lejon Hamann  Thomas Meixner  Paul A. “Ty” Ferre  Christopher Castro  William E. Wright  Guo-Yue Niu  Rebecca Minor  Greg A. Barron-Gafford  Nathan Abramson  Bhaskar Mitra  Shirley A. Papuga  Michael Stanley  Jon Chorover 《水文研究》2021,35(3):e14082

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Heat tracing of heterogeneous hyporheic exchange adjacent to in‐stream geomorphic features     

Laura K. Lautz  Nathan T. Kranes  Donald I. Siegel 《水文研究》2010,24(21):3074-3086

There are many field techniques used to quantify rates of hyporheic exchange, which can vary in magnitude and direction spatially over distances of only a few metres, both within and between morphological features. We used in‐stream mini‐piezometers and heat transport modelling of stream and streambed temperatures to quantify the rates and directions of water flux across the streambed interface upstream and downstream of three types of in‐stream geomorphic features: a permanent dam, a beaver dam remnant and a stream meander. We derived hyporheic flux estimates at three different depths at six different sites for a month and then paired those flux rates with measurements of gradient to derive hydraulic conductivity (K) of the streambed sediments. Heat transport modelling provided consistent daily flux estimates that were in agreement directionally with hydraulic gradient measurements and also identified vertical heterogeneities in hydraulic conductivity that led to variable hyporheic exchange. Streambed K varied over an order of magnitude (1·9 × 10^?6 to 5·7 × 10^?5 m/s). Average rates of hyporheic flux ranged from static (q < ±0·02 m/day) to 0·42 m/day. Heat transport modelling results suggest three kinds of flow around the dams and the meander. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A simple carbon cycle representation for economic and policy analyses     

Michael J. Glotter  Raymond T. Pierrehumbert  Joshua W. Elliott  Nathan J. Matteson  Elisabeth J. Moyer 《Climatic change》2014,126(3-4):319-335

Integrated Assessment Models (IAMs) that couple the climate system and the economy require a representation of ocean CO₂ uptake to translate human-produced emissions to atmospheric concentrations and in turn to climate change. The simple linear carbon cycle representations in most IAMs are not however physical at long timescales, since ocean carbonate chemistry makes CO₂ uptake highly nonlinear. No linearized representation can capture the ocean’s dual-mode behavior, with initial rapid uptake and then slow equilibration over ∽10,000 years. In a business-as-usual scenario followed by cessation of emissions, the carbon cycle in the 2007 version of the most widely used IAM, DICE (Dynamic Integrated model of Climate and the Economy), produces errors of ∽2^°C by the year 2300 and ∽6^°C by the year 3500. We suggest here a simple alternative representation that captures the relevant physics and show that it reproduces carbon uptake in several more complex models to within the inter-model spread. The scheme involves little additional complexity over the DICE model, making it a useful tool for economic and policy analyses.  相似文献   

Integrated assessment of smallholder farming’s vulnerability to drought in the Brazilian Semi-arid: a case study in Ceará   总被引：1，自引：0，他引：1  

Diego Pereira Lindoso  Juliana Dalboni Rocha  Nathan Debortoli  Izabel Ibiapina Parente  Flávio Eiró  Marcel Bursztyn  Saulo Rodrigues-Filho 《Climatic change》2014,127(1):93-105

Smallholder farming is among the most vulnerable sectors due to its great social and economic sensitivity. Despite future climate change, current climate variability is already an issue of concern that justifies adaptation efforts. In Brazil, the Semi-Arid Region is a climate hotspot, well known for both historic socioeconomic setbacks, and agriculture failures caused by dry spells and severe droughts. In 2010, the Brazilian government enacted the National Policy on Climate Change, which states as one of its key goals the identification of vulnerabilities and the adoption of adequate measures of adaptation to climate change. The improvement of vulnerability assessment tools is a response to the growing demand of decision makers for regular information and indicators with high spatial and temporal resolution. This article aims at undertaking a comparative assessment of smallholder farming’s vulnerability to droughts. An integrated assessment system has been developed and applied to seven municipalities located in the Brazilian Semi-Arid Region (within the State of Ceará). Results show regional vulnerability contrasts driven by institutional and socioeconomic factors, beyond climatic stressors.  相似文献   

Climate extremes in the United States: recent research by physical geographers     

David Retchless  Nathan Frey  Chongming Wang  Li-San Hung 《自然地理学》2014,35(1):3-21

This paper reports our review of research on domestic climate extremes conducted by US physical geographers over the past 15?years. Sections cover extremes in wind, precipitation, lightning, and temperature, as well as derivative climate extremes (droughts, floods, and storm surges). Themes considered include: the spatial and temporal distribution of the climate extreme; its implications for our understanding of the physical processes that produce it; the spatial and temporal distributions of the extreme’s economic and human costs; lessons for assessment, policy, and management; and scale. We conclude that most of the works reviewed inadequately address the human basis of vulnerability to climate extremes, and encourage physical geographers to work with colleagues from the other subfields of geography and the social sciences to develop the holistic understanding of vulnerability needed to effectively adapt to the more extreme climate projected under climate change.  相似文献   

An Examination of ENSO’s Effect on the Monthly and Seasonal Climate of Hong Kong from a Statistical Perspective   总被引：1，自引：0，他引：1       下载免费PDF全文

李细明  郑逸樑 《Acta Meteorologica Sinica》2011,25(1):34-50

This study aims to examine the effect of El Nino and La Nina on the monthly and seasonal climate of Hong Kong against the ENSO-neutral situation from a statistical perspective. Monthly and seasonal temperature and rainfall of Hong Kong and monthly number of tropical cyclones (TCs) coming within 500 km of the city over the 59-yr (1950-2008) period are examined under three ENSO situations, namely El Nino, La Nina, and ENSO-neutral. It is found that, compared with the ENSO-neutral situation, El Nino tends...  相似文献   

Hillslope response to knickpoint migration in the Southern Appalachians: implications for the evolution of post‐orogenic landscapes     

Sean F. Gallen  Karl W. Wegmann  Kurt L. Frankel  Stephen Hughes  Robert Q. Lewis  Nathan Lyons  Paul Paris  Kristen Ross  Jennifer B. Bauer  Anne C. Witt 《地球表面变化过程与地形》2011,36(9):1254-1267

The southern Appalachians represent a landscape characterized by locally high topographic relief, steep slopes, and frequent mass movement in the absence of significant tectonic forcing for at least the last 200 Ma. The fundamental processes responsible for landscape evolution in a post‐orogenic landscape remain enigmatic. The non‐glaciated Cullasaja River basin of south‐western North Carolina, with uniform lithology, frequent debris flows, and the availability of high‐resolution airborne lidar DEMs, is an ideal natural setting to study landscape evolution in a post‐orogenic landscape through the lens of hillslope–channel coupling. This investigation is limited to channels with upslope contributing areas >2.7 km², a conservative estimate of the transition from fluvial to debris‐flow dominated channel processes. Values of normalized hypsometry, hypsometric integral, and mean slope vs elevation are used for 14 tributary basins and the Cullasaja basin as a whole to characterize landscape evolution following upstream knickpoint migration. Results highlight the existence of a transient spatial relationship between knickpoints present along the fluvial network of the Cullasaja basin and adjacent hillslopes. Metrics of topography (relief, slope gradient) and hillslope activity (landslide frequency) exhibit significant downstream increases below the current position of major knickpoints. The transient effect of knickpoint‐driven channel incision on basin hillslopes is captured by measuring the relief, mean slope steepness, and mass movement frequency of tributary basins and comparing these results with the distance from major knickpoints along the Cullasaja River. A conceptual model of area–elevation and slope distributions is presented that may be representative of post‐orogenic landscape evolution in analogous geologic settings. Importantly, the model explains how knickpoint migration and channel–hillslope coupling is an important factor in tectonically‐inactive (i.e. post‐orogenic) orogens for the maintenance of significant relief, steep slopes, and weathering‐limited hillslopes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Evaluation on the two filling functions for the recovery of forest information in mountainous shadows on Landsat ETM + Image   总被引：1，自引：0，他引：1  

SHAHTAHMASSEBI Amir reza  MOORE Nathan 《山地科学学报》2011,8(3):414-426

In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roifill and imfill,in order to improve the accuracy of forest mapping over mountainous regions.These two methods were applied to Landsat Enhanced Thematic Mapper (ETM +) multispectral image from Dong Yang County,Zhejiang Province,China.The performance of these methods was compared with two conventi...  相似文献