Optimal design of snow stake networks to estimate snow depth in an alpine mountain range

Monitoring and estimation of snow depth in alpine catchments is needed for a proper assessment of management alternatives for water supply in these water resources systems. The distribution of snowpack thickness is usually approached by using field data that come from snow samples collected at a given number of locations that constitute the monitoring network. Optimal design of this network is required to obtain the best possible estimates. Assuming that there is an existing monitoring network, its optimization may imply the selection of an optimal network as a subset of the existing one (if there are no funds to maintain them) or enlarging the existing network by one or more stations (optimal augmentation problem). We propose an optimization procedure that minimizes the total variance in the estimate of snowpack thickness. The novelty of this work is to treat, for the first time, the problem of snow observation network optimization for an entire mountain range rather than for small catchments as done in the previous studies. Taking into account the reduced data available, which is a common problem in many mountain ranges, the importance of a proper design of these observation networks is even larger. Snowpack thickness is estimated by combining regression models to approach the effect of the explanatory variables and kriging techniques to consider the influence of the stakes location. We solve the optimization problems under different hypotheses, studying the impacts of augmentation and reduction, both, one by one and in pairs. We also analyse the sensitivity of results to nonsnow measurements deduced from satellite information. Finally, we design a new optimal network by combining the reduction and augmentation methods. The methodology has been applied to the Sierra Nevada mountain range (southern Spain), where very limited resources are employed to monitor snowfall and where an optimal snow network design could prove critical. An optimal snow observation network is defined by relocating some observation points. It would reduce the estimation variance by around 600 cm² (15%).     

Rainfall variability and hydrological and erosive response of an olive tree microcatchment under no‐tillage with a spontaneous grass cover in Spain

Most studies on runoff and soil loss from olive orchards were performed on plots, despite the fact that measurements that examine a range of erosive processes on different scales are essential to evaluate the suitability of the use and soil management of this type of land. The main environmental limitations of much of the land used for olive orchards in the Mediterranean are the steep slopes and the shallow soil depth – and this was the case in the study area. Soil erosion and runoff over two hydrological years (2005–2006 and 2006–2007) were monitored in an olive orchard microcatchment of 6·1 ha under no‐tillage with spontaneous grass in order to evaluate its hydrological and erosive behaviour. Moreover, soil parameters such as organic matter (%OM), bulk density (BD) and hydraulic saturated conductivity (Ks) were also examined in the microcatchment to describe management effects on hydrological balance and on erosive processes. In the study period, the results showed runoff coefficients of 6·0% in the first year and 0·9% in the second. The differences respond to the impact of two or three yearly maximum events which were decisive in the annual balances. On the event scale, although maximum rainfall intensity values had a big influence on peak flows and runoff, its importance on mean sediment concentrations and sediment discharges was difficult to interpret due to the likely control of grass cover on volume runoff and on soil protection. In the case of annual soil erosion, they were measured as 1·0 Mg ha^?1 yr^?1 and 0·3 Mg ha^?1 yr^?1. Both are lower than the tolerance values evaluated in Andalusia (Spain). These results support the implementation of no‐tillage with spontaneous grass cover for sloping land, although the reduced infiltration conditions determined by Ks in the first horizon suggest grass should be allowed to grow not only in spring but also in autumn. In addition, specific measurements to control gullies, which have formed in the terraced area in the catchment, should be included since it is expected that they could be the main sources of sediments. Copyright © 2010 John Wiley & Sons, Ltd.     

Did tillage erosion play a role in millennial scale landscape development?

Landscape evolution models (LEMs) quantitatively simulate processes of sedimentation and erosion on millennial timescales. An important aspect of human impact on erosion is sediment redistribution due to agriculture, referred to herein as tillage erosion. In this study we aim to analyse the potential contribution of tillage erosion to landscape development using LEM LAPSUS. The model is calibrated separately for a water erosion process (i) without tillage and (ii) with tillage. The model is applied to the ~250 km² Torrealvilla case study catchment, SE Spain. We were able to simulate alternating sequences of incision and aggradation, that are important on longer (millennial) timescales. Generally, model results show that tillage erosion adds to deposition in the lower floodplain area, but neither water erosion alone nor water with tillage erosion together could exactly reproduce the observed amounts of erosion and sedimentation for the case study area. In addition, scale effects are apparent. On hillslopes, tillage may contribute importantly to erosion and may fill local depressions. If assessed on the catchment scale, sediments from tillage erosion eventually reach the lower floodplain area where they contribute to deposition. However, water erosion was observed in the model simulations to be the most important process on the catchment scale. This is the first time that tillage erosion has been explicitly included in a landscape evolution model at a millennial timescale and large catchment scale. Copyright © 2012 John Wiley & Sons, Ltd.     

Eocene post-rift tectonostratigraphy of the Rockall Plateau, Atlantic margin of NW Britain: Linking early spreading tectonics and passive margin response

A regional study of the Eocene succession in the UK sector of the Rockall Plateau has yielded new insights into the early opening history of the NE Atlantic continental margin. Data acquired from British Geological Survey borehole 94/3, on the Rockall High, provides a high-resolution record of post-rift, Early to Mid-Eocene, subaqueous fan-delta development and sporadic volcanic activity, represented by pillow lavas, tuffs and subaerial lavas. This sequence correlates with the East Rockall Wedge, which is one of several prograding sediment wedges identified across the Rockall Plateau whose development was largely terminated in the mid-Lutetian. Linking the biostratigraphical data with the magnetic anomaly pattern in the adjacent ocean basin indicates that this switch-off in fan-delta sedimentation and volcanism was coincident with the change from a segmented/transform margin to a continuously spreading margin during chron C21. However, late-stage easterly prograding sediment wedges developed on the Hatton High during late Mid- to Late Eocene times; these can only have been sourced from the Hatton High, which was developing as an anticline during this interval. This deformation occurred in response to Mid- to Late Eocene compression along the ocean margin, possibly associated with the reorganisation to oblique spreading in the Iceland Basin, which culminated at the end of the Eocene with the formation of the North Hatton Anticline, and the deformation (tilting) of these wedges. A series of intra-Eocene unconformities, of which the mid-Lutetian unconformity is the best example, has been traced from the Rockall Plateau to the Faroe-Shetland region and onto the Greenland conjugate margin bordering the early ocean basin. Whilst there appears to be some correlation with 3rd order changes in eustatic sea level, it is clear from this study that tectonomagmatic processes related to changes in spreading directions between Greenland and Eurasia, and/or mantle thermal perturbations cannot be discounted.     

西班牙交通基础设施与城市体系建设

从社会和地方融合、均衡性与土地异质性、交通网等级体系和支路网与交通可持续性四个角度探讨西班牙交通基础设施网建设对土地开发和土地规划相关国家法规的影响。从城市地理学视角分析中央政府基于改善城市和区域连接度和可达性进行的高速公路网、高铁网、机场和港口等交通基础设施规划,通过1950年代以来土地开发和房价涨跌、新兴产业培育和交通状况改善刺激不同级别城市蔓延和分化的人口增长,重塑西班牙国家城市体系格局。随后,概括了蔓延的城市增长模式和房地产与交通投资泡沫破裂后带给区域增长中心的影响,对通过交通基础设施规划进行投机性投资政策进行了批评。最后建议中央政府应该避免投机投资行为,基于现有的城市体系层级改善核心城市和大城市周边的机动性,优化基础设施建设,建立新的城市与区域增长模式。     

西班牙的房地产泡沫:城市化与城市建设

聚焦于西班牙1996-2007年间的房地产泡沫,此次危机与西班牙前两次经历的地产泡沫有着相似的背景条件：将住房建设作为利好投机性投资。但几次泡沫供给结构却不同：此次住房供给主要为分散式,不同于以往的集中供应;旅游地产大量出现;房屋拥有型社会形成。作者认为供给结构的改变并非危机的主要原因,并提出了造成房地产泡沫的四个关键要素：符合一定条件的土地、土地规划的配合、充足的资金与可获得的土地所有权。结论是：政策的制定直接影响土地利用、发展规划、金融系统与个人资产、造成住房由使用品变为投机投资的对象、银行体系信用缺乏保障,最终导致了住房库存量陡增,大量房屋拆除事件与失业率攀升等经济和社会方面的不良影响。     

A demand analysis of the Spanish canned tuna market

The Spanish market for canned fish is one of the biggest in the world. It is still largely supplied by a robust national industry which has survived globalisation when all other European countries failed to preserve their two-century old industry. What is so special about this relationship between Spanish consumers and canned fish? This research analyses the nature of the demand for canned fish, and particularly canned tuna, a rather inexpensive and storable food product, to show how Spanish households are sensitive to price and income changes. The price and expenditure elasticities are estimated through a time-based Almost Ideal Demand System (AIDS) model. A Johansen’s multivariate time-series analysis was developed through a vector error correction model, the misspecification tests supporting the use of this model. The empirical analysis found that the Spanish demand for canned fish in Spain is rather price inelastic, whatever the species, but substitutability is found between the different canned fish products. The results also demonstrate that canned tuna over-reacts positively to expenditure changes compared to other fish species, presenting a nature of luxury good compared to other canned fish products.     

The Iberian-Roman Humid Period (2600-1600 cal yr BP) in the Zoñar Lake varve record (Andalucía, southern Spain)

The Iberian-Roman Humid Period (IRHP, 2600-1600 cal yr BP), is the most humid phase of the last 4000 yr in southern Spain as recorded in the sedimentary sequence of Zoñar Lake (37°29′00″N, 4°41′22″ W, 300 m a.s.l.). A varve chronology supported by several AMS ¹⁴C dates allows study of the lake evolution at annual scale in response to human impact and climate changes. There are four climate phases within this period: i) gradual transition (2600-2500 yr ago, 650-550 BC) from a previous arid period; ii) the most humid interval during the Iberian-Early Roman Epoch (2500-2140 yr ago, 550-190 BC); iii) an arid interval during the Roman Empire Epoch (2140-1800 yr ago, 190 BC AD 150); and iv) a humid period synchronous with the decline of the Roman Empire (1800-1600 yr ago, AD 150-350). Varve thickness and geochemical proxies show a multi-decadal cyclicity similar to modern North Atlantic Oscillation (NAO) (60, 20 years) and solar variability cycles (11 yr). The timing and the structure of this humid period is similar to that described in Eastern Mediterranean and northern European sites and supports the same large-scale climate control for northern latitudes and the Mediterranean region.     

Sedimentary processes caused by felsic caldera-forming volcanism in the Late Miocene to Early Pliocene intra-arc Aizu basin, NE Japan arc

Six large Late Miocene to Quaternary calderas, > 10 km in diameter, cluster together with several medium to small calderas and stratovolcanoes in a 60 × 30 km area of the Aizu volcanic field, southern NE Japan arc. These caldera volcanoes were built on a WNW–ESE trending highland coincident with a local uplifted swell since Late Miocene. The flare-up of felsic volcanism occurred synchronously along the NE Japan arc. Pyroclastic flow sheets from the calderas spread over the surrounding intra-arc basins and are interstratified with various sediments. Geochronological data indicates that the large-caldera eruptions have occurred six times since 8 Ma, at intervals of 1 to 2 million years. Late Miocene to Early Pliocene extra-caldera successions in the basin consist of nine sedimentary facies associations: (1) primary pyroclastics, (2) lahars, (3) gravelly fluvial channels, (4) sandy fluvial channels, (5) floodplains, (6) tidal flats, (7) delta fronts, (8) pro-delta slopes, and (9) pro-delta turbidites. The distribution of facies associations show westward prograding of volcaniclastic aprons, made up of braid delta, braidplain, pyroclastic flow sheet, and incised braided river deposits. The extra-caldera successions record: 1) an increase in felsic volcanism with an associated high rate of volcaniclastic sediment supply at about 10 Ma, prior to catastrophic caldera-forming eruptions; and 2) progradation of volcaniclastic aprons toward the back-arc side in response to the succeeding caldera-forming eruptions and sea-level changes, until about 3 Ma.     

Early Cretaceous fish trails from La Rioja, Spain

We report a new find of the fish trail Undichna unisulca in fluvial sediments of the Lower Cretaceous Oliván Group of the Cameros Basin (Aptian-Albian; Valtrujal, La Rioja, northern Spain). It is the second Mesozoic record of Undichna unisulca after the first discovery in the Lower Cretaceous of central Spain (Las Hoyas, Cuenca, central Spain). The trails are characterized by single sinusoidal waves which in this case are often surrounded by well-preserved lateral levees that rule out an undertrail hypothesis.The continental depositional setting, a floodplain fluvial system, reflects the known broad palaeoenvironmental distribution of Undichna and confirms its occurrences in freshwater settings.