Rainfall events and climate change in Mediterranean environments: an alarming shift from resource to risk in Eastern Spain     

Camarasa-Belmonte  Ana M.  Rubio  M.  Salas  J. 《Natural Hazards》2020,103(1):423-445

Natural Hazards - Consequences of climate change in Mediterranean environments are difficult to predict, partly because daily data do not fit with the timescale of Mediterranean processes, and...  相似文献   

Evolution of temperature in granule and intergranular space     

J. Koza  L.R. Bellot Rubio  A. Ku era  A. Hanslmeier  J. Rybk  H. Whl 《Astronomische Nachrichten》2003,324(4):349-351

The temporal evolution of temperature in a dissolving granule and in an adjacent intergranular space is presented. The semi‐empirical evolutionary models have been calculated using an inversion method applied to 4‐min time series of Stokes I spectral line profiles. The models are presented in the form of the functional dependence of temperature T(log τ₅, t) on optical depth τ₅ at 500 nm and time t. The observed disappearance of the granule is accompanied with overall cooling of the granular photosphere. Temperature changes greater than 100 K have been found in deeper (log τ₅ ≥ 0) and upper layers (log τ₅ ≤ –2) whereas the intermediate layers are thermally stable. The intergranular space, which is 2 arcsec off the granule, keeps the temperature structure of the layers from log τ₅ = 0.5 to log τ₅ = –2 without global evolutionary changes except short‐term and spatially confined heating. Finally, the significant temperature changes in the upper layers (log τ₅ ≤ 2.5) observed during the time interval of 4 min are found to be typical for the granular and intergranular photosphere.  相似文献   

The use of MRS in the determination of hydraulic transmissivity: The case of alluvial aquifers     

Juan L. Plata  Flix M. Rubio 《Journal of Applied Geophysics》2008,66(3-4):128

Magnetic Resonance Sounding (MRS) is nowadays accepted as a new geophysical method that can be used for a reliable determination of the ground water content distribution in the top 150 m. A great effort has also been made in MRS development to deduce the hydraulic transmissivity, based on empiric relationships of the permeability with a factor F which is calculated with NMR parameters measured at laboratory scale. To use this relationship under field conditions a calibration coefficient C_T = T_pt / F has to be previously established, which demands the knowledge of the transmissivity T_pt evaluated in the pumping test. The transmissivity can then be calculated at any other site of the same aquifer using the relation T_mrs = C_TF. The C_T values reported suggest a certain relationship with the lithology, but with a great dispersion and contradictory results. MRS surveys carried out in alluvial aquifers in Spain have shown that the value of C_T evaluated at one site may not be valid at another place of the same aquifer, because of the great heterogeneity of this kind of geological environment. The demand of a pumping test at each site where a MRS is measured invalidates the method actually used for MRS transmissivity evaluation. More than 50 MRS have been used to propose a new methodology. The aquifers visited cover a great range of transmissivities (from 2 × 10^− 6 to 9 × 10^− 3 m²/s). The MRS signal amplitude varies between 20 and 1400 nV, the signal/noise ratio is in the range from 0.6 to 42, and the value of the decay time constant varies from 200 to 800 ms. It has been demonstrated that when the transmissivity increases, the value of F decreases, and C_T increases, except for certain groups of MRS taken at the same aquifer or part of one aquifer, for which F increases with T_pt, keeping C_T constant. A function C_T(F) of the type C_T = mF^− n has been obtained that allows the transmissivity evaluation without the need of T_pt. Considering that both values of transmissivity, T_pt and T_mrs, are subjected to deviations due to the experimental errors as well as due to evaluation errors, the prediction achieved by the proposed equation is rather good. To perform a better evaluation of the values of the coefficients m and n it is necessary to have a greater number of MR soundings of good quality and with a trustworthy inversion at locations where a really comparable and good performed pumping test is available, covering a sufficient range of transmissivities. Though the data we have used do not always fulfil these conditions, the result is promising. Once a trustable function is available, the forecast of the transmissivity using MRS will not need the existence of any pumping test in the area. The general extension of this methodology demands the availability of MRS taken at all kinds of geological and hydrogeological environments, which is impossible without the existence of a universal MRS data base.  相似文献   

Comparison between the indirect approach and kriging with samples of different support for estimation using samples of different length     

Marcel?Antonio?Arcari?BassaniEmail author  Jo?o?Felipe?Coimbra?Leite?Costa  Waleska?Campos?Guaglianoni  Ricardo?Hundelshaussen?Rubio 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(3):785-797

In this paper we compare two estimation methods to deal with samples of different support: (1) the indirect approach using accumulation and (2) kriging with samples of different support. These two methods were tested in a simple example. The estimates of the two methods were compared against a benchmark scenario. The benchmark consisted of kriging using a complete set of samples on the same support. The effects of the nugget effect, variogram range and type on the weight of long samples, the estimate, and the error variance were assessed. Kriging with samples of different support led to lower error variance and to estimates closer to the estimates of the benchmark scenario. Furthermore, in the case of spatially continuous attributes (low nugget effect), the indirect approach assigns greater weight to long samples than kriging with samples of different support. A cross validation study comparing the two methods with a database from a bauxite deposit was performed. The results of the cross validation study showed that kriging with samples of different support resulted in more precise estimates.  相似文献   

Long-term perspective on the relationship between phytoplankton and nutrient concentrations in a southeastern Australian estuary     

Michaela E. Larsson  Penelope A. Ajani  Ana M. Rubio  Kristy Guise  Ross G. McPherson  Steven J. Brett  Kevin P. Davies  Martina A. Doblin 《Marine pollution bulletin》2017,114(1):227-238

Sixteen years (1997–2013) of physicochemical, nutrient and phytoplankton biomass (Chlorophyll-a (Chl-a)) data and a decade (2003-2013) of phytoplankton composition and abundance data were analyzed to assess how the algal community in a temperate southeastern Australian estuary has responded to decreased chronic point source nitrogen loading following effluent treatment upgrade works in 2003. Nitrogen concentrations were significantly lower (P < 0.05) following enhanced effluent treatment and Chl-a levels decreased (P < 0.05) during the warmer months. Temperature and nutrient concentrations significantly influenced temporal changes of Chl-a (explaining 55% of variability), while salinity, temperature, pH and nutrient concentrations influenced phytoplankton abundance and composition (25% explained). Harmful Algal Bloom (HAB) dynamics differed between sites likely influenced by physical attributes of the estuary. This study demonstrates that enhanced effluent treatment can significantly decrease chronic point source nitrogen loading and that Chl-a concentrations can be lowered during the warmer months when the risk of blooms and HABs is greatest.  相似文献   

Analysis of groundwater mining in two carbonate aquifers in Sierra de Estepa (SE Spain) based on hydrodynamic and hydrochemical data     

Sergio Martos-Rosillo  Miguel Rodríguez-Rodríguez  Francisco Moral  José Javier Cruz-Sanjulián  Juan Carlos Rubio 《Hydrogeology Journal》2009,17(7):1617-1627

The carbonate aquifers of Lora and Mingo form part of the hydrogeological unit of Sierra de Estepa (SE Spain). By means of time series analysis and a 1D numerical groundwater model, groundwater exploitation was quantified and the mean annual recharge in both systems was estimated (2001–2004). During this period, the Lora and Mingo aquifers received an average groundwater recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year, respectively, whereas an average of 0.34 × 10⁶ m³/year and 0.21 × 10⁶ m³/year, respectively, was extracted. These conditions led to a conspicuous lowering of the water table in both systems. In addition, the analysis of the evolution of the main hydrogeochemical parameters of the groundwater showed that the increased pumping rates produced an increase in total dissolved solids, and chloride and sodium ions in both aquifers. In the case of the Lora aquifer, the only ion that presented decreased levels was nitrate. The results show that groundwater pumping in both aquifers should not exceed the mean annual recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year in the Lora and Mingo aquifers, respectively. Nevertheless, it would be advisable to reduce pumping rates to below these values in order to restore piezometric levels and improve groundwater quality for different uses in the future.  相似文献   

Application of groundwater sustainability indicators to the carbonate aquifer of the Sierra de Becerrero (Southern Spain)   总被引：3，自引：1，他引：2  

L. J. Lambán  S. Martos  M. Rodríguez-Rodríguez  J. C. Rubio 《Environmental Earth Sciences》2011,64(7):1835-1848

The objective of this study was to test the applicability of groundwater sustainability indicators defined by UNESCO, together with the International Academy of Environmental Sciences (IAES), the International Association of Hydrogeology (IAH) Group on Groundwater Indicators and the Geological Survey of Spain (IGME), to the aquifer scale. We selected four main indicators based on their relevance in the field of groundwater sustainability and because they proved to be the most reliable, based on the data collection and methodology utilized. These indicators were applied to a small—26 km² of permeable outcrops—carbonate aquifer situated in the province of Seville (southern Spain), which has semi-arid climate conditions (500 mm/year). The integral application of all these indicators in this particular groundwater body leads us to conclude that, at present, the aquifer is undergoing intensive use. Therefore, the exploitation of its water resources is surpassing the threshold of sustainability when both the quantity and the quality of the groundwater are taken into consideration. The continued increase in exploitation generates a descending trend in the evolution of the piezometric levels, a consequence of adaptation to the new hydrodynamic situation, and also results in exhaustion of the springs that drain the aquifer in undisturbed conditions. At the same time, there is a trend of increasing salinity in the groundwater and a risk of contamination by nitrate which, according to the EU Water Framework Directive and the Groundwater Daughter Directive (EU Official Journal of the European Communities L327, 2000; EU Official Journal of the European Communities L372/19, 2006), should be controlled and reduced. In the future, application of the methodology described here may prove useful for the evaluation of similar systems, either in southern Spain or in other countries with semi-arid climates.  相似文献   

A Chart for Judging Optimal Sample Spacing for Ore Grade Estimation     

Vanessa Cerqueira Koppe  Ricardo Hundelshaussen Rubio  João Felipe Coimbra Leite Costa 《Natural Resources Research》2017,26(2):191-199

Mineral deposit grades are usually estimated using data from samples of rock cores extracted from drill holes. Commonly, mineral deposit grade estimates are required for each block to be mined. Every estimated grade has always a corresponding error when compared against real grades of blocks. The error depends on various factors, among which the most important is the number of correlated samples used for estimation. Samples may be collected on a regular sampling grid and, as the spacing between samples decreases, the error of grade estimated from the data generally decreases. Sampling can be expensive. The maximum distance between samples that provides an acceptable error of grade estimate is useful for deciding how many samples are adequate. The error also depends on the geometry of a block, as lower errors would be expected when estimating the grade of large-volume blocks, and on the variability of the data within the region of the blocks. Local variability is measured in this study using the coefficient of variation (CV). We show charts analyzing error in block grade estimates as a function of sampling grid (obtained by geostatistical simulation), for various block dimensions (volumes) and for a given CV interval. These charts show results for two different attributes (Au and Ni) of two different deposits. The results show that similar errors were found for the two deposits, although they share similar features: sampling grid, block volume, CV, and continuity model. Consequently, the error for other attributes with similar features could be obtained from a single chart.  相似文献   

Morphology and downslope sediment displacement in a deep-sea valley,the Valencia Valley (Northwestern Mediterranean)     

Suzanne O'Connell  Belen Alonso  Kim A. Kastens  Andrés Maldonado  Alberto Malinverno  C. Hans Nelson  Alberto Palanques  William B. F. Ryan 《Geo-Marine Letters》1985,5(3):149-156

The Valencia Valley is a Quaternary, 200 km long deep-sea valley in the Valencia Trough, Western Mediterranean Sea. A swathmapping survey approximately mid-way along the valley length, where the floor has an average gradient of 1:250 (0.2°), shows valley walls that rise 200 to 350 m above the valley floor, with slopes of 2 to 18°. Sediment forming the walls is undergoing retrogressive, upslope-directed slumping with increasing bedding disruption along steeper walls. The valley exhibits a winding course with steep outer and gentler inner walls around bends, and bedforms on the valley floor. Lateral migration around bends is less than 5 km and the valley is deeply entrenched into Quaternary-bedded sediments.  相似文献   

A Deep-sea Channel in the Northwestern Mediterranean Sea: Morphology and seismic structure of the Valencia Channel and its surroundings   总被引：2，自引：0，他引：2  

Belen Alonso  Miquel Canals  Alberto Palanques  Jean-Pierre Rehault 《Marine Geophysical Researches》1995,17(5):469-484

The 400 km long Valencia Channel occupies the axis of the Valencia Trough in the Northwestern Mediterranean. Four different types of seismic reflection profiles were used to analyze the morphology and structure of the Valencia Channel with regard to the role played by both margins, Balearic and Iberian, of the Valencia Trough. From a detailed morphoseismic analysis of the Valencia Channel, its upper, middle, and lower courses can be characterized as follows: (1) in the upper course, tributaries are short and only slightly incised, with recent mass-transport deposits occurring on the adjacent continental slopes; (2) in the middle course, the channel deepens, and tributary valleys merge into it; and (3) the lower course begins after a sudden change in the direction of the channel, has a meandering path, is flanked by levees, and is fed by some valleys.During the Pliocene and Quaternary, at least four erosional and filling phases are observed in seismic profiles of the lower course of the Valencia Channel. The varying intensity of mass-transport processes and associated retrogressive slumping, which are related with fluctuations in sediment supply and relative sea-level changes, have played a major role in the formation, maintenance and deepening of the Valencia Channel. In addition to these sedimentary processes, a basement tectonic control and some morphostructural features affect the direction of the Valencia Channel locally.  相似文献