Energy balance and evaporation loss of an agricultural reservoir in a semi‐arid climate (south‐eastern Spain)

A typical agricultural water reservoir (AWR) of 2400 m² area and 5 m depth, located in a semi‐arid area (southern Spain), was surveyed on a daily basis for 1 year. The annual evaporation flux was 102·7 W m^?2, equivalent to an evaporated water depth of 1310 mm year^?1. The heat storage rate G exhibited a clear annual cycle with a peak gain in April (G ～ 45 W m^?2) and a peak loss in November (G ～ 40 W m^?2), leading to a marked annual hysteretic trend when evaporation (λE) was related to net radiation (R_n). λE was strongly correlated with the available energy A, representing 91% of the annual AWR energy loss. The sensible heat flux H accounted for the remaining 9%, leading to an annual Bowen ratio in the order of 0·10. The equilibrium and advective evaporation terms of the Penman formula represented 76 and 24%, respectively, of the total evaporation, corresponding to a annual value of the Priestley–Taylor (P–T) coefficient (α) of 1·32. The P–T coefficient presented a clear seasonal pattern, with a minimum of 1·23 (July) and a maximum of 1·65 (December), indicating that, during periods of limited available energy, AWR evaporation increased above the potential evaporation as a result of the advection process. Overall, the results stressed that accurate prediction of monthly evaporation by means of the P–T formula requires accounting for both the annual cycle of storage and the advective component. Some alternative approaches to estimating R_n, G and α are proposed and discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of the telluric and magnetotelluric methods in selection of sites for nuclear plants

The paper deals with the application of the telluric method and of magnetotelluric soundings including experimental and model data on the localization of tectonic disturbances in connection with the selection of appropriate sites for nuclear plants.     

Volcanic hazards in the surroundings of Pico de Orizaba,eastern Mexico

Volcanic hazards from Pico de Orizaba volcano are presented here tor the first time. Some 1.3 million people live within the hazard zone, which in the most severe case would encompass the Mexican Gulf coast, east of the volcano. Three major cities located in the eastern part of the hazard zone account for 800 000 of this population and about 200 000 people live within a 20 km radius of the volcano. Probability calculations are presented as an attempt to quantify the hazards in the surroundings of the volcano. Such quantification can be of use in planning for future land use within the hazard zones.A zone of about 10 km radius centred on the top crater is a high hazard zone for gravity-driven flows and fallout ejecta. For large volume eruptions, the radius could be extended to 120 km to the east and 60 km to the west. The asymmetrical distribution is related to the topography of the volcano. Hazards from Pyroclastic-fall deposits are principally to the west of the volcano, since easterly winds are dominant in the area lava-flow hazards are greatest within a 10 km radius from the summit crater. Pyroclastic flow hazards are high up to 20 km from the volcano summit.In the case of reactivation of the volcano, melting of a glacier covering the summit of Pico de Orizaba having a volume equivalent to some 45 × 10⁹ litres of water, would produce lahars which would descend the flanks of the volcano.     

Biogeographic implications of a packrat midden sequence from the Sacramento Mountains, south-central New Mexico

Thirteen packrat (Neotoma spp.) and two porcupine (Erethizon dorsatum) middens from 1555 to 1690 m elevation from the Sacramento Mountains, New Mexico, provide an 18,000-yr vegetation record in the northern Chiuahuan Desert. The vegetation sequence is a mesic, Wisconsin fullglacial (18,000–16,000 yr B.P.) pinyon-juniper-oak woodland; a xeric, early Holocene (ca. 11,000–8000 yr B.P.) juniper-oak woodland; a middle Holocene (ca. 8000-4000 yr B.P.) desert-grassland; and a late Holocene (ca. 4000 yr B.P. to present) Chihuahuan desertscrub. The frequency of spring freezes and summer droughts in the late Wisconsin probably set the northern limits of Pinus edulis and Juniperus monosperma at about 34°N, or 6° south of today's limit. Rising summer tempratures in the early Holocene eliminated pinyon and other mesic woodland plants from the desert lowlands and allowed the woodland to move upslope. At this time pinyon-juniper woodland and pine forest dominated by Pinus ponderosa probably began their spectacular Holocene expansions to the north. Continued warming in the middle Holocene led to very warm summers with strong monsoons, relatively dry, cold winters, and widespread desert-grasslands. Desertscrub communities in the northern Chihuahuan Desert did not develop until the late Holocene when the biseasonal rainfall shifted slightly back toward the winter, catastrophic winter freezes decreased, and droughts in all seasons increased. The creosote bush desertscrub corridor across the Continental Divide between the Chihuahuan and Sonoran deserts was probably connected for the first time since the last interglaciation.     

A detailed study of the duality relation for the least squares adjustment in euclidean spaces

The Euclidean spaces with their inner products are used to describe methods of least squares adjustment as orthogonal projections on finite-dimensional subspaces. A unified Euclidean space approach to the least squares adjustment methods “observation equations” and “condition equations” is suggested. Hence not only the two adjustment solutions are treated from the view-point of Euclidean space theory in a unified frame but also the existing duality relation between the methods of “observation equations” and “condition equations” is discussed in full detail. Another purpose of this paper is to contribute to the development of some familiarity with Euclidean and Hilbert space concepts. We are convinced that Euclidean and Hilbert space techniques in least squares adjustment are elegant and powerful geodetic methods.     

Magmatic gases in well fluids aid the mapping of the flow pattern in a geothermal system

Gas composition and silica concentrations of well fluids are used in conjunction with pressure, temperature and enthalpy data to obtain a model of the drilled part of the Krafla geothermal field (Northeast Iceland).A magma chamber is located at 3–8 km depth under the field. Magmatic gases emanate from the chamber and travel via a channel reaching the surface at the Hveragil eruptive fissure. The composition of the gases is apparently modified on the way, in that sulphur, which presumably is in the form of sulphur dioxide to begin with, is removed on the way, and what remains is in the form of hydrogen sulphide at the end. It is suggested that the major removal mechanism is the deposition of pyrite and pyrrhotite during the passage of the gases through the hydrothermal system.The hydrothermal system is divided into a lower part whose temperature exceeds 300°C and whose fluids are to a varying extent affected by the magmatic gases, and an upper part whose temperature is ca 200°C. This upper part is a run-off from the lower part but the magmatic effects have mostly disappeared there.     

Sequence stratigraphy of Holocene incised-valley fills and coastal evolution in the Gulf of Cádiz (southern Spain)

This first sedimentary interpretation of two incised-valley fills in the Gulf of Cádiz (southern Spain), which accumulated during the last fourth-order eustatic cycle in response to fluvial incision, changes of sea level, and correlative deposition, relates the filling of the estuarine basins and their barriers with four regional progradation phases, H₁ to H₄. The cases studied are the wave-dominated Guadalete, and the mixed, tide and wave-dominated Odiel-Tinto estuaries. The sequence boundary is a type-1 surface produced during the lowstand of the Last Glacial period ca. 18 000 ¹⁴C yr BP. No fluvial lowstand deposits were found in the area. Due to rapid transgression the valley fills consist of transgressive and highstand sediments. The maximum landward advance of the estuarine barriers occurred ca. 6500–6000 ¹⁴C yr BP during the maximum of the Flandrian transgression, but there is no evidence of sea level rising appreciably above the present. A large part of the estuaries was filled during H₁ (ca. 6500–4400 ¹⁴C yr BP) but ravinement by shifting tidal inlets destroyed most of the coeval barriers. During the H₂ phase (ca. 4200–2550 ¹⁴C yr BP) sedimentation was favoured by arid conditions and concentrated in the axial estuarine zones and the barriers. Between H₂ and H₃ prevailing winds changed from W to WSW, increasing spit growth to the east and south-east. Progradation of bay-head deltas and flood-plains during H₃ (ca. 2300–800 ¹⁴C yr BP) and H₄ (500 yr ago to the present) further reduced the accommodation space in the largely-filled valleys, and sediment by-passed the estuaries and accumulated in the estuarine barriers as fast-growing spits. Arid conditions and increasing human activity have caused rapid coastal modifications.     

DISTRIBUTION OF DYNAMIC WATER LEVEL IN A SHALLOW LAKE

ABSTRACT

The shore of a large and shallow reservoir or lake may incur damages caused by high or low static water level, as well as from dynamic water level rises induced by wind; thus, the random variables representing, respectively, static water level and wind-induced rise must be added. The case study of Lake Balaton, Hungary, illustrates a proposed methodology to estimate, on the one hand, the distribution function of monthly static water level and on the other hand, that of monthly maximum rise caused by wind (seiche plus waves). We consider one section of lake shore which is homogeneous from the viewpoints of types of structure, dominant winds and corresponding values of fetch, so that a well-defined damage function can be used later for that section. A convolution of the two distribution functions is performed to yield the distribution function of monthly maximum water level. On the basis of existing data, normal distributions are suggested for either static or dynamic water levels. Extensions and transferability of the methodology are discussed.     

Constraining peak P–T conditions in UHP eclogites: calculated phase equilibria in kyanite‐ and phengite‐bearing eclogite of the Tromsø Nappe,Norway

Kyanite‐ and phengite‐bearing eclogites have better potential to constrain the peak metamorphic P–T conditions from phase equilibria between garnet + omphacite + kyanite + phengite + quartz/coesite than common, mostly bimineralic (garnet + omphacite) eclogites, as exemplified by this study. Textural relationships, conventional geothermobarometry and thermodynamic modelling have been used to constrain the metamorphic evolution of the Tromsdalstind eclogite from the Tromsø Nappe, one of the biggest exposures of eclogite in the Scandinavian Caledonides. The phase relationships demonstrate that the rock progressively dehydrated, resulting in breakdown of amphibole and zoisite at increasing pressure. The peak‐pressure mineral assemblage was garnet + omphacite + kyanite + phengite + coesite, inferred from polycrystalline quartz included in radially fractured omphacite. This omphacite, with up to 37 mol.% of jadeite and 3% of the Ca‐Eskola component, contains oriented rods of silica composition. Garnet shows higher grossular (X_Grs = 0.25–0.29), but lower pyrope‐content (X_Prp = 0. 37–0.39) in the core than the rim, while phengite contains up to 3.5 Si pfu. The compositional isopleths for garnet core, phengite and omphacite constrain the P–T conditions to 3.2–3.5 GPa and 720–800 °C, in good agreement with the results obtained from conventional geothermobarometry (3.2–3.5 GPa & 730–780 °C). Peak‐pressure assemblage is variably overprinted by symplectites of diopside + plagioclase after omphacite, biotite and plagioclase after phengite, and sapphirine + spinel + corundum + plagioclase after kyanite. Exhumation from ultrahigh‐pressure (UHP) conditions to 1.3–1.5 GPa at 740–770 °C is constrained by the garnet rim (X_Ca^Grt = 0.18–0.21) and symplectite clinopyroxene (X_Na^Cpx = 0.13–0.21), and to 0.5–0.7 GPa at 700–800 °C by sapphirine (X_Mg = 0.86–0.87) and spinel (X_Mg = 0.60–0.62) compositional isopleths. UHP metamorphism in the Tromsø Nappe is more widespread than previously known. Available data suggest that UHP eclogites were uplifted to lower crustal levels rapidly, within a short time interval (452–449 Ma) prior to the Scandian collision between Laurentia and Baltica. The Tromsø Nappe as the highest tectonic unit of the North Norwegian Caledonides is considered to be of Laurentian origin and UHP metamorphism could have resulted from subduction along the Laurentian continental margin. An alternative is that the Tromsø Nappe belonged to a continental margin of Baltica, which had already been subducted before the terminal Scandian collision, and was emplaced as an out‐of‐sequence thrust during the Scandian lateral transport of nappes.