Reliable yield of reservoirs and possible effects of climatic change

Abstract

Statistics of seasonal and daily rainfall in nine regions covering the United Kingdom are presented, together with the best currently available predictions of changes in rainfall and evaporation, based on various general circulation model (GCM) assessments of the climate 40 years ahead. On that basis, runoff sequences are generated for the region of northwest England with north Wales (NWE & NW, humid temperate) and for southeast England (SEE, temperate but less humid), both for the current climate and for the year 2030 estimate, the latter incorporating higher evaporation losses. The future annual runoff is reckoned as 8% less than the current average in the SEE region and 4% less than that in the NWE & NW region. Direct supply reservoir yield versus storage graphs are then derived in each case for a range of duration-based probability of emptiness, their yields (i.e. sustained draw-off rates) and storage capacities being expressed as proportions of current annual runoff. The year 2030 graphs fall systematically below those for the current climate, representing 8% to 15% loss of yield from existing storage in the SEE region and 4% to 25% loss of yield in the NWE & NW region.     

Thermal histories of angrite meteorites: Trace element partitioning among silicate minerals in Angra dos Reis,Lewis Cliff 86010, and experimental analogs

Abstract— We measured rare earth element (REE) abundances in selected silicate phases in the angrites Angra dos Reis (AdoR) and Lewis Cliff (LEW) 86010 in order to further clarify the thermal history of AdoR. We also carried out a preliminary experimental study designed to examine apparent REE partitioning between silicates (fassaite, olivine, kirschsteinite, and melt) in synthetic analogs of angrites under disequilibrium conditions at liquidus temperatures. Silicates in AdoR are homogeneous with respect to major, minor, and trace elements, which is consistent with the interpretation that AdoR underwent extensive subsolidus equilibration. REE distributions in olivine and kirschsteinite in AdoR are similar to those in LEW 86010 and are consistent with the formation of kirschsteinite by exsolution from olivine during cooling and/or annealing. There is no evidence for a disequilibrium trace element signature that could have been inherited from rapid cooling at liquidus temperatures. This is supported by our petrographic observations of the occurrence of kirschsteinite within olivine aggregates in AdoR. Olivine/kirschsteinite pairs in AdoR record closure temperatures around 600–650 °C.     

Structure of gravel beaches and their relationship to tidal range

The height of accretionary gravel beaches, determined by the vertical distance between the large sphere zone at the seaward margin and the large disc zone at the landward margin, is determined mainly by tidal range. As the beach builds seaward, this height translates into thickness and so the complete thickness of gravel beach accumulations is a good indicator, in the geological record, of tidal range. Beaches with a small tidal range have the zone between the large discs and the large spheres compressed and sometimes steepened. These beaches are characterized mainly by cusps and berms, both of which yield steeply dipping, seaward building, cross‐strata. Beaches built by large, persistent waves generally have a steep profile, whereas those with small wave height appear to have a shallow profile. Cusps generally have extremely well‐sorted gravels, often in an openwork fabric and with a landward crown of coarse gravel that may grade seaward into shape‐sorted, gently dipping gravels. Berms, which may extend for hundreds of metres along the coast, comprise, in section, very well‐sorted cross‐stratified gravels that may intermittently build seaward for a distance >15 m. Extensive selection pavements typify beaches with a high tidal range and comprise sheets of gravel which are well‐sorted and dip at comparatively low angles towards the sea. These selection pavements form beds that, in section, can be >50 m in seaward length; they grow from clasts, supplied to them from swash or backwash, and which are selected by the fabric of the existing sheet. In some cases, the selection pavements can be very mature having only a specific clast shape and size remaining. Total preservation of the beach sequence in the geological record is more likely to take place in areas of rapid deposition of sediments, such as the marine fringes to a fan delta.     

Fine particle deposition to initially starved,stationary, planar beds

Reported here are results from new flume experiments examining deposition and entrainment of inert, silt‐sized particles (with spherical diameters in the range from 20 to 60 μm) to and from planar, impermeable and initially starved beds underlying channel flows. Bed surfaces comprised smooth or fixed sand‐size granular roughness and provided hydraulically smooth to transitionally rough boundaries. Results of these experiments were analysed with a simple model that describes the evolution of vertically averaged concentration of suspended sediment and accommodates the simultaneous delivery to and entrainment of grains from the bed. The rate of particle arrival to a bed diminishes linearly, and the rate of particle entrainment increases by the 5/2 power, as the value of the dimensionless Saffman parameter S = u_*³/g’ν approaches a threshold value of order unity, where u is the conventional friction velocity of the turbulent channel flow, g’ is the acceleration due to gravity adjusted for the submerged buoyancy of individual particles and ν is the kinematic viscosity of the transporting fluid. This transport behaviour is consistent with the notion that non‐cohesive, silt‐sized particles can neither reach nor remain on an impermeable bed under flow conditions where mean lift imposed on stationary particles in the viscous sublayer equals or exceeds the submerged weight of individual particles. Within the size range of particles used in these experiments, particle size and the characteristic size of granular roughness, up to that of medium sand, did not affect rates of dimensionless arrival or entrainment to a significant degree. Instead, a new but consistent picture of fine‐particle transport is emerging. Silt‐sized material, at least, is subject to potentially significant interaction with the bed during intermittent suspension transport at intermediate flow speeds greater than the value required for initiation of transport (ca 20 cm sec^?1) but less than the value (ca 50 cm sec^?1) required by the Saffman criterion ensuring transport in fully passive suspension or, equivalently, ‘wash‐load’.     

1988 COMPILATION OF ELEMENTAL CONCENTRATION DATA FOR USGS AGV-1, GSP-1 AND G-2

Concentration data on up to 90 individual constituents in USGS AGV-1, GSP-1, and G-2 have been collected from 1270 journal articles and technical reports. These data are summarized in consensus (mean) values with uncertainties expressed as +/- one standard deviation. Mean values are also calculated as a function of analytical procedure and all raw data are given in the tables. Recommended values are proposed based upon data criteria used by NIST (National Institute of Standards and Technology, formerly the National Bureau of Standards or NBS).     

Rock varnish in the Sonoran Desert: microbiologically mediated accumulation of manganiferous sediments

Rock varnish occurs in virtually all environments, most commonly in arid and semi-arid climates, including Antarctica. Rock varnish consists of thin layers of intimately mixed aeolian and chemical sediments often showing botryoidal and more rarely stromatolite-like morphologies. Typical rock varnish samples collected at Twin Peak Mountain Park, near Phoenix, Arizona, consist of abundant quartz, with plagioclase, illite and a mixed layer, Fe-clay mineral, probably corrensite. EDS, SEM (BSE) and TEM analyses revealed that the typical Mn, Fe minerals occur as minute particles; some of these particles and other mineral grains are attached to filaments. XRD and electron diffraction showed that the Mn.Fe-bearing particles are poorly crystalline. The filaments, based on morphological criteria, are virtually indistinguishable from fungal filaments. Most filaments are fragments, probably broken by scraping during sample collection. Coccoid and rod-shaped forms, resembling cyanobacteria and other bacteria, respectively, are also present. Unlike definitive minerals, these filaments disintegrated in the concentrated energy of the SEM electron beam at the instrumental and experimental conditions used. In addition, no filamentous, rod-shaped or coccoid forms were observed in samples hydrolysed with 6 N HCl for 24 h at 100°C. Bacteria and fungi in powdered rock varnish were cultured on four media, incubated aerobically in the dark at 25°C. The culture media yielded dense growths of spore-forming bacteria and filamentous fungi. One fungus and two Bacillus isolates oxidized and concentrated manganese. Control experiments revealed that fungi and bacteria are present on and below the surfaces of rock varnish. Free and hydrolysed, peptide/protein-bound amino acids were identified in the rock varnish. Amino acids showed virtually no racemization with the exception of D/L asp = 0.1. Relatively high molecular weight humic matter was also separated from the rock varnish. High-resolution mass spectrometry revealed non-hydrocarbon moieties, similar to a Suwannee River (FL) humic acid standard. Micro-organisms and their original biochemical compounds do not seem to be preserved for long in the accreting varnish layer. The studies showed that the filaments helped to trap mineral particles of rock varnish, and that bacteria and fungi abetted Mn concentration. Some structures in the layers of rock varnish resemble stromatolites and present definitions would allow them to be termed as such.     

Origin of authigenic carbonates in sediment from the deep Bering Sea

Forty beds of authigenic carbonate were identified from the deep Bering Sea in cores taken on Leg 19 of the Deep Sea Drilling Project. Carbonate minerals were mainly high-magnesium calcite and protodolomite, less commonly siderite, rhodo-chrosite, low-magnesium calcite, and manganosiderite. Authigenic carbonates cement and replace diatom ooze, ash and bentonite beds, and, less commonly, clastic beds. Replacement zones are as much as 60 cm thick. Eighty-five per cent of carbonate beds occurred below 400 m sub-bottom depth and 70% in sediment older than 4 m.y. δ¹³C values averaged -17.20^0/00 PDB and δ¹⁸O ranged from 18.59 to 34–11^0/00SMOW. The carbon was derived from oxidation of organic matter under anaerobic conditions during bacterial reduction of sulphate, or from CO₂ produced in concert with CH₄ during degradation of organic matter. The cations (Ca, Mg, Fe, Mn) were derived from alteration of ash beds. In Bering Sea deposits, ash beds altered to smectite within about 3–5 m.y. Carbonate precipitated simultaneously at different stratigraphic levels within the 627–1057 m sections at temperatures of 7–85°C. No apparent calcite precursor of biogenic origin was found for these authigenic carbonates.