Hydraulic modelling of subglacial tunnel channels,south‐east Alberta,Canada

One of the key issues associated with the hypothesis of catastrophic subglacial drainage of the Livingstone Lake event is whether flows of such large magnitudes are physically feasible. To explore this issue, a one‐dimensional hydraulic network flow model was developed to investigate the range of peak discharges and associated flow parameters that may have been carried by a tunnel channel network in south‐east Alberta, Canada. This tunnel channel network has been interpreted elsewhere to carry large discharges associated with subglacial meltwater flows because of the convex longitudinal profiles of individual channels. This computational modelling effort draws upon established and verified engineering principles and methods in its application to the hydraulics of this problem. Consequently, it represents a unique and independent approach to investigating the subglacial meltwater hypothesis. Based on the modelling results, it was determined that energy losses resulting from friction limit the maximum peak discharge that can be transported through the tunnel channel network to 10⁷ m³ s⁻¹, which is in reasonable agreement with previous estimates of flood discharges for proposed megafloods. Results show that flow through channels with convex longitudinal profiles occurs when hydraulic head exceeds 910 m (Lost River) and 950 m (Sage Creek) , respectively. These are considerably below the maximum head capable of driving flow through the system of 1360 m, beyond which ice is decoupled from the bed across the pre‐glacial drainage divide. Therefore, it is concluded that these model results support the hypothesis of catastrophic subglacial drainage during the Livingstone Lake event. Copyright © 2000 John Wiley & Sons, Ltd.     

Remote sensing of soybean stress as an indicator of chemical concentration of biosolid amended surface soils

The accumulation of heavy metals in the biosolid amended soils and the risk of their uptake into different plant parts is a topic of great concern. This study examines the accumulation of several heavy metals and nutrients in soybeans grown on biosolid applied soils and the use of remote sensing to monitor the metal uptake and plant stress. Field and greenhouse studies were conducted with soybeans grown on soils applied with biosolids at varying rates. The plant growth was monitored using Landsat TM imagery and handheld spectroradiometer in field and greenhouse studies, respectively. Soil and plant samples were collected and then analyzed for several elemental concentrations. The chemical concentrations in soils and roots increased significantly with increase in applied biosolid concentrations. Copper (Cu) and Molybdenum (Mo) accumulated significantly in the shoots of the metal-treated plants. Our spectral and Landsat TM image analysis revealed that the Normalized Difference Vegetative Index (NDVI) can be used to distinguish the metal stressed plants. The NDVI showed significant negative correlation with increase in soil Cu concentrations followed by other elements. This study suggests the use of remote sensing to monitor soybean stress patterns and thus indirectly assess soil chemical characteristics.     

Patterns of Surf Smelt, Hypomesus pretiosus, Intertidal Spawning Habitat Use in Puget Sound, Washington State

Surf smelt Hypomesus pretiosus are an important part of the Salish Sea food web and obligate beach spawners, yet little is known about the spatiotemporal distribution of spawning and beach characteristics related to spawning success. We counted smelt eggs at 51 sites around Camano Island, Puget Sound, Washington every 2?weeks for 1?year and at 13 of those 51 sites each month in the following year. At each site, we measured beach characteristics hypothesized to affect spawning habitat suitability as measured by egg abundance and mortality. Eggs were collected at 45 sites and pooled by month for analyses. Few sites (N?=?10, 19.6?%) contributed 87?% of total eggs and 89?% of all live eggs collected. Mean total egg counts at sites were higher (p?<?0.019) in Jul?CSep (1,790.7, SE?=?829.5) than in Jan?CMar (26.1, SE?=?10.2). Principal component and regression analyses suggested that aspect, fetch, solar radiation, and beach temperature predicted egg abundance but not mortality. Because a small proportion of sites appear to support most spawning activity, a conclusion consistent with year?2 egg counts, impacts to relatively few beaches could greatly affect surf smelt production.     

The phase curve survey of the irregular saturnian satellites: A possible method of physical classification

During its 2005 January opposition, the saturnian system could be viewed at an unusually low phase angle. We surveyed a subset of Saturn's irregular satellites to obtain their true opposition magnitudes, or nearly so, down to phase angle values of 0.01°. Combining our data taken at the Palomar 200-inch and Cerro Tololo Inter-American Observatory's 4-m Blanco telescope with those in the literature, we present the first phase curves for nearly half the irregular satellites originally reported by Gladman et al. [2001. Nature 412, 163-166], including Paaliaq (SXX), Siarnaq (SXXIX), Tarvos (SXXI), Ijiraq (SXXII), Albiorix (SXVI), and additionally Phoebe's narrowest angle brightness measured to date. We find centaur-like steepness in the phase curves or opposition surges in most cases with the notable exception of three, Albiorix and Tarvos, which are suspected to be of similar origin based on dynamical arguments, and Siarnaq.     

Density Measurements of Shock Compressed Matter Using Short Pulse Laser Diagnostics

In this paper, experimental results on X-ray and proton radiography of shock compressed matter are presented. It has been performed at the Rutherford Appleton Laboratory (RAL) using three long pulse beams to generate a shock wave in a multi-layer foil and a short pulse beam to create either an X-ray or protons source for a transverse radiography. Depending on the probe material (aluminium or carbon foam) a Molybdenum Kα source or a proton beam are used. Density data of the shocked aluminium, in the multimagabar regime are presented.     

Rheological differences between Archaean and younger crust can determine rates of Quaternary vertical motions revealed by fluvial geomorphology

Surface uplift is widely observed in subaerial regions of continental crust that are distant from plate boundaries, often revealed by river terrace staircases with altitude ranges of several hundred metres, which typically span the Quaternary. This characteristic geomorphology has been explained by forcing of flow in the weak lower‐crustal layer by surface processes: non‐steady‐state erosion and cyclical loading by ice‐sheets and sea‐level fluctuations. This study tests this interpretation, by showing that analogous river‐terrace staircases are absent in Archaean crust, which lacks the weak lower‐crustal layer found elsewhere.     

Book reviews

Theory and management of tropical fisheries. Edited by D. Pauly and G. I. Murphy. Proceedings of the ICLARM/CSIRO Workshop on the Theory and Management of Tropical Multispecies Stocks. 12–21 January 1981, Cronulla, Australia. 1982. 360 p. $US21.50 surface; hardbound.

Animals of the estuary shore : illustrated guide and ecology. By Malcolm B. Jones, 1983. University of Canterbury publication No. 32. 162p., 140 figures, 11 keys. ISBN 0900–392–32–0 (soft cover, spiral bound). Price NZ$7.50.

Numerical ecology. By L. Legendre and P. Legendre, 1983. Elsevier Scientific Publishing Company, Amsterdam. $US83.00.

The control of oil pollution (revised edition). Edited by J Wardley‐Smith. Graham & Trot‐man Limited, London. 1983. 285 p., 98 figures, 17 tables. ISBN 0.86010 3382. £19.00/$US35.00.

Physical oceanography in Australia. Edited by J. Imberger. Reprinted from the Australian Journal of Marine and Freshwater Research, Volume 34, 1–230, 1983. CSIRO, Melbourne 1983.     

Reduced abundance of banded kokopu (Galaxias fasciatus) and other native fish in turbid rivers of the North Island of New Zealand

Laboratory experiments demonstrated that migrant juvenile banded kokopu (Galaxias fasciatus Gray) were more sensitive to suspended sediment (SS) than other native fish species. If juvenile migrants avoid waters made turbid by SS and their recruitment to adult habitats up stream is reduced, then adult abundance may decline in turbid rivers. To test this, we compared the abundance of diadromous native fish between turbid and clear rivers. The duration (% time) for which SS concentrations exceeded 120 mg litre^‐1 (a critical level from laboratory experiments) during the migration season (August‐December) was estimated for over 150 New Zealand river sites. Turbid rivers were defined as those where SS concentrations exceeded 120 mg litre^‐1 for over 20% of the time and clear rivers as those where SS concentrations exceeded 120 mg litre^‐1 for less than 10% of the time. Eight turbid rivers and seven clear ones were identified where sufficient data on SS and native fish populations existed to permit a comparison. The mean occurrence of banded kokopu was reduced by 89.5% in turbid rivers and, although other diadromous fish species were also less common, banded kokopu was most affected. Densities of adult banded kokopu were also significantly lower in optimal stream habitats in three turbid compared with three matched clear rivers. We therefore concluded that the abundance of adult banded kokopu was reduced in turbid rivers and propose that this is because of reduced recruitment of juveniles in turbid rivers.     

Land use,associated eel production,and abundance of fish and crayfish in streams in Waikato,New Zealand

Abstract

The density and biomass of fish and crayfish, and the production of eels, was compared among streams in native forest, exotic forest, and pasture. Populations were estimated by multiple‐pass electroshocking at 11 sites in hill‐country streams in the Waikato region, North Island. Three sites were in native forest, four in exotic forest, and four in pasture. Length of stream sampled at each site was 46–94 m (41–246 m² in area), and catchment areas up stream of the sites ranged from 0.44 to 2.01 km².

A total of 487 fish were caught. The species were longfinned and shortfinned eels, banded kokopu, Cran's and redfinned bullies, and common smelt. Eels were the most abundant fish in all three land‐use types, and shortfinned eels were more abundant at pastoral sites (mean density 1.11 fish m^?2) than longfinned eels (mean density 0.129 fish m^?2). Banded kokopu were present only at forested sites. Mean fish densities were greater at pastoral sites (1.55 fish m^?2) than under either native forest (0.130 fish m^?2) or exotic forest (0.229 fish m^?2). Mean fish biomass was also greater at pastoral sites (89.7 g m^?2) than under native forest (12.8 g m^?2) or exotic forest (19.3 g m^?2). Longfinned eels made a greater contribution to the fish biomass at all sites than did shortfinned eels. Densities of crayfish were high (0.46–5.40 crayfish m^?2), but were not significantly different between land‐use types. Crayfish biomass ranged from 1.79 to 11.2 g m^?2. Total eel production was greater at pastoral sites (mean 17.9 g m^?2 year¹) than at forest sites (mean 2.39 gm^?2 year^?1).