Modeling basin-scale hydrology in support of physical climate and global biogeochemical studies: An example using the Zambezi River

Human activity is an important agent defining the contemporary hydrologic cycle. We have documented the potential impacts of impoundment, land use change and climate change on the Zambezi River system in southern Africa and found that they can be substantial. A full analysis requires construction and parameterization of a simulation for the entire catchment. This paper develops a strategy for implementing catchment-scale models of the major hydrologic processes operating within the basin. A coherent data set for calibrating the models has also been assembled. The algorithms consist of a Water Balance (WBM) and a Water Transport (WTM) operating at 1/2^o spatial scale and at monthly timesteps. These models transform complex patterns of regional climatology into estimates of soil water, evapotranspiration, runoff, and discharge through rivers of various size. The models are dependent on the characteristics of the terrestrial surface, principally soil texture and land cover. A simulated river network is also required. Additional tabular data sets are essential for model testing and calibration. These include subcatchment areas; observed river discharge at selected points; flooding, storage and loss characteristics of major wetlands; floodwave translation; and, volume, surface area, withdrawal and evaporative losses from impoundments. An important design consideration for the numerous impoundments in the Zambezi requires an understanding of the seasonal variation in discharge, in particular how it might respond to climate and land use change. The research strategy offered here lays a framework for addressing such issues. Although the primary focus of this work is hydrologic, we discuss how the model can be extended to consider constituent transport and biogeochemical cycling issues at the continental scale.     

Toxicity of No. 2 fuel oil to coon stripe shrimp

Bioassay of a No. 2 fuel oil dispersion with shrimp in a continuous flow system using measured waterborne oil as the indicator of oil concentrations reveals a treatment more definable than those previously described in terms of volume ratios and produces lower lethal concentrations. Shrimp 96-h LC₅₀ was 0.8 mg/l in this study as compared to values from 1.5 to 50 mg/l reported for other methods. Mean concentrations in tests do not give significant differences in concentration with respect to day of the test or spatial distribution in the exposure tanks.     

Data reporting norms for 40Ar/39Ar geochronology

Data reported in ⁴⁰Ar/³⁹Ar geochronology studies are commonly insufficient to allow computation of ages. This deficiency renders it difficult to compare ages based on different standards or constants, and often hinders critical evaluation of the results. Herein are presented an enumeration of the data that should be reported in all ⁴⁰Ar/³⁹Ar studies, including a discussion in support of these requirements. The minimum required data are identified and distinguished from parameters that are useful but may be derived from them by calculation. Finally, recommendations are made for metadata needed to document age calculations (e.g., from age spectrum or isochron analyses).     

Electoral behaviour behind the gates: partisanship and political participation among Canadian gated community residents

Gated communities have been characterised as representing processes of 'forting up' and 'civic secession', in which their residents use gating as a strategy for withdrawing from political life and from taking collective responsibility for others. The assumption is that the residents of private gated communities should be less likely to participate in political life, and/or be more likely to support political parties on the right who advocate privatisation, reduced government expenditures and lower taxes. If the act of living in a gated community is associated with either greater support for parties and policies on the right of the political spectrum, or limited political participation, then the growth of such forms of privatised communities has potential implications for the future of urban politics and even for national political systems. However, despite surveys that have dealt with social attitudes 'behind the gates', insufficient attention has been paid to the politics of gated community residents. This paper fills this gap through a comparative analysis of electoral behaviour during the 2006 federal election at the level of the polling station. Electoral participation and partisanship in 27 gated communities in three Canadian metropolitan areas is compared against that of non-gated residents. Regression analysis is conducted in order to determine whether gated community residents differ from their non-gated counterparts in the way they vote and their levels of electoral turnout, after controlling for social composition. The potential implications of this research are then discussed.     

Palaeomagnetism of the Tudor gabbro, Ontario: evidence for divergence between Grenvillia and interior Laurentia

Summary. After thermal and alternating field (AF) cleaning, the characteristic high blocking temperature A component of natural remanent magnetization (NRM) of the Tudor gabbro of southern Ontario has a mean direction D = 326°, I =–46° ( k = 132, α₉₅= 4.8°, N = 8 sites). The corresponding palaeopole, 133°E, 12°N ( dp = 4°, dm = 6°), confirms the palaeopole 137°E, 17°N (α₉₅= 8.4°) reported earlier by Palmer & Carmichael, based on AF cleaning only. The A NRM has unblocking temperatures > 515–525°C which exceed the estimated 500°C peak temperature reached locally during ∼ 1050 Ma Grenvillian regional metamorphism. The A NRM therefore predates metamorphism and is probably a primary thermoremanence (TRM). The age of the Tudor NRM has previously been taken to be about 675 Ma, but recent ⁴⁰Ar/³⁹Ar dating by Baksi has shown that this is the time of post-metamorphic cooling to 200–250°C. Hornblendes record initial cooling of the intrusion to 590±20°C at 1110 Ma and this is the best estimate of the age of the A remanence. Successful Thellier-type palaeointensity determinations on 11 Tudor samples confirm that the A NRM is a TRM and indicate a palaeofield at this time of 18–27 μT, about 50–70 per cent of the present field intensity at 27° magnetic latitude. The anomalous Tudor A palaeopole, which lies well to the west of both 1000–800 Ma Grenvillian palaeopoles and 1100–1050 Ma poles from Interior Laurentia, is interpreted as recording divergence between Grenvillia and Interior Laurentia just before the Grenvillian orogeny, rather than a post-metamorphic extension of the apparent polar wander path as previously assumed.     

Frequency response corrections for eddy correlation systems

Simplified expressions describing the frequency response of eddy correlation systems due to sensor response, path-length averaging, sensor separation and signal processing are presented. A routine procedure for estimating and correcting for the frequency response loss in flux and variance measurements is discussed and illustrated by application to the Institute of Hydrology's Hydra eddy correlation system.The results show that flux loss from such a system is typically 5 to 10% for sensible and latent heat flux, but can be much larger for momentum flux and variance measurements in certain conditions.A microcomputer program is included which, with little modification, can be used for estimating flux loss from other eddy correlation systems with different or additional sensors.     

AN HISTORICAL APPROACH TO MOBILITY RESEARCH *

Most existing work on residential mobility has assumed that the household relocation decision is an intrinsically significant object of inquiry. In contrast, we argue that mobility derives its significance primarily from the particular historical and locational contexts within which it occurs. We suggest, therefore, that future mobility research should be directed away from the development of a theory of mobility per se and toward a more explicit articulation of mobility studies to existing theories of urbanization and social change.     

Simple analytical Green's functions for ray perturbations in layered media

The total Green's function for two-point boundary-value problems can be related to the propagator for initial-value problems. A very simple expression for the Green's function is obtained when the unperturbed medium may be described by material with a constant gradient in quadratic slowness. The derivation requires a correct understanding of assumptions made in the propagator solution. Expressions are also obtained for Green's function in multilayered media.