Focused infiltration of snowmelt water in partially frozen soil under small depressions

Ephemeral puddles in small closed depressions can play an important role in the hydrology and ecology of many landscapes, by storing runoff water, recharging soil moisture and shallow groundwater, and by providing food and habitat for many organisms. Infiltration of snowmelt water under small depressions (<1000 m²) has been studied in the St. Denis National Wildlife Area in Saskatchewan, Canada, located within the northern glaciated prairie of North America where numerous depressions of varying sizes exist. The depressions stored most of the snowmelt runoff generated within their respective watersheds. The water level in a typical depression declined at 0.6 mm/h while the underlying frozen soil was thawing. This rate was likely limited by the rate of downward movement of the thawing front, which was functioning as a moving impermeable boundary. The rate of thawing was controlled by the external energy input from the ground surface. Standing water in depressions efficiently trapped incoming radiation and conducted it to the thawing front. The recession rate increased to 1.1 mm/h when the soil under the depression thawed completely. The recession rate at this later stage appears to be limited by the hydraulic conductivity of the subsoil (0.04–4 mm/h), which is much smaller than the topsoil conductivity (10–20 mm/h).     

Indigenous knowledge for natural resource management: a comparative study of Māori in New Zealand and Dusun in Brunei Darussalam

Indigenous people often exclusively depend on the natural resources available within the ecosystems where they live, and commonly manage their resources sustainably. They have developed, and continue to develop indigenous knowledge systems which encompass sustainable management of natural resources. This study compares indigenous knowledge of natural resource management developed by two different communities in two different environments—Maori in the temperate environment in New Zealand and Dusun in the tropical environment in Brunei Darussalam, and comparatively evaluates the role of indigenous knowledge in sustainable resource management in three categories of knowledge such as spatial and seasonal distribution of natural resources, sustainable harvesting, and habitat management. The comparison reveals that despite the differences in environment and the great geographical distance between the two communities, there are remarkable similarities between the two knowledge systems in concepts, principles, strategies and technologies used in natural resource management.

Integrating Geospatial Technologies in Fifth-Grade Curriculum: Impact on Spatial Ability and Map-Analysis Skills

This study explores the effects of geographic information systems (GIS) curriculum on fifth-grade students' spatial ability and map-analysis skills. A total of 174 students from an urban public school district and their teachers participated in a quasi-experimental design study. Four teachers implemented a GIS curriculum in experimental classes over six weeks while three teachers continued with regular teaching in control classes. Both groups completed pre- and post-tests measuring spatial ability and map-analysis skills. Students in the GIS classes demonstrated more growth over time in spatial ability and map-analysis skills than did their peers in the control classes.     

The value of climate forecasting

A short survey is given of the concepts associated with meteorological forecast verification and value. Apart from matters of mathematical detail the field has not advanced greatly over the last thirty years. If significant skill develops in long-range (i.e. climate) forecasting, it will be more than ever necessary for the general user to understand the possible consequences—in particular that there can be many circumstances where some forecast skill is worse than none at all. Some highly idealized agricultural examples are used to illustrate the point. It is emphasized that some numerical measure of confidence will have to be associated with (or be built into) probability precasts of climate.     

Protecting speciality cropland from urban development: the case of the Okanagan Valley,British Columbia

Mapping from air photos reveals coinsiderable urbanization of the Okanagan fruitlands between 1966 and 1981. For a number of years reduced areas of fruitland have been compensated for by increased productivity, but the limit of increased productivity has nearly been reached and there are no significant amounts of new land to be planted to fruit. The British Columbia Land Commission Act, with its Agricultural Land Reserve (ALR) programme was a bold attempt at preventing the urbanization of prime agricultural land in British Columbia. Undoubtedly the urban conversion of the Okanagan Valley fruitlands has been slowed from what would have occurred without the ALR programme. Nevertheless, sequential maps and records of appeal applications indicate that considerable urban conversion of fruitland is still occurring. There is also evidence that the current British Columbia government's commitment to the ALR programme is waning. If the future urban development patterns and political climate continue along recent trends, it is difficult to be optimistic about preserving the Okanagan fruitlands for future generations.     

Using recovery data to extend the effective duration of pumping tests

Collection of water-level recovery data is a common practice for pumping tests. The resulting data can provide some of the most useful information from the tests, but are rarely used to their full value. van der Kamp (1989) proposed a general method that uses recovery data to extend the effective duration of pumping. The method is straightforward to implement and applicable for simple or complex hydrogeologic settings. The only assumption invoked is that the response remains linear such that the principle of superposition can be applied. No other assumptions about the properties of the aquifer are required. The method can greatly increase the value of pumping tests by extending the effective duration of the tests for as long as significant residual drawdowns are observed.     

Limits of tidal energy dissipation by fluid flow in subsea formations

Tidal loading causes fluid flow through permeable seafloor and between regions of contrasting elastic properties or porosity within subsea formations. We examine theoretically the dissipation of energy by these flows and its global significance as a mechanism for tidal energy dissipation. Expressions are given for energy dissipation rates in layered formations due to vertical flow caused by tidal loading, but the results can be used to constrain dissipation by other flow patterns. We consider flow near the seafloor, in gas-bearing sediments, and in highly fractured permeable igneous crust. Energy dissipation by the first two mechanisms is negligibly small globally, although it may be locally significant under extreme conditions. Under favourable conditions, flow in fractured crust may have greater energy dissipation, but the total amount is limited by the thickness of the permeable layer. Based on our current understanding of subsea hydrogeology, tidally induced flow in subsea formations appears to make little contribution to the observed global tidal energy dissipation.     

Trends in middle- and upper-level tropospheric humidity from NCEP reanalysis data

The National Centers for Environmental Prediction (NCEP) reanalysis data on tropospheric humidity are examined for the period 1973 to 2007. It is accepted that radiosonde-derived humidity data must be treated with great caution, particularly at altitudes above the 500 hPa pressure level. With that caveat, the face-value 35-year trend in zonal-average annual-average specific humidity q is significantly negative at all altitudes above 850 hPa (roughly the top of the convective boundary layer) in the tropics and southern midlatitudes and at altitudes above 600 hPa in the northern midlatitudes. It is significantly positive below 850 hPa in all three zones, as might be expected in a mixed layer with rising temperatures over a moist surface. The results are qualitatively consistent with trends in NCEP atmospheric temperatures (which must also be treated with great caution) that show an increase in the stability of the convective boundary layer as the global temperature has risen over the period. The upper-level negative trends in q are inconsistent with climate-model calculations and are largely (but not completely) inconsistent with satellite data. Water vapor feedback in climate models is positive mainly because of their roughly constant relative humidity (i.e., increasing q) in the mid-to-upper troposphere as the planet warms. Negative trends in q as found in the NCEP data would imply that long-term water vapor feedback is negative—that it would reduce rather than amplify the response of the climate system to external forcing such as that from increasing atmospheric CO₂. In this context, it is important to establish what (if any) aspects of the observed trends survive detailed examination of the impact of past changes of radiosonde instrumentation and protocol within the various international networks.     

A FEniCS-based programming framework for modeling turbulent flow by the Reynolds-averaged Navier-Stokes equations

Finding an appropriate turbulence model for a given flow case usually calls for extensive experimentation with both models and numerical solution methods. This work presents the design and implementation of a flexible, programmable software framework for assisting with numerical experiments in computational turbulence. The framework targets Reynolds-averaged Navier-Stokes models, discretized by finite element methods. The novel implementation makes use of Python and the FEniCS package, the combination of which leads to compact and reusable code, where model- and solver-specific code resemble closely the mathematical formulation of equations and algorithms. The presented ideas and programming techniques are also applicable to other fields that involve systems of nonlinear partial differential equations. We demonstrate the framework in two applications and investigate the impact of various linearizations on the convergence properties of nonlinear solvers for a Reynolds-averaged Navier-Stokes model.