Modeling the Usefulness of Spatial Correlation Analysis on Karst Systems

Cross-correlation analyses on field data collected in karst aquifer systems can be used to develop a conceptual understanding of the aquifer. This includes the use of many data sets from the same aquifer to develop an understanding of how properties vary spatially. We focus on a method for characterizing the distribution of recharge, which is becoming increasingly important in regions where urban development encroaches on these important sources of water. Spatially varying precipitation data and cross-correlation analysis provide a means of spatially characterizing recharge locations on a karst aquifer. Our work expands on the numerical experiments conducted by Padilla and Pulido-Bosch (1995) using the numerical ground water model MODFLOW to introduce spatially varying parameters. The numerical experiments include conduit-controlled, matrix-controlled, and mixed karst systems with more than one precipitation time series input. The results show that spatially varying parameters can be inferred based on the cross-correlation of precipitation data and spring discharge. Simulations were completed using aquifer parameters derived from studies of the Barton Springs segment of the Edwards Aquifer. The simulations indicate that spatial variability within an aquifer can be inferred using cross-correlation analysis. A field study using these methods is summarized for Barton Springs near Austin, Texas.     

Application of 3D hydrodynamic and particle tracking models for better environmental management of finfish culture

Hydrographic conditions, and particularly current speeds, have a strong influence on the management of fish cage culture. These hydrodynamic conditions can be used to predict particle movement within the water column and the results used to optimise environmental conditions for effective site selection, setting of environmental quality standards, waste dispersion, and potential disease transfer. To this end, a 3D hydrodynamic model, MOHID, has been coupled to a particle tracking model to study the effects of mean current speed, quiescent water periods and bulk water circulation in Mulroy Bay, Co. Donegal Ireland, an Irish fjard (shallow fjordic system) important to the aquaculture industry. A Lagangrian method simulated the instantaneous release of “particles” emulating discharge from finfish cages to show the behaviour of waste in terms of water circulation and water exchange. The 3D spatial models were used to identify areas of mixed and stratified water using a version of the Simpson-Hunter criteria, and to use this in conjunction with models of current flow for appropriate site selection for salmon aquaculture.The modelled outcomes for stratification were in good agreement with the direct measurements of water column stratification based on observed density profiles. Calculations of the Simpson-Hunter tidal parameter indicated that most of Mulroy Bay was potentially stratified with a well mixed region over the shallow channels where the water is faster flowing. The fjard was characterised by areas of both very low and high mean current speeds, with some areas having long periods of quiescent water. The residual current and the particle tracking animations created through the models revealed an anticlockwise eddy that may influence waste dispersion and potential for disease transfer, among salmon cages and which ensures that the retention time of waste substances from cages is extended.The hydrodynamic model results were incorporated into the ArcView^TM GIS system for visualisation and interrogation of results and to allow effective holistic environmental management and site selection for fish cage aquaculture.     

Mapping Human Terrain in the Joint Army–Navy Intelligence Study of Korea (1945)

The concept of human terrain has become a prominent element of U.S. military strategy. It is a means to capture the cultural–geographical qualities of an enemy or target population. An early effort to map human terrain is found in the Joint Army–Navy Intelligence Study (JANIS) of Korea (1945). We argue that the JANIS report on Korea was paradigmatic for the U.S. military's contemporary geographical work and offers insights into the cultural politics of human terrain mapping. This explains why the JANIS text is cited by the National Geospatial-Intelligence College (NGC) today as an historical model. This article not only offers a window into the history of geography counterinsurgent but also shows that geography has been entwined with empire.     

Determining the climatic requirements of trees suitable for agroforestry

After fossil fuel burning, clearing of forests for agriculture is the second most significant factor increasing levels of atmospheric carbon dioxide. Replanting trees on previously cleared land around the world could reduce the buildup of atmospheric carbon dioxide. However, forests were usually cleared to grow crops or graze animals, so there is no possibility of completely restoring forests on most cleared lands. There is a need to develop agroforestry systems, which integrate trees with agricultural activities.One of the key problems in developing successful agroforestry systems is identifying which trees can be successfully grown in different areas. This problem will become even greater as tree breeding produces a wider variety of genotypes available for planting. General methods are described to identify where a particular tree (species, provenance or clone) with potential for use in agroforestry systems can be grown. The methods also help to identify locations where particular trees are growing under relatively extreme climatic conditions for that taxa. Conditions at these locations should be carefully evaluated as more reliable future climatic scenarios are developed. In the meantime they could be monitored to provide early warning of the effects of climatic and atmospheric change.     

River system discontinuities due to lateral inputs: generic styles and controls

In alluvial river systems, lateral inputs of water and/or sediment at junctions or undercut hillsides can disrupt what would otherwise be smooth downstream trends in mainstream bed elevation, channel gradient, and bed grain size. Generic styles of mainstream response to lateral inputs are investigated using a one‐dimensional sediment routing model with multiple grain size fractions. Numerical experiments isolate the effects of three para‐meters: ratio of tributary to mainstream water flux (QR), ratio of tributary to mainstream bedload flux (FR), and ratio of tributary to mainstream bedload diameter (DR). The findings are not unduly sensitive to the choice of initial conditions or to approximations made in the model. The primary distinction is between junctions that aggrade, causing local profile convexity with interrupted downstream fining, and junctions that degrade. The immediate effects of aggradation extend further upstream than downstream, whereas degradation is much more subdued and has no upstream impact. Aggradation is typical of coarse inputs (DR > 2), and degradation of fine inputs (DR < 1), but very high ratios of QR to FR also promote degradation. Both aggrading and degrading junctions can lead to a change in mainstream bed grain size well below the junction, with higher ratios of QR to FR producing a coarser distal bed. The effect of a tributary reflects the interplay between additional bed load and additional discharge to transport it. Copyright © 2006 John Wiley & Sons, Ltd.     

Commentaries on “Evaluating the Geographic in GIS”

In this article, four geographers who are also GIS practitioners critique “Evaluating the Geographic in GIS.” Sparked by the arguments in that article, they pose fundamental questions about how geography can best contribute to GIS practices.