An evaluation of grid size uncertainty in empirical soil loss modeling with digital elevation models

This paper presents a study on the effect of topographic variability on grid-based empirical estimation of soil erosion and sediment transport with raster geographic information systems (GIS). An original digital elevation model (DEM) of 10 m resolution for a case watershed is resampled to six realizations of greater grid sizes for a comparative examination. The Universal Soil Loss Equation (USLE) and a distance-based sediment delivery equation are applied to the watershed to calculate soil loss from each cell and total sediment transport to streams, respectively. The results suggest that the selection of the DEM gird size has considerable influence on the soil loss estimation with the empirical models. The estimate of total soil loss from the watershed decreases significantly with the increasing DEM cell size as the spatial variability is reduced by the cell aggregation. The empirical modeling approach is a useful tool for qualitative assessment of soil erosion, provided that spatial variability can be adequately represented by applied DEMs. However, discretion is suggested for its applications to quantitative estimation of soil loss concerning the sensitivity to the grid size selection.     

MULTIVARIATE ANALYSIS OF WATER QUALITY IN THE RICHIBUCTO DRAINAGE BASIN (NEW BRUNSWICK,CANADA)1

ABSTRACT: Specific conductivity, pH, dissolved oxygen, carbon, phosphorous, and nitrogen species were measured at 36 stations in the Richibucto River drainage basin, including the estuary, in New Brunswick, Canada, over the six‐year period 1996 through 2001. Each station was sampled between 1 and 26 times (mean = 7.5, standard deviation = 6.0) during the ice free seasons without regard to tide. There was significant variance among stations in most parameters. Principal component analysis (PCA) was used to identify the processes explaining the observed variance in water quality. Because of the high variability in specific conductance, stations were first grouped in a freshwater subset and an estuarine (brackish water) subset. For freshwater stations, most of the variance in water quality was explained by pH and total organic carbon, as well as high nutrient concentrations. These high nutrient concentrations, along with water salinity, which varies with flow and tides, are also important in determining water quality variability in brackish water. It is recommended that water quality parameters that were found to explain most of the variance by PCA be monitored more closely, as they are key elements in understanding the variability in water quality in the Richibucto drainage basin. Cluster analyses showed that high phosphorous and nitrate concentrations were mostly found in areas of peat runoff, tributaries receiving treated municipal effluent, and lentic zones upstream of culverts. Peat runoff was also shown to be acidic, whether it is runoff from a harvested area or a natural bog.     

Remediation and stewardship: Coexisting processes to protect health and the environment

Organizations that manage property that poses risks for surrounding communities need to practice stewardship. Stewardship is defined as carrying out the responsibility to manage land and facilities in a sustainable manner, while being accountable to others who have a stake in those resources. This article reviews six case studies of organizational stewardship and derives a set of five lessons learned, along with four challenges. Lessons include developing stewardship goals, good stakeholder relationships, multiple approaches to safety, and encouraging innovation and stable funding. Challenges include bureaucratic processes, burdensome regulations, organizational continuity, and inter‐organizational cooperation. These crosscutting lessons learned about how to achieve success or avoid failure in long‐term management of resources can be applied to all types of public and private agencies, including the long‐term management of environmental contamination. © 2003 Wiley Periodicals, Inc.     

Electricity in the marketplace: Reconfiguring the consumption of essential resources

This paper critically examines how privatisation and liberalisation of electricity provision is reconstructing energy consumption practices. The paper discusses the commercial restructuring of the electricity industry in the UK over the last four years, illustrating how a reconfiguration of production and consumption interests is transforming the utility marketplace: differentiating the value of resource units, distinguishing between infrastructure suppliers and stratifying utility customers. This process is shown to be resulting in differential forms of service provision as utility companies actively engage with more lucrative customers, presenting opportunities for environmental innovation, while disengaging from unprofitable customers and heightening social polarisation.