Testing of a GIS model ofEucalyptus Iargiflorens health on a semiarid,saline floodplain

Irrigated agriculture has resulted in substantial changes in water flows to the lower reaches of the River Murray. These changes have led to large-scale occurrences of dieback inEucalyptus largiflorens (black box) woodlands as well as increased inputs of salt to the river. Management options to address problems of this scale call for the use of spatial data sets via geographic information systems (GIS). A GIS exists for one floodplain of the River Murray at Chowilla, and a simple model predicted six health classes ofEucalyptus largiflorens based on groundwater salinity, flooding frequency, and groundwater depth.To determine the usefulness of the model for vegetation management, the quality of both the model and the GIS data sets were tested. Success of the testing procedure was judged by the degree of spatial matching between the model's predictions of health and that assessed from aerial photographs and by field truthing. Analyses at 80 sites showed that tree health was significantly greater where groundwater salinity was less than 40 dS/m or flooding occurred more frequently than 1 in 10 years or depth to groundwater exceeded 4 m. Testing of the GIS data sets found that vegetation was misclassified at 15% of sites. Association was shown between GIS-predicted values and field-truthed values of groundwater salinity but not groundwater depth. The GIS model of health is a useful starting point for future vegetation management and can be further improved by increasing the quality of the data coverages and further refining of the model to optimize parameters and thresholds.     

CONTINUOUS SIMULATION FOR WATER QUALITY PLANNING1

ABSTRACT: This paper describes a methodology for the evaluation of water quality plans analogous to procedures used in flood control planning, where flood damage frequency curves provide the basis for determining flood control benefits. The proposed method uses continuous water quality simulation to develop long term information from which water quality frequency curves can be obtained. This frequency information allows the evaluation of the impact of proposed water quality control plans taking into consideration the variable nature of the water resource. Using treatment costs and other economic indicators of water quality, the frequency information can be used to estimate the cost-effectiveness and economic efficiency of alternative plans. The method is demonstrated in a semi-hypothetical environment; real hydrologic and climatic characteristics are assigned to a hypothetical watershed configuration. Alternative management plans are simulated and analyzed for both physical and economic impacts. The advantages of continuous simulation and its use in water quality planning are explored.     

Modeling of gas-phase photodegradation of chloroform and carbon tetrachloride

The relationship between the irradiance in a photoreactor and the rate of photodegradation of organics is essential in the scaling-up of photoreactors to treat large volumes of air contaminated with organic pollutants. In this study, the analysis is adopted to compare results obtained from two different photoreactors. Initially, the applicability of two light models in calculating the irradiance in two photoreactors was evaluated. Thereafter, kinetic models of ultraviolet (UV) photooxidation of chloroform (CHCl3) and carbon tetrachloride (CCl4) from the archived literature were tested using experimental data under various operating conditions and different irradiances. Sensitivity analyses were conducted using different values of model parameters to determine the significance of each parameter on the photodegradation of the two chlorinated organics. For compounds that undergo photolysis as a primary mode of degradation, the rate of photodegradation at low initial concentrations can be predicted easily by the following equation: d[C]/dt = -2.303Iave, lambdaepsilonlambdaphilambda[C]. Although the photodegradation of chlorinated organic compounds in dry and humid air can be predicted well, it is difficult to predict the Cl* sensitized oxidation occurring at high initial concentrations. A good agreement between the simulated and experimental data provides a sound basis for the design of large-scale reactors.     

INFLUENCING WATER LEGISLATWE DEVELOPMENT WHAT TO DO AND WHAT TO AVOID1

ABSTRACT: Whomever would affect water policy development must influence the water legislative process. This paper discusses in the context of the Model State Water Allocation Code the following ten ideas about doing that: (1) seek the right timing for enactment; (2) set modest goals; (3) prepare a well-drafted proposal; (4) recognize diversity by offering legislative choices; (5) consider the impacts of adoption; (6) make alliances; (7) respect executive influence; (8) become involved in legislative interaction; (9) be flexible; and (10) persist. Heeding these ideas, although not guaranteeing enactment, is sure to be educational for participants and useful to legislators.     

Using community relations to reduce costs during remediation projects

Almost everyone who has been involved in a site remediation project has seen schedules slip and costs escalate due to political pressure from the public or the press. While focusing on remediation technologies and containment techniques to control costs, many organizations have neglected a major cost driver—public opinion. This article examines community relations from the perspective of an organization trying to control costs during a site remediation project. It details the strong correlation between the cost of a site cleanup and the level of public dissatisfaction and provides an organization with specific strategies on how to use proven communications techniques to lower costs. Examination of several case studies is provided, including a study involving a site in which community representatives actively worked to reduce project costs. It is clear that any responsible cleanup must be protective of public health and the environment. But it is becoming increasingly apparent that wise allocation of available resources has a profound effect on the program's ability to ensure public and environmental safety. In many cases, it has been proven that some costly cleanups—for example, involving excavation—sometimes actually increase risk by creating an exposure pathway where none existed before. In turn, such cleanups waste resources that are needed elsewhere. The challenge in dealing with this complicated issue is to help stakeholders understand the true ramifications of the choices that are faced at each site. If these stakeholders feel uninformed, powerless, or excluded from the process, it is likely that they will be unable to enter a productive discussion. The community relations programs outlined in documents such as a Superfund guidance can be helpful in familiarizing the community with site-related issues and with gathering public input. These activities act as a baseline for the programs discussed in this article. However, existing programs are not focused on providing a strategic advantage in reaching cleanup solutions and balancing health and environmental considerations with economic considerations.     

Smart Growth and Sustainable Development: challenges, solutions and policy directions

In this paper, we focus on the issues related to development densities that emerged from our study of sprawl and development issues in three regions of British Columbia, Canada. We chose to focus on this aspect of the Smart Growth agenda because, while many of its other elements enjoy wide support across social interests, the goal of achieving a higher density urban fabric is highly controversial. We proceeded by collecting data on development densities and 13 indicators of community sustainability in 26 municipalities. The results suggest that the density of communities is associated with efficiencies in infrastructure and with reduced automobile dependence, with the ecological and economic implications which flow from that. However, it does not necessarily correlate with greater affordability of housing or more access to green space. In fact, if anything, we discovered a negative relationship between housing affordability and green space per capita and higher land-use densities. In a second stage of the research, we conducted a qualitative analysis of a subset of six municipalities and identified key policy issues for moving ahead with the Smart Growth agenda. The paper concludes with a discussion of the policy issues that emerged from these case studies.     

POTENTIAL PHOSPHORUS LOAD REDUCTIONS UNDER THE LAKE OKEECHOBEE REGULATORY PROGRAM1

ABSTRACT: Nutrient loading from beef pastures located within the northern Lake Okeechobee watershed in Florida, has been identified as a source of phosphorus contributing to the accelerated eutrophication of the lake. Since 1989 within the watershed, 557 agricultural drainage sites, mainly beef pasture, have been monitored for compliance under a regulatory program. Of those sites, 154 were actively monitored for phosphorus concentrations from October 1, 1998, to September 30, 1999. Of these 154 sites, 77 were considered to be out of compliance (OOC). An OOC site is defined as having runoff with a 12‐month average phosphorus concentration exceeding the permitted discharge limit. The average annual phosphorous load from the 77 OOC sites for an eight‐year study period from October 1, 1991, to September 30, 1999, was estimated using measured concentration values and simulated runoff obtained from an agricultural nonpoint source pollution model, CREAMS‐WT. The 77 OOC sites produced an estimated average annual 46 metric tonnes of phosphorus load, of which an estimated 22 tonnes of phosphorus reached Lake Okeechobee on an average annual basis. The remaining estimated average annual 24 tonnes of phosphorus load was retained by streams and wetlands in the discharge transport system between the sites and the lake. The estimated average annual load reaching Lake Okeechobee from the OOC sites represented 11 percent of the phosphorus load above a five‐year average annual target load for the lake. However, the OOC site drainage areas represented only 3 percent of the northern watershed that drains into the lake. Of the 77 OOC sites, 12 sites had an average annual phosphorus loading rate equal to or greater than 3.0 kg/ha and were placed on the priority list for the Critical Restoration Project in the Lake Okeechobee watershed. To estimate the possible phosphorus load reductions from the 77 sites, two scenarios were modeled. The first scenario reduced phosphorus concentrations in runoff to the permitted discharge limits under the Lake Okeechobee regulatory program. The second scenario changed current land uses to native rangeland with an estimated annual offsite total phosphorus areal loading rate of 0.114 kg/ha. These two scenarios are hypothetical with assumed concentration values and loading rate. Model results showed that the first management scenario reduced the average annual phosphorus load to the lake by an estimated 15 tonnes. The second scenario reduced the average annual phosphorus load to the lake by an estimated 21 tonnes.     

Documenting lemming population change in the Arctic: Can we detect trends?

Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.     

Mobility of dimethoate residues from spring broccoli field

Dimethoate [O, O-dimethyl-S-(N-methylcarbamoyl-methyl) phosphorodithioate] is a broad-spectrum systemic insecticide currently used worldwide and on many vegetables in Kentucky. Dimethoate is a hydrophilic compound (log K_OW = 0.7) and has the potential of offsite movement from the application site into runoff and infiltration water. The dissipation patterns of dimethoate residues were studied on spring broccoli leaves and heads under field conditions. Following foliar application of Dimethoate 4E on broccoli foliage at the rate of 0.47 L acre^?1, dimethoate residues were monitored in soil, runoff water collected down the land slope, and in infiltration water collected from the vadose zone. The study was conducted on a Lowell silty loam soil (pH 6.9) planted with broccoli under three soil management practices: (i) soil mixed with municipal sewage sludge, (ii) soil mixed with yard waste compost, and (iii) no-mulch rototilled bare soil. The main objective of this investigation was to study the effect of mixing native soil with municipal sewage sludge or yard waste compost, having considerable amounts of organic matter, on off-site movement of dimethoate residues into runoff and infiltration water following spring rainfall. The initial deposits of dimethoate were 6.2 and 21.4 μ g g^?1 on broccoli heads and leaves, respectively. These residues dissipated rapidly and fell below the maximum residue limit of 2 μ g g^?1 on the heads and leaves after 10 and 14 d, respectively, with half-lives of 5.7 d on broccoli heads and 3.9 d on the leaves. Dimethoate residues detected in top 15 cm of soil (due to droplet drift and wash off residues from broccoli foliage) one day (d) following spraying, were 30.5 ng g^?1 dry soil in the sewage sludge treatment, and 46.1 and 134.5 ng g^?1 dry soil in the yard waste and no mulch treatments, respectively. Water infiltration was greater from yard waste compost treatment than from no mulch treatment, however concentrations of dimethoate in the vadose zone of the three soil treatments did not differ.