ECONOMIC FORECASTING FOR VIRGINIA'S WATER RESOURCE PROGRAMS1

ABSTRACT: Water resource and water quality management planning depend, to a large degree, on forecasts of industrial activity and population projections. A flexible economic data base is especially important where planning follows varying formats of geographical and industrial detail. Records of employment and payroll are collected in the administration of Unemployment Insurance (U.I.) programs and are available from State Employment Agencies. These statistics have been collected over a long period of record (thirty-five years). Many years of record are available on punched-cards or magnetic tape and may be arrayed and manipulated by computer. This basic approach has been followed in Virginia. Historical U.I. payroll and employment records for the period 1956 through 1970 were procured on magnetic tape. This data was arrayed by major hydrologic area and by regional planning district. Projections of manufacturing activity were then generated by fitting several exponential equations to annual payroll data in two-digit Standard Industrial Classifications. These exponentials were then extrapolated to provide a range of industrial projections. Other parameters of manufacturing activity were then correlated to the payroll data to generate projections of indexes such as employment, value-added, and gross manufacturing output. U.I. payroll data is now being correlated to parameters in non-manufacturing categories. Projections for industries such as trade and services will link extrapolated payroll data with benchmark correlations of payroll and sales receipts.     

Predator diversity and ecosystem functioning: density modifies the effect of resource partitioning

The link between biodiversity and ecosystem functioning is now well established, but the challenge remains to develop a mechanistic understanding of observed effects. Predator-prey interactions provide an opportunity to examine the role of resource partitioning, thought to be a principal mediator of biodiversity-function relationships. To date, interactions between multiple predators and their prey have typically been investigated in simplified agricultural systems with limited scope for resource partitioning. Thus there remains a dearth of studies examining the functional consequences of predator richness in diverse food webs. Here, we manipulated a species-rich intertidal food web, crossing predator diversity with total predator density, to simultaneously examine the independent and interactive effects of diversity and density on the efficiency of secondary resource capture. The effect of predator diversity was only detectable at high predator densities where competitive interactions between individual predators were magnified; the rate of resource capture within the species mixture more than doubled that of the best-performing single species. Direct observation of species-specific resource use in monoculture, as quantified by patterns of prey consumption, provided clear evidence that species occupied distinct functional niches, suggesting a mechanistic explanation of the observed diversity effect.     

Establishment, persistence, and introgression of entomopathogenic nematodes in a forest ecosystem.

Entomopathogenic nematodes (EPN) are currently marketed worldwide for use in inundative biological control, where the applied natural enemy population (rather than its offspring) is expected to reduce insect numbers. Unlike classical biological control, in inundative control natural enemy establishment is not crucial in order to achieve pest suppression. Field trials in Irish forestry provided the opportunity to test predictions regarding the establishment of two exotic (Steinernema carpocapsae and Heterorhabditis megidis) and two indigenous (Steinernema feltiae and Heterorhabditis downesi) species. Nematodes were inundatively applied to pine stumps to control populations of pine weevil, Hylobius abietis, on three clearcut sites, and their persistence and spread monitored for up to five years. All species were recovered three years after application but only S. feltiae was recovered in years 4 and 5. Limited horizontal dispersal to 20 cm (but not 100 cm) was observed, but the majority of nematodes were recovered close to the area of application. Steinernema feltiae was also recovered from nearby stumps to which it had not been applied, indicating possible phoretic dispersal by weevils or other stump-associated fauna. EPN were not recovered from stumps outside the treated area, suggesting that such dispersal is quite localized. Two strains of S. feltiae (Irish and exotic) were applied. Amplified fragment length polymorphism (AFLP) analysis on 11 populations isolated from soil four years later showed that all had a much closer affinity to the applied Irish strain, suggesting persistence of this genotype and extinction of the exotic one. Some strains were clustered close together, and this is interpreted in the light of possible population genetic scenarios. The findings from the field study confirm predictions based on background knowledge of the species and demonstrate the importance of medium-term studies, as a 3-year study would have overestimated the risk of establishment of exotic species. Short-term persistence and spread of S. carpocapsae, S. feltiae, and H. downesi was also studied in pine forest mesocosms. Similar trends to field results, such as limited horizontal dispersal, even vertical distribution, and more abundant recovery of S. feltiae than of other species, point to the utility of mesocosm studies as a predictive tool.     

EFFECTIVE WATER PRICING1

ABSTRACT: When the goal of water pricing is elevated from mere cost recovery to deriving the greatest value from scarce water and associated nonwater resources, conventional rate regimes are found to be deficient. To address the challenge of creating rates that are both efficient and budget-balancing, several theoretical and practical aspects of rate-making are considered. Purposeful selection of rate parameters for a specific billing system is demonstrated to serve efficiency and cost recovery objectives. Attention to non-accounting opportunity costs is an important system element, but these costs are often not fully borne by the utility or its customers. In situations where this issue is serious, state or federal pricing policy may be necessary.     

Toxicity of copper in an oxic stream sediment receiving aquaculture effluent.

Sediments were collected from a stream (upstream, outfall and downstream) receiving copper laden catfish pond effluent to assess toxicity to non-target biota. No significant reduction in Hyalella azteca survival or growth (10 d), or Typha latifolia germination and root and shoot growth (7 d) were observed after exposure to upstream and outfall sediments. A significant reduction in H. azteca survival was observed after exposure to the downstream sediment sample; however, no reduction in T. latifolia germination or seedling growth was detected. Bulk sediment copper concentrations in the upstream, outfall and downstream samples were 29, 31, and 25 mg Cu/kg dry weight, respectively. Interstitial water (IW) concentrations ranged from 0.053 to 0.14 mg Cu/l with 10 d IW toxicity units > or = 0.7. Outfall samples were amended with additional concentrations of copper sulfate so that bulk sediment measured concentrations in the amended samples were 172, 663, 1245, and 1515 mg Cu/kg dry weight. Survival was the most sensitive endpoint examined with respect to H. azteca with a no observed effects concentration (NOEC) and lowest observed effects concentration (LOEC) of 1245 and 1515 mg Cu/kg, respectively. NOEC and LOEC for T. latifolia root growth were 663 and 1245 mg Cu/kg, respectively. IW copper concentrations were > or = 0.86 mg Cu/l with H. azteca intersitial water toxicity unit (IWTU) concentrations > or = 1.2. Sequential extraction qualitatively revealed the carbonate and iron oxide fractions which accounted for a majority of the copper binding. In this instance, the copper which was applied to catfish ponds does not appear to be adversely impacting the receiving stream system.     

Foraging habitats and migration corridors utilized by a recovering subpopulation of adult female loggerhead sea turtles: implications for conservation

From 1998 to 2008, 68 adult female loggerhead sea turtles (Caretta caretta) were instrumented with platform transmitter terminals at nesting beaches in Georgia, North Carolina (NC) and South Carolina (SC) on the East Coast of the United States of America (30°48′N, 81°28′W to 33°51′N, 77°59′W). The majority of post-nesting loggerheads (N = 42, 62 %) migrated to foraging habitats in the Mid-Atlantic Bight during May–October, with a subsequent migration occurring during November–March to foraging habitats south of Cape Hatteras, NC. Nine (13 %) loggerheads initially foraged in the near-shore, coastal areas of the South Atlantic Bight, but moved to offshore habitats—closer to the Gulf Stream—during November–March, while fourteen (21 %) loggerheads remained in foraging areas along the mid-continental shelf off of the eastern coast of Florida and/or continued southward to Florida Bay and the Bahamas. The present study delineates important, post-nesting foraging habitats and migration corridors where loggerheads may interact with commercial fisheries—providing managers opportunities to develop and implement optimally effective conservation actions for the recovery of this threatened species.     

Decomposition analysis of the effects of vehicle safety technologies on the motor vehicle collision–related mortality rate from 1994 to 2015

Abstract

Objective: Though the mortality rate for motor vehicle collisions (MVCs) has been decreasing since the 1960s with the advent of the first federal seat belt laws in 1968, MVC remains a leading cause of death for individuals aged 1 to 44 years. The purpose of this study is to examine the effects of frontal (FABs) and side airbags (SABs) and electronic stability control (ESC) on the components of the MVC mortality rate.

Methods: The MVC mortality rate from 1994 to 2015 was separated into its components of exposure of vehicles, exposure of travel, collision density, injury incidence, and case fatality rate. Year was categorized on the availability of safety technology in vehicles: 1994–1997 (first-generation FABs mandated), 1998–2001 (sled-certified, second-generation FABs mandated), 2002–2006 (increasing prevalence of SABs and ESC), 2007–2011 (advanced airbags mandated), and 2012–2015 (ESC mandated, SAB in over 90% of vehicles, introduction of advanced safety systems). Relative contributions (RCs) of the components to changes in the MVC-related mortality rate were calculated as the absolute value of the component’s beta coefficient divided by the sum of the absolute values of all components’ beta coefficients. Negative binomial regression–estimated rate ratios (RRs) for the changes in the rate of each component by year category compared to the prior year category.

Results: Significant decreases in the MVC mortality rate were observed for 2007–2011 and 2012–2015. The decrease in 2007–2011 was due in most part to an 18% decrease in the injury incidence (RR?=?0.82, P?<?.0001, RC?=?63%), though there was a noted contribution by the decrease in vehicle miles traveled (RR?=?0.95, P?<?.0001, RC?=?15%). The continued decrease in mortality in 2012–2015 was due is most part to the 10% decreased case fatality rate (RR?=?0.90, P?<?.0001, RC?=?66%) because there was no significant change in the vehicle miles traveled and injury incidence.

Conclusions: The results of this study highlight the effects of vehicle safety technologies on the MVC-related mortality rate and can help direct prevention efforts. Through the study period, there was no meaningful contribution to decreases in the MVC-related mortality rate due to components related to exposure (i.e., vehicles per population and the rate of vehicle miles traveled), suggesting that prevention efforts at decreasing exposure prevalence would have little effect on the MVC-related mortality rate. Instead, prevention efforts should continue to focus on event-phase methods to decrease injury occurrence and mitigate injury severity during the collision.     

Selenium in surface and irrigation water in the Kendrick irrigation district, Wyoming

High selenium (Se) concentrations have been found in surface waters in the Kendrick Reclamation Project, Wyoming. Precipitation and irrigation water moving over seleniferous soils are contributing causes, and drought may exacerbate this. This study surveyed Se concentrations and discharges in local surface streams, irrigation drains, and the delivery canal. Sites were sampled monthly and analyzed for Se and total suspended solids (TSS). A completely randomized design with two factors (soil parent material and location, inside or outside irrigation district) was used. Mean Se concentrations were 64 μg L^???1 inside the irrigation district on shale soils, 17 μg L^???1 inside the district off shale soils, 5 μg L^???1 outside the district on shale soils, and 3 μg L^???1 outside the district off shale soils. Correlations between discharge and Se concentrations were generally negative, while correlations between discharge and Se load were generally positive. There was little correlation between load and concentration, and little correlation between TSS and Se. A comparison of Se concentrations in streams and drains showed Se concentrations were significantly higher (p?<?0.001) in streams during the irrigation season, but not in the off-season (p?=?0.515). We conclude that higher discharges decrease Se concentration, but increase load. Conversion from flood to sprinkle irrigation may increase Se concentrations by reducing discharge, but decrease Se loads going into the N. Platte River, and will likely alter the timing and magnitude of flows. Both load and concentration should be considered when implementing Se regulations and standards.     

Support Vector Machine Modeling Using Particle Swarm Optimization Approach for the Retrieval of Atmospheric Ammonia Concentrations

This study was performed in order to improve the estimation accuracy of atmospheric ammonia (NH₃) concentration levels in the Greater Houston area during extended sampling periods. The approach is based on selecting the appropriate penalty coefficient C and kernel parameter σ ². These parameters directly influence the regression accuracy of the support vector machine (SVM) model. In this paper, two artificial intelligence techniques, particle swarm optimization (PSO) and a genetic algorithm (GA), were used to optimize the SVM model parameters. Data regarding meteorological variables (e.g., ambient temperature and wind direction) and the NH₃ concentration levels were employed to develop our two models. The simulation results indicate that both PSO-SVM and GA-SVM methods are effective tools to model the NH₃ concentration levels and can yield good prediction performance based on statistical evaluation criteria. PSO-SVM provides higher retrieval accuracy and faster running speed than GA-SVM. In addition, we used the PSO-SVM technique to estimate 17 drop-off NH₃ concentration values. We obtained forecasting results with good fitting characteristics to a measured curve. This proved that PSO-SVM is an effective method for estimating unavailable NH₃ concentration data at 3, 4, 5, and 6 parts per billion (ppb), respectively. A 4-ppb NH₃ concentration had the optimum prediction performance of the simulation results. These results showed that the selection of the set-point values is a significant factor in compensating for the atmospheric NH₃ dropout data with the PSO-SVM method. This modeling approach will be useful in the continuous assessment of NH₃ sensor discrete data sources.