Regulation of pesticide discharge into surface and groundwater under uncertainty: A model for environmental risk‐profitability tradeoffs and policy selection

The presence of contaminants in environmental media as well as the desire to maintain a high level of economic activity has led to an important and difficult decision‐making problem for both public policy decision makers and the general public. In one sense, all of the interested parties are likely to be concerned about the potential health risks posed by the presence of contaminants in environmental media and the need to design/implement policies for their mitigation and/or removal. At the same time, however, there also appear to be concerns about the cost of these policies. These costs could be measured in terms of the potential losses in economic activity that are likely to occur when a policy is adopted. The policy can be selected from a range of alternatives, with the choice being driven in part by the stakeholders represented in the policy decision problem. In this case, two general goals might be considered: minimizing environmental risk and minimizing the economic impact of the policy considered. These two objectives are likely to be viewed as conflicting goals, and the nature of the tradeoffs between them must be taken into account in the policy selection process. This paper presents the development of a zero–one weighted goal programming model that can be used to select a preferred policy that minimizes surface and groundwater contamination as well as the economic costs of environmental policy selection. A safety rule model is developed first and then extended to the zero–one weighted goal programming formulation. The stochastic aspects of these structures are emphasized throughout. The paper also addresses a number of issues related to implementation of the model.     

Economic Value of Instream Flow for Non-Commercial Whitewater Boating Using Recreation Demand and Contingent Valuation Methods

Whitewater river kayaking and river rafting require adequate instream flows that are often adversely affected by upstream water diversions. However, there are very few studies in the USA of the economic value of instream flow to inform environmental managers. This study estimates the economic value of instream flow to non-commercial kayakers derived using a Travel Cost Method recreation demand model and Contingent Valuation Method (CVM), a type of Contingent Behavior Method (CBM). Data were obtained from a visitor survey administered along the Poudre River in Colorado. In the dichotomous choice CVM willingness to pay (WTP) question, visitors were asked if they would still visit the river if the cost of their trip was $Y higher, and the level of $Y was varied across the sample. The CVM yielded an estimate of WTP that was sensitive to flows ranging from $55 per person per day at 300 Cubic Feet per Second (CFS) to a maximum $97 per person per day at flows of 1900 CFS. The recreation demand model estimated a boater’s number of trips per season. We found the number of trips taken was also sensitive to flow, ranging from as little as 1.63 trips at 300 CFS to a maximum number of 14 trips over the season at 1900 CFS. Thus, there is consistency between peak benefits per trip and number of trips, respectively. With an average of about 100 non-commercial boaters per day, the maximum marginal values per acre foot averages about $220. This value exceeds irrigation water values in this area of Colorado.     

EVALUATION OF MANAGEMENT PRACTICES TO CONTROL AGRICULTURAL POLLUTANTS1

ABSTRACT: The objective of this study was to evaluate the effectiveness of various land-use practices upon the production of nonpoint source pollutants from small agricultural watersheds in Northern Virginia. Pollutant production at each watershed was determined by individual monitoring stations. Data analysis consisted of a determination of the site specific pollutant yield for similar watersheds subjected to differing crop management approaches. These collected data were then compared to those generated by a parametric, event model developed for this investigation. This synthetic data base was used to eliminate or reduce errors resulting from monitoring site differences and to extend the collected data for additional comparisons.     

The development and application of a multilevel decision analysis model for the remediation of contaminated groundwater under uncertainty

A study was initiated which combined elements of stochastic hydrology, risk assessment, simulation modeling, cost analysis and decision making to define the optimum remediation choice(s) for a Superfund site in the southern United States. The effort focused upon the premise that groundwater remediation is inherently complex due to uncertainties in the geological matrix as well as in contaminant concentrations at points of compliance and/or exposure. The technical analyst should supply the decision maker with estimates of these uncertainties as well as the cost penalties required to reduce them to manageable levels. Monte Carlo transport modeling was employed to define the probability of contaminant excursions from the site, while geostatistical simulation identified a joint plume configuration and its attendant probability. Bayesian modeling was used to define the worth of additional data. These individual components were combined within a Decision Model to identify optimum remediation configurations for a given levels of risk tolerance which could be supplied by the decision maker or affected community. Sensitivity analyses were conducted to define ranges over which the decision would not be affected by variation in the respective decision parameter.     

Multi-substrate, multi-option groundwater transport model

A user friendly, finite-difference groundwater transport model, called “Multi-substrate, Multi-option Groundwater Transport Model (MMGTM)”, has been developed to afford users several options in defining a transport sequence. In addition to advective-dispersive transport, the model incorporates a variety of adsorption and biological decay mechanisms. Adsorption can be simulated for linear, Langmuir, or Freundlich isotherms coupled with equilibrium or non-equilibrium mass transfer. Biological decay can be simulated for first-order or Monod-type approaches, and can be linked to oxygen consumption and transport. Aqueous and sorbed phase decay can be simulated.Further, the transport of two substrates and oxygen can be simulated concurrently and the interaction between them can be described as competitive, diauxic-like or simultaneous. The growth of biomass and its effect as an adsorbent can also be simulated by means of a stoichiometric yield coefficient and a biomass/adsorbent conversion factor. Continuous or pulse input of solute in conjunction with either constant-mass-flux or constant-concentration boundaries can be selected. Menu screens allow the user to configure each problem while parameters can be input individually or called from a separate data file. The input data can be viewed, modified or saved before simulation. Output is visually displayed of the screen as breakthrough and profile curves, while also being saved to an ASCII file on a disk for subsequent processing.