Title: Lending insight to environmental problems characterized by conflicting objectives Abstract: In environmental planning problems, decision makers' goals often fundamentally conflict. Faced with limited budgets, planners realize that increasing their systems' performance could cause increased costs, negative impacts to the environment, or conflicts among stakeholders. Multi-objective decision support techniques are increasingly used to generate planning alternatives for such planning problems, with the idea that exposing multiple candidate alternative solutions can positively contribute to the planning process. For example, we have investigated a multi-objective decision support process for water supply planning in the Tarrant Regional Water District of Texas, finding better solutions to balance multiple supply reservoirs; and for the design of groundwater contamination strategies, gaining increased contaminant degradation with reduced pumping rates. Our research group uses multi-objective evolutionary algorithm search, simulation models, interactive visualizations, and high performance computing to solve multi-objective decision support in a number of different domains that span civil and environmental engineering. This presentation will first introduce the methodology for multi-objective decision support. The remainder of the presentation will explore several key areas where multi-objective approaches can actually add insight to our understanding of environmental problems, in addition to providing new planning alternatives. First, a series of decision support experiments will show that changes to the optimization problem formulation (decision variables, objectives, and constraints) fundamentally alters the solution algorithms' ability to find answers to decision problems. Second, we will show how our approach can contribute to the creation of new environmental regulations, using an example from unconventional oil and gas development in Colorado. Finally, we will discuss how our suite of tools can help aid in performance assessment of quantitative hydrological models such as conceptual and physically-based snow models.