Environmental management has increasingly become a participatory process. In recent times, emphasis has been placed on watershed-based solutions to remediate the problems of diffuse source pollution and to engage stakeholders in designing solutions. Water quality models are an integral part of this process; such models are often inaccessible to lay stakeholders. A review of the literature suggests that properly applied partnerships have several benefits that go beyond decision-making. Stakeholder education and enhancements to the eventual outcome from stakeholder insight and support are two such benefits. To aid engineers and scientists, who often do not interact directly with other stakeholders, several best practices were identified that may be applied to develop, manage, and evaluate stakeholder partnerships. Environmental Decision Support Systems (EDSSs) have been shown to be an effective way to promote stakeholder partnerships in environmental decision-making. Many current EDSSs were designed to be used by experts, thus limiting their effectiveness for stakeholder engagement. Often, these EDSSs, if designed for lay stakeholders, were not coupled with water quality models. To demonstrate that complex water quality models may be made accessible to stakeholders, without any significant changes to the modeling scheme, a web-based EDSS was developed for the Occoquan Reservoir, located in northern Virginia, U.S.A., and its tributary watershed. The developed EDSS may also be readily extended to other watersheds and their modeling programs. The current implementation of the EDSS enables users to modify land use and analyze simulated changes to water quality due to these modifications. A local-network server cluster, based on the Locally Distributed Simultaneous Model Execution (LDSME) framework, was also developed and served as a backend to the EDSS. The server cluster can support simultaneous execution of multiple water quality models or any other software on disparate computers. This system was employed to study pre-development and other land use modification scenarios in the Occoquan Watershed. The pre-development scenario offers an easy-to-understand and universally-applicable baseline for measuring waterbody and watershed restoration progress. It enabled computation of a measure called the "developed-excess," which is independent of local conditions and may be used for comparisons among various watershed sub-divisions or between watersheds. / Ph. D.