Millions of dollars are invested in water monitoring programmes across the country each year and a variety of organisations, groups and individuals are responsible for the design, collection and assessment of water management and water quality improvement programs. The capacity to undertake monitoring and assessment programs vary within these groups and assistance is often required to produce technically sound and economically feasible monitoring programs. The validity and the usefulness of the collected data/information is dependent on the statistical robustness, quality control and quality assurance procedures deployed in monitoring plans. Setting monitoring objectives, selecting appropriate key and supplementary indicators, proper representation of the aquatic population, and the use of correct instruments and methods are a few important aspects of any monitoring plan. Further, data management, data analysis, interpretation, uncertainty estimates and the quantification of decision errors are essential in the process of defensible decision making. The Integrated Monitoring and Assessment System (IMAS) is a suite of tools that has been developed to support both new and existing programs in addressing the common concerns organisations face in planning and conducting water quality monitoring plans. A survey was conducted using more than 18 eWater Cooperative Research Centre partner organisations to investigate end-user requirements, existing tools, and available knowledge. Based on survey results, the IMAS product project and specifications for tools were formulated. The IMAS Decision Support System (DSS) has been designed using contemporary science and state of the art DSS technology, which includes interactive tools, databases, knowledge bases, statistical tools, web-links, templates, decision-making processes, a comprehensive collection of relevant information and help materials. Available materials, guidelines, technical reports and software tools were extensively reviewed in the process of designing IMAS products. A number of existing and modified tools (prototype/beta versions) have been tested and released through workshops held in Queensland and very positive responses were received from end-users. These tools include eGuide (electronic version of searchable water quality related documents), Monitoring Plan Tool, Water Quality Guideline setting Tool, Loads Estimation Tool and "Multiple Levels and Lines of Evidence" (MLLE) software as an assessment tool. Prototypes of monitoring objective setter, indicator selection tool and a sample optimisation tool are being developed. A common shell for water quality data processing and analysis including time series data management has been developed mainly to share common input data for calculating variety indices and evaluations. The IMAS software package consists of monitoring plan designer, data processing and analysis tools, assessment and reporting guides together with an assortment of information for designing monitoring plans. The IMAS tools will facilitate the development of well targeted monitoring programs, coupled to key performance indicators for environmental management. They will assist community groups, catchments managers, natural resource managers and water quality monitoring groups with the interpretation and communication of results from monitoring and assessment. The DSS developed under IMAS will ensure the quality (accuracy, precision, repeatability, representative and comparability) of collected data. This will also guarantee the maximum return from investments made on water monitoring programs across the country.