The dissolved organic matter (DOM) present in a reservoir is comprised of a mixture of allochthonous and autochthonous sources. The relative amounts depends on the biological and physico-chemical features of the reservoir-catchment system. Factors such as the soil physical properties and mineralogy are important since the DOM will come into contact with the soil as it is transported from one environment to another. A geochromatographic process may take place where fractions of DOM are selectively adsorbed from the water by the soil''s mineral matrix. Another important factor influencing the character of allochthonous DOM is the nature and degree of microbiological activity in the reservoir and the surrounding catchment. The character of DOM is also influenced by the climate, soil types and the type of vegetation in the catchment. This study examined thirteen reservoir catchment systems in south-eastern Australian and compared features of the catchments in relation to water quality parameters of the reservoirs. Bulk water quality parameters of the reservoirs were compared both with the catchment characteristics and in terms of treatability by alum coagulation.