Ideal and actual ground-water-quality monitoring networks are proposed for the San Joaquin Valley basin in California. The ideal network, which comprises several subnetworks, provides direction in the development of an actual network of wells currently monitored by known operating agencies. The ideal network can serve as a basis for the future expansion of the actual network as more wells are included in the inventory of active monitoring networks. The management objectives of these networks are to develop a general baseline of ground-water quality, to identify temporal and spatial trends in ground-water quality, and to identify large-scale sources of contamination of ground water. The networks are based on an information structure that includes land use, surface and subsurface geology, ground-water levels, surface- and ground-water quality, possible sources of contamination, and active ground-water-quality monitoring networks. Development of the categories and subcategories of network objectives, which are needed to describe the quality of the ground water in the basin, makes clear the inadequacy of the currently operated networks. The expansion of ground-water-quality monitoring in the San Joaquin Valley, therefore, would be necessary to approximate adequately the ideal network.
