A ground-water-quality monitoring network was developed for the Lower Mojave River valley to define the ground-water quality of the valley. Basin geohydrology, geology, land use and water-level and water-quality data were factors considered in developing objectives for an ideal network. These objectives were used in selecting well locations for the conceptual ground-water-quality monitoring network. The conceptual network was used as a guide in the design of the ground-water-quality monitoring network. Active monitoring sites are wells that are currently being monitored by some agency and were selected whenever possible because of budgetary constraints. In areas where no wells are currently being monitored, new well locations were selected and are considered proposed monitoring sites. A sampling regimen is also included. (USGS)