Southern Nevada is located in the Mojave Desert, one of the driest areas in the United States. With the rapid urbanization and associated land disturbance, and the potential change in climate, understanding the environmental processes that govern near-surface ecosystems is very important. Mass and energy movement across the soil-atmosphere interface influences a suite of environmentally important processes including local and global element cycling (i.e., CO2, nutrients, metals), water cycling, and many important coupled biogeochemical processes. One limitation to upscaling or downscaling environmental processes in the areas of hydrology, biogeosciences, mathematical modeling, and global environmental change lies in the limited number of facilities that permit multi-scale environmental research. As part of a statewide effort, Nevada was recently awarded a grant by the National Science Foundation (project began August 2005), focusing on the scaling of subsurface and landscape-interface environmental processes in arid settings. This program is entitled “Scaling Environmental Processes in Heterogeneous Arid Soils,” or SEPHAS. The program calls for the installation of seven weighing lysimeters which will house either intact or repacked blocks of soil, depending on need. Two dimensions are currently under design: 2m cubes and larger caissons up to 5m by 5m by 2m deep. The lysimeters will rest on highly accurate balances, with expected resolution ~0.0004% of total mass, equivalent to ~0.04 mm water depth. Each lysimeter will be instrumented depending on the needs of the research community and experimental goals. Data collected using automated systems will be archived and available to facility researchers through the Internet. Facility design is underway and groundbreaking is planned for late 2005 or early 2006. When completed, the SEPHAS program will allow researchers to investigate mass and energy budgets, carbon sequestration, nitrogen fixation, soils development, and soil/plant interactions, all specifically related to arid soils. The poster presentation will describe the facility design, current status, and the hypotheses that Nevada researchers are planning to address.