The Nebraska Sand Hills are one of the largest grass-stabilized dune systems in the world. They also lie over one of the largest groundwater reservoirs in North America. In many interdunal valleys in a large portion of the western Sand Hills, groundwater comes near to or above the land surface forming lakes, wet meadows and lush grass-covered fields. The uplands have a much more sparse cover of bunch grasses with some low shrubs, cacti and other semi-arid species.

The region's climate is semi-arid and the supply of groundwater to the vegetation of the interdunes is undoubtedly important to the maintainance of these communities. However, it is unknown as to what extent evapotranspiration of groundwater into the atmosphere alters the local moisture environment of the Sand Hills and what role this moisture may play in allowing vegetation to persist on the dunes. As recently as 800 years ago, the Sand Hills became remobilized during an extended drought period. Our investigation, using MM5 with idealized forcing, quantifies the local impact of near-surface water supply on the moisture environment of the dune uplands within the Sand Hills and attempts to determine if this local source of atmospheric moisture could play a key role in maintaining the stabilizing vegetation cover.