Groundwater resources of the Southern High Plains/Ogallala Aquifer in Texas and New Mexico are being depleted due to groundwater mining for irrigation. Inevitably, resource depletion leads to calls for water conservation in agriculture. Conservation can take two forms: a reduction in irrigation depth, and a reduction in irrigated area, which in economics are termed the “intensive margin” and “extensive margin” of agricultural water use. In the Southern High Plains, we find different effects on water table elevation arising from these two approaches. This research presents a coupled model of landscape and groundwater hydrology. Model results indicate that a 50% reduction in irrigation water application would limit loss in irrigable area to about 1% of existing irrigable land per year. This is approximately half the rate of depletion from a ‘business as usual’ scenario. Relative benefits of each conservation approach varied: areas with a high density of irrigated land experienced greater benefits from a reduction in irrigation depth, whereas reducing irrigated acreage maintained water tables more in areas with a low density of irrigated land. This project demonstrates that strategies for irrigation water management can support conservation goals. However, model results also demonstrated that even a 50% reduction in irrigation water use –which would be politically and economically unfeasible in Texas and New Mexico – would still result in overall depletion of the regional aquifer.