bolson

1. (chiefly southwestern US) A relatively flat and arid valley that is surrounded by mountains and that drains into a central basin.Examples: "In three separate bolsons in West Texas, electrical-resistivity soundings and seismic-refraction profiles have been used . . . to estimate the alluvium thickness and ground-water quality."; "The image of a colossal purse is helpful in envisioning a bolson in the landscape: an extensive, saucer-shaped basin, closed at the bottom and surrounded on all sides by mountain slopes."; "The water in the Mesilla Bolson, which is recharged by the river above it, is part of a major lawsuit between Texas and New Mexico. . . . A settlement could impose new restrictions on wells tapping the bolson in both states."SouthwesternUS