The pilot reported that he was landing on the runway 12 ramp area and entered the downwind leg of the airport traffic pattern at 1000 feet above the ground. The pilot reported that downdrafts caused the glider's rapid loss of altitude and was unable to reach the landing area. The pilot landed in a field northwest of the airport where the glider impacted a mesquite bush with the left wing and ground looped. The glider sustained substantial damage to the fuselage, canopy, and left wing. Runway 12 is 8,810 feet long by 150 feet wide. The ramp area that parallels the runway to the north side is 7500 feet long by 350 feet wide. A weather reporting station five miles south of the accident site reported winds from 140 degrees at17 knots and gusting to 24 knots prior to the accident. A review of local weather data showed there were no strong lifting mechanisms for the formation of clouds or precipitation near the surface at the time of the accident and the pilot likely encountered gusty surface winds while descending to the airport. The pilot reported no preimpact mechanical failures or malfunctions with the glider that would have precluded normal operation.