STS090-752-036 San Luis Valley, Colorado, USA April 1998 The San Luis Valley in south central Colorado has an arid climate and is intensively cultivated for commercial agriculture. Even in this small-scale image, the widespread use of center pivot irrigation techniques is apparent. Notice several dendritic drainage patterns within the valley. These drainage patterns include the San Luis and Saguache Rivers in the northern section of the valley and the Rio Grand near the southwestern side. These patterns are enhanced by the highly mineralized surfaces (whitish looking saline soils) where agriculture is no longer possible due to the salinity of the soils. Great Sand Dunes National Monument is visible in the center of the picture. The snow-covered Sangre de Cristo Mountains border the east side of the San Luis Valley.