BIG BEND The Impact of Human Use Upon the Chisos Basin and Adjacent Lands NPS Scientific Monograph No. 4

The effect of Chisos Basin activity on these two areas is extremely difficult to assess. The basin makes demands upon both for water and also has impact upon Oak Creek Canyon from above, since the total of all basin runoff water enters Oak Creek Canyon. This runoff contains large amounts of soil, rock, introduced and exotic plants and seeds, organic material from horses, and camping-hiking debris. This can be readily observed below the pouroff where large quantities of rock, clones of Sorghum halpense, paper, and cans are found. Fortunately, the clones of S. halpense fail to survive further down the wash, although many survived long enough to flower.

No immediate effects were apparent to indicate that water usage from Oak Springs was having an adverse influence upon the vegetation; however, large cottonwood trees were found dead in the streambed around and above the water barrel. Since no comparative information is available, impact cannot be definitely assessed. It is of interest that Casey (1968) indicates that Oak Springs was constantly flowing and that vegetables and fruits were productively raised along the watercourse. The large cottonwoods and oaks at the Cattail Falls parking area would certainly suggest such conditions. A comprehensive study of the vegetation along the ravine, with supporting evidence from growth-ring comparisons of shrubs and trees, could provide more accurate information.

Since Cattail Falls drainage is from the upper slopes of Ward Mountain, basin activities do not affect the falls' microclimate. The pool of the small canyon has become smaller and more shallow since 1964 due to increased quantities of gravel and silt. The increased vegetation around the pool may be preventing the movement of silt and rocks downstream, thus building a larger bar which becomes compacted by walking and eventually is vegetated.

Again, no immediate effect due to reduced water could be detected; however, a similar study of vegetation and growth-ring analyses could provide an approach. This study should include work on Cottonwood Wash and immediate springs in the area such as Gano Springs, where many dead cottonwoods can be observed.