Wild Mexican rivers provide the base datum for judging erosion damage

Evidence

In many cases we literally do not know how good a performance to expect of healthy land unless we have a wild area for comparison with sick ones. Thus most of the early travelers in the Southwest describe the mountain rivers as originally clear, but a doubt remains, for they may, by accident, have seen them at favorable seasons. Erosion engineers had no base datum until it was discovered that exactly similar rivers in the Sierra Madre of Chihuahua, never grazed or used for fear of Indians, show at their worst a milky hue, not too cloudy for a trout fly. Moss grows to the water’s edge on their banks. Most of the corresponding rivers in Arizona and New Mexico are ribbons of boulders, mossless, soil-less, and all but treeless. — Aldo Leopold, A Sand County Almanac, 701

Categorization

• XREF: The ‘wild area as control/norm’ concept is the methodological core of Reading the Landscape — reading present landscape against a pre-disturbance template. — connects to: Apparent farm solvency conceals ongoing topsoil loss to erosion — Aldo Leopold, A Sand County Almanac: With Other…, 425
• SEED: Angles on how ‘pristine’ baselines are located at all — the Chihuahua discovery of a comparative river is a vivid method story for a piece on disturbance baselines.
• QUESTION: Are there comparable cross-border ‘unused’ comparison sites used today for rivers elsewhere?