Effects of a ski area on the water quality and invertebrates of a mountain stream

Past studies of the Rio en Medio, New Mexico, U.S.A., have shown significant changes in water quality and in invertebrate communities below the Sante Fe Ski Area. The present study was undertaken to determine how far downstream the effects of the ski area extend.. The concentration of every major nutrient except SO₄ was found to increase below the ski area and the only mechanism for recovery seemed to be dilution by downstream tributaries. Increased sediment loads below the ski area were also recorded. Peaks of sediment transport were associated with snow melt and summer rains. Much of the increased sediment below the ski area appeared to settle out in the upper reaches of the Rio en Medio. Composition and diversity of stream insects appeared to be little affected. However numbers and biomass of invertebrates were significantly reduced below the ski area. These reductions were attributed to the effects of increased sediment load. Some recovery of invertebrate production was recorded at distances of 700 to 2200 m below the ski area.