This report describes in detail the result of 1987-88 studies of hydrology, water chemistry, soils, and vegetation in the Big Meadows-Green Mountain Trail Pond wetland complex, which is at an elevation of 2,865 m in the Rocky Mountain National Park in north-central Colorado. Five water sources affect the complex and each water source somewhat differently structures the hydrological character, vegetation, and water chemistry of various portions of the wetland complex. Twelve plant communities that make up the wetland complex are described and characterized relative to hydrology, soils, and water chemistry measurements taken throughout the complex. The water table is highest in May and lowest in fall and early winter. The growing season usually lasts only 3 months (late May to late August), and water tables fluctuate drastically among years depending on the depth of the snowpack. Thus, plants and soils have developed under a hydrological regime involving large annual variability. Soil saturation during July seemingly is the critical variable for peat formation in the study area. Sites with a water table within 20-30 cm of the surface in July usually support peat soils. Oxidation-reduction potential measurements indicate that for any soil depth, the soils stay reduced for up to 3 weeks after a water table drop below that depth.