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In 1957, the average annual volume of water for domestic and industrial use was 22,600 acre-feet, or about one percent of the total consumptive use at that time (Iorns et al. 1965). In the late 1950's, the demand for water grew with the increase in steam-electric power production. Coupled to an increasing population (nearly 300,000 in 1950) and gas and oil extraction, water use increased to 132,000 acre-feet in 1965 (Upper Colorado Region State-Federal Inter-Agency Group 1971). By 1975, substantial population increases (estimate of 431,400) and industrial development in the upper basin increased water use to 215,000 acre-feet or six percent of the total consumption by man. The greatest volume of water used in the upper basin for municipal and industrial reasons is in the Green River Subregion, where mineral ex- traction and steam-electric generation demands are greatest. Use is also high in the San Juan-Colorado Subregion where steam-electric generation consumes about five percent of the total (Table 1.2). Analyses of Historic Records Man-induced changes in flow of the upper Colorado River have resulted in manifest changes in water quality and fish habitat. Water depletions and augmentations have affected the littoral areas, pool-riffle proportions, streambed scouring, temperature, and sedimentation. Habitat alterations are difficult to measure, but changes in flow and water quality can be quantified and used as an index to habitat quality. This information is adequate for establishing general trends, but is not sufficiently speci- fic for use in correlations with biological changes in the upper basin. For example, depletions occur primarily during the irrigation season (April- September), and much less water withdrawal occurs during the winter. De- pletions during the warm months are proportionately greater than those shown on yearly summaries (Figure 1.2) because the large fluctuations during summer are averaged over the whole year. Also, depletions vary from basin to basin, and summaries are not specific enough to show these differences. Historic recorded flows of six major rivers in the upper basin were examined to evaluate trends in water depletion and augmentation. Data 18