Quality of water of the Colorado River, 1925-40

The study of the quality of water of the Colorado River and its tributaries has been a continuing one since 1925. The data so obtained have been useful in the planning and construction of dams and reservoirs, the utilization of the water within the basin, and in planning the economy of areas outside of the basin, partially or wholly dependent on the diversion or importation of water from the Colorado River or its tributaries. Much chemical quality data of the Colorado River and its tributaries collected during the period from 1925 to 1940 have not been published in detail.

The purpose of this report is to make available for consultation and ready reference those previously unpublished data collected for the period 1925 to 1940, mainly between 1930 and 1940. Included among these data are many detailed chemical analyses of composites of daily samples and single samples of the Colorado River and its main tributaries and less detailed analyses of many other samples. In a few instances, for continuity of the record, analyses are included that have been published in Survey reports. Discussions of the quality of water of the Colorado River basin either in published reports or in mimeograph form are available; therefore, this report will include only tabulated data.

Data obtained for the period 1925 to 1930 for the most part were published in three Geological Survey Water-Supply Papers, 596-B, 636-A, and 638-D, all out of print. Summary data for the streams in the Colorado River basin for the period 1925 to 1943 were published in U.S. Geological Survey Water-Supply Paper 970, "Quality of surface waters of the United States, 1943". These summaries consist mainly of annual weighted averages of chemical analyses, dissolved-solids loads, and extremes of dissolved solids and hardness. Analyses of samples from Lake Mead are available in a series of reports, "Lake Mead Density Currents Investigations", by the Bureau of Reclamation /1937 -1940, Vols. I and ll; 1940 -1946; Vol. III/. Data on the suspended sediment in the Colorado River for the period 1925-1941 were published in 1947, in U.S. Geological Survey Water -Supply Paper 998. Since 1940 results of water-quality investigations in the Colorado River basin have been published in the annual U.S. Geological Survey reports, "Quality of surface waters of the United States".