Calcite supersaturation and precipitation kinetics in the Lower Colorado River, All-American Canal and East Highline Canal
Article first published online: 9 JUL 2010
This paper is not subject to U.S. copyright. Published in 1983 by the American Geophysical Union.
Water Resources Research
Volume 19, Issue 3, pages 653–661, June 1983
How to Cite
1983), Calcite supersaturation and precipitation kinetics in the Lower Colorado River, All-American Canal and East Highline Canal, Water Resour. Res., 19(3), 653–661, doi:10.1029/WR019i003p00653.(
- Issue published online: 9 JUL 2010
- Article first published online: 9 JUL 2010
- Manuscript Accepted: 16 FEB 1983
- Manuscript Received: 30 AUG 1982
In situ pH determinations and analysis of major ions in solution indicated that the lower Colorado River is supersaturated with respect to calcite throughout the entire daily cycle, in both winter and summer. Although the ion activity product was 4 to 6 times greater than the calcite solubility product, there was no detectable precipitation. Chemical analyses of water samples taken along 350 km of the river and canals from Parker Dam to the Salton Sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows. Laboratory kinetic studies indicated that calcite crystal growth rates with Colorado River water are about 30% of the rate for pure Ca-HCO3 waters and about 70% of that for synthetic Colorado River water. Calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite. Critical supersaturation levels necessary for heterogeneous nucleation do not occur; a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime H2CO3 levels.