Seepage and Evaporation Determination Using a Liquid Level Interferometer (Laser)

Research Project Technical Completion Report (A-109-Ariz.) For: United States Department of the Interior, Project Dates: 1981-1983, September 1, 1983. / The Research on which this project is based was financed in part by the U.S. Department of the Interior, as authorized by the Water Research and Development Act of 1978 (P.L. 95-467)A liquid level interferometer has been built to measure changes in water level to an accuracy of /8. A novel magnetic suspension is used to position the floating retroreflector of a laser interferometer. Direction sensing is achieved by dual optical channels phased near quadrature by means of an absorbing beamsplitter. The interferometer (laser) has been used to measure very accurately the drop in water level of a lined reservoir. The drop in water level thus provides a precise method of measuring evaporation. It was found that this drop in water level essentially ceased when the relative humidity approached very closely or equaled 100 percent during early morning calm periods. This provides a method of determination of seepage loss. In an unlined reservoir during calm periods when the relative humidity is 100 percent any remaining drop in water level is due to seepage. The laser can measure this rate.This item is part of the Water Resources Research Center collection. It was digitized from a physical copy provided by the Water Resources Research Center at The University of Arizona. For more information about items in this collection, please contact the Center, (520) 621-9591 or see http://wrrc.arizona.edu