Since the first dye trace was performed in 1877 to trace the sinking portions of the upper Danube river, fluorescent dyes have remained the best and most used tools for determining groundwater flow. Very low toxicity and extremely low detection limits combine to make fluorescent dye tracing a standard tool for development of a site hydrogeologic model, particularly in the area of risk assessment.

The methods that Crawford Hydrology Laboratory have developed are the result of 25 years of scientific research and practical field experience. As dye tracing has grown into a high-tech science, our methods have set new standards. Regulators from 8 states, the US EPA and the USGS, as well as consultants from many Environmental Consulting Firms, have our field and laboratory procedures on-file for use as reference when working in areas of carbonate bedrock.

Fluorescent dyes are the most successful water tracers ever developed. Fluorescein (a green fluorescent dye) was first created in 1871. Six years later, in 1877, it was used to trace the sinking portions of the upper Danube river. A few years later a more water-soluble, disodium salt form of the dye was introduced under the trade name “Uranine” (Kass 1998). Today there many fluorescent dyes, but only about 10 of them are considered safe enough to use for dye tracing. Over one hundred and twenty years later, Uranine is still one of the best fluorescent dyes available for water tracing.