Allen H. Christensen Randall T. Hanson Peter Martin Steven M. Crawford Gregory A. Smith John A. Izbicki 1999 The U.S. Geological Survey has developed a combined well-bore flow and depth-dependent sample collection tool. It is suitable for use in existing production wells having limited access and clearances as small as 1 inch. The combination of well-bore flow and depth-dependent water-quality data is especially effective in assessing changes in aquifer properties and water quality with depth. These are direct measures of changes in well yield and ground-water quality with depth under actual operating conditions. Combinations of other geophysical tools capable of making these measurements, such as vertical-axis current meters used with wire-line samplers, are commercially available but these tools are large and can not easily enter existing production wells. application/pdf 10.3133/fs19699 en U.S. Geological Survey U.S. Geological Survey combined well-bore flow and depth-dependent water sampler reports