Document Type

Article

Publication Date

1994

Publication Source

U.S. Army Corps of Engineers

Abstract

This report provides details for the construction of a hot-bead thermistor current meter which is capable of measuring water velocities on a millimeter spatial scale and for the construction of a compact and accurate calibration system. Hot-bead thermistor current meters can be built with response times of 200 ms capable of measuring velocities between 0.1 and 80 cm s-1. The construction of a sturdy probe for application in lotic systems such as high gradient Hawaiian streams was achieved by the use of heavy-duty acrylic tubing, small stainless steel gas-chromatography tubing, and flexible Tygon spaghetti tubing. An acrylic handle anchors the electrical cable at one end and the thermistors at the other. The following criteria were central to the development of the calibration system a accurate calibration b compact unit for storage and use in limited laboratory space c leak-proof system d inexpensive design requirement for readily available materials and e construction requirements for the use of hand tools. The thermistor current meter has been used to measure velocities in the water column and around various substrate features in riverine habitats. More detailed spatial velocity measurements were made in streams by dividing a habitat into small grid cells. With fine spatial scales e.g., grid sizes of 200 to 300 cm 2 or less and repetitive sampling under varying water flow conditions, insights into relationships between various spatial and temporal characteristics of microhabitat velocities were made. The current meter has been used to determine ambient velocity profiles around a variety of benthic stream.

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