The Model 90 GeoFlo Borehole Groundwater Flowmeter is an easy-to-use portable instrument capable of direct measurement of water flow rates in rock boreholes. This extremely sensitive flowmeter operates on heat-pulse principles. The direct readings, displayed on the screen of the laptop computer as ml/min. upflow or downflow, eliminate the need for dye and salt tracer tests. The flowmeter gives measurements within five minutes and is capable of taking as many as 80 field measurements per day. It has a depth capacity to 450 feet and a flow range of 0.5 ml/min. to 1 liter/min. K-V Associates Inc.