I've got an open ditch behind my home that is becoming an increasing threat to my flood risk. Measuring the water depth is a fairly simple project using ultrasound, but I'd also like to measure flow volume. The dimensions are easy enough, but how do I measure the average speed of the water? Extra credit for devising a method that doesn't involve touching the water. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .