Storm Water Management
Accurate Measurement of Storm Water Precipitation Using High Accuracy / Low Maintenance Scintillation Technology
Storm water management and similar environmental programs require accurate real-time measurement of precipitation (instantaneous rain rate and liquid water equivalent for snow.) Accurate measurement is important to being able to calculate the runoff of pollutants into waterways and municipal sewage treatment systems, among others. Planning and corrective measures can only become cost effective and helpful when the critical parameter – rain rate – is accurately known. Sadly, this is an area where virtually every group involved falls drastically short by selecting initially inexpensive mechanical measuring instruments that underperform and always wind up costing much more in the long run.
Currently, the instrument of choice is the tipping bucket rain gauge. This device was invented in 1662. While it has served its purpose well up through the 1980’s, better technology is available today. Tipping bucket gauges and related mechanical gauges, such as the weighing rain gauge, have common severe limitations in both accuracy and reliability. These gauges suffer from mostly under-estimation errors due to sampling intervals, wind induced deformations, surface wetting, evaporation, splash issues, orifice clogging due to insects, droppings and wind-blown debris along with limited dynamic range. For freezing precipitation, either environmentally unfriendly antifreeze chemicals or large amounts of heat are needed to make any kind of measurement.
Since the mid 1980’s, sensor technology has existed to very accurately measure rain and snowfall by means of opto-electronic precipitation-induced scintillation. This technology, available today as the APG-815 All Precipitation Gauge, has none of the common errors of mechanical gauges, is much more accurate and needs virtually zero maintenance. These optical sensors have been used in a wide variety of applications – even on data buoys since 1997 the Tropical Rainfall Measuring Mission (TRMM) – a joint U.S.-Japan space project to measure rainfall over the Pacific ocean and thus supply the ground truth for calibrating space-borne sensors. The APG-815 lifetime operating cost figured over even a few years is actually more economical than any of the mechanical gauges. Come learn how to increase your measurement accuracy AND reduce your program costs!
