The Roaring Billy water level and rainfall recorder is situated on the Haast River in the lower Haast catchment, 47 km upstream of the township of Haast. The site has a catchment area of 1020 km2
. Lowest water levels are recorded during the winter months when levels can fall to 0.6 metres but normal water levels are closer to 1.2 metres. A high flood water level of 7.6 metres was recorded at this site in May 1978.
This site records a mean annual rainfall of 5750 mm and daily falls of up to 400 mm.
This site is operated by the National Institute of Water & Atmosphere as part of the National Hydrometric Monitoring Network, and is a part of the West Coast Regional Council Flood Warning Network.