Snow Fence Shielding of Precipitation Gages

Wind has long been recognized as a major source of error in the measured catch by precipitation gages. The generally accepted Alter or Nipher shields improve the characteristics of the gage to catch precipitation during the occurrence of wind. However, they do not provide all of the protection desired, especially for snow. A study has been undertaken by the Wyoming Water Resources Research Institute to investigate the possibilities of shielding the entire gage with snow fencing. The study has been conducted on the Pole Mountain Division of the Medicine Bow National Forest near Laramie, Wyoming, at an elevation of 8,200 ft. The configuration of the study plot is described and the data collected from observations during the first winter are presented and analyzed. Basically, the results indicated that an unshielded precipitation gage catches about one-third of the defined standard. A gage which is shielded by either snow fences or an Alter shield catches approximately two-thirds, and gages shielded with both an Alter shield and snow fence catch the equivalent of the standard.