Within a single study area, the rainfall levels can vary dramatically. For instance, one of RJN’s clients saw 1.56 inches of total rainfall in 50 minutes throughout the center of the study area, but during that very same 50 minutes, the eastern part of the study area had only .1 inches of total rainfall. Had RJN not been measuring at multiple rain gauge sites, the overall analysis of the entire study area would be both incomplete and inaccurate.
The video shown below depicts this rain event:
According to RJN’s Thomas Romza, P.E., “In this video, I enclosed the study area where we were flow monitoring. A rain event came through that produced very large amounts of excess flow in the sanitary sewer system. The storm system that hit the area was very localized as can be seen in the video. If we would have only used one rain gauge (labeled 1 in the video) we would not have captured the intensity of the rain event as the most heavy rains were just west of that gauge.”
And without comprehensive, correct, and complete data, it is much more difficult to develop helpful, sustainable recommendations. In other words, if there isn’t good rain data or the rain gauge sites currently set up don’t give the most comprehensive and accurate picture of the study area, RJN engineers have nothing substantial enough to analyze. It is like Romza says, “After all, without good rain data we have nothing to compare the flow data to.”
This is why rain gauge placement is critical to the success of a flow monitoring program. Engineers and technicians often need multiple rain gauge sites to collect enough data and to understand the complete picture for a study area.
What’s more, adding rain gauges is a low-cost way to ensure the most complete and accurate data is collected during storms. As Romza put it regarding the video shown above, “In the past with this client, we have only used one rain gauge, but we decided this time around that since each rain gauge is less than 3% of the contract value, we could use two rain gauges to more accurately understand the rain events during the monitoring period.”
Thus, overall, the cost of adding additional rain gauges is minimal, especially in consideration of the benefits, which include more comprehensive and accurate data.
In summary, if your municipality or organization wants a complete picture of its study area, then it should hire experts like the engineers and technicians at RJN Group, Inc. who know when multiple rain gauges can help the study and understand that comprehensive and accurate data collection is critical in making the right recommendations to ensure the proper functioning of the sewer system. RJN professionals also know the most cost-effective approaches toward this without putting accuracy in jeopardy.