Last year, the Corps’ Albuquerque District purchased and installed rain gauges to act as an early warning system in canyons heavily burned by the Las Conchas Fire, which, at the time, was the biggest fire in New Mexico history and torched upwards of 150,000 acres.
The gauge data provides information on rain falling on Bland, Cochiti, Medio, Sanchez, Capulin, Alamo, and Lummis canyons. The information also helps predict the likelihood of slope failures or landslides.
New Mexico’s monsoon season normally produces small rainfall events, almost daily. As these short duration, high intensity rains fall on areas burned by fires, large floods may occur, particularly because the fire turned the soil to a water repellent state. The hydrophobic soil causes the rain to run off the canyons and collect all types of debris in the process. The lack of vegetation, or the waxy remains of melted vegetation, exacerbates the problem.
The gauges, called tipping bucket gauges, have a small bucket resting atop the gauge that collects water. When enough rainwater enters the bucket (0.01 inch), an arm rocks and keeps a tally of the total rainfall. In this way, the gauges monitor precipitation.
For the most part, the gauges are located in rugged terrain full of steep slopes with little vegetation. For one of the gauges, it is a six-mile hike from the closest road.
At nearby Cochiti Dam and Reservoir, a large earthen embankment dam which helps to control the amount of water released down-stream to the Rio Grande, District employees use the information to estimate the potential amount of inflow to the reservoir.
Excessive rain during a short period triggers text message alerts. These text alerts are received by the District and organizations such as the Bureau of Indian Affairs, Pueblo de Cochiti, USGS, National Weather Service and the Forest Service. The alert system is activated when one of the gauges measures a quarter of an inch of rain in fifteen minutes. When rain falls at this increment flash flooding is expected, so alerts notify emergency responders and allow them to determine if evacuations are necessary.
District Civil Engineer Carlos Aragon said, “One of the limitations [of rain gauges] is that they are only able to measure the rainfall falling directly over the gauge.”
Regardless, the current rain gauges contribute data to the pool of information collected by local and federal agencies to help protect people. District employees are looking to improve the early warning system even further by adding video cameras and stream gauges, which will provide further insight into a storm event.
District Hydraulic Engineer Stephen Scissons said, “The rain gauges are a great tool for monitoring rain trends during monsoon seasons and help to provide accurate safety measures.”