New Mexico CoCoRaHS
Volunteers measure and map precipitation in their community
By Leeann DeMouche
New Mexico’s unique geography and climate have allowed the state to become one of the most productive agricultural regions in the United States. The mountains of Colorado and New Mexico capture and store winter precipitation that is then used for summer irrigation in upper and lower valleys along the Rio Grande.
New Mexico’s Rio Grande Basin is experiencing rapid population growth, development of the rural countryside and decreasing municipal groundwater supplies. Residential or lifestyle agriculture is widespread in the areas irrigated by the Rio Grande and is practiced by both newcomers and residents whose roots in the region are hundreds of years old.
In New Mexico, it is well-known that there is a great deal of geographic variability in precipitation from individual storms, particularly the thunderstorm/thundershower type of precipitation that occurs during the summer. In fact, it is not at all uncommon for one area of a large field or landscape to receive rain while an adjacent area remains dry. This complicates soil-water balance calculation and plans for efficient and effective irrigation application. A network of rain gauges are fostered to assist this irrigation monitoring process.
CoCoRaHS, the Community Collaborative Rain, Hail and Snow Network, is a grassroots volunteer network of backyard weather observers of all ages and backgrounds working together to measure and map precipitation (rain, hail and snow) in their local communities. By using low-cost measurement tools, stressing training and education, and using an interactive Web site, CoCoRaHS hopes to provide the highest quality data for natural resource, education and research applications (Doesken, 2005). The goal of the NMSU College of Agriculture and Home Economics Water Task Force Cooperative Extension team is to work closely with the New Mexico State Climatology Center and the Colorado State University Climatology Center assisting with the development and implementation of the CoCoRaHS program in New Mexico.
The reliability of a network of rain gauges for a particular rainfall event depends on the coverage area and the number of precipitation gauges. This simply translates to the number of rain gauges per unit area. The more rain gauges per unit area, the more reliable the estimate of precipitation or irrigation for the soil-water balance, and thus better input for the decision regarding irrigation applications.
An important feature of the CoCoRaHS network is its simplicity. Participants use a standard 4-inch diameter rain gauge to measure precipitation. Volunteers receive training and complex instructions on measuring rain, hail and snow using his or her rain gauge. These observations are submitted each day to the project’s Web site (www.cocorahs.org), where they are processed and mapped by climate analysts. In addition to the daily precipitation observations, volunteers can submit reports of intense rain or hail during major storms. These reports are then sent directly to the appropriate National Weather Service (NWS) office where they can be used for the issuance and verification of flood and severe thunderstorm warnings.
In addition to providing potential life saving information, CoCoRaHS data is used by engineers, hydrologists, weather forecasters, city planners, emergency managers, attorneys, teachers, historians and others for such applications as flood forecasting, drought monitoring, precipitation verification (e.g., forecast models and radar estimated precipitation) and climate trends. This volunteer network offers information that would not otherwise be available.
Official NWS sites in New Mexico consist of 15 Automated Surface Observing Systems (ASOS) and approximately 200 Cooperative Observer Program locations (COOP). While precipitation observations from COOP stations are typically considered more reliable because they are read manually, the network suffers from relatively poor spatial resolution.
The CoCoRaHS network is not intended to replace the current weather observation system but to provide additional data for a more accurate picture. Official weather observing sites in New Mexico are often separated by distances of 20 miles or more and do not capture individual storms. Due to the small scale of individual storms and the high variability of topography and precipitation in our state, our goal is to have a rain gauge every square mile within the metropolitan areas and as many as possible in the rural communities. Because of the simplicity and low cost of the equipment (approximately $29 per gauge), CoCoRaHS is an economically feasible option for filling in the gaps between official weather observing sites in New Mexico.
The primary objectives for the New Mexico CoCoRaHS network are to increase the density of precipitation data available throughout the state by encouraging volunteer weather observing and providing accurate high-quality precipitation data for the many end users on a timely basis. These objectives overlap with those of the 2003 New Mexico State Water Plan.
Presently, CoCoRaHS has more than 600 observers throughout New Mexico. CoCoRaHS is now into its third year of the program, and future training and placement of rain gauges will focus on rangeland and rural communities. Presently participants are working with NWS to supply rain gauge data to those areas where radar coverage is nominal to none.
The Rio Grande Basin Initiative has been a supporter of this project along with the New Mexico Floodplain Managers Association, Office of the State Engineer, Governor’s Drought Task Force and NWS.
