New Mexico Geological Society Annual Spring Meeting — Abstracts

An integrated hydrogeological study was conducted to characterize the soil types and to assess the influence of infiltration and evaporation on the hydrologic budget for small pond at the Las Vegas National Wildlife Refuge in northeastern New Mexico. Fieldwork was conducted in September 2002 at Melton Pond, a representative pond (0.029 mi²) within the refuge surface water system. Soil sampling and infiltration testing was completed during time when the pond had been dry for several months. Ten soil samples were collected and separated into clay, sand, and silt fractions for classification. The soils underlying Melton Pond consist predominantly of clay with minor sandy clay and clay loam. A double ringed infiltration system was used to measure infiltration rates. Infiltration rates varied from 20.0 to 144.0 mm/hr averaging 55.2 mm/hr. Air temperature, wind speed, and relative humidity data over a fifteen-year period were obtained from the Las Vegas Municipal Airport and used to calculate evaporation rates. Results indicate that evaporation varies from 0.45 (November) to 2.26 (June) acre-ft per month totaling 15.36 acre-ft per year. Since Melton Pond holds 58 acre-ft of water, the results suggest that a significant amount of water is lost to infiltration throughout the year. This result is supported by the observed groundwater seeps in the Gallinas River Canyon that are recharged by pond leakage. Since the hydrogeologic characteristics of Melton Pond are representative of conditions throughout the Las Vegas region, the significant surface water losses to groundwater leakage need to be accounted for as the municipality considers the benefits of an acequia-Iining plan.