A Water-Budget Approach to Determine Potential Groundwater Recharge from Two Domestic Sewage Disposal Fields

From January 2011 to December 2012 the U.S. Geological Survey, in cooperation with Bernalillo County Public Works, used a water-balance approach to estimate the amount of potential groundwater recharge from two domestic sewage disposal fields in Eastern Bernalillo County, New Mexico. Potential groundwater recharge from domestic wastewater (effluent) was estimated as the volume of effluent discharged to the disposal field in excess of the volume of effluent lost to evapotranspiration (ET) from the disposal field. The amount of effluent lost to ET from the disposal field was estimated as the amount of ET loss on the disposal field in excess of the amount of ET loss on the terrain surrounding the disposal field. Penman-Monteith model calculations of ET were calibrated with field measurements of actual ET collected on the disposal field and on the surrounding terrain using a portable hemispherical ET chamber. Results from the two sites indicated that potential groundwater recharge from disposal-field effluent during 2011 to 2012 was 53% to 72% of the volume of effluent entering the disposal field for each site.