Water management and determination of consumptive water use in irrigated agricultural settings depend on understanding factors such as surface-water diversions, groundwater withdrawals, evapotranspiration, tail-water runoff, and deep-percolation return flow of water beneath irrigated fields. To improve understanding of deep-percolation return flow beneath irrigated fields, the U.S. Geological Survey, in cooperation with the Central Colorado Water Conservancy District, conducted a study to estimate deep-percolation return flow at two irrigated sites in the Central Colorado Water Conservancy District during the 2008 and 2009 irrigation seasons. At one site, deep percolation was monitored beneath an agricultural field irrigated by flood furrows, and at a second site, deep percolation was monitored beneath an agricultural field irrigated by a center-pivot sprinkler.