Evaporation Estimates for the Devil’s Lake Basin

Water levels in the Devil’s Lake basin of northeastern North Dakota have risen substantially since 1993 causing flooding and damage to agricultural land and infrastructure. A proposed flood mitigation method is to remove water from the basin through irrigation and evapotranspiration (ET). Constraints on the project include predominantly clay-loam surface textures, many of which are imperfectly drained, and the inability to use subsurface drainage to remove excess water. Objectives of this paper are to estimate ET for selected crops using a soil water balance approach and compare these ET values to those from a locally-developed irrigation scheduling algorithm, a remote sensing algorithm, and eddy covariance methods. Data were collected during the 2006 to 2008 growing seasons from 25 data collection stations spread across 10 field sites. Rain and irrigation were measured with manual rain gauges, deep percolation with fluxmeters, soil water contents with neutron attenuation, and water table depths with ground water monitoring wells installed at 18 stations. The ET values will be compared using correlation and nonparametric tests. With unbiased data for ET water loss, managers can assess whether gains in ET for irrigated vs. nonirrigated crops warrant the use of large-scale irrigation in the basin for flood mitigation. This paper represents analyses completed to date and outlines procedures for comparison of ET estimates.