Spatial mapping of evapotranspiration over Devils Lake basin with SEBAL: application to flood mitigation via irrigation of agricultural crops

Excessive precipitation since 1993 has produced extensive flooding in the Devils Lake basin in northeastern North Dakota, USA. Irrigation of agricultural crops has been proposed as a flood mitigation tool. Ten test fields were equipped with center pivot irrigation systems to compare test field evapotranspiration (ET) with ET for crops in the predominantly nonirrigated basin. An irrigation scheduling analysis indicated 2006 was a favorable year to estimate the maximum ET gains achievable via irrigation. An ET map for 2006 using the Surface Energy Balance Algorithm for Land (SEBAL) for 54 % of the basin, and land use and soil survey data, was used to compare ET estimates at the test fields with ET estimates across the study area. May–September ET was estimated by SEBAL as 394 mm for wheat and 435 mm for corn across the study area, while corn ET at irrigated test sites was 452 mm. Because the 17-mm ET advantage by irrigating corn was substantially smaller than the 41-mm ET advantage for corn versus wheat, we conclude widespread irrigation development to mitigate flooding is not justified. Coarse-textured soils exhibited some seasonal ET deficits, but their small areal extents and parcel sizes offer virtually no opportunity for flood mitigation.