Evapotranspiration measurements for a semi-arid wetland in the Sacramento-San Joaquin Delta, California, USA (Foremerly Paper 1.8)

The purpose of this study was to obtain estimates of evapotranspiration (ET) for a small, restored wetland in the Delta. The Typha spp-Schoenoplectus acutus wetland in this study is a prototype for a bigger restoration projected anticipated for the Delta region. There are very few known ET rates for wetland plant species and plant community types within the arid and semi-arid climate regime, and in particular, the studies rarely span more than a few weeks in the summer. Our study spans the growing seasons of three years (2002-2004) and resulted in an ET average of 6.01 mm/day (SD = 1.87) with a range of 0.80 to 12.20 mm/day. The monthly means of daily reference evapotranspiration (ETo) rates ranged from 0.71 to 7.86 mm (overall mean for the study period = 4.0 mm; SD = 2.31), while daily ET rates from the restored wetland ranged from 0.87 to 8.57 mm (overall mean = 3.75 mm; SD = 2.28). Several climate variables are responsible for the variations in rates of ET, however, analysis has revealed that wind direction and the temperature of standing water in the wetland were of particular importance.