The experiments were conducted in 2004–2005 and 2007–2008, and the treatments in the two growth seasons were denoted as ‘T1’ and ‘T2’, respectively. The planting crop was winter wheat (T. aestivum L.). The field management and the development of the growth stage of winter wheat are shown in Tables 2 and 3. Three constant groundwater depths were 0.7, 1.1 and 1.5 m in the period from 23 March to 8 June 2005 during which the treatments received precipitation (Table 4). There was only one constant groundwater depth, 1.5 m, in the period from 20 March to 5 June 2008 during which the treatment did not receive precipitation. To quantify the ET_gw under the condition without irrigation, no irrigation was applied for all experiment treatments in both growth seasons.