干湿循环作用下稻田地下水补给过程变化特征

The Impact of the Alternate Dry and Wet in Controlled Irrigation on Capillary Rise in Paddy Fields

[目的]探究节水灌溉模式条件下稻田地下水补给特征。[方法]采用定地下水埋深的蒸渗仪开展试验,分析节水灌溉干湿循环下稻田地下水补给量变化过程,研究地下水补给对节水灌溉稻田作物需水的贡献及对土壤水分的调节作用。[结果]控制灌溉稻田地下水补给过程频繁,当稻田干湿循环过程中土壤水分降至一定限度时,稻田地下水补给量在复水后(灌水或降雨)1 d内出现峰值,稻季共出现16次峰值。控制灌溉稻田稻季地下水补给量达253.98mm,约占水稻需水量的51.1%。稻田干湿循环中,在稻田地下水补给与土壤水入渗的综合作用下,30 cm深度以下土壤含水率保持稳定,0~30 cm深度土壤含水率总体呈下降趋势。[结论]节水灌溉干湿循环下稻田地下水补给量显著增加,有效补给了水稻需水。浅地下水埋深条件下,稻田地下水补给过程直接影响水稻根区土壤水分变化。

[Objective]The purpose of this paper is to investigate experimentally the change in capillary rise and groundwater recharge in response to alternate dry and wet associated with controlled irrigation in paddy fields.[Method]The experiment was conducted in lysimeters with the depth of groundwater table kept at 0.5 m. During the experiment, we measured the change in groundwater recharge and soil moisture distribution, which was used to calculate evapotranspiration and capillary rise.[Result]Groundwater recharge peaked one day after irrigation or precipitation when soil moisture dropped to lowest level during a dry-wet cycle. The measured temporal change in groundwater recharge had multiple peaks during the growth season. The overall recharge was 253.98 mm, increasing by 244.65 mm compared the 9.33 mm recharge under flooding irrigation. About 51.1% of the evapotranspiration under controlled irrigation was due to the capillary rise from the groundwater. The soil moisture in depth below 30 cm remained almost constant during the experiment due to the capillary rise from the groundwater, while the soil moisture in top 0~30 cm soil layer decreased as time elapsed.[Conclusion]Controlled irrigation increased capillary rise from groundwater in paddy field significantly, compared with flooding irrigation. More than half of the evapotranspiration under controlled irrigation originated from groundwater due to the increased capillary rise. The results presented in this paper are helpful for optimizing water management in paddy fields.