摘要
在灌溉季节,尤其是下游灌区,农田地下水位较高,作物可就地利用部分浅层地下水,从而减少灌溉需水量,达到节水减排的双重目的。大田作物对浅层地下水利用量的估算是合理制定灌溉淋洗制度及控制土壤盐碱化的前提,但其估算存在一定困难。该文假设当农田灌溉、排水等水文气象条件一致时,某一作物对浅层地下水的利用量等于该田块有、无作物(即裸地)2种情况下造成地下水位差异的水量。据此,首先建立了浅层地下水利用量的计算模型,并以某一半干旱灌区为例,利用田间水文模型-DRAINMOD模拟出有、无作物2种条件下农田地下水位变化过程,然后,计算了棉花、小麦轮作期内对浅层地下水的利用量;在此基础上,进一步分析了浅层地下水利用条件下土壤剖面的盐分平衡。结果显示,该文提出的计算模型能够较好的反映大田实际情况;研究时段内,田间地下水埋深平均值为2.1 m,单位面积上作物利用浅层地下水量为305.8 mm,主要发生在作物生长阶段,其中棉花生长季内地下水利用量约为160 mm。盐分平衡计算结果显示,浅层地下水的利用使得水位以上土壤剖面盐分含量增加,但1 m以内根区土壤盐分在降雨和灌溉作用下得到一定的淋洗,未超出作物耐盐极限,不会对产量造成显著影响。研究成果可为相关灌区制定合理的灌溉制度及提高水资源利用效率提供科学依据。
In the irrigated agricultural areas, especially in the downstream regions, the poor drainage condition or blocked drainage outlet often result in high water table during the irrigation season. Such condition may be properly used to encourage crops to use in-situ shallow groundwater in order to reduce irrigation application and the subsequent drainage discharge. This will help improve the irrigation water use efficiency and mitigate the negative impact of agricultural drainage. To estimate the amount of shallow groundwater use in field condition, however, is often difficult due to the complex relationships among soils, crops and the field hydrology. In this paper, we presented a method for calculating shallow groundwater use by field crops based an assumption that crop uptake of groundwater caused the timely difference in water table depth between the fields with and without crops, providing that the weather condition and the irrigation and drainage practices were similar. With a case study in a semi-arid irrigation area Shaanxi, China, we demonstrated the application of the proposed method in a cotton and wheat rotational field; the daily water table depths under the two different surface cover conditions were predicted with the field hydrology model- DRAINMOD, which has been tested at the same site previously; the salt accumulation in crop root zone under shallow groundwater use was predicted with a simple salt balance model. The difference in potential evapotranspirations(PET) in the fields with and without crops were calculated separately and fed into the model as inputs in order to represent the different effect of PET on field hydrology in DRAINMOD. The sub-irrigation module in the DRAINMOD was used to simulate the effect of high water level in drainage ditches due to the occasional block up of the drainage outlet. The calculation results showed that the approach used in this paper produced reasonable estimate of water balance in comparison with the actual field conditions; the DRAINMOD predicted soil moistu
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第22期89-97,共9页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金(51279159)
陕西省教育厅重点实验室项目(14JS060)
关键词
地下水
模型
盐度
DRAINMOD
水盐平衡
耐盐极限
灌区
groundwater
models
salinity
DRAINMOD
salt and water balance
salt tolerance
irrigation area
