不同作物覆盖对农业区地下水入渗补给的影响分析

Effects of different crop covers on vertical groundwater recharge

灌溉入渗是卫宁平原地下水的主要补给来源,研究不同农作物对地下水的灌溉入渗补给对于准确评价地下水资源量十分重要。本研究基于卫宁平原灌区2个包气带水分运移原位试验点系统观测数据,运用Hydrus-1D软件建立了试验点的包气带水分运移数值模型;设置了单次灌溉量、生长期天数、最大根系埋深和叶面积指数四种影响因子,应用模型分析了其对地下水入渗补给量的影响,计算了不同作物种植期内地下水垂向入渗补给量。结果表明:试验点地下水入渗补给量以灌溉入渗补给量为主。单次灌溉量的大小对地下水垂向入渗补给量的影响最为显著,其次是生长期天数和最大根系埋深,叶面积指数对地下水垂向入渗补给量的影响最小。随着地下水位埋深的增加,农作物种植因子对地下水入渗补给的影响也会增大。不同时期的降雨入渗系数为0.02～0.25;受次降雨量和降雨频率影响差异较大。灌溉入渗系数大小与作物种类关系密切:玉米种植期内的灌溉入渗系数为0.78,茄子种植期内的灌溉入渗系数为0.51,枸杞种植期内的灌溉入渗系数为0.6～0.63。综合考虑研究区作物类型和地下水位埋深(117～267 cm),给出了研究区农田区域在作物单次灌溉量为50～150 mm情况下,对应的灌溉入渗系数参考值。

Irrigation infiltration is the main source of recharge for groundwater in the Weining Plain.Studies of groundwater recharge from irrigation under different crop covers are important for the accurate evaluation of groundwater resources.In this study the Hydrus-1D is used to simulate the moisture migration in the vadose zone using the observation data of two in situ experiments which were carried out in Zhongwei and Zhongning.The effects of four factors,such as the single irrigation amount,growth duration,maximum root depth and leaf area index,on groundwater recharge via infiltration are analyzed.The groundwater recharge via vertical infiltration during the different crop planting periods is calculated.The results suggest that the groundwater recharge via infiltration mainly comes from irrigation.The single irrigation amount has the most significant effect on the groundwater recharge via infiltration,followed by growth duration and the maximum root depth.The leaf area index has the smallest impact on it.With the increasing groundwater depth,the impact of crop factors on groundwater recharge will also increase.The coefficients of recharge from rainfall in different periodsrange from 0.02 to 0.25,which is greatly affected by the rainfall amount and frequency.The coefficient of recharge from irrigation is closely related to crop species which is 0.78 in the maize planting period,0.51 in the eggplant planting period,and 0.6-0.63 in the Lycium barbarum planting period.Considering the crop type and groundwater depth(117-267 cm) in the study area,the reference value of coefficient of recharge from irrigation under the condition of single irrigation amount ranging from 50 mm to 150 mm is given.