渠井用水比对灌区降水响应及其环境效应分析

    Response of precipitation to ratio of canal to wells and its environmental effects analysis in combined well-canal irrigation area

    • 摘要: 渠井结合灌区适宜渠井用水比例关系灌区地下水环境和区域农业可持续发展。该文以人民胜利渠灌区为例,集合了灌区1954-2014年农业用水量及降水量、研究区域2008-2014年渠井用水比、地下水埋深、地下水水化学特征数据,分析了降雨量、地下水动态特征与渠井用水比例的相关性,以期探明渠井结合灌区渠井用水比对降雨的响应及其对土壤和地下水环境的影响。结果表明,典型渠井结合灌区渠井用水比与年降水量呈线性正相关;渠系上游地下水水位变化较下游更为剧烈,在用水水平、用水方式一致条件下,渠井用水比例越大,地下水埋深超过11 m区域增幅越小,较大的渠井用水比例对于上游地下水位下降减缓效果明显;平水期、枯水期,由于渠井用水比例不合理,地下水无序开采且超采严重,区域地下水碱化趋势明显;受气候变化影响,近5 a渠灌水量仅为多年均值的75.52%,未来区域降水量具有减小趋势,这势必进一步加剧农业水资源紧缺的形式。为了满足农业的正常生产,增加灌区地下水开采成为唯一解决途径,这势必加剧地下水的碱化趋势及地下水超采区的扩大。因此,确定灌区适宜的渠井用水比例对于灌区水资源的科学利用与农业的可持续发展具有重要意义。

       

      Abstract: Abstract: The suitable ratio of canal to well in the combined well-canal irrigation area can contribute to safety of groundwater environment and sustainable regional agriculture production. In order to investigate the influence of canal-to-well ratio on regional soil salinity accumulation, dynamics of groundwater depth, and groundwater hydrochemical characteristics in combined well-canal irrigation area, this study was carried out in a typical area in the People's Victory Canal area in China. The agriculture water consumption and precipitation in the People's Victory Canal area from 1954 to 2014 were collected, and the canal-to-well ratio, dynamics of groundwater depth and hydrochemical characteristics of groundwater from 2008 to 2014 in the research area were analyzed. The relationships between precipitation, groundwater depth, groundwater hydrochemical characteristics and the canal-to-well ratio were explored. The results indicated that there was a significant positive correlation between canal-to-well ratio and annual precipitation in research area (P<0.05). The variation coefficient of groundwater depth in the upstream of branch canals was higher than that of downstream of branch canals. Accumulated variation in soil electrical conductivity at 0-100 cm depth of 2nd branch canal was less than that of 1st branch canal and 3rd branch canal by 4.77% and 5.55%, respectively. Compared with the year of 2013, the area of groundwater depth greater than 11 m in 1st branch canal, 2nd branch canal and 3rd branch canal during the wintering period of winter wheat in 2014 was increased by 31.78%, 25.07% and 40.81%, respectively. When the water consumption amount and method were same, the high canal-to-well ratio can result in a small increase of area with groundwater depth beyond 11 m, indicating that the high canal-to-well ratio can alleviate the deterioration of groundwater depth. Alkaline trend of groundwater during dry and normal seasons in the research area was obvious owing to unrestrained groundwater exploitation. Affected by climate change, the reduction of precipitation in the combined well-canal irrigation area was obvious. Meanwhile, average irrigation amount by canal in the past 5 years was 2.90×108 cm3, accounting for 75.52% of mean annual irrigation amount. On the other hand, ground water overdraft in the research area would be remained in order to ensure agricultural sustainable production, which would be bound to aggravate alkaline trend of groundwater and expand the range of deep groundwater zone. It could be concluded that the suitable ratio of canal to wells decreased the groundwater exploitation and alleviated the alkaline trend of groundwater environment, moreover, maintained the reasonable groundwater depth.

       

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