| 摘要: |
| 毛乌素沙地种植区地下水埋深较浅，地下水与土壤水分之间联系紧密，为揭示春玉米生长过程中水分运移关键过程，本文基于原位监测，利用Hydrus-1D建立模型研究毛乌素沙地的田间水分动态。结果发现：在包气带中，40 cm 深以上土层水分受根系吸水和气象条件影响变化剧烈，50 cm深以下土层水分变化受地下水影响显著；在玉米整个生长期内，蒸发量占蒸散量的比例为31%，地下水对玉米生长的水分贡献总量为220.09 mm，占玉米耗水总量的37.9%；为了减少深层入渗，实现节水灌溉，在当前地下水埋深条件下，可将每次的灌溉量减少为原水量的72%；地下水位的下降会减少玉米对地下水的利用，并增大灌溉需求量，模拟发现，当平均地下水埋深下降至147 cm深时，玉米生长将不再利用地下水。研究成果可为毛乌素沙地的农田水分利用及生态环境保护提供重要的理论依据和参考信息。 |
| 关键词: Hydrus-1D 水分动态 蒸散发 地下水利用 |
| DOI：10.7515/JEE182035 |
| CSTR：32259.14.JEE182035 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41790443，31700414）；中央高校基本科研业务费项目（310821171007，310821173701） |
| 英文基金项目:National Natural Science Foundation of China (41790443, 31700414); Fundamental Research Fund for the Central University (310821171007, 310821173701) |
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| Field water dynamics in Mu Us Sand Land with shallow groundwater table |
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BAO Han, ZHANG Guobiao, HOU Lizhu, SHEN Jiangen
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1. School of Highway, Chang’an University, Xi’an 710064, China
2. School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
3. Jiaxing Huantai Engineering Consultation Co. LTD., Jiaxing 314000, China
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| Abstract: |
| Background, aim, and scope The vegetation water consumption is one critical part composing the transport processes of water and heat in the Soil-Plant-Atmosphere Continuum (SPAC), especially for the arid areas. For the arid areas, water is not only the main factor restricting plant growth, but also vital for the maintenance of the local ecological environment. The Mu Us Sandy Land (MUSL) in the northwest of China is dominated by arid climate with relatively shallow groundwater table, and the MUSL groundwater variation is closely related to that of soil moisture. Considering the critical role of water in the development of agriculture in MUSL region, it will be of great importance to study the field water dynamics in the Mu Us Sandy Land. Since spring maize is the primary crop in the MUSL region, here we examined the key water transport processes during the growing season of spring maize by combining model simulations with field measurements. Materials and methods In order to quantify field water dynamics in the MUSL region, one typical field at the Hailiutu catchment was selected to conduct this study. We collected in-situ measurements of hydrologic factors including soil water content, soil water potential and groundwater table during the whole growing season of spring maize from May to October (a total of 155 days). Soil water content was measured at the depth of 10 — 90 cm with10-cm-spacing every 5 days using Time Domain Reflectometer (TDR). Three TDRs were set with the distance of 3 m in this study. Soil water potential was measured with Watermark (with seven sensors) every 10 minutes at six depths. The MiniDiver was applied to monitor groundwater table every 10 minutes. A Bowen-ratio meteorological station was used to observe meteorological variables including wind speed / direction, net radiation, air temperature / humidity and rainfall. On this basis, we parameterized and validated the Hydrus-1D model, and used it to evaluate the field water dynamics during the growing season of spring maize. Results The soil water content above the depth of
40 cm strongly varied with influences of irrigation and rainfall events, while the soil water content below the depth of 50 cm varied similarly with the groundwater dynamics. The simulation results from Hydrus-1D model indicated that, evapotranspiration (ET) of spring maize during the whole growing period reached 580.32 mm, in which 31% were contributed by evaporation, and the ET amount during the jointing, earing and filling periods accounted for 71.8% of the whole ET amount. The dynamics of evaporation and transpiration were found to be significantly related with the variation of leaf area index (LAI), with correlation coefficients of −0.599 and 0.712, respectively. The contribution of groundwater for maize growing was 220.09 mm, which accounted for 37.9% of the total ET amount. The model outputs showed that there were about 8.5 mm of infiltration under the present irrigation amount (~30 mm). Meanwhile, simulation results also indicated that spring maize would not utilize the groundwater when the average depth of groundwater table fell to 147 cm, and the irrigation amount thus turned to be maximum (432.45 mm). Discussion The field soil water content varied dramatically during our study period. However, the main factors influencing the dynamics of soil water content at different depths were different. The soil water content at shallow depths was mainly affected plant growth and meteorological conditions, while the variation of soil moisture at the deep depths was dominant by groundwater dynamics. The evaporation and transpiration and their relative magnitudes varied along the growing season of spring maize due to influences of LAI, which resulted in that the transpiration peaked during earing period and evaporation peaked during sowing period. Conclusions The field water dynamics of spring maize in the MUSL region were closely related with plant growth, meteorological conditions and groundwater table, and the main factors influencing the dynamics of soil water content at different depths were different. The ET mainly occurred during the jointing, earing and filling periods. In order to reduce the deep infiltration and meet the need of water-saving irrigation, the irrigation amount could be reduced to 72% of the original standard at the present groundwater table. For the shallow ground water table, obvious water transport process existed between ground water and soil water, and ground water contributed to the water consumption of spring maize. However, spring maize would not utilize the groundwater when the average depth of groundwater table fell to 147 cm. Recommendations and perspectives Understanding the field water dynamics of spring maize in the MUSL region is not only essential in providing reference basis to the local farmers to improve irrigation use efficiency, but also informative for the water-saving agriculture and ecological environmental protection in Mu Us Sandy Land. |
| Key words: Hydrus-1D water dynamics evapotranspiration groundwater utilization |
