Estimation of baseflow nitrate loads by a recursive tracing source algorithm in a rainy agricultural watershed
Estimation of baseflow nitrate loads by a recursive tracing source algorithm in a rainy agricultural watershed
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DOI：
10.1002/hyp.13597
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发表时间：
2019-11
影响因子：
3.2
通讯作者：
Shengjia He;Yun Hao;Jianhong Wu;Jun Lu
中科院分区：
文献类型：
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作者：
Shengjia He;Yun Hao;Jianhong Wu;Jun Lu
基流已成为许多集约化农业流域硝酸盐面源污染的重要来源。基流养分负荷分离的不确定性是由水文气象因素对基流衰退和基流养分负荷衰退的影响引起的。这些不确定性在现有的分离算法中尚未得到很好的解决，这些算法基于简单的基流速率-负载关系。在本研究中，基于非线性水库算法和水文气象校正的基流养分负荷衰退参数开发了递归追踪源算法（RTSA）。该方法用于减少由于不同气候条件下不同负荷衰退的变化而引起的基流硝酸盐负荷估算的不确定性。在典型多雨农业流域进行的 RTSA 验证得出纳什-萨克利夫效率、均方根误差观测标准差比以及 R2 值分别为 0.91、0.30 和 0.91。利用RTSA估算了2003年至2012年中国东部长乐河流域基流硝酸盐氮（N─NO3-）负荷。结果表明，基流硝酸盐输出量占年均 N─NO3- 负荷总量（18.0 kg/ha）的 62.0%。基流 N─NO3- 输出总量在春季最高（3.6 千克/公顷），其次是夏季（3.2 千克/公顷）、冬季（2.3 千克/公顷）和秋季（2.1 千克/公顷）。基流对河道硝态氮总量的贡献大小依次为：冬季（69.88%）>春季（66.59%）>秋季（60.36%）>夏季（54.04%）。研究期间每月基流 N─NO3- 负荷和流量加权浓度大幅增加（Mann-Kendall 检验，Zs > 2.56，p < .01）。如果没有适当的对策，基流硝酸盐可能会对未来的水面构成严重的长期风险。
Baseflow has become an important source of nitrate nonpoint source pollution in many intensive agricultural watersheds. Uncertainties in baseflow nutrient load separation are caused by the effects of hydrometeorological factors on both baseflow recession and baseflow nutrient load recession. These uncertainties have not been addressed well in the existing separating algorithms, which are based on simple baseflow rate–load relationships. In the present study, a recursive tracing source algorithm (RTSA) was developed based on a nonlinear reservoir algorithm and hydrometeorology‐corrected baseflow nutrient load recession parameter. This approach was used to reduce the uncertainty of baseflow nitrate load estimation caused by variations in different load recessions under varying climate conditions. RTSA validation in a typical rainy agricultural watershed yielded Nash–Sutcliffe efficiency, root mean square error‐observation standard deviation ratio, and R2 values of 0.91, 0.30, and 0.91, respectively. The baseflow nitrate–nitrogen (N─NO3–) loads from 2003 to 2012 in the Changle River watershed of eastern China were estimated with the RTSA. The results indicated that baseflow nitrate export accounted for 62.0% of the mean total annual N─NO3– loads (18.0 kg/ha). The total baseflow N─NO3– export was highest in spring (3.6 kg/ha), followed by summer (3.2 kg/ha), winter (2.3 kg/ha), and autumn (2.1 kg/ha). The contribution of baseflow to total nitrate in the stream decreased in the order of winter (69.88%) >spring (66.59%) >autumn (60.36%) >summer (54.04%). The monthly baseflow N─NO3– loads and flow‐weighted concentrations greatly increased during the research period (Mann–Kendall test, Zs > 2.56, p < .01). Without proper countermeasures, baseflow nitrate may represent a serious long‐term risk for water surfaces in the future.