Water flow resistance along the pathway from the plow layer to the drainage canal via subsurface drainage in a paddy field
Water flow resistance along the pathway from the plow layer to the drainage canal via subsurface drainage in a paddy field
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稻田中耕层通过地下排水至排水渠路径的水流阻力
DOI：
10.1016/j.agwat.2020.106391
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发表时间：
2020
影响因子：
6.7
通讯作者：
Ohno Satoshi
中科院分区：
文献类型：
--
作者：
Nishida Kazuhiro;Harashima Takaaki;Yoshida Shuichiro;Ohno Satoshi
地下排水系统的功能衰退已成为在轮作稻田中种植高地作物的一个问题，因此有必要开发确定其根源的方法。本研究的目的是量化的水流阻力（WFR）沿着路径从耕层排水渠道通过老化的地下排水在粘土稻田。水文监测是在一个粘土质稻田进行的，地下排水系统安装在20多年前，监测期间种植大豆。使用连接到排水口的流量计测量表面和地下排水速率。使用安装在威尔斯井中的张力计或压力传感器测量沿着路径的水压。假设连续水流通过的路径，从测得的总水头梯度和排水流量的截面WFR的时间演变。然后，计算潜在的水平和垂直水流率，定义为最大可能的驱动力除以最小WFR的商。在降雨过程中，地下排水率迅速增加后，排水开始，变得很高，随着时间的推移几乎恒定，然后逐渐下降。当地下排水率较高时，从耕层到集水沟的垂直方向总水头梯度较大，而耕层内的水平水头梯度很小。垂直剖面和水平剖面的潜在流量分别为2.1-5.7 mm/h和6.2 ~ 79 mm/h以上，表明垂直WFR主要决定潜在地下排水速率。我们的研究结果表明，同时测量的压力分布沿着水通路和地下排水率是一个有前途的方法，用于诊断老化的地下排水系统。
The functional decline of subsurface drainage systems has become a problem for the cultivation of upland crops in rotational paddy fields, necessitating the development of methods to determine its origin. This study aimed to quantify the water flow resistance (WFR) along the pathway from the plow layer to the drainage canal via aged subsurface drainage in a clayey paddy field. Hydrological monitoring was conducted in a clayey paddy field where subsurface drainage was installed over 20 years ago and soybeans were cultivated during the monitoring. The surface and subsurface drainage rates were measured using flowmeters attached to the drainage outlet. The water pressures along the pathway were measured using tensiometers or pressure transducers installed in the wells. Assuming continuous water flow through the pathway, the time evolution of the sectional WFR was determined from the measured total head gradient and the drainage discharge. Then, potential horizontal and vertical water flow rates, defined as the quotient of the maximum possible driving forces divided by the minimum WFR, were calculated. During rainfall events, the subsurface drainage rate increased rapidly after the start of the drainage, became high and nearly constant with time, and then gradually decreased. When the subsurface drainage rate was high, the total water head gradient in the vertical direction from the plow layer to the collecting drain was large, while the horizontal water head gradient in the plow layer was very small. The potential flow rates of the vertical and horizontal sections ranged from 2.1–5.7 mm/h, and from 6.2 to over 79 mm/h, respectively, indicating that the vertical WFR mainly determined the potential subsurface drainage rate. Our results suggest that simultaneous measurement of the pressure distribution along the water pathway and the subsurface drainage rate is a promising method for the diagnosis of aged subsurface drainage systems.