Negligible contribution of reservoir dams to organic and inorganic transport in the lower Mimi River, Japan
Negligible contribution of reservoir dams to organic and inorganic transport in the lower Mimi River, Japan
复制标题
DOI：
10.1016/j.jhydrol.2017.10.020
复制
发表时间：
2017-12
影响因子：
6.4
通讯作者：
K. Nukazawa;Kousuke Kihara;Yoshihiro Suzuki
中科院分区：
文献类型：
--
作者：
K. Nukazawa;Kousuke Kihara;Yoshihiro Suzuki
河流通过形成从高地森林到沿海地区的物质运输网络，发挥了重要的生态作用。大坝影响这些系统中有机和无机循环的方式尚不清楚。在此，我们研究了日本三个梯级水坝的水化学各组成部分的纵向剖面：山原水坝、西沟水坝和大内原水坝，它们位于产沙的Mimi河沿岸，在不同的水流条件下。分析了2012 - 2014年中低流量和高流量期间3座大坝下游河道中悬浮物（SS）、浊度、总铁（TFe）、溶解铁（DFe）、总有机碳（TOC）、总氮（TN）、总磷（TP）、腐殖质（HS）和主要离子组分（Na+、Mg2+、Ca2+、Cl−、NO3−和SO42−）的水质成分。我们分别利用每小时浊度数据和流量数据（即L-Q模型）估算各组分的每小时负荷，并将结果综合起来估算年通量。比较了两种方法之间的年通量，验证了传统L-Q模型的可预测性。浑浊度估算的TOC、TN、DFe和HS的年通量值相似，而SS、TFe和TP的年通量在大坝下游呈增加趋势。在大坝中，高流量时TP和TFe的估算通量比例较高（74% ~ 94%）。考虑到地理条件（例如，大坝之间没有主要支流），结果表明，在洪水事件期间，水库中积累的TP和TFe可能会被SS冲刷并通过短高水坝向下游输送。假设这一过程，水库大坝可能只对所研究的集水区的有机和无机运输做出了部分贡献。SS、TFe和TP通量的百分比误差范围为- 7.2%至- 97%（2013年TP通量除外），这突出了在使用L-Q模型时低估这些组件的风险。
Rivers fulfill an essential ecological role by forming networks for material transport from upland forests to coastal areas. The way in which dams affect the organic and inorganic cycles in such systems is not well understood. Herein, we investigated the longitudinal profiles of the various components of the water chemistry across three cascade dams in Japan: the Yamasubaru Dam, Saigou Dam, and Ohuchibaru Dam, which are situated along the sediment-productive Mimi River in different flow conditions. We analyzed the following water quality components: suspended solids (SS), turbidity, total iron (TFe), dissolved iron (DFe), total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), humic substance (HS), and major ionic components (Na+, Mg2+, Ca2+, Cl−, NO3−, and SO42−) in the downstream channels of the three dams during the low–intermediate-flow and high-flow events from 2012 to 2014. We estimated hourly loads of each component using hourly turbidity data and discharge data (i.e., L–Q model) separately, and the results are integrated to estimate the annual fluxes. The annual fluxes between the methods were compared to verify predictability of the conventional L–Q models. Annual flux of TOC, TN, DFe, and HS estimated by the turbidity displayed similar values, whereas the flux of SS, TFe, and TP tended to increase downstream of the dams. Among the dams, estimated flux proportions for TP and TFe were higher during high-flow events (74%–94%). Considering geographic conditions (e.g., absence of major tributary between the dams), the result implies that accumulated TP and TFe in the reservoirs may be flushed and transported downstream with SS over the short height dams during flood events. Assuming this process, the reservoir dams probably make only a fractional contribution to the organic and inorganic transport in the catchment studied. The percent flux errors for SS, TFe, and TP fluxes ranged from −7.2% to −97% (except for the TP flux in 2013), which highlights the risk of underestimating these components when using an L–Q model.