Assistant Professor

Research Fields, Keywords


Graduating School 【 display / non-display


    Iwate University   Faculty of Engineering   Department of Civil and Environmental Engineering   Graduated

Graduate School 【 display / non-display


    Tohoku University  Graduate School, Division of Engineering  Department of Civil and Environmental Engineering  Doctor's Course  Completed

Degree 【 display / non-display

  • Tohoku University -  Doctor (Engineering)


Research Career 【 display / non-display

  • Evaluating biodiversity in river using a hydrological model

    Cooperative Research  

    Project Year: 2010.04  -   

Papers 【 display / non-display

  • Investigation of <i><b>Escherichia coli</b></i> in Urban Steam with Inflow of Treated Wastewater

    SUZUKI Yoshihiro, NISHIYAMA Masateru, NUKAZAWA Kei, ISHII Satoshi

    Journal of Japan Society on Water Environment   41   19 - 26   2018.02  [Refereed]

    Joint Work

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    <p>There is growing concern for the applicability of <i>Escherichia</i> <i>coli</i> as a fecal indicator bacterium in the water environment because <i>E.</i> <i>coli</i> has been reported to regrow in a variety of environments. We investigated longitudinal variation in <i>E.</i> <i>coli</i> counts along a small channel which receives the effluent of treated wastewater. The two fecal indicator bacteria, <i>E.</i> <i>coli</i> and Enterococci, were enumerated, and these bacterial fluxes were calculated from bacteria counts and river flow. As a result, the flux of <i>E.</i> <i>coli</i> was larger downstream of the effluent site than the sum of the fluxes upstream and in the effluent. A high <i>E.</i> <i>coli</i> count was detected in the riverbed sediment of a downstream site. In addition, pulsed-field gel electrophoresis revealed that the genotypes of <i>E.</i> <i>coli</i> isolated from the upstream water, periphyton, and riverbed sediment samples were concordant (similarity = 1.0) . These results indicate that <i>E.</i> <i>coli</i> survived and accumulated in riverbed periphyton and sediment and that <i>E.</i> <i>coli</i> may regrow in a small stream that is strongly affected by treated wastewater. When we assess the fecal pollution in rivers, it is necessary to consider the possibility of <i>E.</i> <i>coli</i> regrowth.</p>

    DOI CiNii

  • Negligible contribution of reservoir dams to organic and inorganic transports in the lower Mimi River, Japan

    Nukazawa K., Kihara K., Suzuki Y.

    Journal of Hydrology   555   288 - 297   2017.12  [Refereed]

    Joint Work

     View Summary

    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.



    Kengo Watanabe, So Kazama, Shunsuke Aita, Kei Nukazawa

      73   I_1153 - I_1158   2017.03  [Refereed]

    Joint Work



    Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research)   72   III_553 - III_558   2016.12  [Refereed]

    Joint Work

     View Summary

    We studied temporal effects of slit installation on a check dam on stream habitat and macroinvertebrates in the Wasada River located at Yamagata Prefecture in Japan. Quantitative sampling of benthic macroinvertebrates and measurement of channel morphology were carried out at the inlet and outlet sites of the two check dams in the studied river more than once per year through 2009 to 2015. The dam at downstream was slit in August 2010. The channel morphology was measured using a high precision Global Position System (GPS) and classified into 7 habitat types (e.g., riffle and pool), which was subsequently used for calculating habitat diversity. As results, while the habitat diversity increased at the inlet site of the slit dam after the slit event, species diversity of benthic macroinvertebrates did not display any trends over time. This may suggest that, at least within a few years, local habitat diversification would only result in a fraction of contribution to species diversity. We observed significant negative correlation between the species diversity and the ratio of lentic habitat (R<sup>2</sup>=0.35, P<0.05) in contrast to an earlier study, indicating that increase in lentic habitat at a given stream (or reach) might diminish species diversity of stream macroinvertebrates.


  • Estimating periphyton dynamics in a temperate catchment using a distributed nutrient-runoff model

    Watanabe K, Nukazawa,K, Aita S, Kazama S

    The 7th International Conference on Water Resources and Environment Research (ICWRER)     2016.06

    Joint Work

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Presentations 【 display / non-display

  • Catchment-scaled species diversity modeling of stream invertebrates using a hydrological simulation

    Nukazawa, K., Kazama, S., Watanabe, K.

    HydroEco2017  2017.06  -  2017.06 

  • Adaptive genetic consequences of climate change for stream insects: a hydrothermal simulation approach

    Nukazawa K, Kazama S, Watanabe K

    第20回国際水理学会アジア太平洋地域会議  2016.08  -  2016.08  International Association for Hydro-Environment Engineering and Research (IAHR)

  • Time series analysis of mitochondrial DNA concentration in freshwater in Japan

    Uchida U, Nukazawa K, Kazama S, Kubota K

    第7回国際水資源環境研究会議  2016.06  -  2016.06 

  • Estimating periphyton dynamics in a temperate catchment using a distributed nutrient-runoff model

    Watanabe K, Nukazawa K, Aita S, Kazama S

    第7回国際水資源環境研究会議  2016.06  -  2016.06 

  • Projected adaptive genetic degradation in a caddisfly species under changing climates

    Nukazawa K, Kazama S, Watanabe K

    第11回生態水理国際シンポジウム  2016.02  -  2016.02  International Association for Hydro-Environment Engineering and Research (IAHR) and the National Committee on Water Engineering of Engineers Australia (EA)

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