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  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>September</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Development and Evaluation of National-Scale Operational Hydrological Forecasting Services in Russia</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Georgy Ayzel</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Aleksei Sorokin</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Russia</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Computing Center of the Far Eastern Branch of the Russian Academy of Sciences</institution>
          ,
          <addr-line>65 Kim Yu Chena Ulitsa</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Khabarovsk</institution>
          ,
          <addr-line>680000</addr-line>
          ,
          <country country="RU">Russia</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Russia</institution>
          ,
          <addr-line>Hydrology, Forecasting, Services, Modelling</addr-line>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>Russian State Hydrological Institute</institution>
          ,
          <addr-line>2-ya Liniya V.O. 23, Saint Petersburg, 199053</addr-line>
          ,
          <country country="RU">Russia</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2021</year>
      </pub-date>
      <volume>1</volume>
      <fpage>4</fpage>
      <lpage>16</lpage>
      <abstract>
        <p>The presented study briefly describes the development and evaluation of two recently developed national-scale operational hydrological forecasting software that ensures their transparency and reproducibility. Launched in March 2020, both services provide reliable short-term hydrological forecasts for hundreds of river basins across Russia for more than one year. The forecasts of river discharge and water level have been openly disseminated on the internet, allowing any interested party to convert them into value by guiding decision-making and early warning of extreme events. Further development of VI International Conference Information Technologies and High-Performance Computing (ITHPC-2021),</p>
      </abstract>
      <kwd-group>
        <kwd>1</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>OpenForecast, and OpenLevels. The developed services are based only on open data and</p>
    </sec>
    <sec id="sec-2">
      <title>OpenForecast and</title>
    </sec>
    <sec id="sec-3">
      <title>OpenLevels services requires a transition to modern computational techniques (e.g., deep learning) with high computing power and reliability requirements. Thus, this contribution also seeks collaboration with computer scientists and experts in highperformance computing to boost the value of introduced forecasting services.</title>
      <sec id="sec-3-1">
        <title>1. Introduction</title>
        <p>
          Operational hydrologic forecasting systems aim to provide up-to-date information about the
current state of water-related variables, such as river discharge or water level, and their reliable
forecast. These systems have particular relevance and high importance for many parties, supporting
water management decisions and ensuring timely early warning of extreme events. The development
of operational hydrologic forecasting systems has coincided
with the emerging cutting-edge
computational resources and could be dated back to the early 1980s. Since then, hydrologists have
worked back-to-back with computer scientists to establish new and support existing forecasting
systems [
          <xref ref-type="bibr" rid="ref1 ref2">1, 2</xref>
          ].
        </p>
        <p>
          Many existing hydrological forecasting systems have been operationalized at different spatial
scales: from a basin- to global [
          <xref ref-type="bibr" rid="ref3 ref4">3, 4</xref>
          ]. These systems differ from each other by the type of underlying
hydrological model, meteorological forcing, utilized weather forecast products, and the way of
forecast dissemination [
          <xref ref-type="bibr" rid="ref5">5</xref>
          ]. However, one thing remains common for every system
— the value they
aim to provide for the end-user. That turned out to be more critical during the covid-19 pandemic
when people moved from cities to suburban areas where the proximity to rivers is much closer.
Therefore there is a higher vulnerability to floods.
        </p>
        <p>A long-lasting and still ongoing crisis in Russian hydrometeorology hinders the development of
operational forecasting systems in Russia. It puts the end-users — the country's citizens — out of
focus for decades. Fortunately, available data, technologies, the passion of young researchers, and the</p>
        <p>2021 Copyright for this paper by its authors.
support of the Russian Fund for Basic Research (RFBR) have recently reached the critical mass that
helped shift the situation from the dead point towards the development of the first national-scale
forecasting services.</p>
        <p>
          In the presented study, we want to introduce two national-scale hydrological forecasting systems
— OpenForecast [
          <xref ref-type="bibr" rid="ref6">6</xref>
          ] and OpenLevels [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ] —, which are in operational use for almost two years,
providing timely and reliable discharge and water level forecasts for up to seven days for hundreds of
hydrological gauging stations in Russia.
        </p>
        <p>The paper is organized as follows. In Sect. 2, we describe the components of both developed
systems. Section 3 describes the obtained results for the first year of systems‘ operational use. We
provide an outlook for further directions of research and development in Section 4.</p>
      </sec>
      <sec id="sec-3-2">
        <title>2. Operational services</title>
        <p>
          In the present section, we describe two operational hydrological forecasting services in Russia –
OpenForecast [
          <xref ref-type="bibr" rid="ref6">6</xref>
          ] and OpenLevels [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ]. These services are conceptually different in both underlying
methods and forecasted variables. OpenForecast utilizes meteorological forecasts and hydrological
models to provide runoff forecasts up to seven days at daily temporal resolution. Instead, OpenLevels
uses a machine learning model fed by water level observations to provide water level forecasts up to
seven days at daily temporal resolution. Both services are in operational use since March 2020.
2.1.
        </p>
      </sec>
      <sec id="sec-3-3">
        <title>OpenForecast</title>
        <p>
          The first version of the OpenForecast system was launched in operation in summer 2018 [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. Since
then, many improvements have been incorporated, and the second version has been released in March
2020 [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ]. A detailed description of the second version's operational setup is provided in [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ].
        </p>
        <p>
          OpenForecast disseminates a seven-day-ahead runoff forecast for 834 hydrological stations on
Russian rivers in different geographical conditions across Russia. The system is entirely based on
open data [
          <xref ref-type="bibr" rid="ref10 ref11 ref12">10, 11, 12</xref>
          ] and open-source software [
          <xref ref-type="bibr" rid="ref13 ref14">13, 14</xref>
          ] that ensures transparency and
reproducibility. There are two major computational blocks – offline and online (Figure 1).
        </p>
        <p>
          Offline routines aim to obtain optimal parameters for hydrological models GR4J [
          <xref ref-type="bibr" rid="ref15">15</xref>
          ] and HBV
[16], which underpin runoff calculation. Online routines run daily to update and further disseminate
runoff forecasts.
        </p>
        <p>OpenForecast is hosted on a standard cloud server with 4Gb of RAM and two CPU threads. The
average computational time for the entire system's run from meteorological data update to publication
on the website is 75 min, from which 60 min are used for runoff calculation by hydrological models.
2.2.</p>
      </sec>
      <sec id="sec-3-4">
        <title>OpenLevels</title>
        <p>OpenLevels is an entirely data-driven system that utilizes operational water level observations at
gauging stations and uses a machine-learning model to extrapolate those observations in the imminent
future based on the found trends (Figure 2). Similar to OpenForecast, OpenLevels also uses only open
data and software. The Unified State System of Information website regarding the situation in the
World Ocean (ESIMO) [17] is the provider of operational water level observations. There are more
than 1000 gauges in Russia, observations from which are operationally delivered using ESIMO. We
use the fbprophet model developed by Facebook [18] as an underlying model for time series
forecasting. fbprophet is based on an additive regression model with main components for fitting
trend, different seasonality components, and change points [18]. In this way, fbprophet could be
considered as a simple yet powerful tool for time-series forecasting.</p>
        <p>The standard run of OpenLevels starts from the update of water level observations in the ESIMO
database. Then, for each station, the individual instance of the fbprophet model is fitted based on the
entire time series of obtained observations. After that, individual model instances run in the
forecasting model to provide expected predictions in the imminent future for up to seven days and
their uncertainty estimates.</p>
        <p>OpenLevels is hosted on the same server as OpenForecast. However, their computational routines
are separated in time so as not to overlap each other. The average computational time for the entire
run of the system is 135 min, from which 120 min are used for model fitting.</p>
      </sec>
      <sec id="sec-3-5">
        <title>3. Results</title>
        <p>The evaluation of OpenForecast and OpenLevels predictive efficiencies has been performed using
ESIMO data of observed water levels [17]. The evaluation period is from March 2020 to May 2021
and covers all phases of the water regime for investigated river basins (gauges). It should be
mentioned that ESIMO data do not undergo quality control and experience long periods during which
the data does not enter the system. In this way, we have performed evaluation exercise only for basins
where more than a full year of data (at least 365 values) is presented. Also, water level observations
have not been available for many basins presented in the OpenForecast system. In this way, the
number of basins used for evaluation is 394 for OpenForecast (Figure 2) and 1017 for OpenLevels
(Figure 3). We used the Pearson correlation coefficient as a significant evaluation metric. For the sake
of brevity, we have calculated the correlation coefficient between forecast and observed values of
runoff (or water level) only for the longest lead time of 7 days. That informs us about the lower
envelope of the prediction efficiency as efficiency decreases with lead time.</p>
        <p>Figure 3 shows the spatial distribution of the correlation coefficient calculated for OpenForecast's
runoff forecast and water level observations for a lead time of 7 days. The median efficiency in terms
of the correlation coefficient is 0.83 with the interquartile range of 0.21 (0.69 and 0.9 for the 25th and
75th quantiles, respectively). In this way, OpenForecast shows a solid performance for the majority of
the analyzed basins in Russia. The most pronounceable deterioration of OpenForecast efficiency is
related to the lower reaches of the Kama river. However, it could be considered an outlier because we
have abnormally high rates of river runoff for five gauges located there. We need to conduct an
additional investigation to reveal possible causes of such behavior.</p>
        <p>During the last year, OpenForecast service has been actively used to inform Russian citizens about
the current and expected short-term changes in runoff. Furthermore, local hydrometeorological
agencies and municipal authorities used OpenForecast results to guide early warning and decision
making. In this way, OpenForecast provided a total value for society.</p>
        <p>In contrast to OpenForecast, OpenLevels service has not been extensively promoted in social
media due to its premature, proof-of-concept status. However, the results of the preliminary
evaluation of its predictive efficiency (Figure 4) show that the machine learning-based fbprophet
model provides reliable data-driven water level forecasts.</p>
        <p>The noticeable difference between OpenForecast and OpenLevels performances has an obvious
explanation. OpenForecast does not use any operationally obtained data for utilization in its
computational workflow. Instead, OpenLevels always assimilates the most recent observations from
the hydrological gauging network to fit up-to-date models. In this respect, OpenLevels substantially
benefits from that kind of data assimilation. However, there are many strategies for incorporating data
assimilation routines into OpenForecast's workflow that may lead to a vivid boost of predictive
efficiency.</p>
      </sec>
      <sec id="sec-3-6">
        <title>4. Conclusions and Outlook</title>
        <p>The presented study aims to provide the preliminary results of the one-year-long evaluation of
national-scale operational forecasting services in Russia — OpenForecast, and OpenLevels. Results
show that both services provide efficient and reliable short-term forecasts of runoff (Figure 3) and
water level (Figure 4). Furthermore, the introduced services are entirely based on open data and
software (Figures 1, 2) that ensure transparency and reproducibility. Both OpenForecast and
OpenLevels services are freely available on the Internet and could be accessed 24/7. Our services
have been actively used to inform every interested person or organization about the current and
expected short-term changes on Russian rivers. Local hydrometeorological agencies and municipal
authorities have used forecasts to guide decision-making and early warning alerts. We hope to
increase further the value of our services for any interested party.</p>
        <p>It should be mentioned that the development of these first national-scale hydrological forecasting
services in Russia would not happen without hydrological data that has been carefully obtained,
processed, stored, and openly distributed by the Russian Federal Service for Hydrometeorology and
Environmental Monitoring.</p>
        <p>Experience that has been accumulated during the continuous operational run of the introduced
forecasting services provides a solid set of possible improvements that have a high potential to boost
services' efficiency, reliability, and value. Among them are operational quality-control of
observations, sub-daily predictions, utilization of emerging deep learning models for runoff prediction
and forecasting [19], data assimilation, utilization of commercial yet open for research data from
regional providers [20]. All these would require a critical build-up of computing resources and
increasing their reliability.</p>
        <p>We are looking forward to further fostering the collaboration with experts in the field of computer
sciences and high-performance computing to ensure the robust development of OpenForecast and
OpenLevels services.</p>
      </sec>
      <sec id="sec-3-7">
        <title>5. Acknowledgments</title>
        <p>The present study was funded by the Russian Foundation for Basic Research (RFBR), project no.
19-05-00087 A.</p>
        <p>The studies were carried out using the resources of the Center for Shared Use of Scientific
Equipment "Center for Processing and Storage of Scientific Data of the Far Eastern Branch of the
Russian Academy of Sciences", funded by the Russian Federation represented by the Ministry of
Science and Higher Education of the Russian Federation under project No. 075-15-2021-663.</p>
      </sec>
      <sec id="sec-3-8">
        <title>6. References</title>
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