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\begin{document}

\title{Hydrological classification of non-perennial Mediterranean rivers and
streams: a new insight for their management within the WFD}



\author[1]{Juan Diego Alcaraz-Hernández}%
\author[1]{Joaquín Soler}%
\author[1]{Gabriel Mezger}%
\author[1]{Alfredo Corrochano Codorníu}%
\author[2]{Belén Calleja Arriero}%
\author[2]{Fernando Magdaleno}%
\affil[1]{TRAGSATEC Group}%
\affil[2]{Espana Ministerio para la Transicion Ecologica y el Reto Demografico}%


\vspace{-1em}



  
  \date{June 15, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Classification of natural flow regimes of non-perennial rivers and
streams (NPRS) is an incipient field of research. NPRS represent
approximately 70\% of the total Mediterranean rivers and are expected to
increase in the next decades as a result of climate change. Due to the
ecological importance of NPRS and the need to improve national
ecological assessment methods within the scope of the Water Framework
Directive (WFD), this paper aims to classify the hydrological regime of
69 non-regulated streams, testing several hydrological indices related
to the frequency, duration, timing, and rate of change in periods of
flow cessation. Using daily flow records, a total of 315 indices were
calculated and their relationships were examined with Principal
Component Analysis (PCA) for different thresholds used to define
zero-flow condition set at 0, 1, 2, and 5 l/s. Redundancy analysis
identified five indices that better describe the patterns of
hydrological variability in Mediterranean NPRS: number of days per year
without flow, annual percentage of months without flow, mean daily of
annual flows, coefficient of variation of Julian date of the annual
start of zero flow and annual rise rate. Using these indices, a
self-organizing map (SOM) was trained in order to categorize the NPRS
into three groups with similar hydrological features. The results of
this study provide a statistically-based hydrological classification of
NPRS in Mediterranean environments. We expect that this classification
will provide useful insights to water authorities to improve the
assessments of the ecological status in this set of water bodies.%
\end{abstract}%



\sloppy


\textbf{Hydrological classification of non-perennial Mediterranean
rivers and streams: a new insight for their management within the WFD}

Juan Diego Alcaraz-Hern\selectlanguage{ngerman}ández\textsuperscript{1}, Joaquín
Soler\textsuperscript{1}, Gabriel Mezger\textsuperscript{1}, Alfredo
Corrochano Codorníu\textsuperscript{1}, Belén Calleja
Arriero\textsuperscript{2}, Fernando Magdaleno\textsuperscript{2}.

\textsuperscript{1} TRAGSATEC Group, C/Julián Camarillo, 6B, 28037
Madrid, Spain.

\textsuperscript{2}Water Directorate, Ministry for the Ecological
Transition and the Demographic Challenge, Plaza San Juan de la Cruz, 10,
28071 Madrid, Spain.

\textbf{Short title}

Hydrological classification of non-perennial Mediterranean rivers and
streams

\textbf{Correspondence}

Juan Diego Alcaraz-Hernández, Tragsatec, C/ Músico José Alcaraz Pérez
71, Alicante, 03008, Spain.

Email: \emph{jdalcaraz@gmail.com};\emph{jalcara2@tragsa.es}

\textbf{Funding information}

Ministry for the Ecological Transition and the Demographic Challenge.
Grant/Award Number: 21.834-060/0411

\textbf{Acknowledgements}

This research is based on project ``Monitoring the effect of the
ecological regime of flows established by the river basin management
plans on the water bodies (21.834-060/0411)'' provided by The Spanish
Ministry for the Ecological Transition and the Demographic Challenge
(MITECO) - DG Water. We also thank Rafael Muñoz-Mas for his help with
the methodology and graphics.

\textbf{Abstract}

Classification of natural flow regimes of non-perennial rivers and
streams (NPRS) is an incipient field of research. NPRS represent
approximately 70\% of the total Mediterranean rivers and are expected to
increase in the next decades as a result of climate change. Due to the
ecological importance of NPRS and the need to improve national
ecological assessment methods within the scope of the Water Framework
Directive (WFD), this paper aims to classify the hydrological regime of
69 non-regulated streams, testing several hydrological indices related
to the frequency, duration, timing, and rate of change in periods of
flow cessation. Using daily flow records, a total of 315 indices were
calculated and their relationships were examined with Principal
Component Analysis (PCA) for different thresholds used to define
zero-flow condition set at 0, 1, 2, and 5 l/s. Redundancy analysis
identified five indices that better describe the patterns of
hydrological variability in Mediterranean NPRS: number of days per year
without flow, annual percentage of months without flow, mean daily of
annual flows, coefficient of variation of Julian date of the annual
start of zero flow and annual rise rate. Using these indices, a
self-organizing map (SOM) was trained in order to categorize the NPRS
into three groups with similar hydrological features. The results of
this study provide a statistically-based hydrological classification of
NPRS in Mediterranean environments. We expect that this classification
will provide useful insights to water authorities to improve the
assessments of the ecological status in this set of water bodies.

\textbf{Keywords}

Non-perennial rivers and streams, intermittent rivers and ephemeral
streams, IRES, hydrological classification, Mediterranean region, SOM.

\textbf{Practitioner Points}

\begin{itemize}
\tightlist
\item
  Natural flow regimes of non-perennial Mediterranean rivers and streams
  (NPRS) are classified using hydrological indices related to their
  frequency, duration, timing, and rate of change in periods of flow
  cessation
\item
  Five indices describe the patterns of hydrological variability in
  Mediterranean NPRS: number of days per year without flow, annual
  percentage of months without flow, mean daily of annual flows,
  coefficient of variation of Julian date of the annual start of zero
  flow and annual rise rate
\item
  Self-organizing map (SOM) categorize the NPRS into three groups with
  similar hydrological features. This classification is compared with
  others existing within the European Union. The similarities and
  differences are discussed to provide useful information for the
  development of specific assessment and management tools within the
  scope of the WFD
\end{itemize}

\textbf{1. Introduction}

Depending on the occurrence of flow or no flow periods of the natural
flow regime, rivers could be classified into perennial or non-perennial.
Although many terminologies have been used over time subject to research
fields (e.g., arid, discontinuous, dry, ephemeral, episodic,
intermittent, interrupted, irregular, non-permanent, seasonal, or
temporary rivers), the term ``non-perennial rivers and streams''
(hereafter NPRS) refers to watercourses that cease to flow at the same
point in time or space. Their defining characteristic is a temporary
lack of surface flow, which leads to isolated pools or dry channels .

According to some estimates, these water bodies comprise at least 41\%
of the length of the global fluvial network . This percentage would
increase in some regions of Africa, America, Australia, and Europe ,
depending on regional factors and local characteristics . Such is the
case of the Mediterranean region, which includes temperate, semiarid or
arid climates, where NPRS could represent 69\% of the total length of
the river network . This is because they are concentrated in the upper
reaches of the basins with small drainage areas and steep slopes leading
to a rapid delivery of water to the river channel, causing a lack of
buffering from variations in precipitation . Considering that the future
effects of global change (such as climatic and land use changes,
impoundments, and increasing human water demands) are expected to be
particularly severe in these freshwater ecosystems, the length and
number of NPRS in the Mediterranean region is expected to increase over
the next decades . As a consequence, non-perennial rivers have
progressively received wider interest by water resource managers and the
scientific community .

Recent studies in NPRS have advanced in characterizing geomorphological
processes , biological communities , water quality , biogeochemical
fluxes , status assessment and river management . All these studies
highlight the importance of the different flow regime patterns
(including the specific duration of the wet and dry phases) for biota
and environmental processes in non-perennial freshwater systems. This is
more evident in Mediterranean climate regions, as they are shaped by
predictable seasonal events of \selectlanguage{english}flooding and drying over an annual cycle,
with a strong inter- and intra-annual \selectlanguage{english}flow variation . The variability in
the flow regime takes on a wide range of possibilities in terms of
duration, frequency, and timing of the zero-flow periods, and rates of
change between flowing and non-flowing conditions . The structure and
functioning of each NPRS is historically adapted to the specific
non-perennial flow patterns, which act as a major driver of their
ecomorphological dynamics . The particular features of the components of
non-perennial flow regimes also affect the human uses linked to the
NPRS, enhancing a variety of socio-ecological non-perennial river
systems, under distinctive biophysical contexts . Thus, ecological
assessment methods of NPRS to evaluate the current status and historical
trajectory of non-perennial freshwater systems require an advanced
understanding of the flow-ecology responses . An improved understanding
of the interaction among human uses, pressures, impacts, and responses
of NPRS, could provide new insights into the most beneficial actions
that should be selected to optimize management approaches to them .
Indeed, developing knowledge about the dynamics that characterize this
type of freshwater ecosystems could help change and improve the
perception and attitudes of society towards NPRS . Both the ecological
and the societal approaches to study different aspects of NPRS, require
further interpretation of the hydrological gradients which characterize
such systems. In this line, improving mechanisms to classify natural
flow temporality would lead to better-informed management decisions
about the NPRS.

The European water policy has been developed by the Water Framework
Directive . The WFD states that, in order to evaluate the ecological
status, the reference conditions for each type of water body have to be
formerly defined. Subsequently, different biological quality elements
(e.g. biological indices based on benthic macroinvertebrates
assemblages, aquatic flora, and fish fauna) are compared with the
reference conditions to establish the ecological status of the water
body . However, there are limitations in the implementation of WFD in
NPRS, as described by : (1) the establishment of a water body in the
case of NPRS (a river stretch to be included in the river basin
management plans) could be omitted due to their small catchment area or
their limited annual discharge, and (2) the classification of river
typologies considering the hydrological variability of NPRS is obviated
due to the scarcity of hydrological data sets characterizing natural
flow conditions. The aforementioned challenges have limited the capacity
of EU member states to define both legally and technically non-perennial
river typologies.

In the case of Italy or Spain, representative examples of Mediterranean
climate conditions, despite the relative wide proportion of
non-perennial rivers in their drainage network, there are no official
studies aimed at classifying temporary flow patterns . In these
countries, water authorities have used time thresholds (e.g., average
number of days or months with no-flow), approved by legislation , to
distinguish between temporary, intermittent, ephemeral and episodic
river waterbodies. These thresholds were proposed based on initial
assessments of flowing periods, on expert judgement or on external
references instead of systematic analyses of continuous non-perennial
flow gradients that could drive to statistically-based typologies (e.g.,
. Thus, the classification approach currently used by water managers
faces several uncertainties. First, the best potential threshold to
define the no-flow condition. Second, the suitability of defining
specific non-perennial flow classes. Finally, the connection of types of
non-perennial flows with ecological assessment methods for the
optimization of restoration measures to mitigate the negative impacts
derived from human activities.

In order to bridge the existing gaps in ecological assessment tools for
NPRS, the ECOSTAT working group of the European Commission is currently
working on a common standpoint to characterize, evaluate, manage, and
monitor NPRS . With the purpose of developing a common method to analyse
the ecological status of NPRS in the EU, research projects such as
MIRAGE (https://cordis.europa.eu/project/id/211732), GLOBAQUIA
(http://www.globaqua-project.eu/), LIFE+ TRivers
(http://www.lifetrivers.eu/), and SMIRES (https://www.smires.eu/) have
recently provided new insights into the functioning of this type of
freshwater ecosystems. MIRAGE project started, for the first time, the
study of temporal responses of rivers to hydrological, biogeochemical,
and sediment transport events for the implementation of the WFD and
specific management under the characteristics of flooding and drought of
temporary streams. GLOBAQUA is an EU-funded project aiming to identify
the prevalence and interaction between stressors under water scarcity,
in order to improve water management practices and policies in rivers,
including NPRS. The LIFE+ TRivers project provided the European river
basin authorities a software (TREHS) to evaluate temporary river regimes
as a first step for their ecological status assessment defined by the
WFD in the NPRS. Finally, the SMIRES project was a COST Action that
established a multidisciplinary network of scientists and experts from
32 countries, to consolidate and expand knowledge on NPRS and translate
it into sustainable and science-based management of NPRS resources and
biodiversity.

Stemming from these efforts, this study aims at providing a
statistically-based classification of non-perennial flow patterns in
rivers and streams of the Western European Mediterranean region. This
region offers an interesting test bed for this analysis for at least two
reasons. First, due to the relative abundance of dryland areas and NPRS.
Second, due to the lack of homogeneous criteria for their hydrological
classification. Specifically, this study assesses natural flow patterns
of unaltered non-perennial rivers focusing on hydrological metrics
related to the frequency, duration, timing, and rate of change in
periods of flow cessation. We hypothesized that non-perennial
Mediterranean rivers and streams can be classified according to a few
hydrological attributes since many of them are redundant in reflecting
inter- and intra-annual flow variability . We also hypothesized that
there is a similar relationship among different thresholds to define
zero-flow conditions (0, 1, 2, and 5 l/s). Linked to previous efforts in
the UE to characterize ecological conditions of NPRS, we expect that the
hydrological classification obtained in this study will provide useful
insights to water authorities to improve the assessment of the
ecological status in this set of water bodies.

\textbf{2. Material and methods}

\emph{2.1. Study area}

The study area includes 69 rivers from 15 basins located in southern
France, Spain, and Portugal covering most of the western part of the
European Mediterranean region (Fig. 1). Briefly, rivers of France are
located on 4 temporary tributaries of the Rhone-Mediterranean basin
district, very close to the Mediterranean Sea. In Spain, we studied 44
rivers, of which 16 are located in river basin districts that flow into
the Mediterranean Sea (Catalonian, Ebro, Jucar, Segura and Andalusian
Mediterranean basins) and 28 into the Atlantic Ocean (Tagus, Guadiana,
Guadalquivir, Guadalete and Barbate basins). The 21 stations of Portugal
drain into the Atlantic Ocean and belong to Guadiana, Algarve, Sado,
Mira, Vouga, Mondego, Lis, Douro, Cavado, Ave and Leca river basin
districts.

In natural conditions, all the rivers in these basins present a
Mediterranean flow regime pattern, which implies two alternate periods:
a high-flow period during the wet season (i.e. autumn to winter) and a
low-flow period during the dry season (i.e. late spring and summer).
However, the basins under study cover a large geographical area
representing a wide gradient of climatic, topographic and geologic
conditions which imply notable differences in hydrological regimes. The
climate is mostly temperate although there are stations located in
semi-arid regions of southern Spain. According to the Koppen-Geiger
classification, the studied NPRS are matched with hot (Csa), warm (Csb),
or cool (Csc) summer Mediterranean climate, and hot (BSh) or cold (BSk)
semi-arid climate . Although the climate has a common pattern with mild
and wet winters, and dry, hot, or cold summers, there are differences in
the range of precipitation and temperature. The land use in the studied
basins is dominated by agriculture, originated by the use of human
society on the natural environment . The rivers and its stream
tributaries are heavily regulated by the construction of dams and weirs,
which have substantially altered the natural flow regime also reducing
the number of unaltered gauging stations with flow data records .

(Here Fig. 1)

2.2. \emph{Hydrologic data}

We used daily flow records from gauging stations in NPRS minimally
impacted by human activities. Due to the lack unaltered stations with
adequate data in Mediterranean NPRS , we assumed that most of them
contained missing data (Table A1). The selection of NPRS in almost
natural conditions implied avoiding hydrological alteration, deviation,
or cessation of water due to transverse barriers (large dams or smaller
weirs) located upstream. Data records were obtained from different
sources. In Spain, they were obtained from the national database of
public gauging stations of CEDEX (Centre for Hydrographic Studies;
https://ceh.cedex.es/), or from the corresponding River Basin Authority.
For this purpose, we first identified gauging stations without altered
flow conditions using the national inventory of barriers on
non-perennial rivers (available at https://sig.mapama.gob.es/geoportal).
In France and Portugal, stations were obtained from SMIRES project
database (https://www.smires.eu/). To identify those gauging stations in
NPRS near to natural conditions, we used the AMBER barrier Atlas
(https://amber.international/european) and hydrological pressures
collected in the European WISE database
(\emph{www.eea.europa.eu/data-and-maps/data/wise-wfd-4}). The Supporting
Information of Table A1 expands the information about the stations such
as river basin where are located, country, coordinates, gauging station
code, the length of the data period, the number of days of the data
series and the number of days with missing data.

Gauging stations with more than 15 years of daily flow records were
used, except one with 11 years in the Tagus basin in Portugal (Table
A1). The median length of the data period was 36 years (IQR=26-43
years). All the series were validated for the calculation of zero-flow
hydrological indices with \emph{smires} package
(https://github.com/mundl/smires). For each station we calculated a set
of 315 hydrological indices that have been previously referred in other
studies focused on perennial rivers (Eng et al., 2017; Olden and Poff,
2003), drought events in NPRS (Costigan et al., 2017; Delso et al.,
2017) and low river flows (Henriksen et al., 2006; Kennard et al.,
2010). Following Richter et al. (1996), the indices were classified into
\selectlanguage{english}five groups characterizing hydrological conditions related to: (i)
magnitude, (ii) frequency, (iii) duration, (iv) timing, and (v) rate of
change of flow or drought events. A list of the calculated indices and
their main characteristics is shown in Appendix B.

Finally, the hydrological indices were encoded for calculation with
the\emph{R} programming language . We used the \emph{lfstat} package to
calculate the number and duration of zero flow events.
The\emph{hydrostats} package was used for calculating the Colwell's
index of predictability and seasonality , and the rate of change in the
magnitude of the flow and the asymmetry (skewness) of the hydrological
series. In order to calculate the indices, three conditions were
adopted. First, all years of the series have been used, even those with
incomplete records. Second, the hydrological year was set at the
beginning of the Julian calendar year. Third, we defined different
thresholds to define the days without daily flow at 0, 1, 2, and 5 l/s.
This is due to false positives of null flows associated with the
restrictions and uncertainties of the measurement of days without flow
in gauging stations of NPRS .

2.3. \emph{Hydrologic classification for non-perennial Mediterranean
rivers and streams}

We used principal component analysis (PCA), an unsupervised learning
statistical technique, to examine the relationships between the
hydrological indices. Given the strong correlation between hydrological
indices , we also utilized PCA to reduce the dimensionality by selecting
prominent metrics for each attribute . Correlation matrices were used to
equalize the contribution of the indices to the PCA regardless of the
scale . Following the PCA analysis, we selected indices with the highest
loading coefficient (in absolute terms) associated to the five first
components that accounted for approximately 70\% of the total inertia
for each of the zero-flow thresholds . Specifically, we reduce by more
than half the hydrological indices with the loading coefficient, but it
was not enough to choose the indices of each attribute that best define
the hydrological pattern of NPRS and respond to the diversity of
Mediterranean temporary flows. Thus, we decided to select one index for
each attribute (magnitude, frequency, duration, timing, and rate of
change) based on expert criteria and supported by statistical analysis.
Here, we used both the repetition of the indices at each threshold with
the highest loading coefficient associated (in absolute terms) to the
first five PCA dimensions and hierarchical clusters based on the
correlation distance for each group of selected indices with PCA of each
attribute (Appendix C). PCAs and clusters were executed with
the\emph{FactoMineR} package .

Self-Organizing Maps (SOM) were used to classify temporal rivers into
hydrological types according to similarities with the selected indices.
SOM is an unsupervised machine learning technique that uses an
artificial neural network to reduce multidimensional data into
two-dimensional nodes heatmap. This is an interactive process that
assigns a weight to each node on the map where the minimum similarity
distance is chosen and the neighbourhood of the nodes is established. We
followed the rule proposed by to determine the optimal dimension of the
number of nodes in the map. The nodes must be close to 5\selectlanguage{english}[?]n where n is
the number of samples analysed (in this study n=345). Consequently, our
map should have approximately 93 nodes distributed by a layer of 9 rows
x 10 columns. Additionally, we also evaluated the quality of the maps by
means of quantization and topographic error of different layers (from 2
x 2 to 10 x 10). To identify clusters on the SOM output map and draw the
boundaries, we applied a hierarchical cluster. The optimal number of
clusters for a SOM output was determined using \emph{NbClust} package in
R , whereas SOM analysis and its graphical representation were generated
with the \emph{Kohonen} package .

2.4\emph{. Comparing methods for Mediterranean non-perennial rivers and
streams classification}

Finally, we compared the relationship of our results with three other
hydrological classifications developed for Mediterranean rivers.
Firstly, we used the classification of the Ministerial Order for
Hydrological Planning of the Spanish legislation that classifies rivers
into four categories depending on the number of days with presence of
water throughout the year: (i) permanent river courses if water flows
every day of the year, (ii) temporal river courses with presence of
water during an average period of 300 days per year, (iii) intermittent
with water flowing between 100 and 300 days per year, and (iv) ephemeral
flowing less than 100 days per year. Secondly, we classified rivers
following the Italian legislation depending on the number of months with
presence of water in: (i) temporal river courses without presence of
water for at least 2 of the last 5 years, (ii) intermittent with more
than 8 months with water, (iii) ephemeral with less than 8 months with
water, and (iv) episodic with water only after heavy precipitation
events. Last, we applied the classification developed by LIFE+ TRivers
project to evaluate the hydrological flow regime in NPRS according to
the aquatic phase on biological communities . This classification is
provided by TREHS free software tool and comprises four aquatic regime
types or hydrotypes classification: permanent or perennial,
intermittent-pools, intermittent-dry, and episodic or ephemeral. To
carry out the comparison between the different classifications, we
conducted an alluvial plot with \emph{ggalluvial} and
\emph{circlize}package.

\textbf{3. Results}

\emph{3.1. Redundancy index analysis}

A total of 315 hydrological indices of magnitude, frequency, duration,
timing, and rate of change have been calculated which characterize the
hydrological series in NPRS for different periods of the year (Table
A3). The PCA showed an inertia ranging between 36.2 and 38.0\% for the
first axis and between 16.3 and 16.9\% for the second (Fig. 2), reaching
approximately 70\% when grouping the first five components for the
thresholds of 0, 1, 2, and 5 l/s. Results revealed multiple linear
correlations between indices. It is also noted that the indices of
frequency and duration of zero flow had a positive correlation with the
first axis, while flow magnitude had a positive correlation association
with the second (Fig. 2).

(Here Fig. 2)

Additionally, the first indices with the highest loading coefficient
associated with the first, second and third dimensions were frequently
the same, only changing for the fourth and fifth dimensions for the
different thresholds (Table C1). Consequently, only 171 indices were
selected for the redundancy index analysis based on clusters with
correlation distance between hydrological indices within the same
attribute (magnitude, frequency, duration, timing and rate of change) in
different thresholds (Table C1 and Fig. C2 to Fig. C7). As a result of
the dimensionality reduction and the redundancy analysis, five
hydrologic indices were selected: number of days per year without flow
(DU035), annual percentage of months without flow (FE052), mean daily
annual flows (MA001), CV of Julian date of the annual start of zero flow
(TI002) and annual rise rate (RC001) (Table 1).

(Here Table 1)

\emph{3.2. Hydrologic classification for non-perennial Mediterranean
rivers and streams}

The optimized SOM with minor quantization and topographic errors
included a grid of 3 x 8 nodes. Fig. 3 shows maps gradually distributed
according to the five selected hydrological indices, thus the gauging
stations with similar characteristics are located into the same node and
remain close to other neighbourhood nodes in a two-dimensional heatmap.
As a consequence of applying the cluster classification, the maps show
two boundaries that divide the maps into three zones, grouping the
stations into three clusters (I, II and III). For example, gauging
stations with high values of number of days per year without flow are
shown in yellow and located in the lower part of the map, while low
values are represented in blue in the upper part of the map. The same
occurs with the annual percentage of months without flow and coefficient
of variation of Julian date of annual start of zero flow. In contrast,
gauging station with low values of the mean daily annual flow are
located in the upper area of the map.

(Here Fig. 3)

With regard to cluster classification, Fig. 4 represents the groups
obtained by training a SOM with the five selected variables whereas
table 2 shows the main characteristics of each cluster. Cluster I is
composed of gauging stations with high values of number of days per year
without flow (231.45 +- 97.07 days/year, see Fig. 4 and Table 2), annual
percentage of months without flow (76.87 +- 23.52\%), CV of Julian date
of annual start of zero flow (2.23 +- 0.92), and annual rise rate (3.69 +-
6.19 l/day). It also included rivers with low values of mean daily
annual flow (0.53 +- 0.70 l/day). Cluster II is an intermediate group
between the other two clusters. It displayed mean values between 144.14
+- 54.40 days/year for the number of days per year without flow and 47.32
+- 15.23\% for the annual percentage of months without flow. It also
exhibited values of 0.72 +- 0.65 l/day for mean daily annual flow, 0.63 +-
0.27 for CV of Julian date of the annual start of zero flow, and 2.00 +-
1.98 l/day to annual rise rate. In contrast, cluster III included rivers
with low values of number of days per year without flow (24.57 +- 25.68
days/year), annual percentage of months without flow (11.25 +- 10.09\%),
Julian date of annual zero flow (0.25 +- 0.17), and annual rise rate
(1.35 +- 1.72 l/day), but with high values of mean daily annual flow
(2.06 +- 3.80 l/day).

(Here Table 2)

(Here Fig. 4)

\emph{3.3. Comparison of classifications for Mediterranean non-perennial
rivers and streams}

The alluvial diagram for Mediterranean NPRS reveals differences between
MATTM, IPH and LIFE+ TRivers hydrotypes classifications and the three
clusters obtained in this study (Fig. 5). Cluster I is represented by
9\% of the stations, compared to 41\% in cluster II and 51\% in cluster
III regarding our SOM classification. Using the MATTM classification,
most stations are intermittent rivers (87\%), followed by ephemeral
(10\%) and episodic (3\%). Using the IPH classification, most are
temporal (62\%), followed by intermittent (35\%) and ephemeral (3\%).
Applying the hydrotypes of the LIFE+ TRivers project, 19\% of the
stations are of episodic type, 1\% of intermittent-dry, 61\% of
intermittent-pools, and 19\% of perennial.

(Here Fig. 5)

Additionally, figure 6 shows the relationships between the categories of
the different classifications. Cluster I is composed of equal parts
(33\%) of ephemeral, episodic and intermittent rivers, cluster II by
ephemeral (18\%) and intermittent (82\%) and cluster III only by
intermittent (100\%) in MATTM classification. Similarly, cluster I is
represented by ephemeral (33\%), intermittent (50\%), and temporal
(17\%); cluster II by intermittent (75\%), and temporal (25\%) and
cluster III only by temporal (100\%) rivers in the IPH classification.
Besides, cluster I is mainly represented by episodic hydrotypes (33\%),
intermittent-dry (17\%), and intermittent-pools (50\%), cluster II by
episodic (25\%), intermittent-pools (71\%), and perennial (4\%), and
cluster III by episodic, intermittent-pools, and perennial (11, 54, and
34\%, respectively). Also, 100\% of episodic and ephemeral rivers on
MATTM are ephemeral and intermittent rivers on IPH, respectively. In
contrast intermittent rivers of the MATTM are intermittent (29\%) or
temporal (71\%) in IPH classification. Moreover, 100\% of the episodic
type of MATTM are also episodic of hydrotype classification, but varies
for the rest of the types due to the ephemeral rivers on MATTM may be
episodic (29\%), intermittent-dry (14\%) or intermittent-pools (57\%)
and intermittent rivers on MATTM may be episodic (15\%),
intermittent-pools (63\%) or perennial rivers (22\%). Finally, 100\% of
the ephemeral type of IPH is also episodic of hydrotypes TRivers
classification. However, intermittent types are 25\% episodic-type, 4\%
intermittent-dry, 70\% intermittent-pools versus temporal types that are
12\% episodic-type, 58\% intermittent-pools, and 30\% perennial.

(Here Fig. 6)

\textbf{4. Discussion}

Hydrological classification is a fundamental tool for the ecological
status assessment of WFD by water managers. The main objective of this
study was to develop a classification with relevant hydrological indices
in order to categorize non-perennial rivers and streams (NPRS) of the
western Mediterranean region. Using unaltered streamflow data, our
analysis suggest that the natural flow regimes of NPRS can be
characterized through the selection of a few indices from a wide set of
attributes of duration, frequency, magnitude, seasonality, and rate of
change of periods of flow cessation . The results highlighted the strong
correlation between variables for the different thresholds used to
define zero-flow condition set at 0, 1, 2, and 5 l/s. This means that
some variables of a few attributes could envelope the inertia of NPRS
flow diversity and be used to classify them. Our analysis of
hierarchical clusters (based on the correlation distance matrix of the
same attribute) and the repetition of indices at each principal
component (for the different thresholds) allowed us to select 5 relevant
metrics of different hydrological attributes, such as number of days per
year without flow (duration), annual percentage of months without flow
(frequency), mean daily annual flows (magnitude), coefficient of
variation of Julian date of the annual start of zero flow (timing) and
annual rise rate (rate of change). Our SOM classification, developed
from a set of 69 gauging stations and the selected 5 hydrological
indices, showed three groups associated with the temporality of the flow
cessation. However, beyond this hydrological characterization of
temporality patterns, there is incomplete development of river typology
in the context of WFD to evaluate the relationship between hydrology of
NPRS and ecology of biological communities, and there is a need to
improve tools to evaluate their ecological status, and integrate the
establishment of measures into national legislation. Below, we briefly
summarize the methodological considerations of the classification and
its relevance to the NPRS management. We also compare it with other
existing classifications to analyse further research needs.

\emph{4.1. Methodological considerations}

As hypothesized, we observed high correlations among the 315 calculated
indices. This was particularly evident between metrics that describe
duration and frequency and those related to magnitude (Fig.2). This
result is not surprising considering the high redundancy and
multicollinearity among hydrological variables . As a consequence,
statistical techniques for selecting a reduced set of non-redundant
indices are necessary to represent the hydrological gradients . In our
study, we first selected 171 indices with the highest loading
coefficient associated with the first dimension of the PCA (Table C1),
and many of them were also correlated (Figs.AC1-AC7). Similar processes
to reduce the number of indices have been reported in previous studies
for hydrological classifications (e.g., . Considering that PCA analyses
provided many indexes for each attribute, we refined the selection using
cluster analysis and repetition of metrics in the first 5 dimensions of
PCA. However, these results need to be interpreted with caution, since
we prioritized the selection of annual indices, such as number of days
or percentage of months without flow per year, mean daily of annual
flows, coefficient of variation of Julian date of the annual start of
zero flow and annual rise rate.

As also hypothesized, our results indicate that the PCA and the
correlations between the indices are analogous for all thresholds 0, 1,
2, and 5 l/s to define zero-flow conditions. Similar results were
obtained by , who found no significant change in zero-flow indices for
thresholds of 1, 2 and 5 l/s. However, they found that upper thresholds
(i.e. 10 l/s) were not suitable for characterizing periods of low flow.
They applied different thresholds considering that river gauge stations
may have different measuring tools and some thresholds may not be
ecologically relevant. In fact, described the causes of zero-flow stream
gauge measures and their consequences (e.g., ecological status,
statistical classification, or hydrological modelling) for understanding
hydrology, biochemical, and ecological processes in NPRS.

We found that number of days per year without flow and annual percentage
of months without flow (identified in the first dimension of the PCA)
contain the greatest degree of variation for all the thresholds used to
define zero flow conditions (Table 1). These metrics, related to
duration and frequency attributes, express stream drying events and are
common to describe the flow temporality . They indicate the
unavailability of water during the dry phase and act as an environmental
bottleneck for species of these ecosystems . Furthermore, indices of
magnitude were found mainly in the second dimension of the PCA. Mean
daily annual flows is repeated in all the zero-flow thresholds and has
been reported as a major variable for hydrological characterization in
perennial rivers . Surprisingly, we found that timing and rate of change
attributes were identified in subsequent PCA dimensions; CV of Julian
date of the annual start of zero flow in the third dimension and annual
rise rate only in the fifth, both described by . Taken together, these
results suggest that duration, frequency and magnitude indices (mostly
selected in the first and second components) are more important than
timing and rate of change indices (selected from the third component).
These findings indicate that these attributes were best at predicting
the temporal variability on the flows; duration and frequency in the dry
phase and magnitude in the wet, reinforcing the importance of these two
phases for the structure and composition of the aquatic fauna . However,
in this study we have retained at least one metric for each of the five
attributes for a better characterization of the variability of the NPRS,
both in dry and wet periods, and to facilitate comparison with other
available classifications.

\emph{4.2. Typology for Mediterranean non-perennial rivers and streams.}

In this study, we considered only hydrological indices to categorize
Mediterranean NPRS based on statistical criteria. The patterns described
by the SOM classification suggest the existence of three groups
(clusters I, II, and III) that reflect the interaction between ranges of
the five attributes values (Fig.3 and 4, Table2). As expected, cluster I
encompasses rivers almost dry during the year with many days and months
without flow (usually with an onset of the dry phase in the first months
of the year), with low daily flows and high annual rise rate. The
cluster II lies between dry rivers (cluster I) and rivers with flows
occasionally interrupted by drought (cluster III) with fewer days and
months with zero-flow and with combinations of high flows. Our results
indicate that the number of days and the percentage of months per year
without flow are the most valuable attributes for Mediterranean NPRS
classification, since they form well-defined groups. Similarly, CV of
Julian date of annual start of zero flow has three compact and
differentiated groups, due to that in rivers with no flow during most of
the year, the dry periods tend to occur earlier . Conversely, the
metrics of mean daily annual flows and annual rise rate (Fig.4) showed
less variability, suggesting a lower discrimination capacity, a
relationship that has also been shown in other studies .

Similarly to other studies , we included the number of zero-flow days to
categorize NPRS. suggests a clear relationship between the duration and
frequency of cessation periods for different ecotypes of the Guadiana
basin, and other authors classified the NPRS according to the number of
days of the dry riverbed as intermittent, ephemeral or episodic. The
work by defines intermittent rivers cease seasonally or occasionally the
flow (usually for weeks to months), ephemeral streams flow only in
response to precipitation or snowmelt events (days to weeks) and
episodic streams maintain surface water only during very short periods
(hours to days), primarily after heavy rainfall events. In this line,
our results are similar to the national legislation of Italy and , where
days or months per year without flow are employed to distinguish between
permanent, temporal, intermittent, and ephemeral water bodies. For
example, in Italy , NPRS are classified according to the number of dry
months as intermittent (less than 8 months per year), ephemeral (more
than 8 months per year) and episodic (only water circulation after
intense precipitation events). In Spain , temporary rivers are defined
as those flowing for more than 300 days per year and possible dry
periods; intermittent rivers are those flowing between 100 and 300 days
per year; and ephemeral rivers are those flowing during less than 100
days per year. Similarly to national legislation, our results indicate
three groups (Fig.3 and 4) which we would define as ephemeral rivers
(cluster I), intermittent (cluster II), and temporal (cluster III), but
we acknowledge notable differences in the range of days and months
without flow ranges (Table 2). Apparently, the ranges of our
classification are not closed but cluster I (ephemeral) would have more
than 181 days or 7 months (59.6\%) with zero-flows, while cluster II
(intermittent) between 100 and 187 days or between 4 (35.8\%) and 7
(56.3\%) months without flow, and cluster III (temporal) with less than
46 days and 2 (20.0\%) months with zero-flows. As far as we know, this
is the first classification in which undisturbed gauging stations to
obtain ranges based on statistical analysis of real data were used,
providing new insights that improve the understanding of the
hydrological dynamics in these water bodies. Their integration into
national legislation, which currently classifies NPRS based on expert
judgement criteria (e.g., Spain and Italy), would undoubtedly lead to
better management strategies aimed at achieving the objectives set by
the WFD.

Nevertheless, the applicability of these results might be affected by
the limited number of NRPS water bodies controlled by gauging stations .
For example, 39\% of France's rivers were NPRS applying a regional
predictive model, but only 20\% of the total gauging stations in France
had zero flow episodes . In addition, some caution is needed when
interpreting the results of this study. Our classification is based on
data from 69 gauge stations, which represent a small proportion of the
total NPRS located in the Mediterranean region. The use of a more
extensive dataset would undoubtedly contribute to a wider and more
robust classification. For example, we noticed a notable lack of
episodic rivers, defined by as rivers with flowing water only during a
few hours or days, depending on the rainfall event and its intensity.
Since our study has used flow data on a daily scale, it was not possible
to detect short-time-scale hydrological changes and none of the gauge
sites used in this study was classified as episodic. Given the
importance of NPRS in terms of the number of these freshwater ecosystems
and considering the limited gauge sites used to measure them, more
hydrological data would provide a more robust hydrological
classification. For this reason, alternative data acquisition of periods
of flow cessation would be necessary. The use of sensor loggers , remote
sensing techniques with unmanned aerial vehicles , empirical
observation, statistical approaches, process-based hydrological
modelling , and multi-temporal satellite data , may solve this problem
though notably increasing the costs .

\emph{4.3. Ecological status and typologies of non-perennial rivers and
streams.}

The Water Framework Directive requires biomonitoring quality elements to
assess the ecological status of rivers. For this purpose, it is first
necessary to define the limits of the water bodies to be included in the
river basin management plans. However, NPRS water bodies are frequently
excluded because many of them have small drainage areas or hydrological
datasets are not available . In addition, NPRS are often omitted from
ecological status assessments because of inadequate knowledge about
their biological and hydrological characteristics (Mazor et al., 2014;
Stubbington et al., 2017). The methodologies in place focused on aquatic
organisms present during the wet phase, whereas dry-phase communities
remain poorly characterized and the metrics used to establish ecological
status in perennial rivers can only be applied in non-perennial rivers
when flow is present . Consequently, the European Commission recognized
the need to include ''temporary rivers'' in national intercalibrations
of the status of their water bodies . However, the inclusion of NPRS in
a single type of water body (temporary rivers) may be imprecise for the
evaluation and transferability of ecological status in Mediterranean
rivers described by WFD, due to the high spatio-temporal variability of
their flows . Therefore, well-defined hydrological typologies that bring
together quality assessment, typologies and hydrology with zero-flow of
NPRS are needed .

Here, we have categorized Mediterranean rivers into three groups based
on the study of the variability of metrics related to their main
attributes of duration, frequency, magnitude, timing, and rate of
change. As expected, the comparison with the other three typologies
(Fig.5 and 6) used to classify NPRS reveals that our groups differ
slightly from the types reported by Spanish and Italian legislation and
the TREHS software . Moreover, our classification is strongly associated
with the temporal change gradient from ephemeral to temporary-types. It
is important to note that the denomination of the typology varies
between classifications, although many of the typologies coincide with
each other (Fig.5). For example, 100\% of the stations grouped in
cluster III are intermittent in MATTM classification or temporary in IPH
classification, 100\% of the episodic or intermittent rivers of MATTM
are ephemeral or temporary in IPH, respectively, and 100\% of the
episodic rivers in MATTM or ephemeral in IPH are episodic in hydrotypes
TRivers classification. The use of a single variable without statistical
basis (number of days per year of zero flow) to classify NPRS makes the
Spanish regulation biased and does not adequately reflect the
hydrological diversity of these ecosystems.

Furthermore, described the difficulties of only using the hydrological
regime to classify non-perennial rivers: i) the main hydrological
features relevant to biological communities in temporary rivers are not
quantitative (i.e. discharges), but qualitative (i.e. the presence of
flowing water, stagnant pools or the lack of surface water); ii) flow
records do not report the permanence of isolated pools in periods of
zero-flow; iii) many NPRS are ungauged, and their natural flow regime
must be evaluated by alternative methods (e.g. remote sensing or
rainfall-runoff models); and iv) the complexity of sampling these
ecosystems due to the difficulty for recognizing the wet and dry phases.
In this context, they developed a novel approach to evaluate the
ecological status of NPRS. It defines four aquatic phases for NPRS, such
as perennial, intermittent-pool, intermittent-dry, and ephemeral. In
this way, used aquatic phases to propose NPRS classification that allows
evaluating their ecological status. Our study has also highlighted some
of these limitations, establishing a non-visual typology based on the
numerical data of the flow series to improve the ecological assessment
using quality elements connected with the hydrological patterns and
pressure gradients. It would also provide a starting point to improve
the management strategies guided to the achievement of the good
ecological status, based on measures related to improve hydrological
alteration and ecological connectivity .

\textbf{5. Conclusions}

In summary, we classified the natural hydrological regimes of NPRS
located in the western Mediterranean region using daily flow data sets
from 69 unaltered gauging stations. Using hydrological series of at
least 11 years of duration, a total of 315 hydrological indices were
calculated using different thresholds to define no-flow conditions (i.e.
0, 1, 2, and 5 l/s). We did not find notable statistical differences
between the different thresholds and after redundancy analysis. A neural
network model was calibrated with the 5 hydrological metrics that better
describe the attributes of flow magnitude, duration, frequency, and
timing of the zero-flow periods, and rate of change between flowing and
non-flowing conditions. The 5 hydrological metrics describe annual
attributes as number of days or percentage of months per year without
flow mean annual flows, coefficient of variation of Julian date of the
annual start of zero flow and annual rise rate. The analysis concluded
that three different categories of NPRS can be defined, namely:
ephemeral, intermittent, and temporal rivers. Ephemeral rivers are dry
for most of the year and would have a low flow during the wet phase with
water in their riverbed. Intermittent rivers have a dry phase not as
long as ephemeral rivers, and, as a rule, more water runs through their
bed. Temporal rivers are more briefly interrupted by a period of
drought. Additionally, our classification revealed ranges that are not
closed and different from the national legislation classifications of
Spain and Italy. Ephemeral rivers could be dry for more than 181 days or
7 months, intermittent rivers between 100 and 187 days or between 4 and
7 months, and temporal rivers less than 46 days and 2 months. Therefore,
our results could serve for the conservation and management of these
rivers, establishing a necessary typology in future studies of
ecological status of WFD, with well-defined groups based on statistical
analysis. The lack of studies addressing the hydrological diversity of
these freshwater ecosystems makes our study a basis for future efforts
aimed at improving management strategies of this type of river courses.
Additionally, future analyses guided to a better characterization of
biological communities associated with different types of NPRS will
allow a better understanding of the ecological implications of
temporality on the biota and will advance in better ecological status
classification and management of these ecosystems. Finally, due to the
relative low number of NPRS analysed, the resulting classification
should be considered as a first approximation and should be tested and
calibrated with other gauging stations not included in the study.

\textbf{References}

\textbf{Tables}

\textbf{Table 1.} Hydrological indices selected from the first five
components of the PCA and the correlation analysis for threshold defined
as zero flow below 0, 1, 2 and 5 l/s.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
Dim. & Code & Hydrological indices & Units & Thresholds
(l/s)\tabularnewline
\midrule
\endhead
1 & DU035 & Number of days without flow (annual) & days/year & 0, 1, 2,
5\tabularnewline
1 & FE052 & Percentage of months without flow (annual) & \% & 0, 1, 2,
5\tabularnewline
2 & MA001 & Mean daily flows (annual) & l/day & 0, 1, 2,
5\tabularnewline
3 & TI002 & CV of Julian date of annual start of zero flow &
Dimensionless & 0, 1, 2, 5\tabularnewline
5 & RC001 & Rise rate (annual) & l/day & 1, 5\tabularnewline
\bottomrule
\end{longtable}

\textbf{Table 2.} Summary of the cluster groups obtained by training
self-organizing maps (SOM) using the hydrological indices selected for
the non-permanent Mediterranean rivers. The mean, standard deviation,
coefficient of variation and interquartile range are included of number
of days per year without flow (DU035, in days/year), annual percentage
of months without flow (FE052, in \%), mean daily annual flows (MA001,
in l/day), CV of Julian date of the annual start of zero flow (TI002)
and annual rise rate (RC001, in l/day).\selectlanguage{english}
\begin{longtable}[]{@{}llllll@{}}
\toprule
Cluster & Hydrological indices & Mean & Standard deviation & Coefficient
of variation & Interquartile range\tabularnewline
\midrule
\endhead
I & DU035 & 231.45 & 97.07 & 0.42 & 181.61 - 307.98\tabularnewline
& FE052 & 76.87 & 23.52 & 0.31 & 59.65 - 96.29\tabularnewline
& MA001 & 0.53 & 0.70 & 1.31 & 0.06 - 0.67\tabularnewline
& TI002 & 2.23 & 0.92 & 0.41 & 1.53 - 2.96\tabularnewline
& RC001 & 3.69 & 6.19 & 1.67 & 0.53 - 2.34\tabularnewline
II & DU035 & 144.14 & 54.40 & 0.38 & 100.41 - 187.11\tabularnewline
& FE052 & 47.32 & 15.23 & 0.32 & 35.83 - 56.31\tabularnewline
& MA001 & 0.72 & 0.65 & 0.90 & 0.24 - 0.99\tabularnewline
& TI002 & 0.63 & 0.27 & 0.44 & 0.44 - 0.79\tabularnewline
& RC001 & 2.00 & 1.98 & 0.99 & 0.51 - 2.72\tabularnewline
III & DU035 & 24.57 & 25.68 & 1.04 & 2.65 - 46.19\tabularnewline
& FE052 & 11.25 & 10.09 & 0.90 & 2.16 - 20.07\tabularnewline
& MA001 & 2.06 & 3.80 & 1.84 & 0.25 - 1.95\tabularnewline
& TI002 & 0.25 & 0.17 & 0.70 & 0.12 - 0.37\tabularnewline
& RC001 & 1.35 & 1.72 & 1.28 & 0.27 - 1.57\tabularnewline
\bottomrule
\end{longtable}

\textbf{Figures}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Figure 1.} Map of the 69 gauging stations used to develop the
hydrologic classification of non-perennial rivers in France, Spain, and
Portugal. Abbreviation of each studied river basin district (see Table
A1) and K\selectlanguage{ngerman}öppen-Geiger classification has been added (see legend on .\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Figure 2.} Principal component analysis of 315 hydrological
indices that describe ecologically relevant flow regime characteristics
such as magnitude (MA), frequency (FE), duration (DU), timing (TI), and
rate of change (RC). The percentage of explained variation (\%) of the
first two dimensions for a threshold of 0 l/s. Only the first 100
variables that contribute most to the dimensions are represented.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

\textbf{Figure 3.} Self-organizing map (SOM) for the variables: number
of days per year without flow (DU035), annual percentage of months
without flow (FE052), mean daily annual flows (MA001), CV of Julian date
of the annual start of zero flow (TI002) and annual rise rate (RC001).
Warm colours (yellow) indicate high values while cool colours (blue)
represent low values for each variable. The U-matrix (unified distance
matrix) and cluster classification applied to the boundaries of the map
is added.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

\textbf{Figure 4.} Box-plots illustrate cluster groups obtained by
training a self-organized map (SOM) with the selected indices; number of
days per year without flow (DU035, in days/year), annual percentage of
months without flow (FE052, in \%), mean daily annual flows (MA001, in
l/day), CV of Julian date of the annual start of zero flow (TI002) and
annual rise rate (RC001, in l/day).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

\textbf{Figure 5.} Alluvial diagram relating sampling stations of
non-perennial Mediterranean rivers, Italian (MATTM), Spanish (IPH) and
hydrotypes classification (aquatic phases of biological communities) of
LIFE+ TRivers project with the three clusters obtained on SOM. The width
of the connection is based on the frequency of occurrence of the
different combinations of the categories of each characteristic.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

\textbf{Figure 6.} Chord diagram relating sampling stations of
non-perennial Mediterranean rivers between different types of SOM
(cluster I, II and III), MATTM (ephemeral, episodic, intermittent and
ephemeral), IPH (ephemeral, intermittent and temporal) and TRivers
(episodic, intermittent-dry, intermittent-pools and perennial)
classification. The width of the connection is based in the percentage
of occurrence between of the categories of each classification.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fig/Fig}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fih/Fih}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fii/Fii}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fij/Fij}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fik/Fik}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Fil/Fil}

\end{center}
\end{figure}

\selectlanguage{english}
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