Cent. Eur. J. Geosci. • 3(2) • 2011 • 215-228 DOI: 10.2478/s13533-011-0019-1
Central European Journal of Geosciences
PINIOS (PENEUS) RIVER (CENTRAL GREECE): HYDROLOGICAL - GEOMORPHOLOGICAL ELEMENTS AND CHANGES DURING THE QUATERNARY
Research article
George Migiros 1 ∗, George D. Bathrellos2† , Hariklia D. Skilodimou 2‡ , Theodoros Karamousalis 1
1 Laboratory of Mineralogy – Geology, Department of Science, Agricultural University of Athens, Greece, 2 Department of Geography & Climatology, Faculty of Geology & Geoenvironment, National & Kapodistrian University of Athens, University Campus, Zografou, 15784 Athens, Greece,
Received 18 March 2011; accepted 5 June 2011
Abstract: The Pinios River is the third longest river of Greece. It drains the entire drainage basin of Thessaly (eastern part of Central Greece), part of which is the largest plain of the country. In this research the hydrological, geomorpho- logical and geological characteristics of the riverine area of Pinios were studied. Classification and grouping of these characteristics were then carried out, which led to the segmentation of the Pinios River into seven sections, each one with its own set of thematic data. These sets assign separate functions and evolutions of the river system during the Quaternary. Specifically, the basin of the present Pinios River, before its evolution into a river basin, comprised three separate and independent systems. The present Pinios River emerged as a river system from the merging of the lacustrine paleoenvironments along with the major tributaries that drained large parts of the present hydrological basin and as soon as the karstic openings of the central hill valley and the Tempi valley took place during the Quaternary. The followed methodology for the segmentation of the river can be used for the study of heterogeneous river systems. Keywords: Pinios River • Quaternary • segmentation • river evolution © Versita Sp. z o.o.
1. Introduction and drains the entire hydrologic basin of Thessaly, dis- charging into the Aegean Sea, where it forms delta.
Its course starts at the northwestern part of the Thes- saly plain, from the confluence of Ion and Malakasiotis The Pinios River is the third longest river in Greece, Rivers. It is surrounded by mountainous areas which en- crosses a large part of the eastern part of central Greece close its drainage basin and form its watershed. To the north are the Titaros Mt. (1,837 m) and the Kamvou- nia Mt. (1,615 m), to the northeast are the Olympos ∗E-mail: [email protected] † E-mail: [email protected] Mt. (2,917 m) and the Ossa Mt. (1,978 m), to the east ‡ E-mail: [email protected] is the Pilio Mt. (1,548 m), to the south is the Orthrys
215 PINIOS (PENEUS) RIVER (CENTRAL GREECE): HYDROLOGICAL - GEOMORPHOLOGICAL ELEMENTS AND CHANGES DURING THE QUATERNARY
Figure 1. The location map of the study area; The drainage basin of Pinios River, its major tributaries, the main mountains, and the classes of elevation.
Mt. (1,726 m) and finally to the west are the Pindos Mt. near the Pinios River and its tributaries [7, 8]. Some of (2,204 m) and the Koziakas Mt. (1,901 m). Internally, the those settlements kept on existing throughout the Bronze plain is divided by a low-lying hill area into a western Age (around 3,200-1,100 B.C.) and were converted into part (Trikala-Karditsa) and an eastern part (Larisa). important strongholds during the historical times. The in- The major tributaries of Pinios River are the Portaikos, habitants of those settlements took advantage of the river Pamisos and Enippeas Rivers to the southwest and the water and used it for water supply, irrigation, defense, and Lithaios, Neochoritis and Titarisios to the north, which cleanliness. The life quality of the inhabitants was further all drain large, geologically heterogeneous areas, through improved by the construction of water ducts and sewerage extensive hydrographic networks (Fig. 1). systems, aqueducts, wells and public baths. But whilst the Pinios River provided local inhabitants in many benefits, The Pinios River crosses various geotectonic environ- it was also responsible for some catastrophic events [9]. ments, which form the tectonic window of the Olympos- Ossa unit, the Koziakas unit and the eastern nappes of Important civilizations have emerged along the course of the Pelagonian zone and the Eastern Greece zone (Sub- Pinios River from the Paleolithic Age until the present pelagonian) [1–3]. day; several great individuals of the antiquity were born Many historical records (historical geomorphology) men- and raised at Thessaly, such as Asclepius [10], the great tion the Pinios River, its tributaries and the plain it healer-god of the ancient world. During the recent his- crosses. A reference [4] names the lowest lying part of the torical period, Pinios and its tributaries shaped the life of western Thessaly plain as Limnaion which in the antiquity the inhabitants of the cities of Thessaly (Larisa, Trikala, meant a low-lying place with little drainage that forms etc.), by attracting residential, industrial, commercial and swamps and lakes. At the eastern part of the plain, during economic activities to the region. periods of increased water flow, the Pinios River supplied The fluvial geomorphological processes and river evolution the ancient lakes of Asmaki and Voiviida (or Karla). are issues of worldwide studies [11–16]. Many researchers The vitalizing potential of the Pinios River has been ex- have focused in morphometric parameters of the riverbeds ploited since the Paleolithic Age [5], since there is much [14, 17–23] and fluvial terraces [24–27] in order to exam- proof of human inhabitation at that time (Theopetra Cave, ine the river evolution. The complexity of the Pinios River nearby Trikala town) [6]. During the Neolithic Age - a system, due to both its physical attributes and the ge- period characterized by the initiation of productive ac- ological structure of the area, comprise the epicenter of tivities (agriculture) and permanent inhabitation - signifi- the current research, with the aim of analyzing the evo- cant settlements (Sesklo, Diminio, Pelinneo) were situated lution of the river during the Quaternary. Hence, studies
216 George Migiros , George D. Bathrellos, Hariklia D. Skilodimou , Theodoros Karamousalis have focused on the hydrological, geological and geomor- 3. Hydrological settings phological characteristics of the Pinios River. Specifi- cally, the heterogeneity of the river system was examined The Pinios River has an approximate length of 205 Km and though the analysis of the morphometric parameters of its hydrological basin covers an area of 10,700 km2. The the riverbed and a study of the fluvial terraces. In the mean annual precipitation is 779 mm and the mean annual present research, an attempt was made to obtain the seg- total flow of the river is 3,500x106 m3. Its hydrological mentation of the Pinios River into different homogeneous basin is divided into three main sub-basins: sections, by the classification and grouping of the above mentioned characteristics. These sections represent dif- • The Trikala-Karditsa basin to the west (area: ferent circumstances for the development and evolution of 5,955 km2, tributaries: Portaikos, Pamisos, Enip- the river system during the Quaternary. peas, Lithaios and Neochoritis). The tributaries of the Pinios River have a radial configuration in their flow direction giving the impression that they drain 2. Data – Methodology the mountainous belt of western Thessaly leading towards the lowland zone. It should be noted that some of the tributaries ended in the swampy area The data collected or created in the context of the current of Trikala – Karditsa and their current connection research were: to the Pinios River was made artificially by humans - Thematic maps (mainly topographical, hydrological, in the 20th century (e.g. Pamissos, Lithaios). geological, hydrogeological, soil and land use) with scales of 1:50,000 or 1:5,000. • The Elassona-Tirnavos basin to the north (area: - Air photos (scales 1:30,000 and 1:15,000 taken between 2,040 km2, tributary: Titarisios). The hydrographic 1998-1999 and 2005-2006) and satellite images LAND- network of Titarisios River has an autonomous de- SAT 5 and QUICKBIRD. velopment draining large parts of the mountains - Meteorological, climatological and hydrological data. Kamvounia, Titaros and Olympus. - Field work. • The Larisa-Karla to the east (area: 2,438 km2, Pin- ios River). The hydrographic network of the eastern As a working scale, the 1:50,000 maps were used for the basin has limited growth, due to the presence of the generic recording and the 1:5,000 maps for the particular- karstic mountain masses of Olympos-Ossa, as well ization and substantiation of data. For the needs of the as of the karstic Lake Karla in the Southeast [28]. current research, a riverine zone having a mean width of 5 Km, was mapped. The riverine zone includes the area The drainage network of the sub-basins is quite complex, of the immediate hydrological, geomorphological and ge- since it drains areas of rather dissimilar geomorphology, ological influence on the evolution and development of the geology and land use. The plain area crossed by Pinios river. River is divided by the presence of a low-lying hill area into two parts (Fig.1): (a) the western, whose altitude The methodology followed by the current research com- varies between 80 – 200 m, and (b) the eastern, whose al- prises: titude varies between 45 – 100 m. The mountainous and a) The collection, evaluation, registration and process of hilly area crossed by Pinios River, has a quite rugged thematic data, digital and numerical. surface with altitudes exceeding 200 m. The most impor- tant gorges are the ones of Kalamaki (internal low-lying b) Creation of thematic maps (morphological, geomo- hill area), Rodia and Tempi (between Olympos and Ossa). prhological geological and hydrogeological) and Through these areas the water flow velocity is high and databases, using ArcGIS 9.3. erosion intense. c) Photo interpretation and photogrammetry of air pho- Furthermore, the existence of large lakes and marshlands tos and satellite images, using specialized software in the plain area should be noted. Examples include (ILWIS and ERDAS). the lake Xinias in western Thessaly in which lake level d) Field work concentrating on descriptions and mea- changes have been recorded during the last 40,000 years, surements of hydrological, geomorphological, and today has been drained for agricultural purpose [29]. geological-hydrogeological characteristics, as well Lake Karla to the eastern plain has been recognized to as thematic mapping. exist in the antiquity, while its extent was extremely vari- able [30]. Currently, an extensive drainage of the lake is e) Integration and evaluation of data. taking place.
217 PINIOS (PENEUS) RIVER (CENTRAL GREECE): HYDROLOGICAL - GEOMORPHOLOGICAL ELEMENTS AND CHANGES DURING THE QUATERNARY
4. Geological settings Table 1. Water influxes into the Pinios River. River section Water influx (m3) According to the geological structure of the area of inter- 1. Confluence of Malakasiotis and Ion rivers 65,000 est, Pinios River crosses Alpine formations of various units 2. Portaikos river 40,000 and post-Alpine formations. More specifically, the Alpine 3. Pamisos river 50,000 formations at its western part belong to the Koziakas unit, 4. Neochoritis river 20,000 at the central part to the Subpelagonian and Pelago- 5. Enippeas river 110,000 nian units, and at its eastern part to the Pelagonian and 6. Kalamaki valley 20,000 Olympos-Ossa units. At the western sub-basin, a great 7. Titarisios river 45,000 part of its length passes through Molassic formations of 8. Rodia valley 10,000 the Meso-Hellenic trough (Eocene-Pleiocene) and Qua- ternary formations, while at the eastern part it crosses 9. Tempi valley 220,000 mostly Neogene and Quaternary formations [3, 34–44]. Sum 580,000 The Koziakas unit is consists mainly of clastic and argilo- siliceous formations, Mesozoic limestones, cherts, schists All of the above, in conjunction with the fertility of the and flysch. The Subpelagonian zone is comprised of ophi- plain areas, necessitated the construction of drainage and olite formations, Mesozoic limestones and flysch. The irrigation projects during the 1960’s. Pelagonian unit comprises gneisses, amphibolites, phyl- lites, schists, Mesozoic marbles, ophiolites and flysch. A systematic study of the Pinios River showed that dur- The Olympos-Ossa unit is a continuous carbonate series ing the dry season, from May until October, water flow (Mesozoic up to Eocene) that passes upward into a fly- is observed only in a few places. During that period, the sch. The Molassic sediments of the Meso-Hellenic trough largest part of Pinios at the western part is almost water- around Pinios River are marls, sandstones, limestones less, whilst in the eastern part stagnant water has been and conglomerates of Oligocene-Miocene age. The Neo- recorded at some parts of the river. At some places, behind gene formations consist mainly of lagoonal or shallowly temporary low earth-fill dams, small ponds are formed. marine sediments (Miocene-Pliocene) and are mostly The only exception during this period is the Tempi area, marls, clays, conglomerates, sandstones, sands, marly and where the flow observed is due to the karstic springs found travertine limestones. The Quaternary formations com- there. According to [31, 32] the Pinios River during the prise alluvial deposits and fans, littoral deposits, screes 3 dry season receives a total influx of about 580,000m ; this and fluvial terraces. In those sediments, sands, sandy is further analyzed in Table 1. clays, silty sands, muds and gravels dominate, sometimes The plain of Thessaly has suffered from flooding since an- in more cohesive forms. cient times. Several structures had been constructed in Tectonics has been an important factor in the landscape order to control the Pinios River 2,500 years ago [33]. development of the study area. According to [45, 46] a Based on historical records, hydrological data from [32] NE-SW oriented extensional phase (Late Miocene–Early and our own measurements, it has been found that Pin- Pleistocene) has initiated the formation of a basin and ios River displays repeatable floods of 25 and 50 year structures consisting of a series of horsts and grabens period of recurrence. The first one is more common and bordered by NW–SE trending faults. The plain of Thes- the second one less frequent and more severe. The flood saly roughly coincides with this major tectonic structure. flow of the 25 year frequent events has been estimated for After a period of quiescence, a new N-S extension af- the western part as 1,420 m3/sec, whereas at the eastern fected the Aegean Region. This phase started during part (nearby the Larisa city) the figure is 2,420 m3/sec. the Middle Pleistocene and it is still active. It gen- The floods of the Thessaly plain take place from Novem- erated new E-W trending basins, superimposed on the ber through April, with the exception of January because inherited ones. At that time, the Ellassona – Tirnavos of the freezing conditions. The water level of Pinios be- basin started developing. According to [44], the western comes a flood event as soon as it rises above 4 m. Crop basin that is part of the Meso-Hellenic trough, is older inundation occurs at the western part when the water level (Eocene-Pliocene). From Eocene until the Pliocene, this rises above 6 m. The comparison of the above can lead to basin was characterized by a lacustrine-terrestrial envi- some conclusions about flood frequency and water levels, ronment, becoming fluvial-terrestrial during the Quater- such as the linkage of the 25 years periodical events with nary. According to [46–48], the eastern sub-basin, that the 3-4 m water level rise and the less frequent ones with is part of the rifts developed in the Pelagonian unit, is the 6 m rise. younger (Miocene-Pliocene). During the Miocene, this
218 George Migiros , George D. Bathrellos, Hariklia D. Skilodimou , Theodoros Karamousalis
Figure 2. Geological formations in the riverine zone of Pinios. 1a: Alluvial and modern deposits, 1b: Littoral sediments, 2a: Terraces, 2b: Old terraces, 3: Alluvial fans, 4: Eluvial deposits, 5: Conglomerates, sandstones, clays, marls, terrestrial-lacustrine deposit, 6: Molassic formations, 7: Flysch, 8: Limestones, 9: Cherts, schists, 10: Crystalline limestones, marbles, 11: Gneisses, schists, 12: Olistholites, peridotites, ophiolites, serpentinites).
Table 2. Geological formations in the riverine zone of Pinios.
Formation Area (km2) (%) QUATERNARY FORMATIONS Alluvial and modern deposits 557.00 48.69 Littoral sediments 3.24 0.28 Terraces 28.97 2.53 Old terraces 0.96 0.08 Alluvial fans 57.31 5.01 Eluvial deposits 0.80 0.07 NEOGENE FORMATIONS Conglomerates, sandstones, clays, marls, terrestrial-lacustrine deposits. 230.18 20.12 MOLASSIC FORMATIONS 21.11 1.85 ALPINE FORMATIONS Flysch 40.53 3.54 Limestones 9.46 0.83 Cherts, schists 8.46 0.74 Crystalline limestones, marbles 96.78 8.46 Gneisses, schists 64.50 5.64 Olistholites, peridotites, ophiolites, serpentinites 24.72 2.16 basin is characterized by a fluvial-terrestrial environment parameters and based on the geological maps of [49]. The that becomes lacustrine-terrestrial during the Pliocene. geological subdivisions are analyzed in Table 2, where Finally during the Quaternary the basin exhibited fluvial- is also documented the area they cover (in km2 and %) terrestrial characteristics again. For the needs of the cur- throughout a riverine zone of 5 Km width. rent research, a generalized geologic map of the riverine zone was created (Fig. 2), taking into account the sedi- The differentiation of the geological substrate along the mentological, lithological, geological and hydrogeological course of Pinios River is further described in the following
219 PINIOS (PENEUS) RIVER (CENTRAL GREECE): HYDROLOGICAL - GEOMORPHOLOGICAL ELEMENTS AND CHANGES DURING THE QUATERNARY
Figure 3. The sections of the Pinios river that were analyzed separately and the locations of the survey profiles.
chapter. the segmentation (a posteriori) of seven relatively homo- It should be noted that the permeability of the rocks and geneous sections (Fig. 3). A further subdivision was made sediments are concordant with the geological structure. wherever one or more properties changed significantly. The only geological-hydrogeological differentiations are Moreover, the Pinios River along its course forms terraces due to the influx of karstic waters. Such springs are lo- [52], which exhibit significant differentiations of their ge- cated at the area of the central and north Koziakas (Por- ometric features. After many observations and field mea- taikos and Pamisos tributaries), at the wide area of Kala- surements in selected places (Fig. 3), survey profiles were maki valley, and at the Tempi valley [50, 51]. drawn (Fig. 4) perpendicularly to the riverbed, so as to demonstrate the terraces and its differentiations. The 1st river section: (A – B) belongs to the braided type 5. Geomorphological settings [52]; the riverbed is wide; the depth is small and has the highest value of slope. The coarse sediment trans- The standardization of some geomorphic characteristics port and deposition is very high creating a bed mainly that were selected to be studied, so as to examine the de- consisting of pebbles and coarse gravels. The course of gree of homogeneity of the river system, both with quali- Pinios commences at the northwestern part by the con- tative and quantitative analysis, is shown at Table 3. The fluence of Ion and Malakasiotis Rivers. Fluvial terraces selection of the appropriate morphometric parameters for were recorded during the fieldwork of this study. External the study of the riverine system was based on the interna- terraces are developed in a level of 3 to 4 m above the tional literature [14, 18, 20, 22, 23] review. It soon became riverbed and younger much lower terraces (0.8 till 2.0 m apparent that there were substantial differences along its above the riverbed) are also formed inside the riverbed course. due to the braided flow. The survey profile P1-P2 (Fig. 4) is representative, where 4 m high flood terrace and one The Pinios River presents different channel patterns: internal at 1 m high can be observed. braided, meandering, sinuous and straight. The differen- tiation between the sections was made on the basis of the In the 2nd section (B – C) the river narrows a lot and is no morphometric parameters of the Pinios riverbed: width, longer braided. The sinuous riverbed represents this sec- terraces, slope, granulometry, direction, and geologic sub- tion. The major tributaries in this section are Portaikos, strate. The sinuosity was calculated on every section in Pamisos, Lithaios and Neochoritis. During the dry season, order to determine the type of riverbed;values of 1.5 or water is added to the hydrological balance of the Pinios greater indicate meandering river and below 1.5 straight River from the tributaries of Portaikos and Pamisos, with [14]. The results of the morphometric measurements led to waters that originate from karstic springs of the Koziakas
220 George Migiros , George D. Bathrellos, Hariklia D. Skilodimou , Theodoros Karamousalis
Table 3. Basic morphometric parameters for the riverine system.
River Subsection River type Riverbed width River ter- Riverbed Riverbed Mean Sinuosity Geologic sub- section (wa: active, wb: races slope (%) granulometry riverbed strate broad) direction A – B Braided Two terraces A – A1 wb: 300-700m 1.00 NW-SE 1.18 (m.v.*: 400m) A1 – A2 wb: 400-1,100m 0.55 gravels > NNW-SSE 1.13 Molassic (m.v. 750m) >sands formations A2 – B wb: 300-750m 0.42 gravels, sands From N-S 1.21 Molassic (m.v. 400m). till NNW- formations It gets narrow SSE near Megarhis, Dialecto (120 m) B –C Straight, Wa≈50m, wb: Three ter- 0.29 - 0.06 gravels 1.41 elsewhere 95-140m. races. The (m.v. 0.08)
221 PINIOS (PENEUS) RIVER (CENTRAL GREECE): HYDROLOGICAL - GEOMORPHOLOGICAL ELEMENTS AND CHANGES DURING THE QUATERNARY
D1 – E N-S 1.83 E –F Meandering One ter- NE-SW elsewhere race found straight alternating across the river. E – E1 Wa: 35-65m 0.47 gravels 1.39 Alpine for- (m.v. 40m) >sands mations (gneisses) E1– F Wa: 40-150m 0.08 sands> grav- 1.50 Alpine forma- (m.v. 70m), wb: els tions (gneisses 180-300m and schists) F–G Straight Wb: 45-55m Two small 0.16 gravels NE-SW 1.06 Alpine for- terraces ≈sands mations (karstified limestones) G–H Delta Wa: 45-95m 0.06 sands NE-SW 1.27 Neogene and (m.v. 65m), wb: Quaternary 85-200m (m.v. formations 140m)
Mt. Three terraces observed in this river section with a and the younger one at +4 m. At the P9-P10 profile there gravelly-muddy riverbed: (a) a higher (older) terrace at is only one terrace that is extensive in the plain area and 6.5–8.0 m that is quite extensive, (b) an intermediate ter- is 4 m above the riverbed. race at 3-4 m not so extensive and (c) an internal low In the 5th river section (E – F) Pinios River crosses the terrace at 0.8-1.5 m made of sand and gravel. The mean- narrow straights of Rodia valley. The river eroded in depth drous forms are of small extent and develop at the 3-4 m the formations of the bedrock creating the long and narrow terraces. The profile P3-P4 represents this river section, valley. After passing from the Rodia valley, Pinios River st where the older terrace is at 8 m (1 ), the intermediate enters in Tempi valley. The indicative of the 5th river nd rd one at 4 m (2 ) and the younger one at 2 m (3 ). section, is the P11-P12 profile. There, the schist substrate The sinuosity of Pinios riverbed significantly increases is revealed and the only terrace is at 2 m high and consists becoming a high-meandered riverbed in the subsection of pebbles and clayey intercalations. C-C1 of the 3rd section (C – D). In addition, changes in In the 6th river section (F – G), the Pinios River runs the flowing direction of the Pinios River are observed. through a deep, long and narrow valley with steep slopes The main feature of this section is the confluence with the formed by the river erosion. This section is characterized Enippeas River, whose hydrographical network is quite by the entrenchment of the river in the Tempi valley and extensive. Pinios also crosses the Kalamaki valley that the straight riverbed. The width of the riverbed is the low- divide the Thessaly plain into two parts, as already men- est amongst the other sections and consists of karstified tioned. In the Kalamaki valley, karstic springs from the limestones. Karstic springs from Olympos and Ossa Mts hilly area, flow into the Pinios River. A muddy-sandy flow into the river. A riverbed developed into a rocky area riverbed is developed. In this section an extensive older that corresponds to this section, with narrow terraces at terrace was observed which is developed at 4 m above the 0.8-3 m above the riverbed. A representative survey pro- riverbed and a younger one at 2 m (profile P5-P6, Fig. 4). file is the P13-P14 one that depicts an older terrace at 3 m and a second one at around 1 m. The flood water The type of meandering riverbed can be seen throughout level must be above 3 m. the 4th section (D – E), while mainly fine coarse sediment th are transported and deposited by the river. At the end The last and unique 7 river section (G – H) of the Pinios of this section the Titarisios River confluences. Karstic river is a delta formed by the deposits of the last 10,000 waters from the springs of Titaros. and Kamvounia Mts years. The delta of the river has a limited area in relation flow into the Titarisios River. The survey profiles P7-P8 to the size of its drainage basin. According to [53], the with an N-S direction and P9-P10 with an E-W direction dominant delta landforms are the numerous abandoned are representative for this section. At the P7-P8 profile, meander channels and beach ridges. the water level is at 72 m and the older terrace is at +8 m The flood conditions of these areas are totally different at the northern slope, the older terrace is lower at +6 m since at the 1st section the riverbed is very wide and the
222 George Migiros , George D. Bathrellos, Hariklia D. Skilodimou , Theodoros Karamousalis
Figure 4. The survey profiles and the recorded terraces [P1-P2: two terraces at altitudes of 224 and 221 m; P3-P4: three terraces (100, 96 and 92 m); P5-P6: two terraces (94 and 92 m); P7-P8: two terraces (78 and 76 m); P9-P10: one terrace (78 m); P11-P12: one terrace (35 m); P13-P14: two terraces (28 and 26 m)].
water level rarely exceeds 3 m. At the 2nd and 3rd section, the lower one forms the present floodplain. The earliest it is more frequent for the flood level to reach the 4 m, so unit of the older deposit dates to the middle of the last it inundates the 3-4 m terrace. At the 2nd section this glacial period (ca. 40,000-27,000 B.P.). terrace is not as extensive as at the 3rd section. High flood events, reaching 7-8 m high, relate mostly to the 2nd and 4th section, which receive larger amounts of water per 6. Discussion time. Especially at the 2nd section, this phenomenon is more intense due to the abrupt narrowing of the riverbed. The Pinios River, along its course, presents significant Furthermore it should be mentioned that the recording of geoenvironmental differentiations, which can lead to a the fluvial terraces of Pinios River is preliminary research, segmentation that determine different circumstances for taking into account only their locations and differentia- the development and evolution during the Quaternary. tions in their geometric features. Therefore the study has The polymorphism of the morphometric characteristics of some limitations and further research is needed to place the Pinios riverbed leads to the hypothesis that the Pin- all the terrace levels in a chronological frame. In addi- ios River was initially not a united hydrographic network tion, it should be noted that according to the literature as it is observed today. [54, 55], in the Larisa basin two floodplain deposits have been recorded. The older one has age Late Pleistocene The climatic alteration in Greece during the Quaternary to Middle Holocene and is now well above the river; and [56, 57] is a significant parameter, along with neotec-
223 PINIOS (PENEUS) RIVER (CENTRAL GREECE): HYDROLOGICAL - GEOMORPHOLOGICAL ELEMENTS AND CHANGES DURING THE QUATERNARY
tonic activity, in the landscape morphology of the Pin- small (0.06%) and the riverbed type is meandering. The ios River. According to [46], during the extensional phase direction of flow is initially E-W and then turns to N-S. (Late Miocene–Early Pleistocene) the palaeogeography The 5th river section receives the waters of Titarisios that of the Thessaly was characterized by fluvial and mainly come from the karstic springs of Titaros and Kamvounia lacustrine conditions that persisted until Villafranchian. Mts. The 6th river section comprises the Tempi valley that This fact demonstrates that the hydrographic network of receives a great deal of karstic waters from Olympos and Pinios River had not been developed in the study area un- Ossa Mts. The 7th section is the deltaic area of the Pinios til this period. A permanent hydrographic network started River. The last three sections emerged from the evolution forming only after the entrenching of the Tempi valley of the old river system of Titarisios. The direction of flow across the Olympus and Ossa Mountains [58]. is mainly NE-SW. All the river systems of western Greece flow from north to south, parallel to the Alpine structures, with the exception Conclusively, the first three river sections (Fig. 5) com- of Aoos River that flows towards the north. At the eastern prised a unified system that drained the western basin terrestrial part of Greece, the mid and lower parts of the and the waters ended up to the paleo-lake of the second th rivers turn to an E-W direction. and third section as far as the Kalamaki valley. The 4 river section was also a paleo-lake of lower altitude that The Pinios River is partly differentiated from the other didn’t connect with the previous one. The waters of the river systems, since its direction of flow presents frequent eastern basin end up there. Later, an independent river changes. Initially it is NNW-SSE, then turns to E and system of the Titarisios was formed [46] that had no con- NNE and just before its discharge into the Aegean Sea, nection either with the previous systems and debouched it turns to E again. It drains two geologically and evolu- to the Aegean Sea. The new course of the Titarisios River tionary different basins, the western and the eastern ones. is now along the Rodia and Tempi valleys (Fig. 5). These basins are divided by a hill series of karstified car- bonate rocks. The connection of the two paleo-lakes (the higher west- ern part of the Thessaly plain with the lower eastern part) st The 1 section of the Pinios River is clearly a braided had been caused by opening of the Kalamaki valley from riverine system with a wide riverbed. Its direction is weathering and karstification of the carbonate rocks dur- NNW-SSE that coincides with the direction of flow of ing the Quaternary [28]. the rivers of western Greece. There is direct control over the direction of flow from the Alpine structure and more This fact enabled the paleo-lake water to drain eastwards specific of that of Koziakas and the Meso-Hellenic trough. and caused the overflow of the eastern basin. Until then This section receives waters mainly from Ion and Malaka- the overflow events were extremely rare since the supply siotis Rivers as well as the karstic springs of Koziakas of the eastern paleo-lake with water was not enough, as Mt. is the case today [32, 33]. The aforementioned overflow led also to the connection of the eastern paleo-lake wa- The 2nd section receives a great amount of water from ters with the Titarisios River system and thus created a the confluence of the four major tributaries, halts being constant flow from the western to the eastern paleo-lake braided and becomes straight and in places sinuous. This and then to the Titarisios River. This constant flow caused river section used to be a lacustrine environment with the draining of the two lakes and the creation of the Pin- swamps and marshes; the present meandering of the river ios riverbed, as well as the development of swamps and is a remnant of that environment and not an evolution of marshes as remnants of those lakes. So, the present Pin- the river system. The direction of flow is dominated by the ios River emerged from the conjunction and evolution of transverse neotectonical structures relating directly to the at least three different and formerly independent systems. Pamisos River as well as to the Portaikos River. This estimation is substantiated by the terraces previously The 3rd river section is the continuity of the paleolacus- mentioned, that are remnants of those paleoenvironments. trine environment, with meanders, as far as the Kalamaki The highest flood level (50 years of recurrence) that corre- valley. This valley is a prominent feature of this section lates with the first 8 m high terrace is the bounding level and divides the Thessaly plain into two halves. This river of the Pinios function as a riverine system. The present section receives water mainly from the confluence with tendency is for the highest flood level to be correlated Enippeas River and the karstic springs of the valley. with the paleo-lakebed. The second 4 m high terrace is The 4th river section receives water only from the previous an eroding one and correlates with the second lower flood sections. There is no major tributary and there are no level (25 years of recurrence). Finally the third rows of karstic springs. In this river section the inclination is very terraces of 2 m high are sliding terraces.
224 George Migiros , George D. Bathrellos, Hariklia D. Skilodimou , Theodoros Karamousalis
Figure 5. Sketch of the paleo-environments of Thessaly plain in Quaternary.
7. Conclusions of independent paleoenvironments and the Pinios River emerged.
A heterogeneous river system, such as Pinios River, can The methodology described in the previous paragraph can be segmented based on the study of its geoenvironment be used for the segmentation and study of any heteroge- and hydrological characteristics. These characteristics of neous river system. Pinios River define the different function and evolution during the Quaternary. The confluence of the tributaries Malakasiotis, Ion, Por- Acknowledgments taikos, Pamisos, Neochoritis, Enippeas, Titarisios and the karstic springs of Koziakas Mt. and the Kalamaki, Ro- dia and Tempi valleys enrich with water the Pinios river This study was carried out with the financial support of system. the Region of Thessaly and project manager Prof. George The Pinios River drains two different geologically and Migiros. evolutionary basins, the western and eastern ones, which are separated by an internal low-lying hill area, com- prised of intensively karstified carbonate rocks. The recording and processing of the geomorphologic data sug- References gests segmentation of the basin into seven river sections with relatively homogeneous characteristics. [1] Mountrakis D., Sapountzis E., Kilias A., Eleftheriades Initially, the first three river sections were a unified sys- G., Christofides G., Paleogeographic conditions in the tem that drained the western basin. The waters flow into western pelagonian margin in Greece during the ini- the western paleolake, as far as the Kalamaki valley. The tial rifting of the continental area. Can. J. Earth Sc., 4th river section consisted of a lower altitude paleo-lake, 1983, 20, 1673-1681 which was not connected to the previous one. The eastern [2] Jacobshagen V., Geologie von Griechenland. [Geol- basin drained to this paleo-lake. Afterwards, a different ogy of Greece] Berlin - Stuttgart (Gebr. Borntraeger), river system - that of the Titarisos - was formed, which 1986 had no connection with either of the two basins and de- [3] Katsikatsos G., Migiros G., Triantaphyllis M., bouched into the Aegean Sea. During the Quaternary, Mettos A., Geological structure of Internal Hel- the weathering of the carbonate rocks caused the open- lenides (E. Thessaly-SW Macedonia-Euboea-Attica- ing of the Kalamaki valley. This led to the connection Northern Cyclades Islands and Lesvos). The Insti-
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