Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece)

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ECOHYD 137 1–13 Ecohydrology & Hydrobiology xxx (2016) xxx–xxx

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Original Research Article

Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece) Sidiropoulos a, Maria Chamoglou a, Ifigenia Kagalou a,b,*

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Q1 Pantelis

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Q2 a Management Body of Eco-development Area of Karla – Mavrovouni – Kefalovriso – Velestino, 38500 Kanalia, Greece Q3 b Democritus University of Thrace, School of Engineering, Department of Civil Engineering, 67100 Xanthi, Greece

A R T I C L E I N F O

A B S T R A C T

Article history: Received 15 June 2016 Accepted 24 April 2017 Available online xxx

In this paper, the restoration of Lake Karla’s ecosystem is studied through the evaluation of its current status. Lake Karla was one of the most important wetlands of Greece with many benefits not only to biodiversity preservation, to water balance of the watershed, but also to local economy in terms of fisheries. Its drainage, in 1962, created a lot of environmental problems and led to the local economy shrinking. After its refilling, the newly reestablished water body is considered a vital aquatic ecosystem since it is listed in the network of Natura 2000. The monitoring results, the pressures and their causes that affected the restoration effort are presented. The assessment of the water quality is achieved by evaluating the results of the monitoring and fieldwork programs that Management Body of Eco-development Area of Lake Karla has performed during the last four years funded by the European Union. The results indicate strong eutrophication along with threats to biodiversity. The delay of implementation of Lake Karla reconstruction project, the decline from the proposed Environmental Terms and the lack of environmental policy are the most important causes of pressures. ß 2017 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.

Keywords: Ecosystem restoration Monitoring Anthropogenic pressures Biodiversity Water resources management Lake Karla Watershed

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1. Introduction

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The term restoration is used to describe various measures and actions, in order to improve, to rehabilitate or to enhance the structure and the function of the aquatic ecosystems (Dufour and Piegay, 2009; Kurth and Schirmer, 2014). The desire to restore freshwaters that have been degraded by land use change, agriculture, or other

Q4 * Corresponding author at: Democritus University of Thrace, School of Engineering, Department of Civil Engineering, 67100 Xanthi, Greece. E-mail addresses: [email protected] (P. Sidiropoulos), [email protected] (M. Chamoglou), [email protected] (I. Kagalou).

environmental stressors has primarily emerged over the last decades (NRC, 1992; Goldyn et al., 2014). Among Mediterranean water bodies, shallow lakes and wetlands are the most threatened ecosystems and of particular importance, although they have received less scientific attention, regarding their values and services such as flood protection, water quality improvement, aquifer or groundwater storage and recharge (Alexakis et al., 2013). During the last years, there have been many re-assessments and changes of strategies concerning lakes’ management (Millennium Ecosystem Assessment, 2005). National and transnational legislation, such as the European Water Framework Directive (European Communities, 2000), requires European fresh waters to be kept at, or restored to a good ecological status. However, Mediterranean lakes, like other ecosystems, are subject to multiple

http://dx.doi.org/10.1016/j.ecohyd.2017.04.002 1642-3593/ß 2017 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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stressors (Beklioglu et al., 2007; Latinopoulos et al., 2016) arising from human activity and from inter-annual and long-term background changes in environmental conditions that can degrade ecological status. The emphasis in restoration and management studies on lakes has progressively shifted from specific water-quality problems, to dealing with environmental issues at a much broader level. Yet, the more sophisticated solutions are those where the entire catchment, the landscape variables and the variety of stressors of the water body to be restored, are taken into account. The relevance of those factors differs regionally (EEA, 2012): while in Northern Europe’s cold temperate lakes, energy plants have affected lake’s hydrology, morphology and connectivity, South Mediterranean catchments are impaired by scarcity, pollution and multi-pressures and services. In addition their response to pressures seems to be quite different from that of the cold temperate in Northern Europe (Beklioglu et al., 2007). Lake Karla (Thessaly, Greece) was considered to be one of the most important shallow lakes in Greece until 1962, when complete drying of the lake took place – creating more agricultural land – and is now being re-constructed, establishing a ‘new’ reservoir. Prior to the 1960s Lake Karla was considered one of the most important ecosystems in the Mediterranean region as it served as a ‘‘hot-spot’’ of biodiversity, as a natural reservoir providing water storage and recharge to groundwater (Zalidis et al., 2004). The importance of restoring Lake Karla and reversing the environmental conditions caused by anthropogenic activities was considered of high importance by the European Union offering multi services, i.e. social, economic and

ecological sustainable development to the region and not just creating a new reservoir. In this paper we discuss the restoration effort of Lake Karla as well as the pressures and their causes that affect this restoration. This is achieved by evaluating the results of the monitoring and fieldwork programs that Management Body of the whole catchment (named as Ecodevelopment Area of Karla – Mavrovouni – Kefalovriso – Velestino) has performed the last years funded by the European Union. Furthermore, this paper is an attempt to highlight the factors affecting the cascading effect of the restoring processes as a precursor to re-establish natural lake’s structure and function.

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2. Methods and materials

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2.1. The study site – biogeographical context

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Former Lake Karla occupied the lowest part of its natural basin and was considered as one of the most important wetlands in Greece until 1962 (Fig. 1). Surface runoff from the watershed and floodwaters of the Pinios River supplied the lake with large quantities of freshwater. Its surface area fluctuated between 40 km2 and 180 km2. In terms of biodiversity, the former Lake Karla endowed with a variety of habitats (pelagic, floating vegetation, shallow marshes with Juncus sp. and Typha sp., emergent vegetation and rocks), had the ability to support a rich fish and bird fauna (Jerrentrup, 1990). The structure and function of Lake Karla was intimately linked with the Pinios River. The river occasionally overflowed, and floodwaters rich in oxygen and nutrients

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Fig. 1. Aerial photograph of Lake Karla in 1945. After Ananiadis (1956).

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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drained into Karla. Much of the surrounding farmland was inundated when floodwaters were held in the lake, but today, the river is levelled aiming to protect from floods. The climate of the area is typical continental with cold, wet winters and hot, dry summers. Mean annual precipitation in the lake’s watershed is about 560 mm and is distributed unevenly in space and time. Mean annual potential evapotranspiration is about 775 mm and the mean annual temperature is 14.3 8C (Vasiliades et al., 2009). The geological structure consists mainly of recent grains of various sizes originating from the lake’s deposits. The plain consists of aquiferous, essentially sandy intercalations separated by layers of clay to silty-clay and is bound by schist and karstic limestones or marbles. Impermeable geological structures cover a 30.6% of the total area and are located on parts of the surrounding mountains, karstic structures cover a 14.5% and are located on the Mavrovouni Mountain at the north-east part of Lake Karla Watershed and finally permeable structures, which

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appear mainly in the plain, cover a 54.9%. The lake’s sedimentary aquifer occupies the largest part of its plain with an extent of 500 km2 and is being over-exploited covering both the irrigation needs of the cultivated areas, as well as the supply water needs of the settlements (Sidiropoulos et al., 2013). The decision for the complete drying of the lake in the 1960s, took place in order to create more land for agriculture and to avoid the flooding of the low elevation lands because of its surface area fluctuations.

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2.2. The project design

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The project idea is based on the approach that: (a) the lentic system could be considered as a part of a river basin (Pinios basin) strongly linked with the other water bodies at catchment level (i.e. smaller reservoirs, streams, marshes, Pagasitikos gulf and groundwater), (b) restoration is thought to be a human-assisted procedure through the recovery of the hydrological, hydromorphological and

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Fig. 2. Map of Eastern Thessaly showing the boundaries of Lake Karla Watershed and Ecodevelopment Area and the location of sampling sites for fish fauna and water quality monitoring.

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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ecological natural processes and not the re-establishment of the pre-drying conditions, and (c) human impacts are unavoidable in human dominated ecosystems as it has been documented by Dufour and Piegay (2009). While the decision to restore part of the former lake has been taken in the early 1980s the re-establishment procedure started a few years ago. The restoration plan proposes the creation of a reservoir in the lowest depression plain of the former Lake Karla that will occupy a maximum area of about 38 km2, through the construction of two embankments, one in the eastern part and one in western part of the lake (Fig. 2). Two main ditches (named 1T and 2T) will transfer the flood runoff of Pinios River to the reservoir located in the lower part of Karla basin simulating the pre-disturbance conditions. Also, four collector channels will concentrate the surface runoff from the higher elevation zones of the watershed and directly divert it into the reservoir. The surface runoff of the lower elevation areas will be pumped into the reservoir. So, the maximum allowable volume of reservoir will reach up the 180 hm3, but only the 60 hm3 will be available to fulfil irrigation needs of the surrounding agricultures because of the environmental restraints, as the primary service of the reservoir will be the establishment of a new wetland (Joint Ministerial Decision, 2000). Among the targeted measures of the final restoration plan were:

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- The establishment of riparian zones to control the diffuse agricultural pollution sources. - The operation of a peripheral buffer zone for the reduction of the nutrients input to the lake. - The establishment of habitats corridors to avoid the ecosystem fragmentation and to improve the re-habilitation. - The re-operation of a controlled outlet to improve flushing effect, minimizing the water retention time. - The construction and operation of an artificial wetland for the improvement of the inflows (1T and 2T ditches). - The construction of a fish ladder near Pinios River pumping station contributing to the conservation of fish diversity. - The establishment of fish nursing areas at the south part of Lake Karla. - The re-organization and the modification of the agricultural strategy in the whole region according to agrienvironmental friendly practices. - Finally, the establishment of a Management Body for the area, which would be responsible for the implementation of the restoration plan, the monitoring program, and the application of the integrated management principles according to local needs. The re-constructed Lake Karla occupies the lowest part of the former Lake Karla. It lies between latitude 398260 4900 to 398320 0300 N and longitude 228460 4700 to 238510 5000 E and has a surface of 38 km2. It is characterized as a shallow lake with a maximum water depth of 4.5 m and a mean depth of 2.5 m. A monitoring program was deployed just after the establishment of the Management Body focusing on the water quality along with the trophic conditions, the

hydrological budget and the new wetland’s biodiversity. The European Directives (i.e. the Water Framework Directive and the Habitat Directive) were used as guidelines for the characterization of the water body and for the assessment of its status. We discuss a part of the monitoring results focused on the hydrological regime, the land uses, the eutrophication trends along with biodiversity issues under the light of the pressures and the undertaken measures.

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2.3. Post-construction monitoring project

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Monthly water samples were taken during the period January 2012 to July 2013, from the upper 50 cm of the water column at three representative sampling stations (Fig. 2). Station 1 (KL1) is a pelagic station, located near the centre of the lake. Its maximum depth is 2.5 m. Station 2 (KL2) is a littoral station, located on the southwest shore of Karla reservoir which is near the secondary input of water that enters by gravity flow into the lake through a drainage channel. Station 3 (KL3) is also a littoral station, located on the north-east shore of Lake Karla and was selected to represent the part of the lake that is exposed to runoff coming from livestock grazing, animal sheds and the mountainous land in the eastern part of Lake Karla catchment. Furthermore, monthly average precipitation, monthly average water volume and monthly lake level were recorded. Water sampling and nutrient analysis followed the methodology proposed by APHA (2005). More details about the sampling and monitoring methodology concerning nutrients and Chlorophyll-a as a proxy of algal biomass have been described in detail and already published (Sidiropoulos et al., 2012; Chamoglou et al., 2014). Statistical calculations were performed with SPSS Statistics, Version 20. Fish sampling was carried out according the European standard for multimesh gill netting (CEN, 2005) and European standard for electrofishing (CEN, 2003). The database of CORINE Land Cover 2000 for Greece (EEA, 1994) was used in order to identify land use types of the catchment area. Acknowledging the literature review concerning the ecosystem services associated with land uses we classified the main deliverables from each one land use category into broad types, i.e. provisioning, regulating, and cultural (Troy and Wilson, 2006; Hao et al., 2012).

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3. Results

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Nowadays, Lake Karla is listed in the network of the Greek protected areas as it is considered as a vital aquatic ecosystem, both in terms of biodiversity but also as a newly re-established water resource accommodating multiple uses. It has been included in the European Natura 2000 Network as: (a) a Site of Community Importance for the conservation of natural habitats and of wild fauna and flora with the code GR 1420004 ‘‘Karla – Maurovouni – Kefalovriso – Velestino – Neohori’’, and (b) a Special Protection Area (SPA) for the conservation of wild bird species, with the code GR 1430007 ‘‘Reservoir area of former Lake Karla’’. It has been characterized, according to

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Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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Table 1 Recorded land uses with their characteristics. Corine code

Land uses

Surface (km2)

Surface (%)

Land change (%) from the 1990s

Associated services

1 2 3

Artificial area Cultivations Forest and semi-natural areas

24.548 624.027 539.382

2.1 52.5 45.4

+23.1 21.7 1.4

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Restored aquatic semi-natural areas

0.853

0.5



Regulating (flood buffering) Provisioning (agricultural products) Regulating (nature conservation), provisioning (forestry) Regulating (habitat restoration, hydrological balance), cultural (ecological and aesthetic value, environmental education), provisioning (fishing)

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Greek Law, since 2010, as a Permanent Wildlife Refuge in order to protect and conserve habitats’ essential breeding, feeding areas, wintering species of wild fauna and spawning and nursery areas of fish of commercial and conservation importance.

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3.1. Land uses

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The CORINE Land Cover 2000 database represents the only land use type database validated at national level. Further information sources, mainly ‘‘grey literature’’ (technical reports, Ministerial documents for land planning) were also used to identify land uses from the 1990s. Basic land use types have been recognized within our study area including: agricultural (arable land/permanent crops/pastures/), artificial (urban fabric/industrial, commercial and transport/artificial non-agricultural vegetated areas) forest and semi-natural (forests/scrubs and herbaceous vegetation/open spaces) and aquatic surfaces. In Table 1 the recorded land uses during 2000 are presented while in the last column the percentage of the land use changes recorded in 1990s corresponding to the start up of the technical project. The drainage of Lake Karla is supposed to be a positive event in terms of agricultural production creating more agricultural land. But at the same time the alteration of the watershed’s function resulted in serious drop of the groundwater aquifer and sea-water intrusion, increase of soil salinity and alkalinity, frequent flooding events, nutrient enrichment through extended agrochemicals application, and of course loss of biodiversity and elimination of nature conservation values. The design of the restoration project and the establishment of the protected area has been addressed the increase of the provisioning services as well as the promotion of regulating services and yet, the re-establishment of the cultural services delivered in the wide area named: Eco-development Area of Karla – Kefalovryso – Mavrovounio – Velestino (Fig. 2).

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3.2. Hydrological regime

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In the former Lake Karla, there was not a natural surface outlet of the aquatic system Pinios River-Lake Karla, while it is thought that discharge took place through a system of karstic sinkholes of Mavrovouni Mountain to Pagasitikos Gulf (Fig. 2). Nowadays, this discharge has been avoided

with the creation of a non-flow embankment, where the new reservoir meets the kartsic structures of Mavrovouni Mountain. So, the new Lake Karla is supposed to be drained artificially, by means of a tunnel (Fig. 2) to the Pagasitikos Gulf, which – at present – is closed and operates only in emergency situations. In Table 2, climatological data (monthly rainfall and temperature) are presented highlighting the warm character of the study area. Fig. 3 demonstrates the water level fluctuation in Lake Karla during the years 2012, 2013 and 2014. The lowest ecological limit as it has been set up by the ‘‘Environmental Terms’’ of the project should be at +46.4 m in order to support the functions of the wetland. It comes clear that the water level in the new reservoir was always lower than this cut off, except once, on the 11/06/2012. That is because the reservoir receives less water inputs since 2012 both from its basin because of unfinished works, and from Pinios River due to an interruption in their connection but also due to the withdraws before the river inflows the reservoir. During the winter period, precipitation feeds the lake while, at the moment, the new Karla reservoir experiences intra-annual water level fluctuations due to the bad and unsustainable management of the inflows from Pinios River.

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3.3. Water quality-eutrophication

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In Fig. 4, the monthly variations of the key-eutrophication parameters (Nitrate-N, Ammonium-N, Total Phosphorus) along with the Secchi depth (SD) and Chlorophyll-a are presented. The water quality variables and the nutrients dynamics are thought to be strong predictors of the trophic status. With regard to nutrient concentrations, Nitrate-N was always the most important form, in terms of percentage contribution, in the Dissolved Inorganic Nitrogen pool, exhibiting higher values during the summer

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Table 2 Descriptive statistics of mean monthly rainfall and T (8C): temperature of air, recorded in area of Karla reservoir during 2012–2013. Mean  SE: average  standard error, min-max: minimum and maximum value. Year

Descriptive statistics

Rainfall (mm)

Air temperature (8C)

2012

Mean  SE min–max

42.78  9.24 0.0–88.0

16.41  2.46 3.5–28.1

2013

Mean  SE min–max

24.14  10.64 0.0–73.4

16.85  2.43 7.5–26.3

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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Fig. 3. Water level fluctuation of Lake Karla.

Fig. 4. Monthly variation of key-eutrophication parameters, Secchi Depth and Chl-a at three sampling stations of Lake Karla water during 2012–2013.

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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ECOHYD 137 1–13 P. Sidiropoulos et al. / Ecohydrology & Hydrobiology xxx (2016) xxx–xxx Table 3 The recorded freshwater fish fauna of the new Lake Karla. Family species Centrarchidae Lepomis gibbosus Gobiidae Knipowitschia thessala Clupeidae Alosa fallax Cobitidae Cobitis vardarensis Cobitis stephanidisi Cyprinidae Alburnus thessalicus Carassius gibelio Chondrostoma vardarense Cyprinus carpio Rutilus rutilus Scardinius erythrophthalmus Squalius vardarensis Poeciliidae Gambusia holbrooki

Common name

Trophic guild

Pumpkinseed

Invertivores

Thessaly goby

Insectivores

Twaite shad

Planktivores

Vardar spined loach Velestino spined loach

Invertivores/ Omnivores Omnivores

Thessaly bleak

Common roach European rudd

Planktivores/ Omnivores Omnivores Herbivores/ Omnivores PlanktiInvertivores Omnivores Omnivores

Vardar chub

Omnivores

Eastern mosquitofish

Insectivores

Prussian carp Vardar nase Common carp

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months, while Ammonium-N reached above the value of 0.2 mg/lt, which is the limiting value for fish intoxication, according to the European Directive (2006/44). Total Phosphorus (TP) fluctuated between 0.004 mg/lt and 0.461 mg/lt appearing also high values during the warm months. Chlorophyll-a ranged between 18.34 mg/cm3 and 403.58 mg/cm3, with higher values recorded during the warmer months indicating strong hypertrophication. The new reservoir did not appear any clear phase during the monitoring period since the Secchi depth ranged between 0.3 and 0.5 m reflecting its turbid character.

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3.4. Biodiversity

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Concerning the biodiversity issues in the new Lake Karla, we present data regarding the fish fauna, since the assessment of fish populations is among the obligatory biological elements, included in the Water Framework

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Directive. During our study, the fish community of the new reservoir is composed by six families and thirteen species, with the family of Cyprinidae being the most dominant both in terms of abundance (75.81%) and biomass (75.72%) (Table 3 and Fig. 5), while the common carp (Cyprinus carpio) accounts the 3.98% in terms of abundance and 8.68% in biomass of the Cyprinidae family. Regarding their food preferences, most of them are planktivores and invertivorous while there is an absence of any predator species. In Table 4 the protected fish fauna, considered as important taxa according to the European Directive (92/ 43/EE), of Lake Karla is presented for the period 2012–2013 as well as their conservation status. There are three fish species listed in the Annex II, two of them i.e. Cobitis vardarencis and Cobitis stephanidisi are endemics with the last one to be exclusively endemic for Lake Karla. The species Alosa fallax uses the Karla site for breeding and nesting (r type) while the Cobitidae species are considered as permanent (p type) through the year. In terms of their abundance the A. fallax is classified as very rare while the two other species as present. The conservation status of the site regarding the three species is considered as average or reduced. Concerning the criterion of isolation which means the fragility of the specific population, the species A. fallax is characterized as almost isolated (in relation to its natural range) while the Cobitidae family species as not-isolated populations. The last column of Table 4 refers to the Global assessment of the value of the site for the conservation of the three species. It is obvious the requirement for excellence of the Lake Karla’ site and also for the nearby areas.

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3.5. Pressures

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In Table 5 the main pressures affecting the new reservoir are presented along with the relevant measures undertaken, the ecosystem’s state and the associated impacts on its goods and services. Pressures were separated in five categories while some of the relevant measures were implemented to a percentage up to 50% while the implementation of other did not started at all. Restoration measures in order to avoid flooding, to cover irrigation needs and to establish the hydrological regime make up the 50% of all implementations measures and they are purely mechanical measures. The

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Fig. 5. Percentage (%) participation of fish families caught in Lake Karla in terms of (a) abundance and (b) biomass.

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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Table 4 Assessment of fish fauna in the referred to in Article 4 of Directive 2009/147/EC and listed in Annex II of Directive 92/43/EEC and site evaluation for them. Species

Population in the site

Site assessment

A/A

Code

Sci. name

Type

Abundance

Conservation

Isolation

Global

1 2 3

1103 5309 5307

Alosa fallax Cobitis vardarensis Cobitis stephanidisi

r p p

V P P

C C C

A C C

A A A

Type: p = permanent, r = reproducing; abundance: V = very rare, P = present; conservation: C = average or reduced; isolation: A = almost isolated, C = population not-isolated within extended distribution range; global: A = excellent value.

Table 5 Main pressures with the relevant measures undertaken, the ecosystem’s state and the consequent impacts. Pressure

Restoration measure

Implementation status

Impacts

Flooding

Implementation of flood protection and mountainous water projects and of collectors/ Diversion of flooded water into the reservoir with the pumping stations operation. Treatment of inflow water to the reservoir, improvement of water quality/Establishment of riparian zones, operation of a peripheral buffer zone, construction and operation of artificial wetland. Tree planting project, creation of land corridors, buffer zones.

60% Constructed: Reservoir and pumping stations Non-constructed: Collectors and mountainous water projects.

Damage to agricultural crops and infrastructures, removal of soil making the land barren.

0% No project or tool has been implemented.

Deterioration of water quality, eutrophication, pressure on biota, changes in the structure and function of the water body, sedimentation, elimination of ecosystem services.

10% Failure on planting growth, incomplete establishment of corridors.

Restoration of hydrological balance, rehabilitation of groundwater. Creation of a 38 km2 water body and supplement channels. Creation of the main reservoir and distributing irrigation channels.

50% Constructed: Reservoir Non-constructed: Water distribution projects.

Habitat loss due to ineffective implementation, habitats isolation, impacts on flow energy, impacts on ecosystem services. Negative hydrological balance of Lake Karla Watershed, continuous degradation of water resources, soil salinization, desertification, land subsidence. Not implementation of social needs, no withdrawals.

Point and diffuse pollution sources

Habitat fragmentation

Hydromorphological alterations

Human needs (irrigation)

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eco-engineering, green measures mainly addressing the habitat conservation and the nutrient’s retention did not yet implemented.

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4. Discussion and conclusions

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Lake Karla, in terms of typology according to the Article 4(3) of the Water Framework Directive EU 2000/60/EC (WFD) has been designated as a heavily modified water body (HMWB) according to the Greek Water Directorate (EGY, 2013). The concept of HMWB was introduced into the WFD in recognition that many water bodies in Europe have been subject to major physical alterations so as to allow for a range of water uses. Yet, the HMWBs were created to allow for the continuation of these specified uses which provide valuable social and economic benefits but at the same time allow mitigation measures to improve water quality. Because of the fact that HMWBs are substantially changed in their character, as a result of physical alterations by human impacts, the environmental objective is to meet ‘‘the good ecological potential’’ instead of the ‘‘good ecological status’’. The new regulated lake Karla needs to be considered as a surface water body in the

50% Incomplete construction of irrigation channels.

Pinios River basin, where it is necessary to meet the environmental objectives of the Directive. Greece has recently developed national methods in compliance with the WFD requirements concerning all Biological Quality Elements for reservoirs (Ntislidou et al., 2016; Petriki et al., 2016; Tsiaoussi et al., 2016; Zervas et al., 2016). We could argue that according to all applied indexes, the ecological potential of Lake Karla falls into less than ‘‘good’’ category. The environmental conditions of the new reservoir have not improved in spite of the undertaken measures. The new reservoir is exposed to point and diffuse pollution sources leading already to a progressive eutrophication and is characterized as eutrophic to hypereutrophic with the frequent occurrence of algal blooms (Management Body, Technical reports 2012, 2013). According Gkelis et al. (in press), the phytoplankton biomass (dominated by cyanobacteria) and the microcystins concentrations were well above the World Health Organization Guideline Value 2 (WHO, 1998) for recreational waters, posing a moderate health risk throughout the year. Cyanobacteria were the taxonomic group with the highest number of species, followed by chlorophytes, diatoms, cryptophytes and euglenophytes while the dominant cyanobacteria were

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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440 Anabaenopsis elenkinii, Sphaerospermopsis aphanizome441 noides, Limnothrix redekei, Planktothrix cf. agardhii and 442 Cylindrospermopsis raciborskii (Gkelis et al., in press). A 443 reduced water transparency due to organic material and 444 plankton, along with the presence of frequent algal blooms 445 (Anabaena sp., Aphanizomenon sp.) reported by Ananiadis 446 (1956), suggests that the lake has been eutrophic since at 447 least the 1950s. The water analysis through the water 448 column, carried out in 1955, revealed that Karla was 449 relatively rich in dissolved nutrients and low dissolved 450 oxygen concentrations near the bottom classifying it as 451 eutrophic. According to the present nutrient and chloro452 phyll-a profile, it becomes clear that Lake Karla is an 453 eutrophicated system, with apparent signals of hypertro454 phication during the warm period. Particularly the TP 455 recorded values are far from maintaining even the 456 mesotrophic conditions in a Mediterranean water body 457 (Meerhoff et al., 2012) while the peak value of TP coincides 458 with high inflows by the drainage channel located at the 459 southeast part of the lake (Management Body Report, 460 2012). Papadimitriou et al. (2013) demonstrated the 461 occurrence of cyanobacteria population in the new Lake 462 Karla and the presence of cyanotoxins in both water and 463 fish tissues. The observed cyanotoxicity which also 464 favoured by the eutrophic, warm character of the reservoir 465 and by the hydrological alterations poses a serious threat 466 Q5 for the public health (Chamoglou, 2013; Kagalou et al., 467 2014). Linear significant correlations were appeared 468 between parameters reflecting the phytoplankton abun469 dance such as Chlorophyll-a values with nutrients as Total 470 P values (r = 0.283, p < 0.05) and Nitrates-N (r = 0.312, 471 p < 0.05) respectively. The correlation coefficients even 472 their statistical significance are rather low suggest the 473 contribution of both nutrients to the eutrophication of the 474 new reservoir but probably other more sophisticated 475 parameters expressing the metabolism of the system 476 (i.e. primary production, respiration, photosynthetic activ477 ity) could be necessary (Joniak et al., 2003). 478 Lake Karla receives all types of pollution acting as a sink 479 for pollutants, suspended matter and toxics since, at 480 present, has an extremely high water retention time since 481 there is no outflow. Although reservoirs share some 482 features with lakes they have their own characteristics. 483 They have larger inputs of nutrients and stronger water 484 level fluctuations than natural lakes which lead to 485 pronounced eutrophication which in turns produces a 486 shift in the biological structure. In Karla reservoir there has 487 been recorded an increase in algal biomass and a shift in 488 zooplankton population towards small-size species 489 (Stabouli et al., 2012) as it often happens in shallow warm 490 lakes (Beklioglu et al., 2007; Alexakis et al., 2013). 491 Changes in hydrological regime cause significant 492 changes in the littoral zone with negative effects on 493 littoral habitats, benthic fauna and on fish spawning areas. 494 It has been documented that alterations in hydrological 495 regime result in frequent variations in chemical elements 496 creating drastic ecosystem changes, generally leading to 497 reduction in biodiversity (Sondergaard et al., 2016). In 498 Lake Karla the continuous decline from the suggested 499 ‘‘lower ecological water level’’ (i.e. 46.4 m a.s.l.) causes 500 accumulation of nutrient concentrations strengthening the

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eutrophication. We have not yet evidence about the extent of the nutrient’s re-suspension effect through the sediment but it is likely to happen since the bottom has a long fertilization experience during the dryness period. Ostrofsky (1978), studying the trophic changes taking place through the maturation of reservoirs suggested that during the first period of the re-filling the nutrient concentrations which have accumulated are rapidly diluted by inflowing water and sedimented by the biological processes. At the next phase, as the sedimentation and the light availability increase, primary producers reach high biomass levels (Strasˇkraba et al., 1993). The boundaries of those phases can be affected by many factors as morphometry, geographic location, retention time and thermal stratification (Soares et al., 2012). The reestablished reservoir is still very young and unfortunately there are no data from the early filling period thus the period of the first phase is quite undistinguishable. Regarding at the nutrient profile along with the dominance of algal blooms (Gkelis et al., in press; personal observations), we assume that the new reservoir is already in the very early of the second phase while this period of ‘‘ageing’’ varies depending on hydrological and biological processes (Strasˇkraba et al., 1993; Gołdyn et al., 2003). Changes in water level and retention time, normally through flushing, directly affects biogeochemical processes and consequently biological responses (Kentzer et al., 2010). Concerning Lake Karla there is an urgent need for a regular flushing out minimizing the retention time. In Mediterranean, irrigation represents the main pressure on river basins accounting for more than 60% of total water use (EGY, 2013), therefore most Greek water bodies show significant alterations in their natural Mediterranean pattern. Our study area is considered as the main agricultural area in the country and so the water needs are extremely high during the newly extended warm period. This, firstly, affects the intra annual hydroecological pattern of the Pinios River and this in turn affects the new Lake Karla since the refilling process includes the supply of large quantities of Pinios River. The negative effects could be magnified if we consider that Pinios River is also characterized by high nutrient loads (Bellos and Savvidis, 2005) thus directly affecting the lake’s water quality and ecological status. During the studied period fish population composed of thirteen species and six families with the family of Cyprinidae being the most abundant family highlighting their ability to gain the advantage to dominate in turbid, warm, eutrophic conditions (Jeppesen et al., 1997). The fish fauna of the new lake is composed almost exclusively of planktivorous and invertivorous species, thus the ‘‘top-down’’ effect (Blindow et al., 1993) is quite weak to control the eutrophic conditions. The new reservoir does not host any piscivore species and the potential introduction might affect biodiversity via competition with the existed species for resources, alteration of habitats even extinction of other species. A biomanipulation project addressing the partial removal of cyprinids might be extremely helpful since it seems very difficult to avoid their colonization. On the other hand, there is very strong evidence to demonstrate that the lake depth, the connectivity (to streams and other

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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lakes) and eutrophication all affect fish abundance, diversity and community composition, as well as the smothering of fish eggs. Many authors suggest that restoration and conservation of aquatic biota requires maintenance of the hydrological regime (Jeppesen et al., 1997; Beklioglu et al., 2007; Reynolds et al., 2012). Regarding Lake Karla, restoration measures addressing the balancing of the hydrological regime are not yet finalized. In addition, the whole catchment is undergoing an increasing warming (Loukas et al., 2014) which primarily affects the primary productivity (Dokulil, 2016). Taking also into consideration the increasing water demand, it may be more difficult to fulfil a good ecological potential without the application of updated comprehensive hydrological studies and without undertaking all proposed and additional efforts to reduce nutrient loading to levels much lower than the present-day expectations. The reduction of nutrient loading through diffuse and point pollution sources was mainly based on the construction of the artificial wetland and riparian zones which hopefully will be established in the next year. Research on the nutrient removal capacity of the wetlands revealed that the maximum potential rate of nitrogen and phosphorous removal typically ranges from 1000 to 3000 kg N/ha/year and from 60 to 100 kg P/ha/year (Verhoeven et al., 2006). In our case the total N loading is 8200 kg/day and the total P loading is 870 kg/day (EGY, 2013) thus a drastic reduction should be achieved ‘‘at source level’’ before entering the riparian zone. The decrease of fertilizer level and the control of the point pollution sources are considered as the only feasible measure. Although nutrient loading is, generally, expected to decline in warm Mediterranean area because of the low precipitation and lower runoff, however much higher concentrations are currently observed due to increased evapotranspiration leading to high concentrations in the remaining water (Jeppesen et al., 2011). Concerning our study area, the climatological data reflect a decrease on the annual precipitation and an increase of about 2 8C in monthly mean air-temperature compared to values recorded four years ago (Vasiliades et al., 2009). The whole catchment of ‘‘Pinios-Karla’’ basin is enlisted in the Nitrate Vulnerable Zones of Europe, thus the fulfilling of the Nitrate Directive’s (1991/696/EC) requirements is considered as an urgent issue. In Lake Karla both nutrients (Nitrogen and Phosphorous) are in excess while Chlorophyll-a values highly regulated by both nutrients, depending on the season (Chamoglou, 2013) and therefore management of eutrophication needs to be addressed in an integrated manner tackling both point and diffuse nutrient’s sources. The restoration site of Lake Karla is part of a large Natura 2000 area. Therefore, management requirements according to the Habitats Directive (HD) should lead to complementary restoration measures for the new wetland and the adjacent terrestrial and aquatic ecosystems. Furthermore regarding European policy the two Directives (i.e. WFD and HD) are closely link while key categories of restoration measures targeting freshwater habitats have joint benefits for water management. As regards Lake Karla although the effects of the refilling, after years of dryness, were undoubtedly positive on the conservation status of

the endemic fish species and the area is again of paramount importance for migratory birds, wintering and breeding waterfowl, waders and birds of prey (Gerakis, 1992) restoration of specific habitats through addressing the hydromorphological alterations and the pollution impacts is of great importance for relevant biota (e.g. fish, macroinvertebrates and macrophyte beds). Many farmers still cultivate their farms close to the wetland’s edge leaving little room for buffering littoral zones that would improve biodiversity and water quality. Although a decrease in agricultural land has been recorded after the wetland’s re-establishment, the intensification of the agricultural sector is probably behind the degradation of habitats contributing to the decline of biodiversity and environmental services. The fish assemblages of the Mediterranean countries have particular characteristics as: few native species, poor knowledge of their ecological preferences, high number of endemism, tolerance to environmental conditions and many invasive species (Vidal, 2008). Prior to 1936, Lake Karla represented a highly productive commercial fishery, with a large diversity of species. Catches were estimated to have been around 1000 tonnes per year. (Ananiadis, 1956). The new Lake Karla hosts four species (C. carpio, Rutilus rutilus, Scardinius erythrophthalmus and A. fallax) which are consider as native to Greece, six species (Alburnus thessalicus, Chondrostoma vardarense, C. vardarensis, C. stephanidisi, Knipowitschia thessala and Squalius vardarensis) are endemic to Greece and the Balkan Peninsula, while three species appearing the highest abundances (Carassius gibelio, Gambusia holbrooki and Lepomis gibbosus) are introduced. Among them, three species (A. fallax, C. vardarensis and C. stephanidisi) are of European conservation interest and covered by the Annex II of Directive 92/43/EEC. Actually, the introduced or translocated fish populations is a common feature in Greek lakes since the introduction of alien species was, during the past decades, the major tool in shaping the commercial fishery with negative effects to the native fauna (Leonardos et al., 2008). In Lake Karla, the item ‘‘abundance’’ of the native species varies between ‘‘very rare and present’’ while the remaining fish stocks are significantly depleted (in terms of abundance and biomass) thus the commercially fishery has collapsed. The extent to which the biodiversity loss can be reversed is thought to be dependent on how fast the remedial actions undertaken. We believe that the suggested restoration measures should be implemented immediately, not in order to create the ‘‘non-impacted conditions’’ but to help us to evaluate the extent that the degraded structure and function of the ecosystem can be restored. The restoration project of Lake Karla is being funded by the European Regional Development Fund (ERDF) and national contributions. The total cost of the restoration is about s152,020,000, of which just over s52 million being financed by the Greek government and the remaining s100 million by the ERDF. A longer delay on the technical works forces Greece to finance the non-finalized subprojects by her own national funds. In parallel, monitoring should be continued, as an obligation towards EU Nature

Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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legislation, incorporating a national/regional monitoring strategy, while the updated restoration guidelines are expected to be further defined after the present data evaluation and to be reported during the 2ed cycle of the RBMPs (including the RBMP of Thessaly District) hopefully in 2017. We certainly have to take into account that Greece during the last six years has faced an austerity policy, the Greek economy remains highly vulnerable while the present economic crisis might pose a serious risk to the Greek environment. Certainly, there remain concerns regarding the main uses’ contribution (as the agriculture) to unsustainable levels of water resources availability and quality, particularly in the Eastern part of Greece including Thessaly Region (Eurostat, 2011). In our case, the balance between agricultural activities and ecosystem’s needs should be considered acknowledging the huge benefits of the Karla’s re-filling project for the farmers and further for the regional economy. The new European legislation framework (EU Official Journal, 2013) which promotes and reforms the environmentally friendly practices in the environmental sensitive areas might be an effective tool. There is a potential dilemma between the objectives of the WFD (achieve the Good Ecological Potential) and the aims of local people so the role of stakeholders involvement should be a priority action. At the same time some austerity-inspired policies are not environmental friendly such as the low funding for the protection of the aquatic Natura 2000 areas, the lack of administrative capacities at local authorities, the low funding opportunities and the pre-existing lack of coordination with frequent conflicts among administrative institutions that handle environmental and water issues. In conclusion, the new Karla’s reservoir as a Natura 2000 protected area could lie at the very core of Europe’s Green Infrastructure (European Commission, 2013). It could not only act as an important reservoir for biodiversity and healthy ecosystem, but also could deliver many ecosystem services to society. The re-established Lake Karla is still far from welcoming a new healthy wetland. It will success to regain its multiple functional role only if we respect the characteristics of the former Lake Karla in relation to present environmental and socioeconomic needs. To our opinion, the urgent recommendations for a healthy new wetland is a synergy of the following:

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1. Implementation of the recommended environmental terms of the project posed by the project design (Ministry of Environment, Planning and Public Works, 2000) and correction of the project’s technical failures. 2. Establishment of the artificial wetland and riparian zone which will upgrade the water quality from the inflows. 3. Preventing of the nutrient loading through implementing relevant EU Directives and applying agro-environmental practices. 4. Avoiding any further delay of the Lake Karla project implementation which could lead to an hysteresis of the ecological restoration of the site. As urgent sub-projects are considered the irrigation system and the flushing system by collecting and delivering the mountainous discharges.

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5. Enforcing the environmental policy avoiding overlapping responsibilities. 6. Promoting the active involvement of the local communities. Increased participation in the whole basin management decisions by a wide range of stakeholders has been widely advocated by the Management Body of Lake Karla.

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Conflict of interest

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None declared.

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Ethical statement

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Authors state that this research was done according to ethical standards and the work described has been carried out in accordance with Publishing Ethics.

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Acknowledgement

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Authors express their special thanks to Dionysis Q6 765 Latinopoulos for his help in editing the paper. 766 Funding body This research has been co-financed by the European Q7 Union (ERDF: European Regional Development Fund) and Greek Nation in the framework of the Operational Program ‘‘Environment and Sustainable Development’’ 2007–2013 – Priority Axis ‘‘Protecting Nature and Biodiversity’’.

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Please cite this article in press as: Sidiropoulos, P., et al., Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece). Ecohydrol. Hydrobiol. (2017), http://dx.doi.org/10.1016/ j.ecohyd.2017.04.002

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