**1. Introduction**

The scientific question on whether the observed recent climate changes are anthropogenic or exclusively natural occurring over time as the natural cycle of climate change has been the subject of several studies in the last few decades [1–3].

The Intergovernmental Panel on Climate Change (IPCC) has recently released the Physical Science Basis report (August 2021), where it is documented that "climate change is already affecting nearly every part of the planet, and human activities are unequivocally the cause" [4]. It is imperative to immediately take action.

Regardless of the main reasons, what the whole scientific community agrees on is that climate change exists and that a new reality is here to be dealt with.

Water is the most vital component of life and is critical for almost all economic activities; as such, it is central to the achievement of sustainable development. The Global Risks Report of 2020 ranks environmental issues (among them, extreme weather events natural disasters, water crisis, failure regarding climate action) first on a list of the top global risks in terms of the impact on humanity [5]. According to the UN, climate change is projected to increase the number of water-stressed regions and exacerbate shortages in already water-stressed regions [6]. Alteration of the water cycle (quantity and quality) and an increase in extremes events are major impacts of climate change on freshwater resources. The planet will face a 40% shortage in water supply by 2030. Hydrological disasters, floods and storms accounted for 44% and 28%, respectively, of all disaster events from 2000 to 2019, affecting 1.6 billion people worldwide [5].

**Citation:** Kolokytha, E. Adaptation: A Vital Priority for Sustainable Water Resources Management. *Water* **2022**, *14*, 531. https://doi.org/10.3390/ w14040531

Academic Editor: Maria Mimikou

Received: 28 December 2021 Accepted: 5 February 2022 Published: 11 February 2022

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**Copyright:** © 2022 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Climate change is characterized by grea<sup>t</sup> uncertainty, affecting the development model of a country directly and decisively, with significant differences in time and space at all levels, namely, local, regional, national and global. In order to reverse or halt the severe consequences of the current climate crisis, we need to work collectively and understand the depth and complexity of this crisis. Two types of responses for climate crisis mitigation and adaptation need to be applied concurrently. Mitigation [7] addresses the root cause of climate change (accumulation of greenhouse gases in the atmosphere), whereas adaptation addresses the impacts of climate change. Adaptation, in brief, anticipates the adverse effects of climate trends and takes appropriate action to prevent or minimize the damage they can cause [8–15]. Since mitigation reduces the rate, as well as the magnitude, of the root cause (warming), it also increases the time available for adaptation to a particular level of the climate crisis.

In the 21st century, "a new global theory" for water and its managemen<sup>t</sup> is needed. Until recently, the hydrologic record of the past was the best guide for the future [16]. However, due to the increase in the rate of extreme events, as well as the non-stationarity and the grea<sup>t</sup> vulnerability and uncertainty in hydrological projections, we need to move from a solely technical and engineering managemen<sup>t</sup> of water to a clear understanding of the complicated links between land, forest, agriculture, biodiversity, energy, health and true integration of the human dimension. We need to make water managemen<sup>t</sup> more adaptive and flexible to be operational under fast-changing global socio-economic and climate-sensitive conditions [17,18]. A major issue in this effort is the reassessment of the global consumption and production model to manage food security, water scarcity and sustainable development through effective adaptations in agriculture.

In their quest for sustainable development, policymakers have to make trade-offs between the benefits and costs of adaptation measures, opinions on how much risk is socially acceptable and other development objectives [19,20].

The objective of the current research was to assess the climate impacts on water managemen<sup>t</sup> in basins with severe water deficits by providing a better understanding of the adaptation options at a local level. More specifically, demand and supply adaptation strategies are explored in river basins with negative water balances and intense agricultural activity. The implementation of adaptation options was achieved by using a comprehensive analysis of both hydrologic and water managemen<sup>t</sup> methods. This approach amplified the premises of sustainability, reflected new paradigms and practices and explained the opportunities for innovative approaches in water resources management. The case study of Mygdonia Basin was used as a representative example, as it is a highly water-stressed agricultural basin with an already negative water regime. Similar cases are encountered, both in other basins in Greece and in the Mediterranean. This article can act as a useful decision-making tool for policymakers to implement adaptation solutions to manage water resources, taking into account climate impacts in the area under study in a sustainable way.

### **2. Materials and Methods**

### *2.1. Water Resources and Uses in Greece*

Greece is located in the eastern part of the Mediterranean Basin, with the most extensive coastline in Europe of 15,000 km along the Mediterranean Sea. The climate is characterized by mild and rainy winters, relatively warm and dry summers and long sunshine duration almost all year long. Although the country is claimed to have adequate water reserves at 6471 m3/capita/year [21], it suffers from a high temporal and spatial distribution of the water supply, which causes significant water shortages in specific regions in Greece [22,23]. The particular geomorphological conditions with the wet mountainous region concentrated along the backbone of the country, the rather dry long coastline and the numerous islands scattered in the Ionian and Aegean seas are responsible for the uneven distribution of the water supply. As a result, plentiful water can be found in the mountains flowing into the sea creating small torrents and rivers during winter, with almost no flow during summer in the dry period [24]. Moreover, there is high spatial and temporal water

demand. Greece is an agricultural country, with 84% of its consumption belonging to the agricultural sector, with strong tourism in the islands and high seasonal water demand in the summer. High urbanization, with half of the population concentrated in two cities (Athens and Thessaloniki), where competition for water for economic activities is high, is another reason for the temporal and spatial water demand in Greece. Furthermore, the dependence of the country on the 16–20% of waters imported by four transboundary rivers reveals the extent of the water problem.

### *2.2. Demand Management versus Supply Management*

Demand managemen<sup>t</sup> has gone largely unaddressed in Greece since most water services focused on infrastructure development rather than on water conservation. This supply-oriented water policy for all these years was based on the "notion" that the solution to the water problem relies unilaterally on the country's capacity for engineering solutions to divert, construct and bring water to where it is needed, no matter how far and how costly this may be, has resulted in negative water balances and the depletion of groundwater reserves in many basins (Central Macedonia, Thessaly, Aegean Islands) [25]. Moreover, tools such as water pricing, especially in the agricultural sector, were only considered a viable option under the condition that all other supply options were exhausted, and overexploitation of surface and groundwater resources had resulted in water depletion. This hydrological reality, together with the fact that climate change will deteriorate the water reserves, calls for a drastic change in managing water for all uses. In such cases of drained water basins, the efficacy of measures that reduce/limit the use of water is questionable. It is highly likely that more drastic measures need to be taken, such as a change in the relevant economic activities and the suspension of the most water-consuming activities among them.

### *2.3. Water Climate Impact Projections in the Mediterranean and Greece*

The Mediterranean Basin is a region that is already greatly affected by climate change [26], which is expected to remain among the "hotspot" regions most affected by climate change in the future, particularly when it comes to precipitation and the hydrological cycle [27–30]. The climate is changing in the Mediterranean Basin faster than global trends [26]. It is expected that heat waves will intensify in duration and peak temperatures, as well as heavy rainfall events, are likely to also intensify by 10–20% in all seasons except summer [31,32]. Precipitation and temperature changes are expected to increase crop water requirements [33] while putting food security in peril [34].

Despite strong regional variations, summer rainfall will likely be reduced by 10 to 30% in some regions, increasing existing water shortages and desertification and decreasing agricultural productivity [33,35]. As a typical Mediterranean country, Greece will experience these impacts. Water resources seem to be particularly affected by climate change in Greece, as it is reported that Greece ranked 26th among the countries that experienced severe water stress in 2019 and this water stress is highly likely to ge<sup>t</sup> worse by 2050 [36].

The Bank of Greece [37] published a detailed assessment of climate projections over Greece. In this report, in order to capture the possible changes in the water potential of the country until the year 2100, hydrological balance components were estimated for the periods of 2021–2050 and 2071–2100 using the emission scenarios A1B, A2 and B2. Details on the emission scenarios can be found in [6]. The results indicated significant changes in the hydrological components for each possible scenario. Specifically, the comparison regarding the changes in rainfall volume and total water potential (surface runoff and groundwater discharge) per climatic scenario in the whole Greek territory under current and future conditions predicted a reduction in rainfall ranging between 3% to 7% and a total water potential reduction (surface runoff and groundwater discharge) by 7–20% for the period of 2021–2050. Concerning the period of 2071–2100, the reduction will continue and most probably will be even higher, ranging from 14% to 22% regarding rainfall and between 30–54% regarding the water potential for the whole country [37]. These findings are in line with the IPCC 2014 report, which predicted (based on climate model A1B) that in the eastern part of the Mediterranean Basin (where Greece is located), rainfall in 2080–2099 will show a decrease of more than 20% compared with the period of 1980–1999. Furthermore, the annual precipitation is expected to decrease in most Mediterranean areas, including Greece, with the annual number of precipitation days being decreased. It is noted that the risk of summer drought is expected to rise, especially in southern Greece, while the duration of the snow season is very likely to be shorter [38,39].

In relation to temperature, according to the IPCC 2014 report, the annual mean temperatures, as well as the evapotranspiration in Greece, are likely to increase more than the global mean, especially regarding maximum summer temperatures.

In Greece, an increase in irrigation and tourist needs, as well as in the pollution load, is expected in the near future [37,40]. Vulnerability to climate change for the period 2050–2100 in comparison with the period 1961–1990 was also assessed. Greece shows a high vulnerability in Central Macedonia and the Western Peloponnese and moderate vulnerability in Thrace, Thessaly, Attica and Rhodes [41–44].

It is evident that the already disturbed water balances in the water basins in Greece will be further accelerated based on the future projections of climate impacts. Obviously, as precipitation has a strong local/regional component, this acceleration will have different results and will be shown first in the most vulnerable regions.

### *2.4. The Mygdonia Water Basin*

Mygdonia Basin is located in Central Macedonia, 11.5 km northeast of the city of Thessaloniki. It occupies an area of 2061.48 km2, with a population of approximately 65,000 inhabitants (ELSTAT2011), and hydrologically belongs to the Water District of Central Macedonia (GR10). It is surrounded by mountains with an altitude of 600–1200 m and the climate is a typical Mediterranean one. The surface flow is seasonal coming from distributed streams in winter, whereas during the dry season, their flow is reduced or almost non-existent.

Mygdonia Basin is a protected wetland according to the Ramsar Convention, with a complex water system comprising Lake Koronia (western part of the basin, 1278 km2), Lake Volvi (eastern part of the basin 783.48 km2) and the Mygdonia groundwater aquifer (Figure 1). The Ramsar Convention encourages the designation of sites containing representative, rare or unique wetlands or wetlands that are important for conserving biological diversity. The Koronia and Volvi wetlands support endemic fish, nesting waterbirds and large numbers of wintering birds, including Anatidae (geese, ducks, swans, etc.). Several nationally rare or endangered aquatic plants also occur here [45].

**Figure 1.** Map of the reference area provided by Malamatatis D. in his PhD.

The mild climate and the fertile soil favor irrigation of these lands and have contributed to the rapid development of agriculture. The economy of the area consists of small local enterprises serving the needs of the local communities. Besides agriculture, residents are mainly employed in livestock, while the secondary section of the economy mainly involves wood and construction enterprises. This information is given by the responsible Koronia–Volvi Management Body.

The overflow of Lake Koronia drains into Lake Volvi through the Derveni stream (Figure 1). The overflow of Lake Volvi drains into the Strymonikos Gulf through the Richios stream. The groundwater flows from the Koronia sub-catchment to the Volvi sub-catchment, and then a part of this discharge outflows to Lake Volvi and another one outflows to the Strymonikos Gulf. There is no flow interaction between the groundwater and Lake Koronia, as the bottom of the lake is impermeable [46].

It is a predominantly agricultural water basin in the Mediterranean region, with 95% of the basin's water being used for agricultural purposes [45], which suffers from unsustainable water managemen<sup>t</sup> practices. During the last few decades, Lakes Volvi and Koronia, along with the Mygdonia Basin aquifer, have undergone severe quantitative and qualitative degradation due to past industrial, agricultural and urban activities. In particular, the water depth of Lake Koronia has progressively decreased since 1970, resulting in complete depletion in the summer of 2008. Lake Volvi, as a larger and deeper lake compared with Lake Koronia, experienced a smaller reduction of its depth. Moreover, the limited recharge to the Mygdonia Basin aquifer and the over-pumping for irrigation caused a significant drawdown of the groundwater table [47]. Central Macedonia (GR10) faces groundwater quantity pressure, as about 25% of the groundwater bodies are characterized to be in a poor/bad quantity state [44].

The environmental problems of the Mygdonia Basin were initially recognized in 1995 when an episode of mass fish deaths took place in Lake Koronia. The environmental collapse of Lake Koronia resulted in the drafting of the "Master Plan for the restoration of Lake Koronia" in 1998. The Master Plan had been oriented toward large-scale infrastructures and a water transfer scheme from the River Aliakmon, which flows in a neighboring catchment. Several of the proposed solutions in the Master Plan raised objections from both the central administration and international institutions since they were hard engineering projects that would cause considerable environmental impacts in the area, mainly altering the Ramsar protected ecosystem and the hydrodynamics of the water systems. In 2004, a "Revised Restoration Plan of Lake Koronia" was carried out to review the first Master Plan.

The overexploitation of the surface water system (Lakes Koronia and Volvi) and groundwater resources during the previous decades, along with the projected decrease in the future water availability due to climate change, indicate the need to highly prioritize concerted action toward adaptation to climate change in the Mygdonia water system [48–50]. Research on Mygdonia Basin is limited and mainly concerns Lake Koronia, although there are some studies on Lake Volvi that mostly focused on water quality issues [51–56]. Some attempts were made to address simulations the restoration of the water balance of the hydrological basin of Lake Koronia by Manakou [57], while Zalidis [58] and Zalidis et al. [59] studied the Master Plan for the restoration of Lake Koronia. Kolokytha [60–63] examined the impact of WFD and EU CAP and the water footprint of crops in the Lake Koronia basin. Veranis [46] studied the hydrogeology of Mygdonia Basin, while the perspectives of the exploitation of the deep aquifer for the restoration of the Lake Koronia were examined by Mylopoulos et al. [64,65]. Our group has tried an integrated approach that investigated the impacts of climate change in the whole Mygdonia water system (conjunctive use of surface and groundwater resources) and the economy of the region [47,49,66].
