**3. Results**

In the last few decades, the water balance of Mygdonia Basin has been constantly negative as a result of the fact that water consumption has been constantly exceeding the natural recharge in the basin. From the study of the water balance of the Mygdonia water system, taking into account the historical reference data (1970–2000) and climate projections, it is evident that the water balance is getting worse as the rainfall is anticipated to further decrease (between −5.45% (period 2020–2050) to −17.99% (2050–2080)). Tables 1–3 summarize and reveal the extent of the water problem. The year 2010 was selected to be the starting year for the future climate and hydraulic study because of the lack of measured meteorological data for the period 2000–2010. The small improvement in the groundwater balance during the 2010–2040 period was mainly credited to the significant reduction in the groundwater withdrawals for industrial use due to the shutdown of industries. The vast majority of the industries that were under operation during the historical reference period are currently inactive, mainly because of the pumped water limitations that were specifically established for the Mygdonia catchment. The total amount of pumped water for industrial use is estimated to be reduced by 90% compared with the historical period.


**Table 1.** Mean water balance of Mygdonia aquifers (hm3/year).

**Table 2.** Mean water balance of Lake Koronia (hm3/year).


In the Mygdonia Basin, different supply- and demand-oriented measures were tested. The supply-oriented measures focused on stream diversion and reservoir construction to enhance the water potential of the water system, which was found to be inadequate to restore the degraded water system. Details can be found in [47].

Three Sustainable Development Strategies (SDS) were formed via the combination of some demand managemen<sup>t</sup> measures to reduce water use and improve water efficiency through the restructuring of crops and changing irrigation systems based on different local, regional, national and international policies.

In the Mygdonia Basin, the dominant crop is cereal, which is a rain-fed crop, and thus does not negatively affect the water balance of the basin. Maize and alfalfa are the highest water-intensive crops and provide high farm income. Low-water-intensive crops, such as cereals and animal feed, provide low farm income. The area per type of crop from data by the Regional Administration of Central Macedonia in the Mygdonia Basin is depicted in Figure 3. From the net agricultural income per crop from data of the Greek Ministry of Environment, Energy and Climate Change (POL1077/2014), the current annual total net farm income in the whole Mygdonia Basin is estimated to be equal to EUR 45,773,037.90.


**Table 3.** Mean water balance of Lake Volvi (hm3/year).

**Figure 3.** The area of each crop in the Mygdonia Basin.

The three Sustainable Development Strategies tested are:

1. **The reduction of the total irrigated agricultural area (SDS1)** related to a national priority (NP), the Rural Development Plan 2014–2020 of Greece and the EU Common Agricultural Policy, according to which, the fallow land measure was proposed to be applied to at least 30% of the irrigated area, while in the set-aside land, all types of agricultural activities are prohibited. In particular, the fallow land measure was proposed to be applied to all kinds of irrigated crops in the study area with the exception of tree plantations and vineyards, which are multiannual crops. Following a trial-and-error method, it was found that the minimum percentage of the irrigated land of the Mygdonia Basin that should be set aside in order to achieve a water surplus of Mygdonia aquifers is equal to 33% and 61% for the short-term (2020–2050) and long-term (2050–2080) future periods, respectively. By applying the proposed SDS1, the irrigation water demand was projected to decrease from 178.38 hm3/year to 119.50 hm3/year in the 2020–2050 period and from 192.91 hm3/year to 75.38 hm3/year

in the 2050–2080 period. If SDS1 is applied, the farmers' incomes will have a reduction from EUR 45,773,037.90 to EUR 35,395,528.60 in the short term (2020–2050) and EUR 26,587,206.00 in the long term (2050–2080). More details on crops can be found in Kolokytha et al. [47].

2. **The expansion of the livestock sector as alternative economic activity along with the restructuring of crops (SDS2).**

Hay production from alfalfa and livestock crops for the needs of the livestock sector is far more (280,201.00 ton/year) than what is needed for the animals (50,327.51 ton/year); therefore, there is significant space to enlarge the livestock sector. SDS2 refers to an increase of 20% of the livestock sector in the Mygdonia Basin based on the report of the Management Body of Lakes Koronia and Volvi. The livestock feed cultivated area, i.e., the alfalfa and the animal feed crops, was proposed to decrease in order to reduce the irrigation water needs in the study area. The maximum acceptable decrease in the livestock feed area was found to be equal to 75%. In the 2020–2050 period, the minimum decrease in the livestock feed area was estimated to be equal to 62% for a water surplus of the Mygdonia aquifers to be achieved. In the 2050–2080 period, even the decrease in the livestock feed area at 75% could not rehabilitate the water deficit of the aquifers; therefore, it was proposed to be accompanied by a reduction in the remaining water-intensive crops in the study area, i.e., maize, tobacco, eastern type tobacco, cotton, sugar beet, sorghum, beans, legumes and potatoes. Of course, the reduction in the irrigated area was projected to decrease the total farm income in the Mygdonia Basin. To compensate for the reduction in rural income, the cut of the irrigated area was proposed to be implemented along with a promotion of crops providing a high net income for farmers so that the economic component of sustainability was also met. The plantation of energy crops for biofuels production, which are projected to be greatly competitive in the future according to European adaptation policies, was tested for the restructuring of crops. Among nine energy crops that were examined in terms of the suitable climate and soil conditions, the irrigation requirements, the harvest period and the net income provided to farmers, *cardoon* is the most suitable one regarding the climatic and environmental conditions of the study area. This particular crop is highly resistant to the Mediterranean climate (high durability in the low temperatures of the Mediterranean winter, high adaptability to arid conditions with prolonged periods of drought) and provides a high net farm income, about 76,533.33 EUR/km2/year. In particular, cardoon and cereals (rain-fed crops) that improve the food security of the study area were proposed to be promoted.

3. **A combination of the promotion of drip irrigation systems, along with the restructuring of crops (SDS3).** SDS3 concerns the promotion of drip irrigation systems in maize crop cultivation. The future water deficit of the Mygdonia aquifers could not be rehabilitated, even if this measure would be applied throughout the whole Mygdonia Basin. Therefore, the area of the water-intensive crops mentioned in SDS2 needs to be reduced. In the 2020–2050 and 2050–2080 periods, the minimum required decrease in the area of these crops was found to be equal to 35% and 66%, respectively, for the restoration of the Mygdonia aquifers to be achieved. The drip irrigation systems were proposed to be installed at 25% and 35% of the maize cultivated area during the 2020–2050 and 2050–2080 periods, respectively. For the compensation of the farm income loss, crops that provide high net farm income, such as vegetables, potatoes and cardoon, were proposed to be promoted, along with cereals.

The future water balances of the Mygdonia aquifers and Lakes Koronia and Volvi under the Sustainable Development Strategies are presented in Tables 4–9.


**Table 4.** Average annual water balance of the Mygdonia aquifers for the 2020–2050 period under the SDS1, SDS2, SDS3.

**Table 5.** Average annual water balance of the Mygdonia aquifers for the 2050–2080 period under the SDS1–3.



**Table 6.** Average annual water balance of the Lake Koronia for the 2020–2050 period under the SDS1–3.

**Table 7.** Average annual water balance of the Lake Koronia for the 2050–2080 period under the SDS1–3.


**Table 8.** Average annual water balance of the Lake Volvi for the 2020–2050 period under the SDS1–3.



**Table 9.** Average annual water balance of the Lake Volvi for the 2050–2080 period under the SDS1–3.

### *Analysis of the Results*

All three Sustainable Development Strategies are projected to achieve a water surplus of the Mygdonia Basin for both the short-term and long-term future periods. Tables 4 and 5 shows that the significant reduction of discharge for agricultural use is the main reason for the quantitative rehabilitation of the basin. The restructuring of the agricultural sector is proposed to be more intense in the 2050–2080 period compared with the 2020–2050 period in order to compensate for the larger decrease in the recharge to aquifers during the long-term future period. In particular, in the 2020–2050 period, the outflow from Mygdonia aquifers for agricultural use is projected to decrease from 178.38 hm3/year in the no-action scenario to 119.50 hm3/year ( −33.00%) in SDS1, 118.86 hm3/year ( −33.37%) in SDS2 and 118.06 hm3/year ( −33.82%) in SDS3. Furthermore, in the 2050–2080 period, the water withdrawals from the Mygdonia aquifers for irrigation are projected to decrease from 192.91 hm3/year in the no-action scenario to 75.38 hm3/year ( −60.92%) in SDS1, 74.82 hm3/year ( −61.22%) in SDS2 and 74.20 hm3/year ( −61.54%) in SDS3. The improvement of the water availability of the Mygdonia aquifers is not projected to have a positive effect on the water balance of Lake Koronia (Tables 6 and 7 due to the impermeable bottom of Lake Koronia [68], preventing any water flow exchange between the lake and the aquifers. Moreover, the quantitative rehabilitation of the Mygdonia aquifers is projected to increase the water inflow from the Mygdonia aquifers to Lake Volvi and to decrease the water outflow from the lake to aquifers, resulting in an increase in evaporative losses due to the increase of the water availability and surface area of the lake and, finally, to the slight improvement of the water balance of Lake Volvi, as shown in Tables 8 and 9.

In terms of economic sustainability (rural income), the implementation of the fallow land scheme in SDS1 is expected to cause a decrease in the total net farm income in the Mygdonia Basin from 45,773,037.90 EUR/year (no-action scenario) to 35,395,528.60 EUR/year in 2020–2050 and 26,587,206.00 EUR/year in 2050–2080. A compensatory policy in the form of offsets may be a good option.

Increasing livestock farming while reducing alfalfa farming (water-intensive cultivation) and promoting energy crops proposed in SDS2 provide a competitive alternative growth option that is expected to increase the total net farm income from 45,773,037.90 EUR/year (no-action scenario) to 46,194,872.34 EUR/year (+0.92%) in 2020–2050 and 45,901,602.53 EUR/year (+0.28%) in 2050–2080. This strategy is capable of successfully managing the groundwater aquifer deficit. The promotion of drip irrigation systems, along with the crops restructuring proposed in SDS3, is expected to provide a small increase to the farmers' net income from 45,773,037.90 EUR/year (no-action scenario) to 46,267,432.24 EUR/year (+1.08%) in 2020–2050 and 45,971,157.73 EUR/year (+0.43%) in 2050–2080.

Another adaptation scenario based on the European Energy Roadmap 2050 concerned the exploitation of the wind potential, with the installation of wind farms to produce "green" electric energy that can be used in pumping wells for irrigation. The land-use feasibility and economic viability of this plan were examined using the "Greek Special Framework for Spatial Planning for Renewable Energy Sources", which is the main legislative instrument for establishing wind farms according to land-use criteria. It provides criteria and guidelines for the site allocation of RES projects with an emphasis on wind systems and ensures the sustainability of RES investments through their harmonious incorporation within the natural and human environment. The combination of 10 environmental, 1 technical, 5 economic and 3 social criteria resulted in the determination of an eligible area for establishing wind farms based on land-use criteria. The future wind potential of the Mygdonia Basin was estimated using the monthly wind speed projections at a height of 10 m above the surface. The future wind speed data were derived from the SMHIRCA climate model under the IPCC SRES A1B with a spatial resolution of almost 25 km. The annual wind speed in the whole basin at a 10 m height above the surface was found to be less than 4 m/s, which is insufficient since this wind speed is lower than the cut-in speed of wind turbines. The installation of wind turbines at heights of 80, 100, 120 and 140 m above the surface was examined. Finally, it was found that wind turbines should be established at a height of 140 m above the surface, where the generated electric energy by wind was found to be a non-economically viable plan since the total cost of the installation of the wind turbines was estimated to be far more expensive than that from conventional resources to be used in pumping wells for irrigation. Details on the methodology can be found in [66].
