Lake Hévíz Protected Area

The area directly affected by protection is located on the southern part of the Danube region of Hungary, on the border of the Zala Hills and the Keszthely Plateau, on the Zalavár ridge. It is 7 km west of the westernmost town on Lake Balaton, Keszthely, situated in the inner and outer parts of the town of Hévíz, in a southeast direction from the town centre. Area: 60 ha 5062 m² (of which the lake surface area is 4.44 ha).

Guidelines

The Balaton Uplands National Park Directorate, in agreement with the Hévíz Saint Andrew Rheumatology Hospital and Spa as property manager, decided on the expansion of the Hévíz Healing Lake Nature Protection Area for the enhanced protection of the unique Hévíz Lake in the world. The entire settlement of the town of Hévíz, tourism, has significantly increased the possibility of interventions and pollution that endanger the lake (its wildlife, physicochemical properties, and their therapeutic effects).

The expanded nature protection area includes the entire inner protected area of Hévíz Lake, which, except for an outer forest parcel, is under the care of the Saint Andrew State Rheumatology and Rehabilitation Hospital. With this expansion, a unified nature and environmental protection management can be ensured for this inner protected area. This makes it possible for the interests of nature protection and those defined in hydrogeological research to be fully realized.

The intensively protected spring cave and lake, the fundamental criterion of the water's therapeutic properties, depends on water yield. The marshes surrounding the lake are protected by law (ex lege). According to the final report of the VITUKI – MÁFI research, the optimum sulfur circulation occurs at a water yield of 450 – 500 l/s. The final report proposes that “the development of a quantitative protective monument is justified, which ensures that the pressure‑reducing effect of future authorized water extractions does not endanger the regeneration of the Hévíz therapeutic spring in the long term.”

Climate

In general it can be said that the area is affected by a sub‑Mediterranean climate, which manifests in a precipitation maximum at the end of May and in October. A relatively mild winter and a not too hot summer are characteristic.

The average annual precipitation is 500–700 mm.

Annual temperature average: 10.2 °C

January mean temperature: –0.4 °C

July mean temperature: 20.8 °C

Number of snowy days: 20‑25 days

Wind direction and frequency: E – 15%

As a result of the interaction between the lake and the surrounding protective forests, a distinctive local microclimate has developed. Due to the wet areas, the local climate is more balanced, the forests block the winds, and the lake and its surroundings often become enveloped in fog. The lake greatly influences the natural conditions of the park. The most significant modifying effect is the thermal effect, whose physiological impact is the most characteristic alongside the soil conditions. Because of the properties of the warm water, the lake influences the mesoclimate in its surroundings in the following way:

the thermal effect, due to the wind‑break effect of the forest bordering the lake to the north and northwest, is manifested not only directly above the water surface but also farther away

by heating the groundwater, the soil of the lakeshore strip remains unfrozen in winter, or only the surface layer near the water freezes

the evaporated water during severe frosts condenses on the branches of surrounding trees and shrubs as dew or frost, and through the heat released by dew formation and freezing it moderates their stronger cooling

as a result of these three effects, the climate of the shoreline strip (up to 20–40 m from the water) is even more favorable than the region’s otherwise relatively balanced macroclimate, thus

thanks to the nearby groundwater, the water supply is abundant both in winter and summer

since the soil near the lake does not freeze through, the evergreens do not suffer from physiological drought

summer is only a few degrees, or not at all, warmer than the autumn‑winter‑spring period, the conditions being significantly milder near the warm water mass

Hydrology

The water of Lake Hévíz is continuously supplied by the springs of the source cave. The funnel‑shaped lake’s spring cave, opening at a depth of 38.5 m, is the mountain‑peripheral breakthrough point of one of the large underground flow systems of the Transdanubian Central Mountains. The springs emerge on the northern side of the Keszthely Plateau along an east‑west structural line from Upper Pannonian conglomerate and sandstone. In a single cavern, the waters of warm and cold springs mix. A mud ridge divides the cavern in two. Here the thermal water originates: on the eastern side water at 26.3 °C (≈10 %) emerges, while on the western side water at 41 °C (≈90 %) emerges.

The lake’s total water volume is renewed every few days. To the north the water is taken up by the Ó‑Berek canal via the northern outflow, and to the south by the Hévízi outflow. Within the Hévízi therapeutic lake TT area there is another canal, the Úsztatómajori canal, which meets the same fate as the Hévízi outflow. Ultimately the lake’s water reaches the Zala River and then Lake Balaton.

Plant associations

The western park forest belongs phytogeographically to the Pannonian flora region of the Transdanubian flora area of the Zala region.

The composition of tree species deviates greatly from the natural forest type appropriate to the local climate and soil conditions. The natural vegetation cover would be a Pannonian beech-oak forest. In the shrub and grass layer of the forest we find the species characteristic of this association: common hazel, striped dogwood, dwarf birch, wild garlic, snowdrop, etc. In reality, the upper canopy layer consists of groups of black pine, larch, and red pine planted by the Festetics family for landscaping purposes. The dominant tree species in the lower canopy layer are acacia, linden, green maple, mountain maple, early maple. In the forest grass layer, broom, meadow sage, fragrant lilac, and dwarf pine are abundant. The 100‑year‑old or older beeches in the stand evoke the past. The forms of the beech trunks testify to former meadow management.

The plant community of the Lake Hévíz peat mound belongs botanically to the Pannonian phytogeographic region, specifically to the southwestern Transdanubian phytogeographic area of the Zala flora.

Lake Hévíz, together with the surrounding peat and marsh areas, forms a single hydrogeological, ecological and phytogeographic unit. Human influences are now dominant over the original natural components.