Fehérvárcsurgó reservoir

The Fehérvárcsurgó reservoir is located in Fejér County, next to Fehérvárcsurgó. It was created by enlarging the Gaja stream; it feeds and provides its outflow. The multi-purpose (flood‑peak reduction, industrial and drinking‑water extraction, water‑quality‑improving dilution water, agricultural) reservoir type: valley‑dam reservoir. The reservoir is situated in the low‑mountainous and hilly area of the Bakony Mountains’ eastern edge, in the valley section of the Gaja stream, 1.5 km from the settlement of Fehérvárcsurgó. Here the valley of the Gaja stream widens in a basin‑like manner for about 2.8 km. In the D‑section of the reservoir the valley section narrows to roughly 100 metres, the so‑called Vaskapu gorge. This terrain feature was already exploited at the end of the Middle Ages and a earth dam was built. The present valley dam was constructed on the site of the medieval dam, in the 20 + 280 km stretch of the Gaja stream. Thus the reservoir was built by enlarging the Gaja stream with a valley‑dam structure. The reservoir’s catchment area is 273 km2.

It was built in 1971-72 as part of the Kincsesbánya Rákhegy II bauxite mine investment. The bauxite mining carried out at great depth for about 25 years required a subsidence exceeding 200 m of the karst water level and the continuous extraction of a very large amount of water (1‑2 m³/s). Since the Gaja stream ran over the mine area on a roughly 2 km long section downstream from the Vaskapu gorge, a significant part of its water could have seeped into the mine through karst water‑conducting layers between the riverbed and the upper level of the mine. Therefore the water of the Gaja had to be diverted into a new riverbed so that it would feed the karst water as little as possible. In order for the water of the Gaja to be able to flow into the side channel that was created, the valley of the stream had to be closed at an appropriate height with a valley‑closing gate. The level of the valley closure was determined by the requirement that the peak flood yield entering the side channel be considerably smaller than the flood water carried by the stream: the reservoir must be able to retain flood waves until they are discharged by the side channel with the lower water‑carrying capacity. Unlike reservoirs built for water‑use purposes, the useful volume of the Fehérvárcsurgó reservoir allocated for flood‑wave retention should preferably be kept empty at all times to accommodate newly arriving flood waves. By diverting the Gaja stream, the deep‑mined bauxite mine area became protected from infiltrations originating from surface waters. After the reservoir was built, the operational discharge of water through the valley‑closing gate in the “original riverbed” of the Gaja – in accordance with the interests of the bauxite mining – was therefore not possible.

Its average water depth is 6–8 metres, but its deepest points can reach 14–15 metres depending on the level of filling. At maximum filling, the water surface can be increased to 223 hectares.

It is one of the country's most beautiful lakes in terms of surroundings. From the surrounding hills and mountains, there is a beautiful view of the lake.

Its altitude above sea level is around 147 m.

History

Before the planning, the area was archaeologically excavated. Based on the excavation, it was proven that during the flourishing of the Roman Empire, in the 2nd century, the Gaja stream was dammed at this location. The enlarged stream was used for water extraction and bathing purposes. It is not sufficiently proven that the water dam also operated under Turkish rule. The opinion that the Turks intended to use it for a possible flooding of Székesfehérvár remained in oral tradition.

The reservoir was created in 1971; originally, the land of the producers' cooperative’s cabbage fields lay there, and three mills also operated on the Gaja stream that supplied water to the lake (these were later abandoned and then demolished because of the reservoir's construction). The stream was diverted for several kilometres, and an earth dam was built in the original river valley.

In 2007, signs of beaver presence were found in the area between the lake and the Gaja valley, which WWF staff also confirmed. The beavers most likely migrated here from the Gemenci forest, located about 100 kilometres to the south.

In May 2010, the previous maximum water level of 500 cm collapsed because breaches in the Mór fishing lake dams threatened Székesfehérvár with a flood wave, so the water authority could not begin releasing water from the reservoir. On the morning of May 19, with a water level of 640 cm, the reservoir contained 11 million m³ of water.

Structure and dimensions of the dam

The dam body has the shape of an elongated irregular‑sided trapezoid. Before construction, the root system and humus were removed to a depth of 0.5 metre. On the dolomite bedrock, the sandy clay is on average 5.0 metres thick, covered by 2.0–3.0 metres of dolomite rubble. The water‑side sealing body consists of sludge. The water‑side filter layer is made of prefabricated concrete elements. The protected‑side filter was covered with a productive layer and humus, then seeded.

Typical dimensions:

Crest elevation above sea level: +156.15 m.

Downstream slope of the spillway: 1:5.5.

Upstream slope of the spillway: 1:2

Average upstream ground level: +142.0 m.

Downstream ground level: +143.85 m.

Flood surcharge level: +152.0 m.

Average water level: +148.0 m.

Minimum water level: +146.0 m.

Maximum base width of the dam body: 25.0 m.

Crest width of the dam: 5.0 m.

The valley dam and the gates are fully constructed, but the reservoir sealing reaches only up to a water depth of 300 cm.

Tourism

The reservoir has a designated beach, and the lake’s gate is also a popular swimming spot among locals. Next to the gate, at lower water levels (about 100 cm), the concrete tongue can be seen; it is about 100 m long and extends toward the middle of the lake. This is a popular walking path. In summer a leisure venue operates on the lake shore, and a boat dock is open year-round.

The National Blue Trail runs along the shore of the reservoir.