Virág Árpád: A Sió és a Balaton közös története. 1055–2005 (KÖZDOK Kft., Budapest, 2005)
The common history of Lake Balaton and the Sió Canal (1055–2005)
THE COMMON HISTORY OF LAKE BALATON AND THE SIO CANAL (1055-2005) 523 In a geographical account prepared in 1730 and preserved in manuscript form, the Sió stream was described as follows: The inflow which Lake Balaton is no more capable of storing spills into the Sió stream on the southern shore. Evidently, this occurs only at times, when the lake level is high. During dry spells the lake retreats and no water is supplied to the stream leaving its deep bed dry enough to wade comfortably. The lake is replenished by the succeeding wet period and starts spilling into the Sió, which meanders for some three miles, then disappears to continue underground for another mile. The water emerges again as a spring, which feeds thenceforth the bed. The description applied probably also to the natural relationship between Lake Balaton and the Sió stream dring the earlier centuries. Similar conditions persisted well into the second half of the 18th century, when - as part of a 1776 plan to reclaim the marshes and drain the lake, further to create a waterway between the Drava and the Danube-Lake Balaton and the Sió stream were represented correctly on maps. (Earlier maps from the 16th—18,h centuries have distorted the lake and her outlet alike.) A cadastral map dating back to the second half of the 18th century has shown the true situation of the middle section of the Sió in considerable detail, including accurately both banks and also the islands in the bed. An 1815 copy of this map is held in the Hungarian National Archives. Map sheets to 1:28 800 scale including 14 sections of Lake Balaton and the Sió stream were plotted on the area of the Kingdom of Hungary during the I. Military Survey between 1782 and 1785. However, these maps were strictly classified and thus inaccessible to civilians until the middle of the 19lh century, when they were replaced by the updated, more accurate, unclassified documents of the II. Military Survey. Maps serving a wide variety of purposes (military, economic, administration, tourism, etc.) and drawn to different scales were published during the 20th century. Those showing the evolution around Lake Balaton and in the Sió Valley are described in details in the text. The southern part of Transdanubia - including the southern shore of Lake Balaton and the Sió Valley was invaded by the Turks in 1541. Over the close to 140 years of Turkish rule the state of the environment and the conditions of human settlement and farming deteriorated perceptibly, while the climate turning wet has contributed to the expansion of marshes and widespread waterlogging in the region. Upon the withdrawal of the Turks around the middle to the 18th century, reclamation of these marshes and land drainage in the Sió Valley became urgent, in that these have hindered transport and represented a health hazard. Work was launched in 1744 on excavating a regular bed for the Sió stream and on draining-reclaiming the Sárvíz marshes (the project took 50 years to complete). Training the River Kapos together with the Sió reach along Simontornya was accomplished during the first decades of the 19th century. Training the middle- and upstream reaches of the Sió were delayed repeatedly after 1830, in that this would have involved inevitably controlling (lowering) the level of Lake Balaton on which various interests clashed. The legal provisions adopted by the Hungarian Parliament in 1827 on controlling the lake level and on excavating the Sió Canal remained ineffective. Level control and completion of the canal were implemented only when the railway line on the southern lake shore was repeatedly damaged in the 1860’s by flooding, wave action and expansion of the ice cover. The railway company and the landowners interested in draining the marshes have come to terms eventually. They have agreed to cooperate in implementing the Sió Canal project and in building at the outlet thereof from Lake Balaton a timber sluice by means of which the lake level could be controlled. The first structure commissioned in October, 1863 was operated by the railway company. Those dissatisfied with (in their opinion) too high, or too low water levels have complained, triggered debates and accused the (mostly innocent) the gate operators with prepossession and corruption. The first sluice continued operating until 1892, when it was replaced by one of higher capacity, built of reinforced concrete and with steel gates. Drawing on the experiences gained with the first, this was
