Bedenko, Iva

Sekol, Lidija

English

idUS. Depósito de Investigación Universidad de Sevilla

–  67  –ZAGREB AND THE SAVA RIVER,                             ASPECTS AND DILEMMASLidija Sekol, architect and city plannerIva Bedenko, architect and city plannerCity of ZagrebCity Bureau for Development Planning and Environmental Protection,1. INTRODUCTIONThe City of Zagreb has developed on the southern side of Medvednica mountain. Further to the south of the old city fl ows Sava, a river with relatively low water level and a wide inundation area. The river changes its character in the Zagreb area, turning from a relatively fast and na-rrow mountain river into a relatively slow and meandering lowland river. Modern high-rise housing are situated south of the river. The city expansion omitted the land along the river, leaving wide areas free for parks and natural reserves. Zagreb is a city that has not developed on the river, but on the contrary, it has fl ed from its inundations. Its sothern border up until mid nineteenth century, a street stretching in the east-west direction, runs along the edge of fl ooding area. Frequent fl oodings of Sava river, and especially the hea-vy fl ood of 1964 which endangered large parts of the city, resulted in levee building as a means of protecting the city. The river is not navigable within the city area. Instead of making it a part of itself, the city has to defend itself from the river.Today the river still presents an obstruction in the city image, yet its green surroundings represent an enormous asset for the cityʼs existence. Most gravel pits still have to be revi-talized, but one of them, lake Jarun has become a leisure centre with rowing tracks. The key elements for planning of regulation and utilization of Sava river are: - fl ood prevention - water distribution - use of hydroelectric potential–  68  –RÍOS Y CIUDADES EUROPEAS: ESPACIOS NATURALES, CULTURALES Y PRODUCTIVOSFigura 1. Sava river2. METHODOLOGY AND ANALYSISWater management plan of Zagreb contains analyses and proposes possible scenarios for use of hydroelectric potential of Sava river. Originally there were two different solutions. The fi rst  proposed fi ve power plants. The second proposed three power plants and fi ve concrete dams instead of two power plants in the inner city area. These dams would ensu-re waterbed stability and even water levels, so the river does not dry out in the city area. Finally, the amendment to the Water management plan of Zagreb included the accepted solution with four power plants.Figura 2. Layout and cross section of solution with four power plants–  69  –ZAGREB AND THE SAVA RIVER, ASPECTS AND DILEMMASBasic characteristics and indicators of Sava power plantsPodsused Prečko Zagreb Drenjeinstalled fl owm³/s 500,00 500,00 500,00 500,00regime fl ow fl ow fl ow fl owdecelerationmeters above sea level133,00 122,00 115,00 109,00required altitudemeters above sea level122,95 116,40 110,45 100,62altitude differencem 9,72 5,30 4,25 8,02power MW 41,00 23,08 19,00 37,00average annual productionGWh/ann. 202,40 121,40 97,60 189,10Sixty percent of the Odra canal is built. The canal, located upstream from the city, recei-ves excess water of the river. By digging the canal fl oor two meters deeper, its capacity can be enhanced by 1000 m³/s. So in case of high waters of 4780 m³/s the canal can bear 2500 m³/s, and 2280 m³/s will fl ow through the city. The decrease in the fl ow through the city can lead to two scenarios. One is that existing levees can be lowered for 95 cm, which would facilitate access to the river and render the adjoining land more attractive. Another is the possibility of narrowing of the inundation area by 140 meters, which would leave a strip of land along the levee.Figura 3. The levee area–  70  –RÍOS Y CIUDADES EUROPEAS: ESPACIOS NATURALES, CULTURALES Y PRODUCTIVOS3. RESULTSSava is Zagrebʼs source of drinking water, so the water-bearing area must be carefully protected. Zagreb lies mostly on alluvial ground, which purifi es water from the river, rendering it clean and potable. Still waters in the Sava surroundings are either gravel pits or backwater. Placement of certain polluters is inapropriate, like the heating plant situated next to the ornithological preserve, or the city dump across the river from the protected water reservoir. The city sewer is released into the river southeast from the city, which does not endanger the city but does pollute its southeastern stream. The hydro-electric power plants are a questionable solution, as their impact on the water resources and the image of the city has not been studied enough.In order to obtain ideas for utilization and protection of the river and its surroundings in 2001. the City Bureau for Development Planning and Environmental Protection has is-sued a competition for development of Sava area within Zagreb. Three equivalent prizes and fi ve honourable mentions were awarded. The majority of projects dealt with regu-lating the riverbed, either with or without the hydro-electric power plants. Protection of drinking water reserves and natural surroundings have also been emphasized.Figura 4. Heating plant and ornithological preserve–  71  –ZAGREB AND THE SAVA RIVER, ASPECTS AND DILEMMASFigura 5. Lake Bundek

Zagreb and the Sava rivers, aspects and dilemmas

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Zagreb and the Sava rivers, aspects and dilemmas

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idUS. Depósito de Investigación Universidad de Sevilla