DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 13/2005 str. 110 <-- 110 --> PDF |
V. Ivančević: BIOLOGICAL AND TECHNICAL REGULATION OF THE SENJ TORRENT "TORRENTE" Šumarski lisl - SUPLEMENT (2005). 91-109 maximal capacity of 39.0 1/sec or 1,225,500 m3 per year. The water system capacity was calculated to meet the needs of the 5,000 citizens of Senj on the basis of daily consumption of 900 m3. This equals the capacity of 10.41 1/sec or 328,500 m3 per annum, which is slightly higher than the minimal capacity. The reconstruction of the water supply system ensured sufficient annual quantities of water, but the increased consumption in summer months would still cause shortages. Pipes of cast iron with diameters of 50, 60 and 80 mm were laid along the water route and pipes with diameters of 50-150 mm were laid in the town network. The total reconstruction costs were 63,709,926 dinars (Figure 7). The construction of the hydropower station Senj in the 1960s ensured undisturbed supply of water for the wider area of the southern continental and littoral area and the adjacent islands. The high-capacity water system was built in the southern part of the Croatian littoral, as was the new water route from Hrmotin to Senj. This solved the problem of water supply for the Town of Senj. The former water supply system from the area of Senjska Draga currently only serves the downstream hamlets. The old water route with the springs and other facilities is in a state of neglect, which is unwise policy. This old water supply system should always be at the disposal in case of major breakdowns in the new water system. Also, its waters could be used to enliven the formerly regulated torrential channel from the cemetery to its entry into the sea, thus providing an original tourist attraction. A constant increase in the number of springs and their inclusion in the Senj water supply system is definitely the result of successful biological- technical operations in the upper slope of the Senj torrent in Senjska Draga. However, no systematic research has been conducted and no reliable conclusions can be drawn. In this case, the only conclusions can be based on the perceptions of the forestry science on a close relationship between biological-technical operations and the intensity of torrents and erosion. Regrettably, no systematic research has been done related to the increase in the number of springs with re lation to vegetation progression. No historical records have been found for this segment. We have used the scarce project documentation relating to the water supply of Senj. However, the documentation does not provide a key answer that would confirm the correlation between a higher number of springs and vegetation progression. The crucial dilemma remains: was a gradual increase in the number of springs limited by financial reasons or was there no need to include new springs? In this case, too, we may stand by the claim that the number and capacity of the springs increased in proportion with the intensity of biological-technical operations, with simultaneous decrease in erosion processes. The former Senj torrent and the resulting erosions in Senjska Draga have been consolidated, but a pilot project designed to further monitor these relations would be more than welcome and would be of exceptional importance not only for the forestry and water management profession but also for other related disciplines. The existing springs should be regulated and a permanent experiment of their capacity set up. Some of them represent highly successful civil engineering solutions, which deserve to be included in the monuments of technical culture. Forestry experts and experts from other related disciplines should gather to further investigate the water capacity of Senjska Draga linked with the former water supply of the Town of Senj. To our knowledge, such successful and extensive regulation of torrents and erosions in Senjska Draga with biological-technical measures has not been accomplished anywhere else in the Mediterranean area. Senjska Draga has become a compulsory destination for home and foreign forestry and other experts, who are invariably impressed by its grandeur. Senjska Draga is a striking example of an outstanding achievement of the Croatian karst forestry profession. It may justifiably rank among the karst forestry professions of the most developed Mediterranean countries, while in some segments it even takes up the leading position. CONCLUSIONS The disappearance of forests in the Senjska Draga valley several centuries ago resulted in devastating torrents and erosions. In its total length of 25 km, the Senj torrent brought an average of 32,000 m3 of sediments annually in the upper slope in Senjska Draga, which then moved towards the lower slope, threatening the Town of Senj. To remove the danger of torrents in the lower slope, the torrential channel from the old city centre was relocated outside the town walls at the end of the 18th century. This partial measure mitigated the danger of torrents, but did not remove it completely. The Inspectorate and special torrent regulation services launched a very successful regulation of the Senj torrent and erosion in the second half of the 19th century. Combined biological-technical measures in its upper slope were used for this purpose. The majority of the work was done at the end of the 19th and the beginning of the 20th century, when 22 |