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Ertuğrul Aksoy, Gökhan Özsoy Uludag University, Faculty of Agriculture, Department of Soil Sciences, Bursa, Turkey Abstract Multi temporal changes of the Uluabat Lake and surrounding areas within the recently declared RAMSAR site have been researched by using RS and GIS techniques. The objectives of this study were: to determine the shoreline and land use/cover changes of Uluabat Lake and surrounding, to determine recent situation of the Uluabat Lake and RAMSAR site, to decide which conservation and management practices will be taken for sustainable use To rich mentioned objectives, multi temporal Landsat 5-TM data acquired ( in 1984, 1993 and 1997, aerial photographs (taken in 1997) and topographical maps (compiled in 1974 using aerial photographs taken 1966) were used. All the data were stored into the computer using ERDAS Imagine and ILWIS software program from CD-ROM, scanner and digitizer. Image subsetting, geographic correction, resolution merging and image enhancement procedures were applied for easy comparison, exact image on map and aerial photographs overlie and better visual interpretation. The results show that Uluabat Lake covers an area of 133.1 km2 in 1984, of 120.5 km2 in1993 and of 116.8 km2 in 1998. It can clearly be seen that the coverage area of the Uluabat Lake have been declined at a rate of about 12 % from 133.1 to 116.8 km2 due to sediments transported by the surface water of surrounding irrigated agricultural land, tributary streams and mainly Mustafakemalpaşa River in a fourteen years period. If we consider Uluabat Lake coverage areas gathered from topographical map 1:25000 scale, the rate of decline will be about 14%. In spite of this, coverage area of the agricultural lands have been increased at a rate of 26 % from 2508 ha to 3393 ha, due to mainly changes of reed areas to agricultural use in the Mustafakemalpaşa river's delta Introduction In the past 50 years, due to rapid increase of the world population and industrial development, the natural resources had been degraded with a great rate. During the same period the air, water and soil pollution increased as an unprecedented way and issues of environmental problems have become more important. Problem is not use of the nature; problem is the miss use of the nature. Destroying forest, overgrazing pasture, drying wetlands, consumption of the fauna with over hunting and fishing accelerate consumption of the natural resources and as a result of these activities, the natural balance formed over the thousand years have been destroyed. In the last decade, some of the most important unprotected and rapid increased environmental problems that faced to human being are the air, soil and water pollution, erosion and climate changes directed by human activities. Increase of environmental problems that affect human life directly and/or indirectly was caused to increase the work to be made for solving these problems and the investment. Recently in all over the world, prevention of the environmental problems before the rising up, determining quality and quantity of biotic and abiotic elements of the ecosystems and keeping them alive in sustainable bases had be come basic aims of the Environmental activities. Worldwide good quality water is scarce. Water an essential element for life, agriculture and industry. It is estimated that the total volume of water in nature is about 1,386 million cubic kilometers. From these, 97.5 % are oceanic (saline water) and only 2.5% fresh water. The greater portion of the fresh water; 68.7 % are in the poles and mountainous region. Next 29.9 % are in the groundwater. Only 0.26 % of the total amounts of freshwater on the earth are concentrated in lakes, reservoirs, and river systems. They are the most accessible for economic needs and very important for water ecosystems. In many countries and regions of the world, irrigation is the principles water user (Shiklomonow, 1993). Lakes are sensitive ecosystems and very attractive for human activities. All lake regions are also vulnerable to environmental pollution. Lake areas are not only man made landscape, recreation areas for tourists and drinking, irrigating water reservoirs. They are also gathering places for migratory birds and habitats of millions of animals and different plants. Uluabat Lake is one of the most important wetlands of Turkey. It is also one of the nine RAMSAR sites in the Turkey. It is surrounded, especially at the northern and Northwestern sides by wet meadows. Almost all shores of the lake are covered with submerged plants. The lake holds the largest white water lily beds which are the most important feeding and wintering area for the term in Turkey. These temporary wetlands are wet in most part of the year, becoming drier in summer. It is one of the most nationally and internationally important area for many aspects such as given below:
· Its location that on the migratory bird route, The wetlands of Lake Uluabat and Its catchments face a number of problems and threats which could these valuable resources change or degrade/disappear. Human activities both direct (discharges to the lake) and indirect (discharges to the watershed) are great contributors to degrade and loss of Uluabat Lake wetlands and to affect water quality. It is important to know what the major threats to the wetlands are, if they are to be managed effectively. The most serious threats to the wetlands of Uluabat Lake are:
· Sand and gravel mining and mineral extraction activities (amongst others sand mine, coal, borium, chromium ore) · Water pollution · Nutrient enrichments ( agricultural use of fertilizer and siltation) · Conversion of wetland areas to agricultural use (mainly in the delta) · Second highway construction on the south and southwest side of the lake Material and Methods Lake Uluabat, the third largest freshwater body in the Marmara Region, is an tectonically depression lake, located between 4440000-4460000 N latitude and 620000-650000 S longitude. Mustafakemalpasa and Karacabey Districts are the two large residential areas around the Uluabat Lake. The main human activity at the lake is fishing. Also, agricultural lands and industry surround the Lake. The Mustafakemalpaşa plain is one of the most productive agricultural areas in Turkey due to its suitable climatic conditions, high quality soils, and developed irrigation scheme. Uluabat Lake covers an area of between 135 to 155 km2 depending on lake level. A large and expanding delta which is cover an 3747.6 ha area in1998 has been formed by silt deposition around the Mustafa Kemalpaşa River mouth in the Southwest section. The silt deposition is mainly resulted by water erosion and mining activities residue form the watershed of the Mustafakemalpaşa River which covers an area of 10136 km2. The hidrological cycle of the Mustafakemalpaşa River is a major affecting all activities on the delta and wetland of the Uluabat Lake. The flow of the Mustafakemalpaşa River at Döllük station ranges from an avarage high of 825 m3/sn in March and an avarage low of 92 m3/sn in September. Due to hidrological cycle and over-absraction of water, water level of theUluabat Lake changes in between 1.5 m and 3.5 m. The used data as a base map were digital satellite data (Landsat TM , full frame, CD ROM, 16 June 1984, 26 June 1993 and 16 August 1998), aerial photographs (1:35000 scale, 1997), topographical map ( 1:25000 scale, 1974) and software programs (ERDAS Imagine 8.3.1, ILWIS 1.4). RS and GIS techniques i.e. creating false color images enhancement, rectification, screen digitizing and resolution merging have been employed to monitor shoreline changes along to Uluabat Lake costs and to determine Land cover/use changes of The Uluabat Lake RAMSAR site. The satellite data from Landsat5 TM available on CD ROM was converted on to ILWIS and ERDAS format. The individual spectral band information was georeferenced through ILWIS program by selecting geographic coordinates from topographic maps and subsequently enlarged by using edge-enhancement filter and stretching for improving the visual aspect of the images (Rosenfeld and Kak, 1976, ITC, 1993). The color composites were prepared by different band combinations of extracted Landsat-5 TM bands. The band combinations which are prepared using band 543 as a RGB were selected, due to best discrimination for multi temporal changes of Uluabat Lake and RAMSAR site. Visual interpretation was applied to elaborate the morpho-dynamic shoreline and land cover/use changes maps. They were elaborated on the basis of interpretation of Landsat images enlarged to scale 1:100000. During the visual interpretation used FCC images for and land cover/use changes in 1998 was given as a sample image which is rendered on DEM as color map (Figure 1). Visual interpretation was made on the bases of color, texture, pattern, shape, size and tone differences of Uluabat Lake on the color composite images in order to identify and classify shoreline and land use/cover changes in 1984, 1993 and 1998 (Sabins,1987 , Lillesand and Kiefer,1987). The represented units in 1998 maps (Figure 2) were only checked and corrected by ground truth, comparison with aerial photographs and using geo-referenced information of 56 observation points gathered from breeding bird surveys of Uluabat RAMSAR site (Welch and Welch,1998). The interpreted units for shoreline and land use/cover changes were digitized both screen and tablet digitizing in order to derive raster based maps.  Result and Discussion In the past, Uluabat Lake's coverage area was given a 160 km2. Due to constructed embankment by the DSİ in 1937-1993 for to protect low lying agricultural lands along the South -Southwest coast and silt deposition, it can be said that the coverage area of the Lake can not be rich again mentioned past coverage. In 1995, DSI's coverage and volume measurement works showed that the coverage areas of Uluabat lake was 155 km2 at the maximum level of water (4.3 m depth) and water volume of the lake was 346 hm3. In contrary, the coverage and volume of the lake were measured at the same works as a 161 km2 and 387 hm3 respectively in 1965. Shoreline changes maps for 1984, 1993 and 1998 gathered visually interpreted Landsat images (Figure 3) also showed that decrease of the coverage and volume of the lake are in continue. It can clearly be seen that the coverage area of the Uluabat Lake have been decreased at a rate of about 12 % from 133.1 to 116.8 km2 due to sediments transported by the surface water of surrounding irrigated agricultural land, tributary streams and mainly Mustafakemalpaşa river in a fourteen years period. If we consider Ulabat Lake coverage areas gathered from topographical map 1:25000 scale, the rate of decline will be about 14%.In spite of this situation, the coverage of the delta has been increased as a rate of 75 % from 2135.8 ha to 3747.6 ha in the same period.   The proportion of the agricultural lands in the delta has also been increased from 578 ha to 1737 ha due to conversion of the reed areas to agricultural lands. The coverage and percentages Land use/cover classes of The Uluabat Lake RAMSAR site which is cover an 21136 ha area, gathered from visually interpreted 1985,1993 and 1998 Landsat images as summarized in table 1.  It is clearly seen that strong tendencies to decrease Uluabat Lake cover and corresponding increases in wetlands and agricultural lands. It can be also said that natural covers such as maquis, shrub&trees, water lilies&reed have been decreased while man-made covers such as agricultural lands, orchards, settlement &roads have been increased. Conclusions Uluabat Lake and its surroundings are currently under stress from direct and indirect anthropogenic activities. The wetlands of the delta are being converted especially into agricultural use due to excess water withdraw in dry period (from june to September) for irrigation of 16,500 ha agricultural lands in the Mustafakemalpaşa plain. On the other hand, drought is a natural agent which threatens the existence of wetlands even the existence of the Uluabat Lake. We can say that the major threats to wetlands of the Uluabat Lake are changed flow patterns as result of river regulation and water extraction for agriculture and industry, and expansion of irrigated agriculture. Sedimentation that caused mainly water erosion due to upland farming and mining activities in the catchments and pollutions are the other important threats. To protect the Uluabat Lake and ıts wetlands from further degradation and loss the fallowing recommendations are given:
· monitoring Uluabat Lake RAMSAR site and catchments of the Mustafakemalpaşa River by using remote sensing and GIS techniques and establish Uluabat Lake information system (ULUBIS) · establish soil and water management plan for the Uluabat Lake catchments area · introduce new irrigation methods and land use types to reduce excess water withdrawal from the lake · investigate of the effects/threats of second highway which is still under construction and Uluabat Lake section is not constructed, on water pollution and breeding birds. We wish to thank to DHKD (Society for the Protection of Nature Turkey) and Ministry of Environment for Satellite data, digitizer and aerial photographs supply and support. References . DHKD,1998. Waterbird Counts at the Midle of the Winter. . Itc, 1993, ILWIS, International Institute for Aerospace Survey and Earth Sciences First Edition, August 30, 1993. Computer Dept. ITC The Netherlands. . Lillesand T.M. and R.W. Kiefer,1987."Remote Sensing and Image Interpratation", Second edition. J.Wiley&Son,.Inc., Newyork 721 pp. . Rosenfeld, A. and A.C., Kak, 1976. "Digital Picture Processing". Academic Press, New York, 457.p. . Sabins, Jr., F.F., 1987."Remote Sensing Principles and Interpretation", Freeman, Newyork, pp. 449. . Shiklomanow, I.A., 1993.World Fresh Water Resources.In:P.H.Gleick (ed.):Water in Crisis, Oxford University Press,p.13-25. . Welch, G. and Welch, H., 1998. Breeding Bird Survey of Uluabat Lake, DHKD,1998. |