Analysis of wetlands using remote sensing and geographic information systems: Akgol sample

Wetlands have numerous functions and significant values in addition to being the richest, most productive and complex ecosystems of the world. According to the Ramsar Convention, wetlands are defined as areas of marsh, reeds, wet meadows, fen or water, that are whether natural or artificial, permanent or temporary, static or flowing, fresh, brackish or salty; including areas of marine water the depth of which at low tide does not exceed six metres. Wetlands are the most important genetic reserves in the world containing 40% of all species and 12% of all animal species. Wetlands are essential components of the natural environment in terms of preserving the natural equilibrium and biodiversity with their variety of functions including drinking water provision, sediment and nutrient storage, flood and climate change control as well as being used for natural remediation, fishing, feeding underground waters and cultural purposes. Through all these roles and purposes, wetlands remarkably contribute to the regional and national economy. Wetland areas play a critical role in regulation of the region's water regime with balancing the recharge-discharge cycle of underground waters, purifying the nitrogen and phosphorus, filtering the chemicals, and providing natural distillation. In addition, wetlands protect the soil through contributions in flood control and support the maintenance of erosion and sediment control by storing flood waters. Wetlands also contribute significantly to the climate conditions of the region, and help increase the level of rainfalls by raising the humidity. 40% of the world's carbon is held in the wetlands especially locked in peat and wooded areas. The importance of the wetlands in the whole ecosystem has been neglected until recently and wetlands have been destroyed due to the increased demand and need for agricultural land and water use as a result of the growth of the population and the economy. Besides, the purposes of urbanization, disease control (especially mosquito control), aquaculture and harbor construction also contribute to this considerable damage. It is stated that the worlds' wetlands have rapidly been destroyed for various reasons in the long run at alarming rate; where in 20th and 21st centuries the process being much more faster, and the total loss of the wetland areas ended up reaching 64-71% since 1900's. As in the whole world, our country have lost ecological and economic functions of 1 million 300 thousand hectares of wetlands as a result of the growing pollution and drying-out in the last 40 years. It is unfortunately hard to speak for the future of the remaining 1,2 million hectares of wetlands. Turkey is considered to hold a significant role in Europe and Middle East in terms of wetlands. However, 72.7% of the annual average of 44 billion m3 of water is consumed for irrigation purposes which negatively affect the future of the wetlands located around those irrigation areas. The construction of dams and the the use of water sources for the purposes of irrigation and obtainment of drinking water, cut off the water flows to the wetlands; results in water sources for the wetlands being diminished and altered; thus threats wetlands to dry out. Wetlands have been polluted as a result of the leachate coming from the nearby solid waste storages, unconscious usage of agricultural chemicals and chemical fertilizers that are flowing untreatedly into the ground water, discharge of domestic and industrial wastewaters. Besides, the whole ecosystem of the wetlands have disturbed and deteriorated by the uncontrolled, unplanned and improper marsh cutting, peat digging, sand and pebble usage. Total natural wetland area in Turkey is about 2.3 % of the country's surface area; and there are 17269 natural wetlands. 921 of these wetlands have the size greater than 8 hectares, having 1714792 hectares of area in total, and constitutes 99.48% of the overall wetland areas. Akgol Wetland Area has been accepted as one of the most important wetlands throughout the country, and has been among the 135 wetlands of international importance. Akgol Wetland was declared as the 1st degree Natural Sit Area in 1992. In 1995, it was declared as the Nature Reserve Area with its 6680 hectares of surface area. Another significant point to consider about Akgol Wetland area is due to its location; it is within the Eregli Plain which has been declared as the "Important Nature Area", meaning that it has the key approach to preserve the nature of all habitats and thus to enable the living species to keep their natural environment. Moreover, Akgol Wetland with being one of the 97 designated Important Bird Areas and situated on the route of migratory birds, hosts thousands of water birds, especially flamingos. Management projects must be established, managed and later on monitored in order to maintain the ecological characters of the wetlands which are considered as the most significant ecosystems in the world. While creating the project management plan, it is important to determine the past and current status of the wetlands; compare the results and analyze the change for selecting the right rehabilitation methods to be applied. Creating a database for wetlands is important for researchers and decision makers in order for them to use these data for planning, managing and tracking the wetlands. Past-term inventories of wetlands are often not available, incomplete, and mostly inconsistent and not readily accessible to users. Looking at the overall, management plans for preserving and improving quality and quantity of the wetlands have been established for a few number of wetlands, and have not been established for the vast majority yet. It is known that Ministry of Agriculture and Forestry Affairs continues to work on creating more management plans for the wetlands; however there has not been a management plan established for Akgol Wetland area even though the area was examined with various aspects during the studies conducted in 2012. In those studies, Akgol Wetland's status and situtation in the past have not been analyzed; thus the phrase "once upon a time, there was over 20 thousand hectares" was used while mentioning the area in the past years. In some sources, it is stated that the area was 21500 hectares, while some others mentioned it as 24000 hectares; but unfortunatelly these numbers could not been confirmed due to the lack of inventories. It is confirmed by thousand of studies that remote sensing data and methods are effective and important in determining, analyzing and monitoring the change in wetlands through time. With this study, the change in the Akgol wetland through time is extracted and determined through the multi-temporal satellite images; and analyzed correlating with the possible causes of the alteration. Water volumes in the wetland are calculated using the water surface areas obtained from the classification procedure, and by using the digital elevation model constructed through 1:25000 digital topographic maps. Obtained water volumes and meterorological data have been used in water budget calculations and for determining the amount of water required for the persistence of the wetland. The field studies for the investigation of the current situation of the wetland and analysis of the environmental problems, were made as a team formed by researchers and scholars from the TUBITAK project (116Y142). The collected results of the soil sample analysis were used in the water budget calculations and the results of the water sample analysis were used for the purposes of rehabilitation suggestions. In order to determine the change in the Akgol wetland usage and land cover over time, Landsat Satellite data were used to classify the 76.615 hectares of area. It is observed that the wetland with 9800 hectares of water surface in 1975, was completely dried out in 2007. With the help of the constructed seawall, the water surface area was raised up to 400 hectares. Despite the ongoing water problems, agricultural areas tend to have an upslope trend reaching 15.500 hectares in 2017, from 12.000 hectares in 1975. The most important artificial reasons behind the water level drop to the current point in the Akgol wetland area, are the dams built across the rivers feeding the area and the attempts to drain the area. The wetland's seasonal change was determined by the classification of 103 satellite images between years 1972 and 2017. The water surface area seen in all four seasons of the year 1970 seems to decrease considerably with the Ivriz Dam started being operated in 1984. The drop of water surface area level in the field has accelerated with the Gödet Dam's start of operation in 1988. It is examined that the wetland lasted throughout the four seasons in 1900's, but by 2000's it only remained in spring as it dried out eventually in summer times. A significant change has not been observed looking at the rainfall amounts of multiple years in Akgol wetland area where it receives half of the average rainfall of the country. The annual rainfall amount in the years between 1965 and 2017 for Ereğli and Karapinar is 307 mm and 278 mm, respectively. The average rainfall amount for Turkey in the years from 1981 to 2010 is 574 mm. The wetland reaches its maximum water value in winter and spring seasons. The water is observed in the area during the spring months by the effect of melting snow and ice and the rainfalls. However, by the end of spring and beginning of summer; the weather gets warmer eventually and evaporation stars taking place; leaving no water for the autumn. Analysing the rainfall and evaporation data for many years, it is seen that total evaporation from April 1st to November 1st is 8.4 times the total rainfall. Looking at the Ereğli and Karapinar's annual average temperature values calculated with IDW, 1 degree (celcius) increase in temperature is detected for the last 52 years and average temperature was calculated as 11.5 degrees (celcius). If this trend continues linearly, expected temperature for 2040 is 13.2 degrees (celcius). Natural factors affecting seasonal variation of water level are rainfalls, whereas the artifical factor is wastewaters coming from Eregli Wastewater Treatment Facility and Eregli Organized Industrial Zone Wastewater Treatment Facility. It is aimed to preserve the water over an area of approximately 350 hectares in all four reasons through the seawall built in 2013 by the State Water Supply Administration. However, it is conducted through the classification and analysis that, due to the inadequacy of rainfall and the wastewater only arriving during the period November to March while agricultural irrigation is not being carried out; the area has left with no water. The most reasonable proposal to supply the wetland with continuous water is to transport wastewaters to Akgol area from Ereğli Wastewater Treatment Facility and Ereğli Organized Industrial Zone Wastewater Treatment Facility by a wastewater tunnel. Through using the rainfall and evoparation analysis data and combining it with the data showing the the amount of discharge from the wastewater treatment facilities; the water budget was calculated. The calculation shows that if wastewater is transported to the area with a tunnel, there will be water present in the wetland in all four seasons. However, the wastewater expected to come from the Wastewater Treatment Facilities are not suitable and not qualified enough for the discharge to the wetland area according to the Water Quality Regulation and it is found that the water approaches to hypertrophic level in the lake. It will contribute greatly to the ecological balance of the wetland area if the wastewaters drained from the Wastewater Treatment Facilities are qualified in conformity with the regulations, and transported to the area. The Wetland Information System was established with the integration of the data obtained, and evaluated from the study. This study shows the importance of creating a geographical information system with the help of various analyzing methods and questioning techniques as well as underlying the contribution of the remote sensing data and methods to the information system. The data provided from this study will also contribute to the formulation of Akgöl Wetland management plan and strategy while being a source for the researchers and decision makers working in wetlands.