An assessment of water reserve changes in Salt Lake, Turkey, through multi-temporal LANDSAT imagery and real-time ground surveys

Bu makale, Tuz Gölü’ndeki suyla kaplı alanlarda meydana gelen zamansal değişimin eş-zamanlı uzaktan algılama verileri ile analiz edilmesini konu almakta olup iki aşamada gerçekleştirilmiştir: (1) Eş-zamanlı yer ve uydu verilerinin birlikte analizi (2) Çok zamanlı LANDSAT uydu verileri ile zamansal değişim analizi. Çalışmanın ilk aşamasında, Tuz Gölü ve yakın çevresinde ayrıntılı bir arazi çalışması yapılmış ve LANDSAT-5 uydusunun 16.05.2005 (saat:1031) tarihindeki üst geçişiyle eş-zamanlı olarak ve yer koordinatları el tipi GPS ile belirlenen noktalarda yersel spektroradyometre ölçmeleri gerçekleştirilmiştir. Uydu görüntülerinin işlenmesi aşamasında geometrik ve radyometrik düzeltme işlemleri gerçekleştirilmiştir. Geometrik düzeltme işlemi ile tüm uydu görüntüleri UTM (Universal Transverse Mercator) projeksiyon sistemine (36. Dilim) referanslandırılmıştır. Bu işlem esnasında karesel ortalama hata (KOH) tüm uydu verileri için ±0,5 pikselin altında bulunmuştur. Daha sonraki aşamada ise uydu verilerini yersel spektroradyometre ölçmeleri ile karşılaştırılabilir hale getirmek amacıyla radyometrik düzeltme işlemi gerçekleştirilmiştir. Bu aşamada, LANDSAT-5 TM uydu verisine ait parlaklık değerleri öncelikle radyans, daha sonra reflentans değerlerine dönüştürülmüştür. Radyometrik düzeltme işlemi sonrasında LANDSAT-5 TM uydu verisinden ve eş-zamanlı yersel spektroradyometre ölçmeleriyle elde edilen yansıma değerlerinin yüksek korelasyona (0.84<R2<0.97) sahip oldukları belirlenmiştir. Daha sonraki aşamada, çok zamanlı LANDSAT-5 uydu verileri ile zamana bağlı değişim analizi gerçekleştirilmiş ve Tuz Gölü’ndeki suyla kaplı alanların 1990-2005 yılları arasında 1/3 oranında azaldığı tespit edilmiştir. Göl çevresinde su kaynaklarının kullanımının kontrol altına alınması ve gölün (en az yılda bir kez olmak üzere) güncel uzaktan algılama verileri ile düzenli olarak izlenmesi önerilmektedir. Anahtar Kelimeler: Tuz Gölü, uzaktan algılama, spektroradyometre, radyometrik düzeltme.This paper focuses mainly on the investigation of water reserve changes in Salt Lake, Turkey, using real-time and multitemporal remote-sensing data. The Salt Lake, which is a specially protected area, is natural resource and the second largest lake in the Central Anatolia in Turkey. The region has been experiencing drought over the last two decades resulting from two main phenomena; (1) uncontrolled use of underground water resources for agricultural purposes, and (2) the lack of precipitation (or natural drought). As a result of this event, very striking coastline changes occurred in the Salt Lake and its vicinity within the last 20-year period. In this study, these changes were analyzed by using multitemporal LANDSAT-5 imagery and real-time ground spectral measurements carried out around Salt Lake, Turkey. The study is performed in two stages: (1) correlation analysis for real-time ground spectral measurements and LANDSAT-5 TM image data and (2) assessment of water reserve changes using multi-temporal LANDSAT imagery. In the first stage of the study, the relationship between ground and satellite spectral data captured on the same day and time was investigated. For this purpose, a real-time field work was done in May, 2005. Taking into account the overpass of LANDSAT-5 TM (16 May 2005, 10:31 local time), spectral measurements were taken on the same day between 9:30 and 12:30 in a total of 20 sample points along the northern coasts of Salt Lake. Sample points were selected along four paralel transects representing four major cover types naturally and regularly located along the coast: lake water, salt, muddy area and bare soil. The distance between samples was approximately 300 m and their locations were recorded with a hand-held global positioning system (GPS) receiver.The measurements were done using an ASD FieldSpec®Pro field-portable spectroradiometer, which consists of a data analyser attached to a laptop computer. In the next stage, LANDSAT scenes (for 1990, 2001 and 2005) covering the study site were geometrically corrected. The images were converted to the UTM coordinate system (Zone 36) using a total of 50 control points both extracted from 1:25000-scale topographic maps and recorded by GPS during the fieldwork. A first order polynomial transformation method was performed to create the output images with 30 m ground resolution. The root-mean-square error of the polynomial transformation is less than half a pixel for all the data set. In the radiometric correction procedure, first, the LANDSAT-5 TM 2005 image and then the 1990 and 2001 historical images were radiometrically corrected to enable comparison with in-situ measurements and with each other. The aim of radiometric correction is to minimize the atmospheric effects and to convert remotely sensed digital numbers (DNs) to ground surface reflectance in order to make the data spectrally comparable. The procedure includes conversions from digital numbers to radiance and from radiance to at-satellite reflectance. After the radiometric correction procedure, the correlation between real-time ground and satellite data was examined. The regression results show that measured surface reflectance and converted at-satellite reflectance are in good agreement with R2 values of about 0.95 in the selected study area. The results show that simultaneous ground and LANDSAT-5 TM data are highly correlated (0.84 R2 0.97). Here, it can be indicated that the use of the real-time data set collected on the same day and time increased the consistency between ground and satellite data. The results also show that sensing using just the spectral band in the near infrared region, such as by LANDSAT TM4, is favourable for distinguishing salt and water in Salt Lake, which has a salt-covered bottom. This plays a key role in determining multi-temporal water reserve changes using satellite sensor data.The results of multi-temporal analysis show that the water reserves in Salt Lake, Turkey, have decreased markedly over two decades. The change of water reserve quantified by using LANDSAT images from 1990 and 2005 is more than 43 ha for a 15-year period. It is suggested that the use of water supplies around Salt Lake should be controlled and that the lake should be monitored regularly by current remote-sensing data (at least annually) for better management of the water resources. Keywords: Salt Lake, remote sensing, field spectroradiometer; radiometric correction.

Spatial Dynamics of Forest Cover and Land Use Changes in the Western Himalayas of Pakistan

The current study deals with the mapping and evaluation of forest and land use cover changes in the western Himalayas, Pakistan. These forest types include i) Moist temperate forests ii) Mixed coniferous forests and iii) Sub-tropical broad leaved forests. Moist temperate forest mostly consists of evergreen conifers with some of oaks and deciduous trees. Subtropical pine forest are mostly dominated by Pinus roxburghii. These forest type are mostly mixed by Pinus roxburghii and other coniferous species like Pinus wallichiana at the upper ranges in Dewal, Angoori, Nambal, Aucha and Khanitak etc. The broad-leaved subtropical forests are recorded on the hills and in the lower slopes of Himalaya near Islamabad and Rawalpindi. The high quantity of vegetation index were observed in winter season as compared to summer. The Landsat satellite images of years 1988, 1998, 2008 and 2018 were classified into land-cover units. Vegetation land decreased in the total area whereas the bare land class increased in the total. Water class further reduced and the built- up class increased up in the Murree area, Pakistan

Monitoring of tectonic movements of southern part of the Tuz Gölü fault zone (TGFZ) with gnss observations

Günümüzde aktif fayların yakın alanlarına kurulan deformasyon ağlarının GNSS tekniği ile izlenmesi sonucunda depreme ait zamanı belirlemek mümkün olmasa da faylar üzerinde biriken gerilmeler yardımıyla muhtemel deprem konumları tahmin edilebilmektedir. Orta Anadolu Neotektonik Bölgesini, Konya-Eskişehir ve Kayseri-Sivas Neotektonik Bölgeleri olmak üzere iki alt neotektonik bölgeye ayıran bir geçiş zonu olan yaklaşık 220 km uzunluğundaki Tuz Gölü Fay Zonu (TGFZ)’nun kırılması durumunda büyüklüğü (M) yaklaşık 6-7 olan bir depreme sebep olabileceği bilinmektedir. Fay zonunun bu potansiyeli dikkate alınarak, bulunduğu alanda meydana gelen deformasyonların hesaplanması amacıyla Tuz Gölü Fay Zonu’nun Güney Kesiminde doğu-batı yönlü profil şeklinde 24 adet nirengi tesisi kurulmuştur. Oluşturulan ağda 2018-2019 yıllarında 3 periyot GNSS ölçüsü yapılmış ve elde edilen sonuçlar GAMIT/GLOBK yazılım takımı ile değerlendirilerek bölgenin güncel hız haritası elde edilmiştir. Yapılan çalışmada, Tuz Gölü Fay Zonu Güney kesiminde Avrasya referans sistemi sabit olmak üzere yıllık 10 ile 35 mm arasında batı ve kuzey batı yönünde bir hareket belirlenmiştir. Noktalara ait standart sapma değerleri 2-6 mm arasında değişmektedir. İlerleyen yıllarda yapılan yeni kampanya ölçüleri ile birlikte standart sapma değerlerinin azalacağı düşünülmektedir.Although the time of the earthquake could not be clearly determined but possible earthquake locations and the stresses on the faults can predicted through monitoring the deformation networks with GNSS technique established around the earthquake producing faults. Tuz Gölü Fault Zone (TGFZ) is approximately 220 km long, which is a transition zone separating the Central Anatolian Neotectonic Zone, Kayseri-Sivas and Konya-Eskişehir Neotectonic Regions as two sub-neotectonic zones, it is known that the TGFZ, may cause an earthquake with a magnitude (M) of approximately 6-7 in case of breaking. Considering this potential of the fault zone, in order to calculate the deformations occurring in the area 24 reference points were constructed in the form of an east-west profile of the southeastern part of the TGFZ. In this network established, 3 periods of GNSS observations between 2018-2019 were measured. GAMIT/GLOBK software was used to process the collected GNSS observations and determine recent velocity fields of the region. In the study, between 10 and 35 mm annually movement was determined in the west and north west direction relative to the Eurasia reference system in the southern part of the TGFZ. The standard deviation of the points varies between 2-6 mm. It is thought that standard deviation values will decrease with the new campaign measurements made in the following years

Automatic extraction of shorelines from Landsat TM and ETM+ multi-temporal images with subpixel precision

A high precision geometric method for automated shoreline detection from Landsat TM and ETM+ imagery is presented. The methodology is based on the application of an algorithm that ensures accurate image geometric registration and the use of a new algorithm for sub-pixel shoreline extraction, both at the sub-pixel level. The analysis of the initial errors shows the influence that differences in reflectance of land cover types have over shoreline detection, allowing us to create a model to substantially reduce these errors. Three correction models were defined according to the type of gain used in the acquisition of the original Landsat images. Error assessment tests were applied on three artificially stabilised coastal segments that have a constant and well-defined land-water boundary. A testing set of 45 images (28 TM, 10 ETM high-gain and 7 ETM low-gain) was used. The mean error obtained in shoreline location ranges from 1.22 to 1.63. m, and the RMSE from 4.69 to 5.47. m. Since the errors follow a normal distribution, then the maximum error at a given probability can be estimated. The results confirm that the use of Landsat imagery for detection of instantaneous coastlines yields accuracy comparable to high-resolution techniques, showing the potential of Landsat TM and ETM images in those applications where the instantaneous lines are a good geomorphological descriptor. © 2012 Elsevier Inc.The authors appreciate the financial support provided by the Spanish Ministerio de Ciencia e Innovacion and the Spanish Plan E in the framework of the Projects CGL2009-14220-C02-01 and CGL2010-19591.Pardo Pascual, JE.; Almonacid Caballer, J.; Ruiz Fernández, LÁ.; Palomar-Vázquez, J. (2012). Automatic extraction of shorelines from Landsat TM and ETM+ multi-temporal images with subpixel precision. Remote Sensing of Environment. 123:1-11. doi:10.1016/j.rse.2012.02.024S11112

Coastline shift analysis in data deficient regions: Exploiting the high spatio-temporal resolution Sentinel-2 products

In most developing countries, coastline shift monitoring using in-situ (ground-based) data faces challenges due, e.g., to data unreliability, inconsistency, deficiency, inaccessibility or incompleteness. Even where practically applicable, the traditional “boots on the ground” methods are labour intensive and expensive, thus imposing burden on poor countries struggling to meet other urgent pressing daily needs, i.e., food and medicine. Remote sensing (RS) techniques provide a more efficient and effective way of collecting data for coastline shift analysis. However, moderate spatio-temporal resolution RS products such as the widely used Landsat products (30 m and 16 days) may be insufficient where high accuracy is desired. In 2015, Sentinel-2 Multi-Spectral Instrument (MSI) remotely sensed products with higher spatio-temporal resolution (10 m and 5 days) and high spectral resolution (13 bands), which promises to improve coastline movement monitoring to high accuracy, was launched. Using two war-impacted countries (Liberia and Somalia) as case studies of regions with data deficiency or of poor quality, for the period 2015–2018, this contribution aims at (i) assessing the suitability of the new freely available high spatio-temporal Sentinel-2 products to monitor coastline shift, (ii) assessing the possibility of filling the missing Sentinel-2 gaps with Landsat 8 panchromatic band (15 m) products to provide alternative data source for mapping of coastline movements where Sentinel-2 data is unusable, e.g., due to cloud cover, and (iii), undertake a comparative analysis between Sentinel-2 (10 m), Landsat panchromatic (15 m), and Landsat multi-spectral (30 m). The results of the evaluation indicate 23% (on average) improvement gained by using Sentinel-2 compared to the traditional Landsat 30 m resolution data (i.e., 32% for Liberia and 14% for Somalia). A comparison of 100 check points from Google Earth Pro (i.e., surrogate in-situ reference data) show 91% agreement for Liberia and 85% for Somalia, indicating the potential of using Sentinel-2 data for future coastal shift studies, particularly for the data deficient regions. The results of comparative studies for Sentinel-2, Landsat panchromatic (PAN), and Landsat multi-spectral (MS) show that the percentages of Sentinel-2 and Landsat PAN that falls within 10 m threshold is much higher than Landsat MS by 35% and 26%, respectively, and for the 2016–2017 period, they provide more detailed mapping of the Liberian coastline compared to Landsat MS (30 m). Finally, panchromatic Landsat data with 15 m resolution are found to be capable of filling the missing Sentinel-2 gaps, i.e., where cloud cover hampers its usability

Impact of the spatial resolution of satellite remote sensing sensors in the quantification of total suspended sediment concentration: A case study in turbid waters of Northern Western Australia

The impact of anthropogenic activities on coastal waters is a cause of concern because such activities add to the total suspended sediment (TSS) budget of the coastal waters, which have negative impacts on the coastal ecosystem. Satellite remote sensing provides a powerful tool in monitoring TSS concentration at high spatiotemporal resolution, but coastal managers should be mindful that the satellite-derived TSS concentrations are dependent on the satellite sensor's radiometric properties, atmospheric correction approaches, the spatial resolution and the limitations of specific TSS algorithms. In this study, we investigated the impact of different spatial resolutions of satellite sensor on the quantification of TSS concentration in coastal waters of northern Western Australia. We quantified the TSS product derived from MODerate resolution Imaging Spectroradiometer (MODIS)-Aqua, Landsat-8 Operational Land Image (OLI), and WorldView-2 (WV2) at native spatial resolutions of 250 m, 30 m and 2 m respectively and coarser spatial resolution (resampled up to 5 km) to quantify the impact of spatial resolution on the derived TSS product in different turbidity conditions. The results from the study show that in the waters of high turbidity and high spatial variability, the high spatial resolution WV2 sensor reported TSS concentration as high as 160 mg L-1 while the low spatial resolution MODIS-Aqua reported a maximum TSS concentration of 23.6 mg L-1. Degrading the spatial resolution of each satellite sensor for highly spatially variable turbid waters led to variability in the TSS concentrations of 114.46%, 304.68% and 38.2% for WV2, Landsat-8 OLI and MODIS-Aqua respectively. The implications of this work are particularly relevant in the situation of compliance monitoring where operations may be required to restrict TSS concentrations to a pre-defined limit

Water quality retrievals from high resolution ikonos multispectral imagery: a case study in İstanbul, Turkey

This paper presents an application of high resolution satellite remote sensing data for mapping water quality in the Goldon Horn, Istanbul. It is an applied research emphasizing the present water quality conditions in this region for water quality parameters; secchi disc depth (SDD), chlorophyl-a (chl-a) and total suspended sediment (TSS) concentration. The study also examines the retrievals of these parameters through high resolution IKONOS multispectral data supported by in situ measurements. Image processing procedure involving radiometric correction is carried out for conversion from digital numbers (DNs) to spectral radiance to correlate water quality parameters and satellite data by using multiple regression technique. The retrieved and verified results show that the measured and estimated values of water quality parameters in good agreement (R 2 > 0.97). The spatial distribution maps are developed by using multiple regression algorithm belonging to water quality parameters. These maps present apparent spatial variations of selected parameters and inform the decision makers of water quality variations in a large water region in the Istanbul metropolitan area...

Konya kapalı havzası'ndaki hidrolojik, iklimsel ve arazi kullanımı/örtüsündeki değişimlerin Tuz Gölü'ne etkilerinin araştırılması ve koruyucu yönetim stratejilerinin belirlenmesi

Son yıllarda artan su talebi nedeniyle, doğal kaynakların yönetimi ve korunması çalışmaları önem kazanmıştır. Bu doğal kaynaklardan birisi de ülkemizin ikinci büyük gölü olan ve Konya Kapalı Havzası’nda yer alan Tuz Gölü’dür. Tuz Gölü’nde tuz üretimi, gölde biriken suyun buharlaşarak tuzun kristalleşmesi esasına dayanmaktadır. Bu nedenle de göldeki su ve tuzla kaplı alanların belirlenmesi ve izlenmesi ülkemiz açısından son derece önemlidir. 1990’lı yıllardan sonra bölgede etkisini artıran kuraklık, bilinçsiz yeraltı suyu çekimi ve Konya Kapalı Havzası’nda açılan kaçak kuyular nedeniyle son yıllarda Tuz gölünün su seviyeleri ve su yüzey alanlarında daralmalar, buna bağlı olarak da tuzla kaplı bölgelerde azalmalar gözlenmektedir.Management and conservation of natural resources has become more important in recent years due to the increase in water requirements. Salt Lake, which is the second-largest lake of Turkey, is one of these important natural resources. Salt production in Salt Lake is through crystallization of salt after evaporation of water. Therefore, it is very important for our country to monitor water reserve in Salt Lake. Dry conditions since 1990s, excessive use of ground water, and water withdrawal from unlicensed well caused decreases in Salt Lake water levels and lake surface areas

Channel regulation monitoring along the Lower Meric River, Turkey, using Landsat-7 enhanced thematic mapper data

Ekercin, Semih ( Aksaray, Yazar )River channelization is a widespread practice including river bed regulation worldwide. A primary goal of channelization is to rehabilitate the floodplain of rivers, modifying the energy regime and sediment transport capacity. This paper presents an application of this process carried out in the floodplain of the Lower Meric River, Turkey. The application was performed by constructing a new channel in two regions along the river in the 1970s. Thus, the river was straightened, isolating its meanders to reduce the floods. These channel regulations are summarized in the paper by using satellite data and historical maps. The Landsat-7 enhanced thematic mapper (2001) image is the base data for interpretation of the present condition of the river channel, and the historical geomorphologic maps are used for the detection of the river bed prior to channelization...

Estimating soil salinity using satellite remote sensing data and real-time field sampling

WOS: 000259125600005This paper presents a new algorithm for estimating the salinity level of soil by using satellite remote sensing data. The study includes a real-time field work performed during the overpass of Landsat-5 satellite on 20/06/2006 over Salt Lake, Turkey. Electrical conductivity (EC) is used as indicator of salinity for developing algorithm by using multiple regression technique. In the image processing step, geometric and radiometric correction procedures are conducted to make satellite remote sensing data comparable with the spectral ground measurements carried out using field spectroradiometer supported by hand-held GPS. Results show that real-time ground and satellite remote sensing data are in good agreement with correlation coefficient values of between 0.92 and 0.97. The developed algorithm gives acceptable and meaningful results with a determination coefficient value of 0.95. Finally, the model is tested at a number of individual sample points, and the test results indicate the validation of the developed model with a R-2 value of 0.75.The Scientific and Technological Research Council of Turkey-TUBITAK [105Y283]This research was funded by The Scientific and Technological Research Council of Turkey-TUBITAK (Grant Number: 105Y283). We would like to thank to Prof. Dr. Dog. an KANTARCI and Assoc. Prof. Doganay TOLUNAY (University of Istanbul, Faculty of Forestry) for their generous supports during the field work and laboratory analysis. We also thank the anonymous reviewers for many useful suggestions