Results of the Monitoring of Water Resources of the Crimean Peninsula According to Satellite Imagery
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RESULTS OF THE MONITORING OF WATER RESOURCES OF THE CRIMEAN PENINSULA ACCORDING TO SATELLITE IMAGERY W W W . C T R C E N T E R . O R G Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery Tetyana Kuchma, Candidate of Agricultural Sciences, Senior Researcher of the Laboratory of Aerospace Probing of the Institute of Agroecology and Nature Management, Senior Lecturer of the Department of Ecology of the National University "Kyiv-Mohyla Academy", Member of the Expert Council for Environmental Protection and Sustainable Development of the Crimean Tatar Resource Center. © Kyiv, 2020 Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 2 Contents Introduction ..................................................................................................... 3 Research methodology .................................................................................... 4 Research results .............................................................................................. 7 Conclusions ................................................................................................... 24 Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 3 Introduction Crimea's water resources, as well as the assessment of the ecological situation on the peninsula, need special attention. The peculiarity of providing Crimea with water resources is: increasing anthropogenic pressure on the state of water resources generated by population growth, use of resources in the process of militarization and in military-industrial needs, and climate change. The problem became particularly acute after the dry summer of 2020, when many media outlets began to report critical water shortages, particularly for utilities and domestic use. To what extent is the shortage critical and to what extent are we dealing with an objective reduction in water supply in the region, and to what extent - in increasing the use of water for the army, industry and population, which is constantly increasing throughout the annexation period. The purpose of this analytical study was to review the water supply situation of the peninsula on the basis of satellite data and open sources and to identify possible factors that, in addition to the often mentioned climate change and water supply through the North Crimean Canal, affect the water balance of the Crimean Peninsula. Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 4 Research methodology The assessment of water resources according to satellite imagery was performed on the basis of the analysis of the dynamics of the water mirror for the 50 largest water bodies (reservoirs and lakes) within the Crimean peninsula. In particular, it was determined by how much the area of the water mirror of reservoirs decreased in 2020, compared to 2015. Open free radar satellite data from the European Space Agency Sentinel-1 with a spatial resolution of 10 meters were used to highlight the area of the water mirror. Radar survey is widely used to decipher the water surface, in particular when analyzing the flood situation. Satellite imagery was processed in the Google Earth Engine software interface, which is a powerful web platform for cloud processing of remote sensing data on a large scale. The data processing algorithm was based on the UN-Spider method1 of the United Nations Office for Outer Space Affairs. The program code is available at2. The surface area of the water surface can change significantly, in particular due to local weather conditions, such as after rains, and largely depends on the mode of water resources management, water intake and runoff, so based on the above algorithm, summer-averaged map layers with contours were created, water mirror as of summer 2020 and summer 2015. Thus, to create a cartographic layer for the summer of 2020, a total of 119 images for the period from 01.06 - 31.08.2020 for the entire territory of the Crimean Peninsula and 58 images for the period from 01.06 to 31.08.2015 were used to map the data for the summer of 2015. QGIS software calculated the difference between the data of 2020 and 2015, which allowed to determine 1 https://un-spider.org/advisory-support/recommended-practices/recommended-practice-google- earth-engine-flood-mapping/step-by-step 2 https://code.earthengine.google.com/af10e30571459100db739559c9246d57 Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 5 the area of drying or reduction of the water mirror. OpenStreetMap3 was used as the basic contours of water bodies. Data for the summer of 2015 were used for comparison with 2020 due to the fact that it was the oldest available summer time period of the satellite image Sentinel-1 (the satellite was launched in 2014). To compare the results, as well as to analyze a longer time series of satellite imagery to study the dynamics of water resources, we also used data from multispectral satellite imagery Landsat-8. The Landsat-8 satellite began operating in orbit in February 2013, before the annexation of Crimea. Due to the combination of image channels taken by this satellite in different spectral ranges, it is possible to determine the biogeochemical features of the territory. In particular, the normalized differential water index (NDWI), which is calculated based on the near and middle infrared image channels, was used as an indicator of the open water surface area. As the water surface area decreases, the NDWI index within the water body contour will also decrease. The Google Earth Engine software interface calculated the average values of the water index (NDWI) within the contours of water bodies for the period 2013-2020 and created graphs of their dynamics. In total, the analysis included 315 images for the specified period (only data with a cloudiness of no more than 10% were used in the analysis). For each analyzed water body, graphs of the dynamics of average annual and average annual NDWI values for the period 2013-2020 were obtained, and the difference between NDWI values for 2013 and 2020 was determined. This analysis was used to identify the trend and the possible year of the beginning of the drying up of reservoirs on the territory of the Crimean peninsula. Based on the results of the analysis, maps of the reduction of the water surface area were created based on Sentinel-1 radar data and Landsat-8 3 OpenStreetMap Contributors (https://download.geofabrik.de) Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 6 multispectral data. Thus, zones of water resources reduction within the Crimean peninsula were identified. To identify climatic and anthropogenic factors affecting water resources, maps of average rainfall, earth's surface temperature and evaporation rate during the summer of 2020 were created. Relevant climatic parameters were obtained from the data set Google Earth Engine and Giovanni NASA4. The illuminance index according to the night satellite survey was used as an indicator of the dynamics of anthropogenic load5. This index is used to assess the dynamics of urbanization, infrastructure development, as well as an indirect demographic indicator. 4 https://giovanni.gsfc.nasa.gov/giovanni/ 5 https://www.lightpollutionmap.info/ Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 7 Research results As a result of the analysis of the state of water bodies within the Crimean peninsula for the summer period of 2020 and 2015, according to the Sentinel-1 satellite radar data, a reduction of the water mirror of almost all water bodies by an average of 32% was revealed. Table 1 lists the 42 largest bodies of water on the peninsula, the area of the reservoir according to OpenStreetMap and the area of drying or reduction of the water mirror in 2020 compared to 2015. Table 1. Decrease in the area of a water mirror in the summer of 2020 in comparison with 2015 according to radar data of Sentinel-1 Area of water Area of water The share of body according mirror decrease in Name of the water reducing the area of sn to OSM summer 2020 body the water mirror cartographic compared to 2015 (%) data (ha) (ha) 1 Aigul lake 3619.7 833.2 23.0 2 Aktash lake 2276.1 226.9 10.0 3 Astana water reservoir 1171.3 300.7 25.7 4 Bakal water reservoir 675.2 22.3 3.3 5 Samarly water reservoir 144.6 27.7 19.2 6 Iuzmak water reservoir 137.1 17.9 13.1 7 Donuzlav 5120.0 555.8 10.9 8 Zahirsk water reservoir 148.3 88.0 59.4 9 Western basin 408.3 233.2 57.1 10 Karach-Kol 322.0 111.9 34.7 11 Kerch water reservoir 179.2 5.1 2.8 12 Kyiat lake 1811.6 511.3 28.2 13 Koiiash lake 456.7 277.5 60.8 14 Chervone lake 2320.5 208.2 9.0 15 Kyzyl-Iar 847.3 290.3 34.3 16 Lyman 154.8 102.4 66.2 17 Marfovske lake 243.2 13.4 5.5 Mizhhirsk water 18 reservoir 316.7 205.0 64.7 19 Moinak lake 172.5 96.1 55.7 Results of the monitoring of water resources of the Crimean peninsula according to satellite imagery 8 Area of water Area of water The share of body according mirror decrease in Name of the water reducing the area of sn to OSM summer 2020 body the water mirror cartographic compared to 2015 (%) data (ha) (ha) 20 Achy lake 232.0 37.7 16.2 21 Dharylhach lake 828.4 46.1 5.6 22 Kachyk lake 462.1 134.3 29.1 23 Stare lake 1208.4 99.1 8.2 24 Ianhul lake 292.9 48.3 16.5 25 Iarylhach lake 170.0 2.0 1.2 26 Oibur water reservoir 483.5 23.4 4.8 27 Panske