Land use analysis of Lake Khanka basin using remote sensing data

The paper presents results of the analysis of the land use map compiled for transboundary Lake Khanka Basin using remote sensing data and geoinformation systems. The map reflects the distribution of 12 land categories in Lake Khanka basin in 2017 (arable land, abandoned arable land, paddy field, abandoned paddy field, shrubs and sparse growth, forest land, open pit, settlements, meadows and pastures, wet meadows and marshes, water bodies, forest cuttings and fire sites). The data of land use structure in the whole Lake’s watershed, in its Russian and Chinese parts are given. Data on the distribution of different land categories in the administrative territories of the rank of districts (Russia) and counties (China) are also presented. The analysis of land use structure showed that about 50 % of the Chinese part of the basin is covered by anthropogenically transformed natural complexes. The share of such lands in the territory of Russia amounts to 28 %. Agriculture is the most important factor in the change of natural complexes in Lake Khanka basin. Before early 1990s, the area of farmland had increased in the basin on both sides of the border, after that there was a significant reduction in cultivated lands, which had lasted for 10 years in the territory of China and for 20 years in Russia. Over the past decade, the area of cultivated areas in the basin and adjacent territories has extended again, which indicates an increase of anthropogenic impact and requires serious attention to monitoring of the ecological state of lands in the basin.

THE KHANKAISKIY STATE NATURAL BIOSPHERE RESERVE: HISTORY AND CURRENT STATE

The Khankaiskiy Biosphere Reserve is located in the drainage basin of Lake Khanka in the Russian Far East. It is of great importance for the biodiversity conservation, especially bird biodiversity in the wetland landscapes under Ramsar Convention. The Khankaisky Reserve was established in 1990, and in 2005 it acquired the status of Biosphere Reserve. In 1986 on the adjacent Chinese territory in the northern part of the lake, the Xingkai-Hu Reserve was established, which received the status of Biosphere Reserve in 2007. An intergovernmental agreement on foundation of the Russian-Chinese Khanka Lake Reserve on the basis of the two Reserves was signed in 1996. The article contains information on the modern structure and functions of the Khankaiskiy Biosphere Reserve, and scientific research in the Reserve within the framework of international cooperation. Some geo-ecological problems in the Lake Khanka drainage basin, which affect the stability of the protected area ecosystems, are briefly discussed.

Recent changes of water level in Lake Khanka and their consequences for its fisheries resources

Interannual variation of the water level in Lake Khanka is considered on satellite altimetry data; its extreme rising in recent years is noted, with the maximum in 2016. Using a simple balance model, contribution of the main components of its water balance to the modern rise is determined, as precipitation in its basin, evaporation, and water discharge through the Sungacha River. Growth of summer precipitation is defined as the main reason of the level rising. However, the water income to the lake does not correlate with the precipitation volume since 2010 that confirms the hypothesis about artificial influence on the water balance of Lake Khanka by its connection with the Mulin River (China) and worsening of the outflow through the Sungacha. As the result, the lake got additionally about 1.3 km3 in 2014–2015 that promoted the level rise to the highest mark. But before and after this period, the water inflow was lower than its expected values, obviously because of its redistribution. Positive influence of the anomalous water level growth on total abundance of commercial fish species is shown. The high level is favorable for reproduction of phytophilic species (Cyprinus rubrofuscus), whereas abundance of pelagophilic species (Chanodichthys erythropterus) declines.

Results of monitoring of Lake Khanka in 2016–2018

Представлены результаты гидрохимических исследований озера Ханка в 2016–2018 гг. В 2015–2016 гг. съемки проводились в период максимального уровня озера. С 2017 г. наблюдалось снижение его уровня. Пространственное распределение температуры воды в целом не менялось из года в год, но при этом изменялись значения температуры. Так, температура воды в 2018 г. в течение всего сезона была выше на 1–2°. Содержание питательных веществ и растворенного кислорода во многом зависело от стока бытовых отходов пос. Камень-Рыболов, стока вод с рисовых чеков, от интенсивности стока впадающих в озеро рек и продукционных процессов. Цветение фитопланктона происходило даже зимой подо льдом, что подтверждалось высоким содержанием растворенного кислорода (до 180 %) под слоем льда. Вместе с тем содержание кислорода зимой в 2016 г., когда уровень озера был самым высоким, было несколько ниже, чем в последующие годы. Подобные межгодовые изменения отмечались и в колебаниях концентрации кремния. Зимой биологическое потребление кислорода (БПК5) также было высоким (6.53 мл/л), что указывало на активное разрушение органических веществ. Питательные вещества меняли свое соотношение в течение года из-за различных источников их поступления в определенные сезоны. Но в целом их значения и соотношение не имели значительных межгодовых колебаний. Наибольшие концентрации минерального азота и фосфора наблюдались осенью, вероятно, из-за сброса воды с рисовых плантаций. Сделан вывод о том, что высокие значения концентрации питательных веществ, БПК5 и содержания взвешенных веществ характерны для озера Ханка и не были обусловлены повышением его уровня. The results of the hydrochemical investigations of the Lake Khanka in 2016–2018 are presented. In 2015–2016, the surveys were carried out in the period of maximum level of the Lake. From 2017, its level recession was observed. The spatial distribution of the water temperature has generally remained the same each and every year but, at that time, the temperature values have changed. So, for example, the water temperature for the entire length of season in 2018 was higher by 1–2°. The content of nutrients and dissolved oxygen has largely depended on the household waste flow of the Kamen-Rybolov settlement, water flows from the rice checks as well as on flow intensity of the rivers falling into the Lake and production processes. The phytoplankton bloom was observed even in winter under the ice which was confirmed by the high content of the dissolved oxygen (up to 180‰) under the ice layer. At the same time, in winter of 2016 when the Lake level was highest the content of oxygen was slightly lower than in the subsequent years. The similar interannual changes were also noted in the silicon concentrations. In winter, the biological oxygen demand (BOD5) was also high (6.53 ml/l), which has pointed to the active destruction of the organic matter. The nutrients have changed their proportions throughout the year due to different sources of their entry during particular seasons. However, their values and proportions had basically no considerable interannual fluctuations. The highest concentrations of the mineral nitrogen and phosphorus were observed in autumn, probably, due to water discharge from the rice paddies. The conclusion was drawn that the high concentrations of nutrients, BOD5 and content of the suspended substances are characteristic of the Lake Khanka and were not caused by rise in its level.

CОВРЕМЕННЫЕ ПРОБЛЕМЫ ПРИРОДОПОЛЬЗОВАНИЯ БАССЕЙНА ОЗЕРА ХАНКА (В СВЯЗИ С КЛИМАТИЧЕСКИМИ И ГИДРОЛОГИЧЕСКИМИ ИЗМЕНЕНИЯМИ)

Озеро Ханка является самым большим пресноводным водоемом в СевероВосточной Азии, имеет особый международный статус и является трансграничным. Последние годы наблюдается аномальный подъем уровня воды в озере. Колебания уровня разной периодичности является характерным признаком для многих озёр. Но за последние 56 лет повышение уровня воды в озере Ханка привело к подтоплению прибрежных территорий и осложнило хозяйственную деятельность на них. С 2015 года сотрудники Дальневосточного отделения Российской Академии Наук ведут научную дискуссию о том, как изменения водного режима озера Ханка могут повлиять на экосистемы, социальную и экономическую сферы прилегающих к озеру территорий, а также как трансформируются типы природопользования. Природопользование ключевой момент устойчивого, рационального, сбалансированного, экономически и экологически оптимального развития территории. Бассейн озера Ханка является уникальным в природном, культурноисторическом, социальном и геополитическом плане, в котором на современном этапе происходят климатические и антропогенные изменения. Важными являются процессы, которые протекают на территории северной части озера Ханка и его бассейна. Со стороны Китая наблюдается интенсивное освоение природных ресурсов, высокий уровень антропогенной нагрузки на экосистемы и высокая плотность населения. Механизмы протекания природных процессов распространяются вне зависимости от государственных границ, это является объединяющим фактором трансграничной территории, которая предопределяет ряд особенностей и проблем. В статье рассматривается современная ситуация в бассейне озера как в природном плане, так и в социальноэкономическом. Даётся краткий обзор сложившейся проблемной ситуации в бассейне озера Ханка, рассматриваются возможные причины такого положения, а также предлагаются пути наиболее подходящих и рациональных решений этого вопроса.Khanka Lake is the largest freshwater reservoir in Northeast Asia. The transboundary lake Khanka (Russia China) is currently attracting general attention: an abnormal increase in its level occurs, leading to flooding of coastal territories and complicating economic activity on them. This is accompanied by a number of other important processes, in particular, activation of abrasion and waterlogging, changes in the hydrogeological regime and microclimate, transformation of ecosystems, etc. Since 2015, employees of the Far Eastern Branch of the Russian Academy of Sciences have been conducting a scientific discussion on how changes in the water regime of Lake Khanka can affect the ecosystems, social and economic spheres of the territories adjacent to the lake, as well as how environmental management types are transformed. Nature management is a key moment of sustainable, rational, balanced, economically and environmentally optimal development of the territory. The basin of Lake Khanka is unique in its natural, cultural, historical, social and geopolitical plan, in which climatic and anthropogenic changes are taking place at the present stage of conditions. The article discusses the current situation in the lake basin both in the natural plan and in the socioeconomic one. A brief overview of the current problem situation in the basin of Lake Khanka is given, possible reasons for this situation are considered, and ways of the most suitable and rational solutions to this issue are proposed.

Water Resources Use in the basin of the Lake Khanka

The article deals with investigation of the Lake Khanka water resources’ use. We have stated that the predominant development of agriculture determines the water resources use on both the Russian part and the Chinese part of the basin. We have assessed the irrigated land areas and water volumes used for this end, as well as economic activities’ impact of the lake water level. On the basis of statistical data, satellite images and published scientific articles we have assessed for the first time the irrigated lands’ dynamics in the Lake Khanka basin over the 1960–2015 period. Analysis of the official information and the expert-restored data on water withdrawal made it possible firstly to estimate the dynamics of water use for irrigation and establish the values of water consumption (irrevocable water losses) during irrigation in the Russian part of the lake basin for the same period. We have established that the source for irrigating rice crops in Russia is the lake itself. The use of Lake Khanka’s waters in China is possible only in low water years. The influence of water use on irrigation in the Russian part of the basin at the lake level for the entire period of rice cultivation was manifested only in its reduction, and to a very small extent. In high water years, the Lake Malaya Khanka acts as a reservoir for the flood waters of the Mulinghe River, which, if discharged into the Lake Khanka, can have an impact on the growth of the Lake Khanka level.