ABSTRACT. -Geoenvironmental Impact Studies for Hydro-Energy Projects: Naryn River in Kyrgyzstan. Kyrgyzstan is the only country in Central Asia where water resources are fully formed in its own territory; these are its hydrological features and benefits. The country has considerable water and hydropower resources on its territory. There are over 25 thousand rivers and streams flowing from the mountains to the surrounding valleys carrying more than 50 cubic km annual water volume. The mountain rivers have a huge potential of water and hydro energy resources allowing Kyrgyzstan to reduce the traditional energy consumption. The hydro-energy projects enforces the socio-economic development of regions to meet the needs in the water, energy, flood control, etc., on the other hand they have a negative impact on the environment. Intensification of landslides, reservoir-induced seismicity, rise of groundwater level and land erosion and other environmental hazards need detailed investigations before, during construction and exploitation of hydropower stations. The geoinformation systems (GIS) and remote sensing technologies are recommended in the geoenvironmental impact studies of hydro-energy projects in the Naryn river basin. The efficiency in the use of integrated information systems created by combining the capabilities of GIS and remotely sensed data confirmed by numerous examples of successful use in practice, e.g. in the modeling of technical, natural and climate parameters to avoid disasters.
<p>Connectivity is crucial for the functioning of river corridors as it determines the natural flow and sediment regime as well as the ability of species to migrate. Thus, it is a property highly relevant for the development of riverine landscapes and their potential of ecosystem service provision. Today, the connectivity of most (large) rivers is affected by anthropogenic infrastructure such as hydropower dams. This is also true for the Aral Sea Basin in Central Asia. The importance of rivers as freshwater resource led to an intensive exploitation of water resources and to the construction of a large number of dams and thus to a fragmentation of the river network. Despite its relevance for the functioning of the river corridors, connectivity remains unexplored for this &#160;basin. This is partly due to the fact that the large scale assessment of connectivity for such data-scarce regions is challenging. For instance, there is the need to delineate a robust and accurate river network from globally available digital elevation models (DEM) as readily available datasets like the Hydrosheds river network suffer from significant errors in this region. In this study, we present a first assessment of the connectivity of the river network in the Aral Sea Basin. In addition, we discuss the challenges associated with large scale modeling of structural connectivity of river networks in data-scarce regions and how to overcome them.</p> <p>We take as a basis a channel network delineated from the 30 m Copernicus DEM along with geomorphon-based major geomorphological units to derive landscape-specific channel initiation thresholds. We use a least-cost path approach for flow routing to avoid artifacts resulting from sink filling. Multispectral satellite time series from the Landsat mission are used to remove abandoned channels and to correct the river network. Additional input are the barriers in the Aral Sea Basin. We use the dam data from Global Dam Watch and complement it by mapping from high resolution Google Earth imagery. The river network and the barrier locations are used to create a graph representation of the river network where river reaches are represented by edges and confluences as well as dam locations by nodes. This river graph is used to compute connectivity metrics such as the dendritic connectivity index, for both the whole network and at the subcatchment scale.</p> <p>The results of our study deliver the first analysis of connectivity of the river network in the Aral Sea Basin. Along with the insights in this particular river basin, we present an approach which is optimized for the application in large, data-scarce study areas. Such static analysis of structural connectivity is of course a first indicator only, and further analysis is required to understand the impact of hydrological and sediment connectivity on the riverine landscapes of the river corridors of the region. Thus, rather than a final result, we see our study on river network connectivity as an important basis for assessing sediment dynamics across the network, natural flow regime and its impairment as well as river and floodplain habitat integrity.</p>
The importance of Remote Sensing (RS) in various scientific and practical studies, including hydrology, is increasing today. New Global Digital Elevation Models (DEM), based on satellite imagery, serve as the main resources in hydrological research due to their openness or low cost, increasing accuracy and improved spatial resolution. The main aims of this work are study the capabilities of Global DEMs based on AW3D30, ASTER GDEM V003 and SRTMGML1 with 30 m spatial resolution in modeling basins of rivers and Issyk-Kul Lake in Kyrgyzstan and their comparative analysis. Topographic maps of the study area were used as sources of verification data when analyzing their spatial accuracy. The influence of the reference point heights above sea level on the accuracy and reliability of the models in high mountainous conditions was also studied. UTM, SK-42, Kyrg-06 and the Albers Equal-Area Conic coordinate systems were used in calculations of the lake basin area. The results of the study showed that the AW3D30 DEM has higher accuracy compared to other models and can be successfully used in modeling river basins in mountainous areas. The catchment areas of the Dzhergalan and Tyup rivers were modeled and calculated based on AW3D30, ASTER GDEM V003 and SRTMGML1 DEMs. The research results on boundaries and areas of the river basins in the lake depression indicate the need for further refinement based on modern remote sensing data, taking into account the differences in the geoid/quasigeoid models used and the reference point heights determined using satellite-based positioning and leveling methods.
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