Natural Earth Data has Rivers and Lake Centerlines and Lakes and Reservoirs.
The USGS Earth Explorer will let you download data from anywhere in the world. Type "Kazakhstan" into the place search criteria box, click over to data sets and type "hydro" into the data set search box. The dataset called GTOPO30 HYDRO1K is a hydrology raster. There's a download ...
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If you are a ESRI ArcGIS Desktop user then they have ArcGIS Online that has these polygons that you can download:
Finally, if you live in those areas or not, you may need to ...