Research of stream flow initiation conditions allocation within Chita River basin

For the purpose of stream network spatial features detection the head of the first order stream in the Chita River basin (Transbaikalia) was considered. Shuttle Radar Topography Mission (SRTM 4.1) digital terrain model (DEM) and topographic map on a scale of 1:100000 were used as the necessary input data. The stream network delineation was made using the internal Adjustable Dispersion Routing Algorithm (ADRA) Terrain Analysis System Geographic Information System software (TAS GIS by Dr. John Lindsay). The ADRA was run with several C parameter values assignments. The C parameter is equal to the specific catchment area multiplied by a squared local slope and its influence on head streams location. The ADRA stream networks were compared with the topographic map stream network. Only perennial streams were taken into account. The analysis of stream networks delineated by ADRA with several value of C parameter revealed the basin division into parts with similar conditions of river flow generation. The drainage divides placement, geographical location, elevation, annual amount of precipitation, within-year variability of precipitation influence on spatial differentiation of these conditions. In general, the increasing of specific catchment area from north to south, from east to west, from higher places to lower ones takes place. In addition to whole basin patterns of relationship there are local ones, which are under the influence of the landscape, hydrogeological, cryological, anthropogenic conditions of locality. They detect on places TAS stream network and topographic map stream network noncoincidence. It is necessary to take into consideration some ADRA errors. They happen when there is a very big slope and a very small catchment area or a very small slope and a very big catchment area. In these conditions many short streams appear, which are not reflected in the topographic map. There are spatial differences in the changes of stream networks delineated by ADRA with various value of C parameter. It is because of spatial differences in the catchment area expansion, basins shape, and slope changes. By the various value of C parameter assignment we can receive various stream networks corresponding to various humidification and hydrological regimes. The less value of C parameter, the more humidification, more portion of overland flow, and more drainage density. If the value of C parameter is increasing the precipitation is decreasing and water exchange between the overland flow and underground flows becomes more significant.

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