A tributary is defined as a smaller stream channel that runs into the larger, main waterway.
Such tributaries provide the Blanco River with a primary source of stream flows. These tributaries make up the smaller sub-basins within the Blanco River Watershed stretching a total of 440 mi² to the boarders of the Blanco River Basin.
The Blanco River Basin is comprised of three smaller sub-basins:
In addition to stream flows, the tributaries also provide essential nutrients and sediments to sustain the diverse biota in the watershed.
As healthy levels of nutrients and sediment are distributed throughout the system, pollutants can be elevated inside the main water way as well. If increased land disturbances, or non-point and point-source pollution levels are present within the wide-spread basin, the water quality of the Blanco River can be compromised.