Diversions → Sources, Sinks or Canals

TopoFlow supports three different types of flow diversions: sources, sinks and canals. Sources are locations such as natural springs where water enters the watershed at a point by some process other than those that are modeled. Similarly, sinks are locations where water leaves the watershed at a point. Canals are generally man-made reaches such as tunnels or irrigation ditches that transport water from one point to another, typically without following the natural gradient of the terrain that is indicated by the DEM. The upstream end is essentially a sink and the downstream end a source.

To use flow diversions, you must provide the required information in specially-formatted text files. Where required, vector-valued input variables such as durations are specified as a list of space-delimited numbers on one line (i.e. terminated by a single end-of-line character). The term pixel ID refers to the integer value that is assigned to a given pixel (i.e. grid cell) when all pixels in the corresponding DEM are numbered sequentially in calendar order , that is, from top row to bottom row and from left to right within each row. Pixel IDs start at zero and are read and processed as long (4-byte) integers.

For sources and sinks, the following information must be provided, each on its own line:

ID     (source pixel ID as long integer; calendar index)
nd     (number of durations and flow rates)
durations     (vector of durations in minutes)
flow rates     (vector of discharges in m3/sec)

For canals, the following information must be provided, again with each entry on a separate line in the text file:

ID1     (start pixel ID as long integer; calendar index)
ID2     (end pixel ID as long integer; calendar index)
time     (travel time between ID1 and ID2, in minutes)
nd     (number of durations and flow rates)
durations     (vector of durations in minutes)
flow rates     (vector of discharges in m3/sec)

Canals are currently assumed to be lossless, so that the flow rates at the two ends are identical, but lagged by the travel time.