树状河网计算的关键是确定计算河道顺序。计算顺序应遵循的原则是：从支流到干流，从上游到下游。这样可以把河网依次分解为一系列的单一河道，用单一河道的计算方法求解。(The key to the calculation of tree like river network is to determine the order of river courses. The following principles should be followed in the calculation sequence: from the branch to the main stream, from upstream to downstream. In this way, the river network can be decomposed into a series of single river channels and solved by a single channel calculation method.)