Increasing frequency of stream diversion is requiring establishment of methods to determine instream flow requirements for riparian resources. Most methods are oriented toward fisheries. Instream flows for fish may not meet requirements for riparian vegetation as plants may need greater flows or flooding events. Using riparian tree growth and controlled releases at Rush Creek, an eastern Sierra Nevada stream, a model was established to show annual flow requirements for maintenance of mean standard tree growth. This model is applicable to cottonwoods (Populus spp.) on Rush Creek. Instream flows for riparian resources must also consider seedling establishment, including timing of seed dispersal and requirements for floodplain wetting. Flow requirements for tree maintenance and seedling establishment are not necessarily the same, but both must be met for long-term maintenance of the riparian community.