Potential for enhancing riparian habitats in the southwestern United States with watershed practices

Abstract

Numerous watershed practices currently being implemented for erosion control and water augmentation purposes have improved hydrologic conditions in southwestern streams and enhanced establishment of riparian vegetation. This paper summarizes some potential opportunities for better managing existing riparian ecosystems, or for creating hydrologic regimes favoring re-establishment of new riparian communities in the southwestern United States. Generally, management opportunities exist where either the amount of water or duration of streamflow can be increased, or both. Various-sized channel structures, ranging from small gully check dams to large flood-control structures, have been used successfully for both stabilizing erodible channels and lengthening streamflow duration. These channel structures trap sediment in upstream deposits which store water and release it slowly over time, thereby producing perennial flow in previously ephemeral streams. In addition to providing a more favorable hydrologic regime, the deposited sediment also provides a nutrient-rich medium which further favors plant establishment and growth. The amount and duration of streamflow through a riparian zone can also be increased by manipulating upslope vegetation where deep-rooted plants are replaced with shallower-rooted species using less water. Case studies documenting these different watershed practices and the resulting riparian communities are discussed.