River water has been historically diverted by aqueduct to feed agricultural systems and the large cities of SoCal, causing many controversies over water rights and the effect of diversion on rivers. By moving water through aqueducts, it is removed from its original system, and as seen in the photo, many are completely exposed to the elements and therefore lose water along their transportation route.

Other methods of water diversion include groundwater pumping, construction of dams, sand and gravel mining which lowers the elevation of river beds, or downcutting or straightening of channel beds which all cause the groundwater level to lower. For riparian trees, this can mean losing root access to the groundwater and eventually, death.

Dams are a form of water withdrawal, but a particularly powerful and harmful one. Dams modify the flows in the rivers below them, which impacts plant and animal life histories that are so uniquely tied to the ebb and flow of the water. They are also a prime suspect in habitat fragmentation and reduce access for aquatic migration, especially in the case of Southern California Steelhead Trout.

Dams also cut off sediment and organic matter transport that help build up floodplains used for agriculture and provide us with food.

Dams can also control and fluctuate water levels which exposes some areas without water, and floods others, decomposing the vegetation underwater and even releasing greenhouse gases which contribute to climate change. Some habitats can be completely inundated when dams are used to create new reservoirs, lost entirely.

Riparian areas often have extremely nutrient rich soils and are useful for food production. Agriculture has both direct and indirect effects on riparian ecosystems. Feces and pollution may run off into rivers, introducing microbial contaminants to the water and the organisms living there. Agricultural runoff also causes excess nutrients in the water due to the use of fertilizers. Many riparian trees have the ability to filter out excess nutrients, however, a few trees can only do so much against the power of industrial agricultural pollution.

Grazers such as cattle are attracted to the shade of riparian trees, but in turn trample the vegetation and soil, as well as forage on riparian plants, removing the source of the very shade they came for.

Land development involves the alteration of riparian habitats for use in urban areas, including the construction of roads, dams, and river channelization. Often, development leads to removal of riparian vegetation, causing less shade (and increased water temperatures), less leaf litter (a vital food source in rivers), and increases bank erosion.

Channelization in particular leads to the complete disruption of natural river flows, and completely separates the river from the soil. This means that not only lose its ability to restore nutrients to the surrounding lands, it also loses its ability to aid in groundwater replenishment.

Vegetation along channelized rivers is also limited, which removes the vital service of filtering excess sediment and contaminants that riparian plants provide. Finally, all of this water flows, unfiltered, into the ocean.