Chapter 2: Characterization of Riparian Areas

Water-Riparian Lotic and Lentic Riparian Areas

Water from a watercourse or water body is the key that differentiates riparian areas from adjacent terrestrial upland areas

 

  1. When the riparian areas are along the banks of moving water (streams and rivers) these are called lotic systems.
  2. If the water is stationary (lakes, ponds and wetlands) these are called lentic systems.
  3. Three types of streams.
    • Perennial streams have flow in the stream channel throughout the year and substantial inputs from groundwater. These areas adjacent to perennial streams are called by some Hydroriparian.
    • Intermittent streams can also have relatively high inputs of groundwater but flow in the stream channel can be for several weeks or months each year. These areas adjacent to intermittent streams are called by some Mesoriparian.
    • Ephemeral streams only flow after precipitation events. The channel of ephemeral streams is generally well above the water table, these streams flow for only a few hours or days following a storm of sufficient magnitude to produce overland flow. These areas adjacent to ephemeral streams are called by some Xeroriparian.
    • Intermittent and ephemeral streams are very often confused with each other, particularly in the arid western United States. The main characteristic difference between ephemeral and intermittent streams is groundwater inputs and connectivity to stream flow.  Ephemeral streams have almost no groundwater inputs and connectivity.  In the arid regions of North America dry washes or arroyos can be ephemeral streams.
    • There is SIGNIFICANT CONTROVERSY in the scientific community over defining riparian areas adjacent to ephemeral streams. The main arguments for scientists that do not include areas adjacent to ephemeral streams are that these areas do not perform the entire spectrum of the riparian ecological functions. In contrast, the scientists that include areas adjacent ephemeral streams as riparian argue that these areas are riparian because they have most of the characteristics that define the wet riparian areas.

    Figure 2.3. Perennial, intermittent and ephemeral streams in association with their vegetation.

      

       

    Figure 2.4. In Arizona you can find ephemeral (top left), intermittent  (top right), and perennial streams (both bottom).