Resources: York River Water Budget - Impacts of Changing Flow
Variation in freshwater flow is the dominant source of seasonal and interannual variability in estuaries, influencing the physics, geology and biology of the estuary.
Changes in freshwater flow affect:
1. inundation of intertidal areas,
2. loadings and advection of materials and organisms,
3. dilution and mobilization of contaminants,
4. estuarine salinity distribution,
5. estuarine stratification, and
6. residence time for water and biota.
Changes in historic flow rates may be due to human use, diversion and impoundment of river water or changing climatic conditions resulting in altered rates and timing of precipitation.
Ecological effects from changing flows in estuaries are most obviously related to salinity alterations. Salinity tolerances dictate species distributions and subsequent trophic interactions. Flow alteration may result in the mismatch of predator and prey availability as the turbidity maximum strength and location is changed.
Long-term salinity alterations will lead to shifts in plant and animal assemblages including:
1. loss/stress of flora and fauna with low salinity tolerance,
2. reduced water quality, and
3. introduction of predatory marine animals.
To establish optimal flows in estuaries for water planning, biological resources anticipated to be affected by altered flow and representative of the ecosystem most likely will be considered as potential indicators of estuarine condition. |
