Streamflow Alteration In Class Discussion (Dec. 1st)

(Image reference)



Link to journal article of the week (must be sign into VT library)
http://www.esajournals.org.ezproxy.lib.vt.edu:8080/doi/pdf/10.1890/100053

“Alteration of streamflow magnitudes and potential ecological consequences: a multiregional assessment.” (Carlisle et al. 2010)

1. What were the ecological consequences of altered streamflow magnitudes, as quantified in this article?

a. (Physical alteration) streamflow magnitudes à altered versus nonaltered. Minimum and Maximum flows inflated or diminished.

b. (Ecological consequences) Fish and Macroinvertebrate communities. Impaired versus non-impaired. Ratio of observed taxa to expected taxa (reference) within region.

2. What happens to biological communities within the altered streams in comparison to reference streams?

a. Nest-guarders replacing simple nesters (can provide oxygen/flow to eggs)

b. Active swimmers replacing benthic and streamlined forms

c. Increased macroinvertebrate taxa with the ability to exit stream

d. Pool-loving taxa, fine-grain substrate loving-taxa

e. Invasion

f. PROBLEM with this article….where are the numbers for abundance data of organisms?

3. What are a few of the physical responses, to alterations in streamflow magnitude, which lead to these ecological consequences?

a. Floods of varying size and timing are needed to maintain a diversity of riparian plant species and aquatic habitat.

b. Reduced magnitude and frequencyà

i. Deposition of fines into gravel (no high flows to remove and transport fine sediments that fill interstitial spaces in productive gravel habitats)

ii. Channel stabilization and narrowing

iii. No import of, habitat providing, woody debris

iv. Floodplain disconnection (floodplains can be important for some species reproductive success-nursery grounds, no high flows to bring in organic matter from floodplain, high flows onto floodplain required for some riparian vegetation success)

v. Vegetation encroachment

c. Increased magnitude and frequencyà

i. Bank erosion and channel widening, bed scouring

ii. Streams that dry temporally, generally in arid regions, have aquatic and riparian species with special behavior or physiological adaptations that suit them to harsh conditions of drought.

d. Flow stabilization

i. Invasion or establishment of exotic species leading to local extinctions, threat to native commercial species and altering biological communities

4. What about the floodplain biological communities? What would diminished flow magnitudes do?

a. Inuadation of floodplain required for some riparian vegetation success

b. Vegetative encroachment into channel

c. Modification of riparian communities by causing plant mortality, reduced growth, competitive exclusion, ineffective seed dispersal or establishment.

5. So what if magnitude is not altered? What about the other four flow components? Are they important and if so, how?

a. IN ADDITION: What about changing magnitude WITHOUT a Dam?

i. This can occur in urban areas. Low flows become elevated in urban areas because waste water enters and increases/elevates baseflows and increases nutrients in water.

ii. ORà from agriculture withdrawls and groundwater pumping

b. Frequency

i. Extreme daily variations below peaking power hydroelectric dams = harsh environment, frequent disturbance. Mortality of aquatic populations suffering from physiological stress,

c. Timing

i. Some species use seasonal flow conditions as CUE to reproduce (Life history traits)

ii. Riparian plant species with specific germination timing (cottonwoods, needs flow peaks to occur before germination period)

d. Duration

i. Change in floodplain inundation, independent of changes in annual volume of flow, can alter the abundance of plant cover types

ii. Loss of riffle habitat with prolonged inundation

e. Rate of change

i. Washout and stranding of aquatic species

6. How could we conduct a study to include the other four components? Would inclusion of these dimensions increase or decrease the severity and likelihood of stream impairment?

a. Use annual hydrographs (timing, duration, rate of change, frequency)

b. Increase

7. What are the issues between arid and wet climate areas?

a. Differences in water management in watersheds

b. Aridà use for agriculture/irrigation/drinking wateràyou get DIMINISHED max and min flows

c. Wetà dams for flood control (you get more elevated MINIMUM flows and unaltered MAX flows)

d. Western US water issues, water rights out west, who owns what issue?

e. Conserving differences between the West and East

f. Desalination of ocean water is too cost and energy expensive

8. How do you balance human needs with ecological requirements?

a. Public educationà current public opinion is concerned with QUALITY and not QUANTITY

b. Policy changes

c. Improved water resource management, instream flow water management, better science

d. Water is a FINITE resource

e. People don’t understand what is going on, need to educate the publicà they drive policy maker decisions.

f. Need a basic government commitment to promise to provide water to the people for basic needs, government protection of aquatic ecosystems

g. Technological improvements! Improve consumption of water, distribution of in-home water plumbing, water reuse