The Danube River. Hydrological Connectivity and Human Influence. By: Pat O Connell, Pat Wilkins, Tiana Royer, and Kevin Gaitsch

Transcription

1 The Danube River Hydrological Connectivity and Human Influence By: Pat O Connell, Pat Wilkins, Tiana Royer, and Kevin Gaitsch

2 Danube River Characteristics Length: 2860 km Drainage Area: 816,000 km 2 Peak Recorded Discharge:14,520 m 3 s - 1 Mean Annual Water Discharge: 6420 m 3 s -1 Mean Annual Suspended Sediment:

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4 Reconstruction of the Characteristics of a Natural Alluvial River-Floodplain System and Hydromorphological Changes Following Human Modifications: The Danube River ( ) By: S. Hohensinner, H. Habersack, M. Jungwirth and G. Sauner

5 Abstract Danube River landscape prior to channelization Changes in fluvial dynamics, hydrological connectivity, and aquatic habitat composition after channelization and flow regulation Current (1991) Danube characteristics

6 Field Locations km long stretch of the Danube in the Austrian Machland (Border of Upper and Lower Austria) Strongly influenced by 3 large alpine tributaries (Inn, Traun and Enns) Contains part of the active zone (AZ): active channel system, vegetated islands, and the adjacent active floodplain.

7 Study Reach

8 Methodologies Used 1812 historical maps, edited for distortions 1812 = before straightening, and building of power plants 1812 map has terrain heights, low water levels, mean water levels, mean annual flood, velocities, vegetation, and river bank erosion 1925 historical map of river used to see effects of straightening

9 Methodologies... Several maps used for current conditions 1991 map focused on Overlayed 3 maps to observe morphological changes such as surface area, sand bars, and natural trenches 3 maps compared to see hydrological connectivity changes

10 3 Maps Used

11 Results General hydromorphological conditions Branched by several islands & gravel bars Sinuous

12 Results

13 Results Terrain topography in the Active Zone Inundation for up to 90 days or more Short distance between groundwater table and terrain surface

14 Results Main channel and floodplain water bodies River system with a very high share of permanently lotic arms. Even at low water, 97% of the total water surface area featured running water

15 Discussion River-floodplain changes due to straightening and regulation Forced into an average 350-m wide, single thread channel with large embankments Construction of two hydropower plants

16 Discussion Habitat reduction and diminished diversity Connected backwaters

17 Discussion Connectivity prior to human interference Assessed via mean water cover area Human induced changes of connectivity Cutting off of backwaters and natural trenches connections in form of channels and natural trenches connections connections left

18 Conclusion Initially high connectivity Interference led to flow pulse to be cut in half Aquatic/terrestrial transition zones Future mitigation will need to reference these factors to create healthy river conditions

19 Hydrological connectivity, and the exchange of organic matter and nutrients in a dynamic river-floodplain system (1999) By: K. Tockner, D. Pennetzdorfer, N. Reiner, F. Schiemer, and J.V. Ward

20 Objective Show relationship between hydrological connectivity and exchange process of nutrients and particulate matter on a part of the river with a still dynamic riverfloodplain system

21 Specifics of Study Measured Specific Conductance Nitrate Suspended Sediments Chlorophyll Dissolved organic matter Fine and coarse organic matter

22 More Specifics Sept Nov Alluvial Zone National Park Done as part of restoration project for segment of the Austrian Danube

23 Hydrological Connectivity Phase I: Disconnection (67.5 %) Phase II: Downstream surface connection and seepage inflow (29.3 %) Phase III: Upstream surface connection (3.2 %)

24 Study Results Site P2 (Upper Channel) and Flood Plain site had similar results. The River (P1) had higher nitrate and sediment concentration than the Flood Plain site (P3). Organic matter in P3 had similar concentrations with P1, including chlorophyll. Both varied though heavily from season to season

25 Correlation Results Correlations found with discharge P1 and P3 concentrations of CPOM P1 concentrations of FPOM and POC P3 positive with nitrates and negative with Oxygen Seasonal Pattern for nitrates

26 Sediment Transport Results P1 transported (606kg Ha^-1yr^-1) 95% FPOM Floodplain acted as major retainer 45% of annual nitrates 50% of annual suspended sediment And released to river Large amounts of dissolved organic carbon And CPOM

27 Overview WWF- Key Threats - new infrastructure, 8 proposed large dams The Danube is an important regional waterway that will continue to face human modification Future mitigation efforts need to put increased focus on keeping hydrological connectivity in place

28 References Hohensinner, S., H. Habersack, M. Jungwirth, and G. Zauner. "Reconstruction of the Characteristics of a Natural Alluvial River-Floodplain System and Hydromorphological Changes Following Human Modifications: The Danube River." River Research and Applications 20 (2003): Wiley InterScience. Web. 27 Apr < Tockner, K., D. Pennetzdorfer, N. Reiner, F. Schiemer, and J.V. Ward. "Hydrological Connectivity and the Exchange of Organic Matter and Nutrients in a Dynamic River-Floodplain System (Danube, Austria)." Freshwater Biology 41 (1999): Print. Wong, CM, CE Williams, J. Pittock, U. Collier, and P. Schelle. "World's Top Ten Rivers At Risk." WWF International (2007): Print.