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Hydrology.ppt
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- 2. Dimensions of riverecosystems • Longitudinal • Lateral • Vertical • Temporal 2
- 3. Longitudinal Changes inStreams • Certain characteristics of streams change predictably from upstream to downsteam – Channels become wider – Flow becomes slower, but greater in volume – Streams become deeper 3
- 4. Longitudinal Changes – ReachScale • Longitudinal changes are also observed at shorter scales than the entire river length • We call this shorter scale the “reach” scale • One example of reach scale changes is the pool- riffle pattern found in many streams draining areas with medium gradient • Riffle is an area of rapid flow over coarse substrate (rocks) whereas the pool is a slower flowing stretch with finer substrate • Path of flow - thalweg 4
- 5. Lateral Patterns • Thereare also some predictable changes laterally • The stream has a low flow channel; the fastest flow is called the thalweg • The stream has banks which define its frequent flow limit • The stream has a floodplain which defines its flow limit on less frequent events, annual or lesser frequency 5
- 6. Lateral Patterns • Somestreams and rivers will have a single dominant channel while others will have a network of interwoven channels 6
- 7. Lateral Features • Asrivers increase in size they may develop a complex floodplain system 7
- 8. Vertical dimensions • Velocitychanges with depth in stream channel • Discharge (Q) = VA Diagram by:Eric G. Paterson Department of Mechanical and Nuclear Engineering The Pennsylvania State University 8
- 9. Vertical Features • Hyporheic (below stream)inter- actions • Exchanges occur with groundwater just below the stream 9
- 10. Lateral and VerticalPatterns • In many large alluvial valleys, creatures that live in ground water and hyporheic water can be found in the subsurface water kilometers from the stream. In other words the stream extends well beyond its channel. 10
- 11. Temporal dimension • Streamflow changes Second by second Hourly Daily Monthly Seasonally Annually Milleniumly 11
- 12. Selected Important HabitatFactors • Substrate • Temperature • Oxygen levels • Flow velocity • Food availability • pH • Nutrient and sediment regimes • Organic input and transport 12
- 13. How are speciesdistributed in space and time? -- Environments contributing to riverine biodiversity Surface water Subsurface water Riparian system Streams Springs Lakes Hyporheic Zone Ground Water Confined Reaches Unconfined Reaches 13
- 14. River --------------------------------------------- FloodplainEdge Spatial distribution of species across a floodplain (lateral dimension) Species Richness 0 50 100 Percent of maximum richness fish Mollusca Odonata Amphibia Macrophytes (Ward and Tockner 2001 fig. 9.3) Species Richness 0 100 Eg. Fish Snails, slugs, mussels, Dragonflies, damselflies Frogs, salamanders, toads Aquatic plants 14
- 15. How do humans affectwatersheds and the hydrologic cycle? 15
- 16. Human caused disturbances •Agriculture • Timber harvest • Mining • Urbanization • Introduction of exotic species • Harvesting of fish and wildlife 16
- 17. Land use/cover and vegetation PhysiographyClimate Landscape controls Nutrient Inputs Solar energy and Organic input Regime Gross reach morphology Habitat Forming Processes Species assemblages Stream Morphology and Conditions Biodiversity Habitat complexes and conditions e.g., pools, riffles, temperature, etc. Sediment and Hydrologic Regime Modified from Roni et al. 2002. 17
- 18. Physical, chemical, andbiological components related to water quality • Light • Temperature • Dissolved ions • Suspended solids • Nutrients and gases • Toxics such as metals and pesticides/herbicides • Biological features • PPCPs (Pharmaceuticals & Personal Care Products) 18
- 19. Photos by R.S.Lindsay Photo by Carrie Inman Agriculture 19
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- 21. Aggregate Mining In-channel mining In-channeland floodplain mining Photos by M. Kondolf 21
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- 23. Forestry, agriculture and urbanization •Remove trees and other vegetation • Reduce organic matter delivery • Build roads 23
- 24. Large storage in soil, channeland valley floor Recharge Natural cleaning Pollutant wash off No recharge Rapid flow limited storage Natural Developed Reduced soil storage Limited infiltration Precipitation 24
- 25. Floods and Urbanization surfacerunoff vs. infiltration natural land cover vs. urban area 25
- 26. How do wemanage watershed? • Dept of Natural Resources Regulations • U.S. Forest Service Regulations • Clean water act • Endangered Species Act • Total Maximum Daily Loads (TMDLs) 26
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- 30. Take Home Messages •Understand the interactions between land use/land cover and components of the hydrologic cycle • Be able to describe what is typically measured in watersheds and why 30
- 31. Hydrology Report ~ 2-3pages due May 25 individually Include: Name, Date, Title Introduction Methods Results and Discussion (w tables) Conclusions Appendix (if needed for raw calculations) 31