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Rivers and Streams

Learn about lotic systems with focus on Wisconsin River and Cannon River watersheds, including stream order, water movement, load, watershed geology, and biotic attributes. Understand key concepts in river ecology.

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Rivers and Streams

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  1. Rivers and Streams K. Wilson

  2. Flowing Water (lotic) Systems • Stream: A mass of water and its load, moving in a more or less definite pattern, generally following the path of least resistance. • Four unique characteristics of streams • Generally unidirectional flow. • Linear in form. • Fluctuating discharge. • Unstable bed.

  3. The Wisconsin River

  4. Overview • The basics of lotic systems • Physical • Chemical • Biological • “Unifying” concepts in river and stream ecology • Key points to take home

  5. Watershed • The area of land that is drained by a given stream or stream system. • Catchment = watershed = drainage basin • Examples include: • The Spring Creek catchment. • The Cannon River watershed. • The Mississippi River drainage basin.

  6. Cannon River Watershed Mississippi River

  7. Mississippi River Basin You are here

  8. Stream Order • Horton-Strahler classification developed in the 1940’s and 50’s. • Surrogate for stream size also correlates with watershed area. • Includes only permanent streams (year-round) • 1st order ~ headwater streams • Tributary: smaller stream flowing into a larger stream

  9. When two streams of the same order join, the stream order increases by one. Two 1st order join to form a 2nd order. Two 2nd order join to form a 3rd order. Not the sum of orders! Example of Stream Order

  10. Water sources • Direct precipitation • Groundwater • Tributaries • Overland flow • Runoff • Subsurface flow

  11. Hydrologic cycle

  12. Short time scalesRunoff = Rainfall – infiltration rate

  13. Long time scalesRunoff = Rainfall – Evapotranspiration Assuming change in storage due to infiltration is zero Determined by: • Climate • Vegetation • Infiltration capacity • Geography

  14. Current Velocity (U or V) • Measured in: • Feet per second (fps) • Meters per second (m/s) • Varies greatly within a cross section • Determined by: • Gradient • Friction • Sinuosity of the channel • Obstructions

  15. Velocity (U) As a Function of Depth

  16. Velocity (U) as a function of channel position

  17. Discharge (Q) • Measured in: • Cubic feet per second (cfs). • Cubic meters per second (m3/s). • Q = WDU. • Where WD is the cross section area of the stream.

  18. Discharge (Q)

  19. Hydrograph

  20. Cannon River Discharge at Welsh 4 October 2002 2500 2.5 Rainfall in Northfield 2000 2.0 1500 1.5 Discharge (ft3/sec) Rainfall (cm/hr) 1000 1.0 Discharge at Welsh 500 .5 0 0 0:00 4:48 9:36 14:24 19:12 0:00 Time

  21. Many tributaries in Cannon River watershed

  22. Water Movement and Load • Load • Dissolved • Elements, ions, and organics (Al, Ca2+, and others) • Gasses (Carbon dioxide, methane, and others) • Solid • Suspended (Wash load) can be measured as turbidity • Bed load can be measured as bed movement

  23. Velocity of water Size of material Factors influencing wash load

  24. Wash load and bed load

  25. Substrate stability • Stable (upstream conditions) • Large rocks • Habitat for slow-growing algae • Crevices for refuge • Unstable (downstream conditions) • Silts, sands • Constantly changing • More burrowing organisms

  26. Watershed Geology • Determines the size of load • Determines availability of nutrients • Factors include • Soil in the watershed • Bedrock / parent material of wash and bed load • Example • Sierra Nevada streams tend to have very low buffering capacity due to low carbonates in parent material (granite)

  27. Channel Morphometry • Determined by: • Climate (precipitation) • Geologic factors • Load • Erodability of local materials • Gradient • Channel cross section

  28. Channel Types • Braided Channel • Wide ranging discharge (Q) • Highly eroded • Meandering • Stable Q • Low gradient • Helical flow

  29. Biotic attributes of streams • Most of the biologic action takes place on or in the substrate. • Primary productivity comes from attached algae (periphyton) or rooted macrophytes (except in large rivers). • Most animal biomass is composed of macro invertebrates (95%). • Hydrology influences biota heavily.

  30. Boundary layers lift Issues organisms must deal with

  31. Organic Matter • Origins • Autochthonous. • Allochthonous. • Size class • Course particulate organic matter (CPOM). • Fine particulate organic matter < 1 mm (FPOM). • Dissolved organic matter < .5 micron (DOM).

  32. Functional Feeding Groups. • Groups or “guilds” that eat the same thing. • Shredders eat CPOM and make FPOM. • Collectors eat FPOM. • Scrapers eat periphyton. • Predators eat the above groups.

  33. Nutrient Spiraling Concept (NSC) • Based on uptake and retention of nutrients. • Uptake length is the average distance traveled by a nutrient from being “released” to being re-assimilated. • Spiral length is a measure of nutrient retention. Shorter spirals mean greater retention and greater “cycling”.

  34. piral length (S) ater transport distance iota transport distance elease ptake

  35. Telescoping ecosystem model • Spiral lengths change with disturbances (floods, dry periods) due to interactions between surface stream, hyporheic zone, parafluvial zone and riparian zone. • Disturbances differentially affect the stream subsections • Minor disturbance impacts surface stream • Major disturbance impacts all components

  36. A stream is more than just the surface water…

  37. The River Continuum Concept (RCC) • Describes organic matter, respiration, primary production, and species composition along a longitudinal gradient from headwater to large river. • Developed for stable, undisturbed north temperate forested watersheds • Longitudinal structure form a gradient of physical forces that change predictably along its length

  38. Stream orders: Small streams 1-3 Medium-sized rivers 4-6 Large rivers > 6 Energy for biological production comes from: Allochthonous Autochthonous Material imported from upstream RCC

  39. Stream reaches differ in: Environ. Conditions Light avail Leaf litter input Invert community Ratio of primary production to respiration RRC

  40. Trends in RRC • From low order to high order • CPOM  FPOM • P/R < 1 -- P/R >1 • Shredders  Grazers & Collectors  Collectors (predators remain about 10%) • High gradient  Low gradient

  41. RCC • Works well with large, cold water rivers geologically constrained riffle-pool channels (no flood plain) • Does not work with large floodplain rivers like the Amazon • Considers only the main channel

  42. Flood-pulse concept • Emphasizes lateral water movement in large rivers • floodplains • floods • Important for: • Reduction in sediments loads • Reduction in nitrate • Breeding habitat for fishes

  43. Aquatic / terrestrial transitional zone (floodplain)

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