Rivers and Streams

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

25. Wash load and bed load

26. 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

27. 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)

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

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

34. 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.

35. Boundary layers lift Issues organisms must deal with

36. 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).

37. 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.

39. 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”.

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

41. 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

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

43. 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

44. 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

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

47. 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

48. 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

49. 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

50. Aquatic / terrestrial transitional zone (floodplain)