Watersheds and Hydrology

1. Watersheds and Hydrology What’s Water Got to Do with It? • More water moves through ecosystems than any other material • The materials that it carries and deposits and the energy that it expends are major drivers in shaping the contour of the land and the habitat availability/suitability for organisms. • A resource that humans cannot live without

2. Watersheds andHydrologyLearning Objectives • Where do we find water? • What is the hydrologic cycle? • How many dimensions does a stream have? 4 How do we characterize stream water? 5 What do we want to know about stream flow?

3. Question 1 Where do we find water?

4. Global distribution of water

5. Global distribution of freshwater

6. Watersheds andHydrology • Where do we find water? • What is the hydrologic cycle? • How many dimensions does a stream have? 4 How do we characterize stream water? 5 What do we want to know about stream flow?

7. Question 2What is the hydrologic cycle? What is the hydrologic cycle? Precipitation Interception Infiltration Evaporation Transpiration Runoff Ground water

8. Watersheds andHydrology • Where do we find water? • What is the hydrologic cycle? • How many dimensions does a stream have? 4 How do we characterize stream water? 5 What do we want to know about stream flow?

9. Question 3 How many dimensions does a stream have?

10. Question 3 How many dimensions does a stream have? • Longitudinal (upstream to downstream) • Lateral (bank to bank and valley wall to valley wall) • Vertical (water surface to bed to hyporheic to ground water) • Temporal (time: seconds to millennia)

11. Longitudinal Changes in Streams • Certain characteristics of streams change ‘predictably’ from upstream to downsteam • Channels become wider • Channels become deeper • Flow becomes slower, but greater in volume

12. Longitudinal Changes – Reach Scale • 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 gradients • Riffle is an area of rapid flow over coarse substrate (sediment) whereas the pool is a slower flowing stretch with finer substrate

13. Lateral Patterns • There are also some predictable changes laterally • The stream has its low flow channel, the low point of which is 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 Thalweg

14. Lateral Patterns • Some streams and rivers will have a single dominant channel while others have a network of interwoven channels

15. Lateral Features • As rivers increase in size they will develop a complex floodplain system

16. Vertical dimensions • Velocity changes with depth in stream channel Diagram by:Eric G. Paterson Department of Mechanical and Nuclear Engineering The Pennsylvania State University

17. Vertical Features • Hyporheic (below stream) inter-actions • Exchanges occur with groundwater just below the stream

18. Lateral and Vertical Patterns • 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 visible channel.

19. Temporal dimension • Stream flow changes Second by second Hourly Daily Monthly Seasonally Annually Millenniumly • Channels migrate • Riparian areas go through disturbance and succession • Seasonal changes in inputs

20. Watersheds andHydrology • Where do we find water? • What is the hydrologic cycle? • How many dimensions does a stream have? 4 How do we characterize stream water? 5 What do we want to know about stream flow?

21. What are the major physical, chemical, and biological components used to characterize water quality?

22. Selected Important Habitat Factors • Light • Substrate • Temperature • Oxygen levels • Flow velocity • Food availability • pH • Hydrologic, nutrient and sediment regimes • Organic input and transport • Toxics and other pollutants • Biological communities

23. Influence of temperature on growth rates 1.0 Midges Daily Growth Rate (mg/day) 0.5 Blackflies Mayflies 0 0 8 16 24 32 Temperature C Modified from Benke 1993

24. Watersheds andHydrology • Where do we find water? • What is the hydrologic cycle? • How many dimensions does a stream have? 4 How do we characterize stream water? 5 What do we want to know about stream flow?

25. What do we want to know about stream flow? Question 5 • Magnitude - how much? • Frequency - how often? • Timing - when? • Duration - how long? • Rate of change – how fast?

26. 1982

27. Mean daily flow (cfs)Juanita Creek Water Year 2010 Oct May

28. Mean Monthly FlowsJuanita Creek Water Years 2005-2009

29. Oct 13 midnight Oct 12 midnight

30. Mean Daily FlowJuanita Creek (cfs)

31. 15 minute flowsJuanita Creek May 27-29, 2004 May 28

32. Unregulated Regulated

33. How much water is enough? • Depends on who or what is using the water • Historically managed for minimum flows (what is the minimum flow that keeps fish alive) • Legal issue of water rights complicates situation

34. Examples of where to locate national data for watersheds and streams • Watershed data • EPA Surf your watershed http://www.epa.gov/surf/ • Climate data (national and international) http://www.ncdc.noaa.gov/oa/ncdc.html • Climate data (Washington) http://www.wrcc.dri.edu/summary/climsmwa.html

35. Examples of where to locate national data for watersheds and streams • Stream data- quantity and quality • USGS Water Resources Data http://water.usgs.gov/data.html • Soils data • http://soils.usda.gov/ • Aquatic biologic indicators • http://www.epa.gov/bioindicators/

36. Take – home messages • Flow regimes play a major role in habitat • Land-use alters flow paths and storage components and hence, flow regimes • Effects vary with spatial and temporal scales • Research on which aspects of flow are most critical to various biotic responses are in progress • Don’t forget the basic processes involved