Lecture 5 Hydrologic Cycle and Surface Hydrology

Transcription

1 LIMNOLOGY SPRING 2010 BIOL 362 / WMAN 446 Lecture 5 Hydrologic Cycle and Surface Hydrology 27 January 2009 Required Readings: Dodds Chapter 4. Hydrology and Physiography of Groundwater and Wetland Habitats. Pages in Freshwater Ecology. Academic Press. Allan, J.D Chapter 1. Poff, N. L., B. P. Bledsoe, and C. O. Cuhaciyan Hydrologic variation with land use across the contiguous United States: Geomorphic and ecological consequences for stream ecosystems. Geomorphology: Poff, N. L., J. D. Allan, M. B. Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks, and J. C. Stromberg The natural flow regime. BioScience 47: Additional Readings: Drever, J. I The geochemistry of natural waters: surface and ground water environments. 3rd ed. Prentice-Hall, Inc. Leopold, L.B A view of the river. Harvard University Press. Ritter, D. F., R. C. Kochel, and J. R. Miller Process geomorphology, 4th edition. McGraw-Hill. Objectives of Lecture: 1. To describe the hydrologic cycle. 2. To understand what happens to water after if precipitates within a typical forested headwater catchment. 3. To understand the difference between ephemeral, intermittent, and perennial streams. 4. To understand the 5 components of the Natural Flow Regime Paradigm. 5. To describe how human activities within a watershed can influence the annual water budget. 1

2 The Hydrologic Cycle A. Distribution of Earth s water Task 1: List the 3 biggest sources of water by percentage B. Distribution of Earth s freshwater Task 2: List the 3 biggest sources of freshwater by percentage C. Residence Times and Turnover Rates D. Hydrologic Cycle (pages ) 1. Reservoirs 2. Fluxes 3. Evapotranspiration 4. Advection 5. Precipitation over land a. Evaporation b. Infiltration and transpiration c. Infiltration and percolation d. Run off: surface or ground water 6. Flow to ocean E. Groundwater (pages 50-54) 1. Percolation of water through soil and pores in bedrock 2. Aquifer 3. Sandstone 4. Impermeable layer 5. Water table F. Groundwater movement (pages 55-56) 1. Flow patterns 2. Potentiometric gradients 3. Changes in flow patterns (Sidebar 4.1) Task 3: List the 3 activities that account for the greatest use of water by humans 2

3 HYDROLOGY The scientific study of the properties, distribution, and effects of water on the earth's surface, in the soil and underlying rocks, and in the atmosphere. SURFACE HYDROLOGY The scientific study of the dynamics of stream flow, including interactions among surface, ground, and soil water. A. FATE OF PRECIPITATION 1. Evaporation / Transpiration 2. Infiltration 3. Runoff B. RUNOFF PROCESSES 1. Hortonian Overland Flow 2. Saturated Overland Flow 3. Shallow Subsurface Flow 4. Groundwater Flow C. BASEFLOW VS. STORMFLOW (Stormflow Hydrograph) 1. Baseflow: precipitation that percolates to the ground water and moves slowly through substrate before reaching the channel. It sustains streamflow during periods of little or no precipitation. 2. Stormflow: precipitation that reaches the channel over a short time frame through overland or underground (usually shallow) routes. D. GAINING VS LOSING STREAMS 1. Gaining / Effluent: receive discharges from the aquifer. 2. Losing / Influent: lose water to the aquifer. E. EPHEMERAL VS. INTERMITTENT VS. PERENNIAL STREAMS 1. Ephemeral: flow only during or immediately after periods of precipitation or snowmelt. Generally flow less than 30 days per year. 2. Intermittent: flow only during certain times of the year. Seasonal flow usually lasts longer than 30 days. 3. Perennial: flow continuously during both wet and dry times. Baseflow is dependably generated from the movement of groundwater into the channel. 4. Protocols for delineating jurisdictional stream channels. F. STREAM DISCHARGE 1. Units cubic feet per second (cfs), gallons per minute (gpm), cubic meters per second (cms) 2. Area Velocity Method (Q=AV) 3. Measuring Current Velocity 4. Gaging Station 5. Discharge Rating Curve 3

4 G. ANALYSIS OF FLOW VARIABILITY 1. Hydrograph 2. Stream Types based on Flow Variability 3. Return Period Analysis The probability or percent chance of a given flow s being exceeded or not exceeded in any give year. Often expressed in terms of Return Period or the average number of years between exceeding or not exceeding the given flows. For example a given flood flow that has a 100-year Return Period is expected to be exceeded, on average, only once in any give 100 year period. In other words, in any given year, the annual flood flow has a 1% chance of exceeding the 100 year flood. T=1/p 4. Low-Flow Frequency Analysis Minimum 7-day average with a 10-year recurrence interval (Q 7,10 ) 5. Bankfull Discharge Discharge that fills a stable alluvial channel up to the elevation of the active floodplain. This discharge occurs when water just begins to leave the channel and spread onto the floodplain. This discharge is considered to have morphological significance because it represents the breakpoint between the processes of channel formation and floodplain formation. AKA channel-forming and effective dishcharge. Often equated with the flow with a 1.5 year recurrence interval (i.e., the Q 1.5 = Q bkfl. 4

5 H. NATURAL FLOW REGIME PARADIGM Poff, N. L., J. D. Allan, M. B. Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks, and J. C. Stromberg The natural flow regime. BioScience 47: Five components of the flow regime regulate ecological processes in river ecosystems: Magnitude: amount of water moving past a fixed location per unit time (discharge) Frequency: how often a flow above a given magnitude recurs over some specified time interval (e.g., 100 year flow event) Duration: period of time associated with a specific flow condition Timing: predictability or regularity of a flow of a defined magnitude (e.g., annual peak flows may occur with low seasonal predictability). Rate of Change of hydrologic conditions: flashiness or how quickly flow changes from low to high and back again 2. The flow regime of a given river is determined by the interaction of the following processes: Climate: timing and amount of precipitation Geology: permeability of bedrock (e.g., Karst vs Sandstone) Topography: steepness of the terrain and overland flow paths Soils: permeability Vegetation: evapo-transpiration and floodplain roughness. 3. The natural flow regime organizes and defines river ecosystems. In rivers, the physical structure of the environment and, thus, of the habitat, is defined largely by physical processes, especially the movement of water and sediment within the channel and between the channel and floodplain. To understand the biodiversity, production, and sustainability of river ecosystems, it is necessary to appreciate the central organizing role played by a dynamically varying physical environment. 4. Human modification of natural hydrologic processes disrupts the dynamic equilibrium between the movement of water and the movement of sediment that exists in freeflowing rivers. Human related disruption of the natural flow regime include: Dams Intensive Land Use: timber harvest, grazing, road building, urbanization Flood Control of Large Rivers: disconnect between river channels and floodplains. 5. Effective management of riverine ecosystems will require that we protect, restore, and attempt to mimic the nature flow regimes as much as possible. 5

6 Important Citations Arndt, SKA, RA Cunjak, and TJ Benfey Effect of summer floods and spatio-temporal scale on growth and feeding of juvenile Atlantic salmon in two New Brunswick streams. Transactions of the American Fisheries Society 131: Dunne, T, and LB Leopold Water in environmental planning. WH Freeman and Co. Gordon et al Stream hydrology: an introduction for ecologists. Wiley, NY. Jacobson, R. B., and D. L. Galat Flow and form in rehabilitation of large-river ecosystems: An example from the Lower Missouri River. Geomorphology 77: Junk, WJ, PB Bayley, RE Sparks The flood pulse concept in river-floodplain systems. Canadian Special Publication of Fisheries and Aquatic Sciences 106: Leopold, L. B A view of the river. Harvard University Press. Cambridge, MA. 298 pp. Leopold, L.B., M.G. Wolman, and J.P. Miller Fluvial processes in geomorphology. Freeman. San Francisco, CA. 522 pp. Lohman, K., JR Jones, BD Perkins Effects of nutrient enrichment and flood frequency on periphyton biomass in northern Ozark streams. Canadian Journal of Fisheries and Aquatic Sciences 49: Poff, N. L., J. D. Allan, M. B. Bain, J. R. Karr, K. L. Prestegaard, B. D. Richter, R. E. Sparks, and J. C. Stromberg The natural flow regime. BioScience 47: Poff, N. L., B. P. Bledsoe, and C. O. Cuhaciyan Hydrologic variation with land use across the contiguous United States: Geomorphic and ecological consequences for stream ecosystems. Geomorphology: Poff, N. L. and J. V. Ward Implications of streamflow variability and predictability for lotic community structure: A regional analysis of streamflow patterns. Can. J. Fish. Aquatic Sci. 46: Richter, B. D Ecologically sustainable water management: managing river flows for ecological integrity. Ecological Applications 13: Roghair, CN, CA Dolloff, and MK Underwood Response of a brook trout population and instream habitat to a catastrophic flood and debris flow. Transactions of the American Fisheries Society 131: Ross, ST, and JA Baker The response of fishes to periodic spring floods in a southeastern stream. American Midland Naturalist 109:1-14. Sun, G., S. G. McNulty, D. M. Amatya, R. W. Skaggs, J. Swift, L. W., J. P. Shepard, and H. Riekerk A comparison of the watershed hydrology of coastal forested wetlands and the mountainous uplands in the Southern US. Journal of Hydrology 263: Ward, JV, and JA Stanford The ecology of regulated streams. New York: Plenum Press. Weng, Z, N. Mookerji, A. Mazumder Nutrient-dependent recovery of Atlantic salmon streams from a catastrophic flood. Canadian Journal of Fisheries and Aquatic Sciences 58: Wolman, MG, and JP Miller Magnitude and frequency of forces in geomorphic processes. Journal of Hydrology 69: