Exploring Hydrology: Water Systems and Cycles

1. U6115: WaterMonday, July 19 2004 The early bird may get the worm… but the second mouse gets the cheese.

2. One thing we should remember from this summer (and the last 6…)

3. Today: Water/Hydrology • Intro to Hydrology • Systems and Cycles • Flux, Source/Sink, Residence time, Feedback mechanisms…

4. U6115 Syllabus: Course Outline • The water cycle part of the class is focused on basic physical principles (evaporation, condensation, precipitation, runoff, stream flow, percolation, and groundwater flow), as well as environmentally relevant applications based on case studies. • Most specifically, students will be exposed to water quantity and issues from global to regional scales and how human and natural processes affect water availability in surface and groundwater systems. • Note: water quality issues will be mentioned but only briefly since they have been covered more extensively in the Environmental Chemistry course (ENVU6220)

5. U6115 Syllabus: Course Outline NJ Class 1: (July 19) Introduction - Water for the world - Lab 1: Global and regional water budgets Class 2: (July 26) Global water issues - Hydrological cycle - Lab 2: Hydrological Forecasts and their Communication to Decision-Makers Class 3: (August 02) Dams & Reservoirs - Lab 3: Reservoirs and greenhouse gases Class 4: (August 09) Condensation/Precipitation – Streamflow/Floods - Lab 4: Precipitation and Flood predictions: A Statistical Analysis Class 5: (August 16) Evaporation - Droughts – Land Use Impact on Streamflow Class 6: (August 18) Groundwater flow - Groundwater transport

6. U6115 Syllabus: Grading (activities) Water (40% of grade) • Labs:100% (4 formal labs) • Mostly minds-on experiments with computers. Lab report due

7. Water for the World The role of water is central to most natural processes • transport • Weathering, contaminant transport • energy balance • transport of heat, high heat capacity • greenhouse gas • ~ 80% of the atmospheric greenhouse effect is caused by water vapor • life • for most terrestrial life forms, water determines where they may live; man is exception

8. Hydrology • literally "water science," encompasses the study of the occurrence and movement of water on and beneath the surface of the Earth • finite though renewable resource • finite in quantity, unlimited in supply, use rate is limited by 'recycling times' • hydrologic sciences have pure and applied aspects • how the Earth works • scientific basis for proper management of water resources (or any natural resource…)

9. Introduction to hydrology use of water in 20th century has grown dramatically

10. Lakes, soil moisture, atmosphere, rivers Water on land Deep groundwater (750-4000 m) 1% 3% 14% Shallow groundwater (<750 m) 11% 74% 97% Ice caps and glaciers Oceans Inventory of water on Earth After Berner and Berner, 1987

11. Cycle Approach • Some Definitions • Transport and transformation processes within definite reservoirs: Carbon, Rock, Water Cycles • Reservoir:(box, compartment: M in mass units or moles) An amount of material defined by certain physical, chemical, or biological characteristics that can be considered homogeneous • O2 in the atmosphere • Carbon in living organic matter in the Ocean • Water in the Ocean • Flux:(F) The amount of material transferred from one reservoir to another per unit time (M/s or M/s.L2) • The rate of evaporation of water from the surface Ocean • The rate of deposition of inorganic carbon (carbonates on marine sediments • Source:(I or Q) A flux of material into a reservoir • Sink: (O or S) A flux of material out of a reservoir

12. More Definitions… • Budget: A balance sheet of all sources and sinks of a reservoir. If sources and sinks balance each other and do not change with time, the reservoir is insteady-state(M does not change with time). If steady-state prevails, then a flux that is unknown can be estimated by its difference from the other fluxes. for a control volume this means: dM/dt = I'-O' • Turnover time: The ratio of the content (M) of the reservoir to the sum of its sinks (O) or sources (I). The time it will take to empty the reservoir if there aren’t any sources. It is also a measure of the average time an atom/molecule spends in the reservoir.Or: 0 = M/O (or M/I) • Cycle: A system consisting of two or more connected reservoir, where a large part of the material (energy) is transferred through the system in a cyclic fashion

13. The Water (Hydrologic) Cycle

14. Reservoir Volume (km3) % Total Biosphere 0.6 103 0.00004 Rivers 1.7 103 0.0001 Atmosphere 13 103 0.001 Lakes 125 103 0.01 Groundwater 9500 103 0.68 Glacial and other land ice (?) 29000 103 2.05 Oceanic water and sea ice 1,370,000 103 97.25 Total 1,408,640103 100 The Water Cycle (in detail) • The volume (M) of water at the surface of the Earth is enormous: 1.37 109 km3! (total reservoir) – The Oceans cover 71% of the Earth’s surface (29% for the continent masses above sea level) Adapted from Berner & Berner (The Global Water Cycle; Prentice Hall, 1987)

15. Fluxes (F in 103 km3/yr) • Of total yearly evaporation, 84% evaporates from the Oceans and 16% from surface of continents. • However, return to Earth via precipitation: 75% falls directly on the Oceans and 25% on the continents. • During the year, the atmosphere transports 9% of Oceans’ evaporation to the continents! • This water is returned via surface streams and as groundwater

16. Errors! • Precipitation and evaporation are difficult to measure precisely over the oceans. They are mostly estimated from models and satellite data. • Groundwater reservoir estimates bear a inherent error in the fact that they are indirectly determined. • Soil moisture and evapotranspiration rates depend on indirect measurements and average soil quality and global/regional respiration rates

17. Residence Time(years – months – weeks) • High probability that a certain fraction of the atoms or molecules forming the reservoir (M) will be of a certain age (mean age of the element when it leaves the reservoir) • The simplifiedresidence timeturnover time The time it would take to empty a reservoirifthe sink (O or “outflow”) remained constantwhilethe sources were zero 0= M/O (or M/I) M = 0O Residence time of water in the atmosphere M = ?; O = ?; 0= ? M = 13 103 km3 S = 297(O) + 99(C) 103 km3/yr = 396 103 km3/yr 0= 0.033 yr = 12 days! Replacement ~30 times/year

18. Residence Time(years – months – weeks) • High probability that a certain fraction of the atoms or molecules forming the reservoir (M) will be of a certain age (mean age of the element when it leaves the reservoir) • The simplifiedresidence timeturnover time The time it would take to empty a reservoirifthe sink (O) remained constantwhilethe sources were zero 0= M/O (or M/I) M = 0O Residence time of water in the ocean M = ?; S = ?; 0= ? M = 1,370,000 103 km3 S = 334 103 km3/yr (evaporation) 0= M/S = 4102 yrs!

19. Continental Mass Balance • quantitative description  applying  the principle of conservation of mass • for continents as control volume this can be written as dV/dt = p- rso- et = 0 (all averaged) • on average this means: p =  rso+ et • the water budget for all land areas of the world is: p=800mm, rs = 310mm, and et = 490mm • the global runoff ration (rs/p) is ~39% there are lots of local and regional variations.

20. System Approach… • Feedback: All closed and open systems respond to inputs and have outputs. Afeedbackis a specific output that serves as an input to the system. • Negative Feedback (stabilizing): The system’s response is in the opposite direction as that of the output. CLOUDS!

21. Bottle half full 59 min System Approach… • Positive Feedback (destabilizing): The system’s response is in the same direction as that of the output.

22. System Approach… • Positive Feedback (destabilizing): • CLOUDS!

23. Surface waters BRF

24. Watershed, catchment, drainage basin Catchement (drainage basin, watershed): the basic unit of volume (control) which is an area of land in which water flowing across the land surface drains into a particular stream and ultimately flows a single point or outlet. dV/dt = p- rso- et = 0 on average  p =  rso + et

25. Catchment Our concern with precipitation and evapotranspiration is in knowing the rates, timing, and spatial distribution of these water fluxes between the land and the atmosphere. dV/dt = p- rso- et = 0 Texas New York

26. Measurement techniques  precipitation  evapotranspiration

28. Evapotranspiration Average statewide evapotranspiration for the conterminous United States range from about 40% of the average annual precipitation in the Northwest and Northeast to about 100% in the Southwest.

29. Annual Precipitation - Australia

30. Annual Evaporation - Australia

31. Annual Evapotranspiration - Australia

32. Rivers and Streams

33. Measurement techniques  flow depth (stage)  discharge

34. Colorado Riverhydrograph Questions: • When does discharge peak and why? • The hydrographs were taken at different locations of the river, what is the difference in the hydrographs and why is there one?

35. Colorado Riverhydrograph • Hydrographs are variable between years • Discharge often peaks in late winter or spring, snowmelt • Reservoirs smooth out extremes

36. Canada del Oro hydrograph  extended periods with no discharge at all! http://water.usgs.gov

37. Santa Cruz River (Tucson, AZ, 1930 vs. 1964 - 1983 flood)

38. Lakes and Reservoirs

39. Reservoir distribution in the U.S.

41. Wetlands Definition (U.S. Fish and Wildlife Service): "WETLANDS are transitional systems between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water. For purposes of this classification wetlands must have one or more of the following three attributes: at least periodically, the land supports predominantly hydrophytes; the substrate is predominantly undrained hydric soil; and the substrate is saturated with water or covered by shallow water at some time during the growing season of the year." Hydrologic conditions: Groundwater (water table or zone of saturation) is at the surface or within the soil root zone during all or part of the growing season. Hydric soils: soils that are saturated, flooded, or ponded long enough during the growing season to develop oxygen-free conditions in the upper six inches Hydrophytic vegetation: plants typically adapted to wetland and aquatic habitats; plants which grow in water or on a substrate that is at least periodically deficient in oxygen due to excessive water content.

42. Wetlands are classified into two general categories: coastal and inland. Coastal wetlands are further classified into marine and estuarine categories Inland wetlands are further subdivided in riverine, lacustrine, and palustrine wetlands.

44. Fens receive water from the surrounding watershed in inflowing streams and groundwater, while bogs receive water primarily from precipitation. Fens, therefore, reflect the chemistry of the geological formations through which these waters flow.

45. Benefits of Wetlands Loss of floodplain forested wetlands and confinement by levees have reduced the floodwater storage capacity of the Mississippi by 80 percent increasing dramatically the potential for flood damage. The 1993 flood proved this prediction to be true and resulted in immeasurable damage

46. Coastal Wetlands Tidal coastal wetlands store carbon densely, holding on to 10% of the global stock of soil organic carbon in only 0.1% of the Earth’s surface. Despite their relatively small area (203 103 km2), tidal coastal wetlands may act as substantial sinks for atmospheric carbon due both to exceptional carbon burial fluxes and negligible CH4 and N2O emissions. Because the projected sequestration efforts in North American croplands (0.5-2.5 Pg C) are of the same order of magnitude as C stocks estimated to exist in the surface meter of wetlands (~4 Pg), major losses of these ecosystems could easily offset any improvement in preservation of SOC within managed croplands even at its highest efficiency. In many coastal regions (i.e. Louisiana Gulf Coast), these wetlands are being lost are substantial rates (50-100 km2/yr)

47. Groundwater

49. Groundwater flow is controlled by • differences in water table (hydraulic head) • hydraulic conductivity (relation between specific discharge – Vol/t – and hydraulic gradient) • Hydraulic conductivity depends on both the nature of the fluid (viscosity) and the porosity of the material Hornberger et al., 1998

50. Measurement techniques  Hydraulic head, conductivity