1. Introduction to hydrology 10.11.2015 H-ESD : Environmental and Sustainable Development Michael Staudt, GTK

2. Table of contents 1.Elements of hydrologic cycle, Hydrology vs. Hydrogeology 2.Hydrogeology, Origin and occurence of groundwater, water table 2.1 Aquifer, aquicludes and aquitards 2.2 Porosity and permeability 2.3 Flow through soil and rocks 3. Groundwater contamination and mining 4. Wells

3. 1. Water Water (H 2 O) is extraordinary in that it coexists on Earth in 3 distinct forms or states, 1: dry solid (ice), 2: wet liquid (water) and, 3: dry, invisible gas (vapor). Dipol Van der Waals bonds strong cohesion

4. 1.1Elements of hydrologic cycle

7. All Water on Earth Oceans__________________97.24% All ice caps/glaciers________2.14% Groundwater_______________0.61% Freshwater lakes__________0.009% Inland seas/salt lakes______0.008% Soil Moisture_____________0.005% Atmosphere______________0.001% All rivers_________________0.0001% Total____________________100% Useable Freshwater on Earth Groundwater________________0.61% Freshwater lakes___________0.009% Rivers___________________0.0001% Total____________________0.6191% Adding ice caps/glaciers______2.14% Total____________________2.7591%

8. Saturated zone is the subsurface zone below the water table where openings are filled with water under pressure greater than that of the atmosphere. Unsaturated zone is that part of the geological stratum above the water table where interstices and voids contain a combination of air and water; synonymous with zone of aeration or vadose zone

9. 1.2 Evapo-Transpiration Evaporation: water molecules exchanged between liquid and vapor state Transpiration: water added to the atmosphere by vegetation Total water loss: Evapo-Transpiration Condensation: needs a nucleus or surface to form when relative humidity is reaching 100% and the air is cooled without losing moisture: dew, frost

10. 1.3 Precipitation Occurs when 1.A humid air mass is cooled to the dew point temperature 2.Condensation or freezing nuclei must be present 3.Droplets must be coalesce to form raindrops 4.The raindrops must be of sufficient size when they leave the clouds

11. An Introduction to Rivers Streams and rivers are part of the hydrologic cycle –Evaporation of water from Earth’s surface –Water returns to ocean underground or across the land Runoff –Surface drainage Streams merge into tributaries and then into rivers Drainage basin, watershed, river basin, or catchment –Area drained by a single stream

12. An Introduction to Rivers, cont. Gradient is slope of river –is shown on longitudinal profile Steep at high elevations –Headwaters Decreases as river reaches base level –Lowest elevation of river, ultimately the ocean –Floodplain Flat surface adjacent to channel

13. Figure 6.9

14. Figure 6.11Figure 6.12

15. Velocity, Discharge, Erosion and Deposition Rivers are the primary transportation and erosion agent in the rock cycle Amount of erosion and deposition depends on stream velocity and discharge –Volume of water flowing through a cross section per unit time (cubic meters per second) –Discharge is constant along river –Changes in area lead to changes in velocity –Narrow channels have higher velocity than wide ones Stream flow widens and slows when moving from high to low gradient –Forms an alluvial fan or delta

16. Materials Transported by Rivers Rivers transport materials along with water Total load consists of: –Bed load in [kg/s] or [m 3 /s] Materials that roll, slide, bounce along bottom mass of bed load ~ longitudal slope * mass of water (Marx, 2000) mean grain diameter –Suspended load in [g/m 3 ] Silt and clay particles that are carried in the water –Dissolved load in [mg/L] Materials carried as chemical solution

17. Characteristics of river flow Hydrographs: Flows plotted over time, measured values usually on a daily basis for one year; averaging for monthly or annual means Duration curves: Discharges of the hydrograph ordered according to magnitude over time. Gives an averaged period of time during which a specific flow rate is not exceeded Source: Marx, 2000

18. How to measure water levels? Balke, 1999

19. Water levels of a river Balke, 1999

20. Stream discharge

21. How to measure flow velocity? Balke, 1999

22. Channel Patterns and Floodplain Formation Braided channels –Contain sand and gravel bars that divide and unite a single channel –Tend to be wide and shallow Meandering channels –Migrate back and forth within a floodplain –Velocity is greater on the outside of curves causing erosion (cut banks) –Rivers slow on the inside of curves causing deposition (point bars) –Floodplains are created during overbank flows –During avulsion streams shift position –Contain pools and riffles

23. Figure 6.14

24. Flooding Natural process of overbank flow Related to: –Amount and distribution of precipitation in drainage basin –Rate at which the precipitation soaks into earth –How quickly surface runoff reaches river –Amount of moisture in the soil

25. Causes of flooding Source: Smith, 2004

26. Flood Description Flood discharge – discharge of the stream at the point where water overflows the channel banks Flood stage – height of water in the river Shown on hydrograph –Graph of stream discharge or water depth over time Flood stage –Elevation of water surface that is likely to cause damage to property Recurrence interval –Average time between flood events of a certain size

27. Flash Floods Typical in upper portion of drainage basin and in small basin of tributaries of larger rivers Caused by intense rainfall of short duration over a relatively small area Common in arid environments with steep slopes or little vegetation and following breaks of dams, levees, and ice jams Most people who die during flash floods are in cars

28. Downstream Floods Cover a wide area Usually produced by storms of long duration that saturate the soil and produce increased runoff Can be caused by combined runoff from thousands of tributary basins –Characterized by large rise and fall of discharge at a particular location

29. Figure 6.20

30. Geographic Regions at Risk Any place that receives precipitation has the potential to flood Floods are number-one disaster in the United States in twentieth century All areas of the United States and Canada are vulnerable to floods –A single flood can cause billions of dollars of property damage and more than 200 deaths

31. No of major floods in Europe

32. Flood events in Europe ESPON 1.3.1 Project, 2004

33. Floods recurrence in Europe ESPON 1.3.1 Project, 2004

34. Floods from 1950-2005 Source: Barredo, 2007 1 to 23: flash floods, 24 to 44: river floods, 45 to 47 storm surge floods. A triangle feature represents very large regional events. No major flood events were reported during the study period in the EU's regions not included in the map.

35. Effects of Floods Primary –Injury and loss of life –Damage caused by currents, debris, and sediment to farms, homes, buildings, railroads, bridges, roads –Erosion and deposition of sediment related to loss of soil and vegetation Secondary –Short-term river pollution of rivers –Hunger and disease –Homelessness

36. Factors Affecting Flood Damage Land use on floodplain Depth and velocity of floodwaters Rate of rise and duration of flooding Season Quantity and type of sediment deposited Effectiveness of forecasting, warning, and evacuation

37. Linkages with Other Natural Hazards Primary effect of hurricanes Secondary effect of earthquakes and landslides Fires –Produce shorts in electrical circuits and erode and break natural gas mains Coastal erosion

38. Human Interaction— Land Use Changes Rivers generally maintain a dynamic equilibrium –Balance between gradient, cross sectional shape, and flow velocity for sediment load That is, increase or decrease in the amount of water or sediment received by a stream changes gradient or cross-sectional shape, changing the velocity Land use changes can affect that equilibrium –Forest to farming creates more erosion and sediment –Sediment will build up the gradient of the stream –Stream will flow faster until it can carry greater amount of sediment –Farming to forest sets the opposite into effect

39. Figure 6.23Figure 6.24

40. Human Interaction— Dam Construction Upstream water slows down, deposits sediment, forming a delta Downstream water devoid of sediment, will erode sediment to transport –Slope of the stream will decrease until equilibrium is reached Figure 6.25

41. Human Interaction— Urbanization Increases magnitude and frequency of floods Urban areas have impervious cover and greater storm sewers –Carries water to stream channels more quickly –Decreases lag time Causes flashy discharge – rapid rise and fall of floodwater Reduces stream flow during dry season –Less groundwater is available Bridges block debris creating dams and flash flooding

42. Minimizing the Hazard— Physical Barriers Include earthen levees, concrete flood walls, reservoirs, and storm water retention basins Levee breaks cause higher energy flows and bottlenecks in upstream areas All physical barriers need to be maintained

43. Minimizing the Hazard— Channelization Straightening, deepening, widening, clearing, or lining existing stream channels –Can improve navigation and decrease flooding Some drawbacks: –Drainage adversely affects plants and animals –Cutting trees eliminates shading and cover for fish and wildlife –Cutting trees eliminates many habitats –Changing the streambed destroys both the diversity of flow patterns and feeding and breeding areas for aquatic life –Degrades the aesthetic

44. Figure 6.33

45. Minimizing the Hazard— Channel Restoration Create a natural channel by allowing the stream to meander and reconstruct variable water flow conditions by: –Cleaning urban waste to allow channel to flow freely –Protecting existing channel banks by not removing trees –Planting additional trees or vegetation where necessary

46. Perception of Flood Hazard Most individuals have inadequate perception of flood problem Local governments have prepared maps of flood prone areas Federal government encourages local governments to adopt floodplain management plans Public safety campaigns have been created to educate public about flash flooding

47. Adjustments to the Hazard— Flood Insurance Maps of 100 year floodplain created to determine risk –Areas where there is a 1 percent chance of floods in any given year New property owners required to purchase flood insurance Building codes limit new construction on floodplain in some countries –Codes prohibit building on 20 year floodplain

48. Figure 6.40

49. Flood recurrence calculation Source: Keller

50. Recurrence Calculation R = N+1/M R: Recurrence interval in years N: Magnitude where M=1(ranking) is the highest discharge on record M: Total number of records

51. Flood hazard zone I Active floodplain area Prohibit development (business and residential) within floodplain Maintain area in a natural state as an open area or for recreational uses only

52. Flood hazard zone II Alluvial fans and plains with channels less than a metre deep, bifurcating, and intricately interconnected systems subject to inundation from overbank flooding Residential densities should be low Flood proofing to reduce loss to structures Dry stream channels should be maintained in a natural state Installation of upstream water retention basins

53. Flood hazard zone III Disected upland and lowland slopes, drainage channels where both erosional and depositional processes are operative along gradients less than 5% Similar to Flood hazard zone 2 Roadways should be reenforced to withstand the erosive power of a channeled stream flow

54. Flood hazard zone IV Steep gradient drainages consisting of incised channels adjacent to outcrops and mountain fronts Bridges, roads and culverts should be designed to allow unrestricted flow of boulders and debris Abandon roadways which are presently occupy the wash flood plains Restrict residential dwelling to relatively level building sites Provisions for subsurface and surface drainage on residential sites Stormwater retention basins in upstream channels After Kenny (1990) in Bell ( 1993)

55. Adjustment to the Hazard— Flood Proofing Raising foundation of buildings above the flood hazard Constructing flood walls or mounds Using waterproofing construction Installing improved drains and pumps

56. Adjustment to the Hazard— Flood Plain Regulation Obtain the most beneficial use of floodplains while minimizing flood damage and cost of flood protection –Structural controls may be necessary on heavily used floodplains –Less physical modification of river is ideal Flood hazard mapping –Shows location of previous flooding –Helpful in land use planning Relocation –Government purchasing and removing homes damaged by floodwaters

57. Table 6.2

58. References – Hydrology Barredo, J: Major flood disasters in Europe: 1950–2005, Nat Hazards (2007) 42:125–148, Spinger Bell, F. : Engineering Geology, 1993 Keller, E. & DeVecchio, D. : Natural Hazards, Earth’s Processes as Hazards, Disasters, and Catastrophes, 2nd & 3rd ed., Chapter 6, Lecture presentation, Pearson Education Inc, 2008 & 2012 Balke, K.-D.: Regional Hydrogeology,Lecture notes, 1999 Marx, W.: Introduction to Hydraulic Engineering,Lecture notes, 2000 ESPON 1.3.1 project, GTK, 2004 JRC website: http://floods.jrc.ec.europa.eu/flood-risk/flood-disasters.htmlhttp://floods.jrc.ec.europa.eu/flood-risk/flood-disasters.html Smith, K: Environmnetal Hazards- Assessing Risk and Reducing Disaster, 4th edition, 2007

59. References – Hydrogeology Bell, F.G.: Engineering Geology, Chapter 4, Blackwell Scientific Publications, 1993 Hölting, B.: Hydrogeologie, 4. Auflage, Enke, 1996 Fetter, C.W: Applied Hydrogeology, Fourth edition, Prentice Hall, 2001 Younger, P.L et al : Mine Water: Hydrogeology, Pollution, Remediation, Kluwer Academic Publishers, 2002