關于繼續(xù)使用部分超募資金臨時補充 課件

1、NWS-COMET Hydrometeorology Course 20 January - 4 February 1999Hydrology PrimerRussell J. Qualls, Asst. ProfessorUniversity of Colorado at BoulderCivil, Env. And Arch.Engineering303-492-5968 (Tel)303-492-7317 (fax)qualls (email)/qualls/AcknowledgmentsDennis L. Johnson, Asst. ProfessorMichigan Technol

2、ogical UniversityDepartment of Civil & Env. Engineering(906) 487 - 3613 (phone)(906) 487 - 2943 (fax)dennisj (email)/dennisj/Topographic Relief of Great Lakes RegionSome Lake Superior FactsSurface Area = 31,700 square milesLand Drainage Area = 49,300 square milesLake Superior covers 39% of the total

3、 basin area!More than 200 rivers enter with 1000s of streams.Max. depth = 1,330 feetVolume = 2,900 cubic milesMore than half of all the great lakes and 10% of earths flowing surface fresh waters!Purpose of the Hydrometeorology Course Increase the participants knowledge and understanding of the inter

4、action between meteorology and hydrology in watersheds:Increase participants understanding of the functional aspects of watersheds;Enhance the participants knowledge of the capabilities, limitations, and applications of new hydrometeorological observing systems;Improve the participants ability to id

5、entify significant mesoscale meteorological events and to produce Quantitative Precipitation Forecasts;Increase participants understanding of the effectiveness of the NWS forecast and warning methodologies and plan future enhancements; and Build awareness of the need for close ties between RFCs and

6、WFOs.Purpose of the PRIMERProvide an introduction between participants & establish backgrounds.Introduce participants to basic terminology and concepts of hydrologic forecasting that will be used throughout the hydrology portion of the COMET Hydromet course. The primer introduces these concepts and

7、specific detail will be provided in week 3.Establish the course objectives as per the expectations of the participants. Establish hydrologic concerns in the various participants regions.In the end, it is intended that participants will understand the hydrologic forecast process, the assumptions in t

8、he process, and the responsibilities associated with interpreting and issuing the forecast.Mission of NOAAs NWSHydrologic Services ProgramTo provide river and flood forecasts and warnings for protection of life and propertyProvide basic hydrologic forecast information for the nations economic and en

9、vironmental well being.Modernized NWS“It is essential to emphasize the complementary aspects of operational hydrology and meteorology in the modernized NWS, while recognizing the uniqueness of RFC and WFO operations. “New or Improved Products.the production of a variety of hydrologic forecast produc

10、ts for an increased number of river locations across the country, including ESP-based productsWhat is ESP?Ensemble Streamflow Production (ESP)Inputs the current moisture level of soil and the precipitation from previous years into a model which produces the diagram seen above. For example, the moist

11、ure content of today would be inputted, along with the precipitation that occurred over the next week, but 50 years ago.This would then be repeated for 49 years ago, 48, etc., and then an average discharge based on history can be determined.NWSOffice of HydrologyDr. Danny FreadDirector, Office of Hy

12、drologyFront Office StaffChief ScientistSpecial Asst. to the DirectorSecretaryProgram AnalystProgram Support AssistantAdministrative Support Technician Dr. Ed JohnsonChief, Hydrologic Operations Division?Chief, Hydrologic Research LaboratoryHydrometeorology an interdisciplinary science involving the

13、 study and analysis of the interrelationships between the atmospheric and land phases of water as it moves through the hydrologic cycle. (Hydrometeorological Service Operations for the 1990s, Office of Hydrology, National Weather Service, NOAA, 1996).Hydrometeorology - LinksHydrologyEngineering/Flui

14、dMechanics In-depth hydrologicanalysis Execution of complexhydrologic models.Adjustment ofmodel parameters, andthe derivation ofhydrologic forecasts forall time scales Applied hydrologicresearch Development andcalibration ofhydrologic models Development ofhydrologic applicationsprocedures.Meteorolog

15、yThermodynamics/atmosphericphysics orientation In-depth meteorologicalanalysis Weather forecast andwarning operations Climatological forecasting Applied meteorologicaland climatologicalresearch. Development and calibrationof meteorological models Development ofmeteorological applicationsand procedur

16、es.HydrometeorologyInterdisciplinaryOrientation Assimilation/use ofWSR-88D basedprecip. estimates Production and/oruse of QPFs andother hydromet.forecasts Use of RFC guidance(e.g. flash flood) inhydrologic warningoperations Use of soil moisturestates fromhydrologic model inatmospheric model Appliedh

17、ydrometeorologicalresearch.A Basic ReviewUnits & Properties of WaterCommon Unit ConversionsArea Volume Runoff Volume Discharge PowerArea1 acre = 43,560 ft21 mi2 = 640 acres1 hectare = 100m x 100m = 2.471 acres = 10,000 m21 km2 = 0.386 mi2Area Volume Runoff Volume Discharge PowerRunoff Volume1-inch o

18、f runoff over 1 square mile : 1/12 feet x 1 mi2 x 640 acres/mi2 x 43,560 ft2/acre = 2,323,200 ft3Area Volume Runoff Volume Discharge PowerDischarge1 cfs = 1 cubic foot per second1 cfs x 7.48 gal/ft3 x 3600 sec/hr x 24 hrs/day = 646,272 gpd = 0.646 MGD1 cfs x 3600 sec/hr x 24 hrs/day = 86,400 cfs/day

19、86,400 cfs/day x 1 ac-ft/43,560 ft3 = 1.983 ac-ft/day ( 2 ac-ft/day)1.983 ac-ft/day x 12 inches/ft x 1 day/24 hrs = 0.992 ac-in/hr1 ac-in/hr x 43,560 ft3/ac-ft x 1 hr/3600 sec x 1 ft/12 inches = 1.008 cfsArea Volume Runoff Volume Discharge PowerHydrologic CycleTopicsPrecipitationEvaporationTranspira

20、tionStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-Reservoirs Precipitation. primary input for the hydrologic cycle (or hydrologic budget). The patterns of the precipitation are affected by large scale global patterns, mesoscale patterns, regional patterns, and

21、micro-climates. Knowing and understanding the general, regional, and local precipitation patterns greatly aids forecasters in determining QPF values. In addition to the quantity of precipitation, the spatial and temporal distributions of the precipitation have considerable effects on the hydrologic

22、response.Precipitation -SnowEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsSnow. nature of the modeling efforts that are required. response mechanisms of snow are at a much slower time scale than for most of the other forms of p

23、recipitation. The melt takes place and the runoff is lagged due to the physical travel processes. Items to consider in the snowmelt process are the current state of the pack and the snow water equivalent of the snow pack., as well as the melt potential of the current climate conditions. A rain-on-sn

24、ow event may produce very high runoff rates and is often a difficult situation to predict due to the integral nature of the runoff and melt processes. The timing of these events is often very difficult to predict due to the inherent lag in the responses.Precipitation -SnowEvaporationTranspirationSto

25、rage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsEvaporation Evaporation is a process that allows water to change from its liquid phase to a vapor. Hydrologists are mostly interested in the evaporation from the free water surface of open water or subsurface

26、 water exposed via the capillary action; however, precipitation that is intercepted by the vegetative canopy may also be evaporated and may be a significant amount in terms of the overall hydrologic budget. Factors that affect evaporation are temperature, humidity and vapor pressure, radiation, and

27、wind speed. A number of equations are used to estimate evaporation. There are also a number of published tables and maps providing regional estimates of annual evaporation.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-Reserv

28、oirsTranspiration Water may also pass to the atmosphere by being taken up by plants and passed on through the plant surfaces. Transpiration varies greatly between plants or crops, climates, and seasons. Evaporation and transpiration are often combined in a term - evapotranspiration. In many areas of

29、 the country and during certain seasons evapotranspiration is a major component of the hydrologic budget and a major concern in water supply and yield estimates.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsStorage

30、 - Surface. Storage - Surface is used to describe the precipitation that reaches the ground surface; however, is not available for runoff or infiltration. It is instead, held in small quantities on the surface in areas, such as the leafy matter and small depressions. In general, surface storage is s

31、mall and only temporary in terms of the overall hydrologic budget; however, it may have an effect on a storm response as it is effectively filled early on a storm event.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-Reservoir

32、sInfiltration Soils, depending on current conditions, have a capacity or ability to infiltrate precipitation, allowing water to move from the surface to the subsurface. . physically based” - soil porosity, depth of soil column, saturation levels, and soil moisture. The infiltration capacity of the s

33、oil column is usually expressed in terms of length per time (i.e. inches per hour). As more water infiltrates, the infiltration generally decreases, thus the amount of water that can be infiltrated during the latter stages of a precipitation event is less than that at the beginning of the event.Prec

34、ipitationEvaporationTranspirationStorage-surfaceInfiltration -SubsurfaceStorage - SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsInfiltration cont. Storms that have high intensity levels may also cause excess precipitation because the intensity (inches per hour) may exceed the current inf

35、iltration capacity (inches per hour). periods of low rainfall or no rainfall will allow the soil to recover and increase the capacity to infiltrate water.Infiltrated water replenishes soil moisture and groundwater reservoirs. Infiltrated water may also resurface to become surface flow. attempt to ac

36、count for infiltration by estimating excess precipitation (the difference between precipitation and excess being considered infiltration), for example, the Soil Conservation Service (SCS) runoff curve number method PrecipitationEvaporationTranspirationStorage-surfaceInfiltration -SubsurfaceStorage -

37、 SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsSubsurface Flowwater may move via several paths.subsurface flow can be evaporated if there is a well maintained transfer mechanism to the surface. This is particularly true for areas of high ground water table (the free water surface of the

38、groundwater) which is within the limits of the capillary action or transport abilities.Vegetation may also transpire or use the water. The subsurface flow may also continue to move with the groundwater table as a subsurface reservoir, which the natural system uses during periods of low precipitation

39、.PrecipitationEvaporationTranspirationStorage-surfaceInfiltration -SubsurfaceStorage - SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsStorage - Subsurface The infiltrated water may continue downward in the vertical, may move through subsurface layers in a horizontal fashion, or a combinat

40、ion of the two directions. Movement through the subsurface system is much slower than the surface and thus there are storage delays. The water may also reach an aquifer, where it may be stored for a very long period of time. In the NWS River Forecast System (RFS), the subsurface storage is represent

41、ed by imaginary zones or tanks. These tanks release the stored water at a given or calibrated rate. The released water from the subsurface zones is added to the surface runoff for convolution with the unit hydrograph.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - Subsurfac

42、eRunoffWater MovementStreamflowStorage-ReservoirsRunoff runoff will be used to collectively describe the precipitation that is not directly infiltrated into the groundwater system. is generally characterized by overland, gully and rill, swale, and channel flows. is that portion of a precipitation ev

43、ent that quickly reaches the stream system. The term quickly is used with caution as there may be great variability in response times for various flow mechanisms. Runoff producing events are usually thought of as those that saturate the soil column or occur during a period when the soil is already s

44、aturated. Thus infiltration is halted or limited and excess precipitation occurs. This may also occur when the intensity rate of the precipitation is greater than the infiltration capacity.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamf

45、lowStorage-ReservoirsOverland Flow Overland flow or surface flow is that precipitation that either fails to penetrate into the soil or that resurfaces at a later point due to subsurface conditions. often referred to as sheet flow. for the purposes of this discussion, overland flow (sheet and surface

46、 flow, as well) is considered to be the flow that has not had a chance to collect and begin to form gullies, rills, swales PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater Movement -Overland flow -Gullies and Rills -Swales -Channel Flow -Stream Channels

47、StreamflowStorage-ReservoirsOverland Flow (cont.) will eventually reach defined channels and the stream system. may also be infiltrated if it reaches an area that has the infiltration capacity to do so. Overland flow distances are rather limited in length - National Engineering Handbook (1972) - ove

48、rland flow will concentrate into gullies in less than 1000 feet. Other (Seybert, Kibler, and White 1993) recommend a distance of 100 feet or less.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater Movement -Overland flow -Gullies and Rills -Swales -Channe

49、l Flow -Stream ChannelsStreamflowStorage-ReservoirsGullies & Rills. sheet flow or overland flow will soon concentrate into gullies and rills in the process of flowing towards the stream network. The location of these gullies and rills may vary from storm to storm, depending on storm patterns, intens

50、ities, current soil and land use conditions. PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater Movement -Overland flow -Gullies and Rills -Swales -Channel Flow -Stream ChannelsStreamflowStorage-ReservoirsSwales swales are of a more constant or permanent

51、nature. do not vary in location from storm to storm. Swales are a natural part of the landscape or topography that are often more apparent than gullies and rills. Flow conditions and behaviors in swales are very close to that which is seen in channels.PrecipitationEvaporationTranspirationStorage-sur

52、faceInfiltrationStorage - SubsurfaceRunoffWater Movement -Overland flow -Gullies and Rills -Swales -Channel Flow -Stream ChannelsStreamflowStorage-ReservoirsChannel Flow Excess precipitation ultimately reaches the stream channel system. the stream system is generally more defined, it is by no means

53、a constant or permanent entity. The stream bed is constantly changing and evolving via aggredation and degradation. Stream channels convey the waters of the basin to the outlet and into the next basin. attenuation of the runoff hydrograph takes place. Stream channel properties (flow properties) also

54、 vary with the magnitude of the flow. PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater Movement -Overland flow -Gullies and Rills -Swales -Channel Flow -Stream ChannelsStreamflowStorage-ReservoirsStream Channels Channels are commonly broken into main ch

55、annel areas and overbank areas. overbank areas are often referred to as floodplains. Stream gaging stations are used to determine flows based on elevations in the channel and/or floodplain. Bank full is often thought of as flood stage although more rigorous definitions are more applicable as they pe

56、rtain to human activity and potential loss of life and property. It is worth noting that the 2-year return interval flow is often thought of as bank-full.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater Movement -Overland flow -Gullies and Rills -Swales

57、 -Channel Flow -Stream ChannelsStreamflowStorage-ReservoirsStreamflow in the public eye - the most important aspect of flooding and hydrology. flooding from streams and rivers have the greatest potential to impact human property and lives; although overland flow flooding, mudslides, and landslides a

58、re often just as devastating. Subsurface flow also enters the stream; although in some instances and regions, stream channels lose water to the groundwater table - regardless, this must be accounted for in the modeling of the stream channel. Channels also offer a storage mechanism and the resulting

59、effect is most often an attenuation of the flood hydrograph.PrecipitationEvaporationTranspirationStorage-surfaceInfiltrationStorage - SubsurfaceRunoffWater MovementStreamflowStorage-ReservoirsStorage - Reservoirs Lakes, reservoirs, & structures, etc. are given a separate category in the discussion o

60、f the hydrologic cycle due to the potential impact on forecasting procedures and outcomes. provide a substantial storage mechanism and depending on the intended purpose of the structure will have varying impacts on the final hydrograph, as well as flooding levels. This effect can vary greatly depend