hydrologic overview & quantities
DESCRIPTION
Hydrologic Overview & Quantities. It is important to understand the big picture when attempting to forecast. This includes the interactive components and hydrologic quantities. Hydrologic Cycle. Precipitation. Evapotranspiration. Interception. Storage. Infiltration. Runoff. Streamflow. - PowerPoint PPT PresentationTRANSCRIPT
Hydrologic Overview & Hydrologic Overview & QuantitiesQuantities
It is important to understand the It is important to understand the big picture when attempting to big picture when attempting to
forecast. This includes the forecast. This includes the interactive components and interactive components and
hydrologic quantities.hydrologic quantities.
Hydrologic CycleHydrologic Cycle
The complexity of what we are trying to The complexity of what we are trying to accomplish….accomplish….
Infiltration
Evaporation & Condensation
The Water Budget
Photosynthesis & Respiration
Antecedent Moisture
Conditions
Transpiration & Interception
Variable Source Area
Time of Concentration The “sphere” concept was borrowed
from Dr. Peter Black: Watershed Hydrology – 2nd Edition, Peter Black, 1996, Ann Arbor Press (ISBN# 1-5704 027-1)
Models try to mimic this!Models try to mimic this!
Basin Process Representation
Infiltration
Excess Precip.
Interception
Storage
Time Series
Time Series
From A Basin ViewFrom A Basin View
Excess Precip. Model
Excess Precip.
Basin “Routing”
Runoff HydrographStream
“Routing”
The Runoff PictureThe Runoff Picture
• Hydrology is long term and short Hydrology is long term and short term….term….
• In this course we will mainly focus on In this course we will mainly focus on the the shortshort term: term:
• Floods & flood flows.Floods & flood flows.
• Generating runoff/high flows.Generating runoff/high flows.
• Predicting/forecasting flows.Predicting/forecasting flows.
• Space/time scales.Space/time scales.
Recipe(s) for a Flood/High Recipe(s) for a Flood/High FlowsFlows
• What causes a flood / high flow?What causes a flood / high flow?
• What are the conditions?What are the conditions?
• What are the types of flooding What are the types of flooding situations?situations?
• Your area or other areas…..Your area or other areas…..
What Are the Defining What Are the Defining Characteristics of a Flood?Characteristics of a Flood?
• Timing – rise time, recession, Timing – rise time, recession, duration.duration.
• Flows – peak flows, magnitude Flows – peak flows, magnitude (statistical).(statistical).
• Precipitation – intensity, duration, Precipitation – intensity, duration, frequency….frequency….
What Controls the Timing, What Controls the Timing, Flow, and Precipitation?Flow, and Precipitation?
• The hydrology – short term and long The hydrology – short term and long term.term.
• The meteorology – short term The meteorology – short term (weather/storm type) and long term (weather/storm type) and long term (climate).(climate).
Short TermShort TermWeather (storm type) & “current Weather (storm type) & “current hydrologic conditions”hydrologic conditions”
Watershed Watershed CharacteristicsCharacteristics
• AreaArea
• SlopeSlope
• Land UseLand Use
• SoilsSoils
• GeologyGeology
• ClimateClimate
• GeomorphologyGeomorphology
Some of the “Right” Some of the “Right” Combinations….Combinations….
• Precipitation –vs.- infiltrationPrecipitation –vs.- infiltration– Precipitation intensity > infiltration ratePrecipitation intensity > infiltration rate– Precipitation total > infiltration capacityPrecipitation total > infiltration capacity– ““Storage” in the system is fullStorage” in the system is full– Human induced high water or flowsHuman induced high water or flows– Natural alterations to the watershedNatural alterations to the watershed
Our Focus - ForecastingOur Focus - Forecasting
• Must be both short & long term..Must be both short & long term..
• The combination(s) of precipitation The combination(s) of precipitation and hydrologic conditions that lead and hydrologic conditions that lead create a potential flooding situation…create a potential flooding situation…
• ““basin hydrology” – basin hydrology basin hydrology” – basin hydrology looks at the hydrologic budget in looks at the hydrologic budget in both the short and long term.both the short and long term.
How much water is there?How much water is there?Distribution of Earth's Waters and Residence Distribution of Earth's Waters and Residence
TimesTimes........Location of
Storage Total Water (acre-feet)
Percent of Total
Percent of Fresh
Residence Time
(years) Total water on
earth 1.033 x 1015 100.0
Oceans 1.0 x 1015 96.8 Total Fresh
Water 3.314 x 1013 3.2 100.0 6977
Ice and Glaciers
2.475 x 1013 75.4 5210
Groundwater Deep
4.62 x 1012 14.0 973
Groundwater Shallow
3.63 x 1012 11.0 764
Lakes 9.9 x 1010 0.3 21 Biosphere 8.1 x 1010 0.24 17.1
Soil Moisture 1.98 x 1010 0.06 4.17 Atmosphere 1.155 x 1010 0.035 2.43
Rivers 9.9 x 1010 0.003 2.1
Units & Properties of Units & Properties of WaterWater
Property Symbol Value Comments Density
(mass/volume) ~1.94 slugs/ft3
~ 1.0 g/cm3 Slug = lb*s2/ft
Specific Weight (weight/volume)
62.4 Lbs/ft3
9.81 kN/m3 g
Specific Volume Specific Gravity s.g. 1.0 for water
@ 32.9o F s.g.fluid =
gfluid/gwater
Vapor Pressure ~0.4 psi Vapor pressure of the fluid - not the
atmosphere
AreaArea• 1 acre = 43,560 ft1 acre = 43,560 ft22
• 1 mi1 mi22 = 640 acres = 640 acres
• 1 hectare = 100m x 100m = 2.471 acres = 1 hectare = 100m x 100m = 2.471 acres = 10,000 m10,000 m22
• 1 km1 km22 = 0.386 mi = 0.386 mi22
Some Common Unit ConversionsSome Common Unit Conversions
VolumeVolume• 1 acre-foot = 1 ac-ft = 1 acre of water x 1 foot 1 acre-foot = 1 ac-ft = 1 acre of water x 1 foot
deep = 43,560 x 1 = 43,560 ftdeep = 43,560 x 1 = 43,560 ft33
• 1 ac-inch = 1 acre x 1 inch deep = 43,560 x 1 ac-inch = 1 acre x 1 inch deep = 43,560 x 1/12 = 3,630 ft1/12 = 3,630 ft33
• 1 ft1 ft33 = 7.48 gallons = 7.48 gallons
• 1 gallon H1 gallon H22O ~ 8.34 lbs.O ~ 8.34 lbs.
Runoff VolumeRunoff Volume
• 1-inch of runoff over 1 square mile :1-inch of runoff over 1 square mile :• 1/12 feet x 1 mi1/12 feet x 1 mi22 x 640 acres/mi x 640 acres/mi22 x 43,560 x 43,560
ft2/mift2/mi22 = 2,323,200 ft = 2,323,200 ft33
DischargeDischarge
• 1 cfs = 1 cubic foot per second1 cfs = 1 cubic foot per second
• 1 cfs x 7.48 gal/ft1 cfs x 7.48 gal/ft33 x 3600 sec/hr x 24 hrs/day = x 3600 sec/hr x 24 hrs/day = 646,272 gpd = 0.646 MGD646,272 gpd = 0.646 MGD
• 1 cfs x 3600 sec/hr x 24 hrs/day = 86,400 1 cfs x 3600 sec/hr x 24 hrs/day = 86,400 cfs/daycfs/day
• 86,400 cfs/day x 1 ac-ft/43,560 ft86,400 cfs/day x 1 ac-ft/43,560 ft33 = 1.983 ac- = 1.983 ac-ft/day (~ 2 ac-ft/day)ft/day (~ 2 ac-ft/day)
• 1.983 ac-ft/day x 12 inches/ft x 1 day/24 hrs = 1.983 ac-ft/day x 12 inches/ft x 1 day/24 hrs = 0.992 ac-in/hr0.992 ac-in/hr
• 1 ac-in/hr x 43,560 ft1 ac-in/hr x 43,560 ft33/ac-ft x 1 hr/3600 sec x 1 /ac-ft x 1 hr/3600 sec x 1 ft/12 inches = 1.008 cfsft/12 inches = 1.008 cfs
PowerPower
• Hp = Hp = HQ/550HQ/550
• 1 hp = 550 ft*lb/sec = 0.7547 1 hp = 550 ft*lb/sec = 0.7547 kilowattskilowatts
weight of water
H = head or elevation difference
Q = flow
Hydropower wants a lot of flow and a full reservoir…..