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
The complexity of what we are trying to accomplish. Evaporation & Condensation Antecedent Moisture Conditions The Water Budget Photosynthesis & Respiration Infiltration Variable Source Area Transpiration & Interception Time of Concentration The sphere concept was borrowed from Dr. Peter Black: Watershed Hydrology 2 nd Edition, Peter Black, 1996, Ann Arbor Press (ISBN# 1-5704 027-1)
Models try to mimic this! Infiltration Time Series Basin Process Representation Excess Precip. Interception Storage Time Series
From A Basin View Excess Precip. Runoff Hydrograph Excess Precip. Model Basin Routing Unit Hydrograph Stream Routing
The Runoff Picture Hydrology is long term and short term. In this course we will mainly focus on the short term: Floods & flood flows. Generating runoff/high flows. Predicting/forecasting flows. Space/time scales.
Recipe(s) for a Flood/High Flows What causes a flood / high flow? What are the conditions? What are the types of flooding situations? Your area or other areas..
What Are the Defining Characteristics of a Flood? Timing rise time, recession, duration. Flows peak flows, magnitude (statistical). Precipitation intensity, duration, frequency.
What Controls the Timing, Flow, and Precipitation? The hydrology short term and long term. The meteorology short term (weather/storm type) and long term (climate).
Short Term Weather (storm type) & current hydrologic conditions
Watershed Characteristics Area Slope Land Use Soils Geology Climate Geomorphology
Some of the Right Combinations. Precipitation vs. vs.- infiltration Precipitation intensity > infiltration rate Precipitation total > infiltration capacity Storage in the system is full Human induced high water or flows Natural alterations to the watershed
Our Focus - Forecasting Must be both short & long term.. The combination(s) of precipitation and hydrologic conditions that lead create a potential flooding situation basin hydrology basin hydrology looks at the hydrologic budget in both the short and long term.
Water, basic element
Water resources
How much water is there? Distribution of Earth's Waters and Residence Times... Location of Storage Total water on earth Oceans Total Fresh Water Ice and Glaciers Groundwater Deep Groundwater Percent of Fresh Residence Time (years) 100.0 6977 75.4 5210 14.0 973 11.0 764 Shallow Lakes 0.3 21 Biosphere 0.24 17.1 Soil Moisture 0.06 4.17 Atmosphere 0.035 2.43 Rivers 0.003 2.1
Water Resources Mean annual precipitation Europe Asia Africa SouthAmeric anorthamerica 734 mm/year 726 mm/year 686 mm/year 1648 mm/year 670 mm/year
Hydrological processes Clouds and atmosferic movement Precipitation Losses Interception Evapotranspiration Infiltration Depression storage Rainfall runoff Flood Routing
Units & Properties of Water Property Symbol Value Comments Density ~1.94 slugs/ft 3 Slug = lb*s 2 /ft (mass/volume) ~ 1.0 g/cm 3 Specific Weight 62.4 Lbs/ft 3 g (weight/volume) 9.81 kn/m 3 Specific Volume Specific Gravity s.g. 1.0 for water @ 0 o C s.g. fluid = g fluid /g water
Water (gas)
Water (solid)
Water (liquid)
No water - desert
Clouds and atmosferic movement
Global cycle
Sun: energy source
Solar Radiation Sun: distance 150 millions of Km Energy received: 1000 W/m 2
Solar Radiation Differences according to the latitude
Solar Radiation Diferences between June and September
Effective Radiation Difference between received and back radiation Ri,, solar radiation,, albedo R e,, back radiation R n = R i (1- ) R e
Clouds Evaporation from seas, lakes and rivers
Clouds
Clouds
Clouds
Clouds
Meteorological phenomena twisters
Hurricanes
Cloud structure Water drops from 0.01 to 0.03 mm Weight from 0,5 to 1 gr/m 3 Growing processes up to 10.000 to 100.000 times initial values Water in clouds can explain 10 to 12 mm
Atmospheric circulation Tropical cells
Tropical cells
Water droplets Condensation Coalescence
Condensation
Coalescence
Droplet aggregation Raindrops up to 3 to 4 mm Terminal velocity 9 a 12 m/s
Water precipitation Water, snow, hail
Types of rainfall Ciclonical / Frontal rain Orographic Convective cells
Frontal rain Cold and hot air masses moving along the planete
Frontal behavior Hot and cold air mass friction
Frontal behavior Hot and cold interface
Frontal precipitations Associated to large areas (tens or hundreds of miles of Km 2 ) Long durations (days) and high total rainfalls but with low rainfall intensities
Orographic rainfalls
Orographic Precipitations Typical Mediterranean pattern During the fall Hot air coming from the Magreb, Mountains close to seaside Heavy rainfalls
Convective cells Afecting to small areas Convective cells appearing and disappearing during the rain period Can produce very intense rainfalls
Convective cells Scheme
Rainfall measurements Precipitation: : mm l/m 2 Intensity mm/h Temporal register: pluviograph or hyetograph
Greatest precipitation data Data on different observatories Annual precipitation Year Month Day 12 h 42 minutes 11680 mm 26470 mm 9300 mm 1870 mm 1350 mm 300 mm Hawaii, Mount Waialeale Cherrapunji,, 1860-01 01 Cherrapunji, July 1861 Reunión, n, March 1952 Reunión, n, February 1964 Holt,, Missouri, June 1947
Rainfall envelope Mathematical relationship P, mm D, hours 0.47 P 425D
Intensity Intensity,, ratio between precipitation and time Hyetograph
Rainfall measurements Pluviometer / pluviograph
Total rainfall
Pluviometer of intensity Tipping bucket gauge
Rainfall monitoring Satellites, qualitative observation
Rainfall radar
Measurement networks INM, rainfall data in 24 h SMC, shorter time series Rainfall radars
Rainfall data analysis Hypothesis: to study the historical rainfall data to predict future rainfall We assume the future rainfall will be the same as the previous one Climatic change effect: to study Application in hydrological studies
Data analysis Time series analysis Qualitative analysis Filling gaps Consistency test (doubles mass) Statistical analysis
Statistical analysis I Annual rainfall series Extremal distributions Gumbel Log Pearson III SQRT ET Associated values to return period of N years
Statistical analysis II Partial duration series, (peak( over threshold) Appropriated to return periods below 10 years
Rainfall data sources AEMET - SMC, time series, in Spain and Catalonia Previous work: : Lluvias máximas m en la España a Peninsular, DGC 2001