Transcript Precipitation probability distribution as a function of duration: shorter

Precipitation statistics
Cumulative probability of events
Exceedance probability
Return period
Depth-Duration-Frequency Analysis
Statistical basis of hydrology
• Meteorological events characterized by statistical variability
– precipitation inputs to watersheds - atmospheric forcing
– resulting runoff, groundwater recharge, streamflow
• e.g. What is the largest rainfall event expected in a
year? 10 years? 100 years? Ditto for flood events or
drought intensity
• e.g. What is the probability of receiving more than 5
inches of rainfall in a day in any year? Of a flood
exceeding a specific discharge or stage?
• Need statistical tools to make these estimates
– often based on assumption of stationarity (historical
record is representative of the future)
Precipitation probability distribution as a function of duration:
shorter duration: skewed, extreme value distributions
longer duration -> more normal distribution