ESTIMATING EXTREME GROUNDWATER LEVELS1

Estimating Extreme Groundwater Levels

18 MARS 2014

Hydrologidagarna, 18 mars 2014

Ezra Haaf

ezha@cowi.se

ESTIMATING EXTREME GROUNDWATER LEVELS2 18 MARS 2014

Estimating extreme groundwater levelsHydrologidagarna, 18 Mars 2014

› Damage caused by:› Buoyancy

› Landslides

› In water resources management

ESTIMATING EXTREME GROUNDWATER LEVELS3

› Unclear which distributions can be used

› Many long time series in SGU’s groundwater network available

› Parameter convergence vs time series length

What is interesting about this?

18 MARS 2014

Hydrologidagarna, 18 Mars 2014

ESTIMATING EXTREME GROUNDWATER LEVELS4

Basic steps to estimation of return levels

18 MARS 2014

Hydrologidagarna, 18 Mars 2014

ESTIMATING EXTREME GROUNDWATER LEVELS5

Distributions tested

18 MARS 2014

› Distributions tested:› Normal

› Generalized extreme value

› Log Pearson type 3

› …

Hydrologidagarna, 18 Mars 2014

ESTIMATING EXTREME GROUNDWATER LEVELS6

Model-adequacy: Anderson-Darling

18 MARS 2014

› 8 series for normal distribution rejected

› GEV rejected for cases with far outliers and negative skewness

› LP3 rejected for far outliers

Hydrologidagarna, 18 Mars 2014

ESTIMATING EXTREME GROUNDWATER LEVELS7

L-moment diagram with Anderson Darling: Normal distribution

18 MARS 2014

Hydrologidagarna, 18 Mars 2014

ESTIMATING EXTREME GROUNDWATER LEVELS8

Convergence of mean of groundwater time series

18 MARS 2014

Hydrologidagarna, 18 Mars 2014

ESTIMATING EXTREME GROUNDWATER LEVELS9

› Normal distribution often good model but not always adequate

› Good convergence of mean value after 12 years

› GEV and LP3 good alternatives

Conclusions

18 MARS 2014

Hydrologidagarna, 18 Mars 2014