Integrated hydrological modelling with selected climate scenarios for assessment of future changes in groundwater levels and runoff in coastal areas Torben O. Sonnenborg Department of Hydrology Geological Survey of Denmark and Greenland (GEUS)

Content Scenarios and climatic changes Challenges Hydrological impact –Groundwater –Stream discharge –Flooding Conclusions

Climate-scenarios (IPCC) A2B

Challenges Distribution of climate model results Spatial resolution The model predicts rain almost every day

Geographical distribution of precipitation

Spatial resolution Resolution –Climate model: 10 – 50 km –Hydrological model: 50 – 1000 m

Frequency distribution of rainfall Time Discharge (m 3 /s) Stream discharge

Challenges Max precipitation located at coast Spatial resolution The model predicts rain almost every day  Difficult to use climate model results directly

Delta Change Method Transformation of precipitation Requires assumption of same dynamics Control periodFuture period Time

Calculated precipitation Precipitation in mm/day Month Delta value

Calculated reference evapotranspiration ET in mm/day

Model area Surface elevation (m) Western Jutland Zealand Net precipitation (mm/year)

Hydrological model – MIKE SHE

Western Jutland - Recharge to the groundwater table Måned Nedsivning (mm) Pr A2 B2 Recharge (mm) Month

Western Jutland - Groundwater level (change) B2A2

Western Jutland - Groundwater level Hydraulic head (m)

Effect of sea level rise (1 m) Change in water level

Western Jutland - Stream discharge Pr A2 B2

Flooding in Storaa river catchment

Flooding in Holstebro New elevation model (laser measurements) Improved description of cross sections and stream valleys Holstebro Width app. 600m m Elevation (m)

Water level in Holstebro Future (A2) Present Water level (m) Year

Flooding in Holstebro (max.)

STOP at red light the path is closed because of flooding

Adaptation!

Conclusions Winter –Increasing groundwater level –Increasing stream discharge –Increasing flooding risk More dynamic hydrological system –Groundwater recharge and level –Stream discharge Uncertainties –Climate results –Extremes (delta change method) –Coupling between hydrology and atmosphere