salinization during dry periods in Dutch polders and necessity of - PowerPoint PPT Presentation

Impact of climate change on salinization during dry periods in Dutch polders and necessity of adaptation strategies J. Velstra, J. Oosterwijk and J. Groen

Human induced land subsidence and land reclamation since medieval times Land reclamation Human induced land subsidence 900 1050 1250 1500 2

Flushing the water system Salt load from seepage (kg/ha/jr) Area with water intake from Lake IJssel and great rivers (july, dry year) Purpose for water intake Supress high salt concentrations 45% Compensate evaporation surface water -> safety dikes 35% Sprinkler irrigation 15% Other use 5% 3

Water shortage 2003 IN OUT 4000 IN from river IJssel OUT Surplus -> Afsluitdijk 3500 Volume (Mm3/mnd) 3000 2500 16 Mm3/d 2000 1500 1000 500 0 jan/02 mrt/02 apr/02 mei/02 jun/02 jul/02 sep/02 okt/02 nov/02 dec/02 jan/03 mrt/03 apr/03 mei/03 jun/03 jul/03 sep/03 okt/03 nov/03 dec/03 feb/02 aug/02 feb/03 aug/03 Month Year Description Recurrence (years) Current Future (2050-scenario) 1976/1990 extremely salt 32.1 17.6 2003 salt 11.1 6.95 1996 average salt 3.33 2.51 1994 brackish 1.64 1.43 2002 moderate brackish 1.19 1.12 4 (Beersma, et.al 2005)

Climate change leads to an increased occurrence of periods with water shortage • Increase of salinization • More flushing to maintain water quality – Sea level rise – Land subsidence – Meteorological changes • Increase demand for sprinkler • Increased evaporation irrigation • More water needed to maintain water levels in surface water • Increase demand for sprinkler • Trend for high yielding crops irrigation and high quality water • Decrease in water availability due to a decrease of water availability from the great rivers (Rhine)

Strategies for measures are being developed Adaptation (Salt tolerant crops, Convert agricultural area to • nature reserve, …) Mitigation (Desalinization, Seasonal water storage, Pipeline • from Germany, …) On national scale discussion on how to divide the water to • different land use functions and parts of the country 6

Strategies for measures are being developed Adaptation (Salt tolerant crops, Convert agricultural area to • nature reserve, …) Mitigation (Desalinization, Seasonal water storage, Pipeline • from Germany, …) On national scale discussion on how to divide the water to • different land use functions and parts of the country What is the necessity for taking measures? • Water intake is demand driven and not monitored • Water shortage is estimated based on the historic actual intake • 7

Strategies for measures are being developed Adaptation (Salt tolerant crops, Convert agricultural area to • nature reserve, …) Mitigation (Desalinization, Seasonal water storage, Pipeline • from Germany, …) On national scale discussion on how to divide the water to • different land use functions and parts of the country What is the necessity for taking measures? • Water intake is demand driven and not monitored • Water shortage is estimated based on the historic actual intake • How much water is needed to maintain good water quality for • farming and safety of dikes Can the intake volume be reduced (current and under future • climate scenarios) 8

Case polder Schermer Reclamed 17 th century • Surface area ( ± 1900 ha) • – < 100 ha surface water – 1800 ha land One main inlet and • inlet inlet several small inlets period april – october inlet Outlet (pumping station) (appr. 30.000 m3/d) Outlet by pumping station • (capacity 170 m3/min, appr. 244.000 m3/d) 9

Typical cross-section Precipitation ± 2.2 mm/d Seepage • • - flux ± 0.5 mm/day Evaporation ± 1.6 mm/d • - concentration 100 - 8000 mg/l Net Prec. ± 0.6 mm/d • North sea Dunes Deep Peat Fresh water Ice pushed polder area lakes ridge Brackish /salt Peat / clay streamline groundwaterlevel 10

Water balance approach Fluxes and chloride balance on a daily basis • – Water – Chloride Land Surface water Precipitation Evaporation Drainage type Crop 1 Precipitation Outlet Inflow Drainage type Ref. evaporation Water balance from Crop 2 Inlet land Seepage Drainage type Crop 3 Seepage Excel Unsaturated zone model SWAP (Kroes, et.al. 2008) 11

Measurements on fresh water lens and salt accumulation Geophysical measurements (CVES) on an agricultural field • 40 m fresh 8m Pipe drain brackish Sept 2009 May 2010 12

SWAP: Fresh water lens and salt accumulation Grass Potato Rooting depth = 30cm Rooting depth = 10-50cm Transp (40cm/yr)> evap(8cm/yr) Transp (15cm/yr) ~ evap(18cm/yr) 13

SWAP: Chloride discharge from ditches and pipe drains 7000 6000 Chloride draingae [mg/l] 5000 4000 3000 2000 1000 0 date ditches percelen greppels pipe drains percelen drains 14

Water balance: Calibration results Measured and simulated flux at the outlet (pumping station) 300000 Outlet (measured) Outlet (calculated) 250000 200000 m3 /day 150000 100000 50000 0 1-Jan-07 1-Jan-08 31-Dec-08 Measured and simulated cumulative flux 20000000 cum_uitslag WATBAL SchZ cum_gemeten Alexander 18000000 16000000 14000000 12000000 [m3] 10000000 8000000 6000000 4000000 2000000 0 15 1-Jan-03 1-Jan-04 1-Jan-05 1-Jan-06 1-Jan-07 1-Jan-08 1-Jan-09 Date

Waterbalance: Calibration results chloride (berekend) Cl-485307 gemaal Juliana, Sch-Z 5000 5000 4500 4500 4000 4000 3500 3500 chloride [mg/l] chloride [mg/l] 3000 3000 2500 2500 2000 2000 1500 1500 1000 1000 500 500 0 0 date date 16

Water balance: Origin of the surface water in the polder 1.0 8000 0.9 7000 0.8 6000 0.7 Chloride [mg/l] Water origin [fraction] 5000 0.6 0.5 4000 0.4 3000 0.3 2000 0.2 1000 0.1 0.0 0 Inlet Flow from land (pipe drains) Flow from land (ditches) Precipitation Seepage Initial 17 Chloride outlet (calculated) Chloride Outlet (measured)

Chloride concentration with different inlet amounts 6000 0 10 5000 20 30 4000 precipitation (mm/d) Chloride (mg/l) 40 3000 50 60 2000 70 80 1000 90 0 100 jan-03 feb-03 mrt-03 apr-03 mei-03 jun-03 jul-03 aug-03 sep-03 okt-03 nov-03 dec-03 No flushing Actual flushing 50% of actual flushing norm crops norm grass and cattle Neerslag (mm/d) 18

Climate scenarios 2050 2100 G G+ W W+ G G+ W W+ Worldwide temperature rise +1°C +1°C +2°C +2°C +2°C +2°C +4°C +4°C Winter average precipitation increase 4% 7% 7% 14% 7% 14% 14% 28% Summer average precipitation increase 3% -10% 6% -19% 6% -19% 12% -38% potential evaporation increase 3% 8% 7% 15% 7% 15% 14% 30% Climate scenarios made available for all meteo stations by • the Dutch Meteorological Institute – Precipitation with daily values – Potential evaporation with monthly averages 19

Chloride concentration with different climate scenarios (no flushing) Chloride concentration without flushing 7000 0 norm crops 10 6000 20 norm grass and Chloride (mg/l) cattle precipitation (mm/d) 5000 30 No flushing 2003 40 4000 No flushing 2003 50 W+2100 3000 60 No flushing 2003 W+ 2050 70 2000 precipitation 80 (mm/d) 1000 90 0 100 jan-03 feb-03 mrt-03 apr-03 mei-03 jun-03 jul-03 aug-03 sep-03 okt-03 nov-03 dec-03 20

Chloride concentration with different climate scenarios (with flushing) 7000 0 10 6000 20 5000 30 precipitation (mm/d) Chloride (mg/l) 40 4000 50 3000 60 70 2000 80 1000 90 0 100 jan-03 feb-03 mrt-03 apr-03 mei-03 jun-03 jul-03 aug-03 sep-03 okt-03 nov-03 dec-03 Actual flushing 2003 Actual flushing 2003 W+2100 50% of actual flushing 2003 50% of actual flushing 2003 W+2100 norm crops norm grass and cattle Neerslag (mm/d) 21

Conclusions and further research Impact of meteorological change is limited, but • Increased salinization due to sea level rise and land subsidence is not – accounted for In current climate and future climate scenarios a reduction of water • intake by 50% is feasible Challenge to move forward to efficient distribution and monitoring • intake. Which should lead to intake amounts adjusted to the specific purpose. Simulations show a decrease of thickness fresh water lens and • salt/brackish water reaching the root zone Processes on a field scale are important but processes not fully • understood. Currently working on: Measurements in different polders for a period of 1-2 years. Water- and – mass balance measurements on a field and polder scale Development of fresh water lenses and salt accumulation in the – unsaturated zone Model simulations include (un)saturated density dependant flow and – transport modeling 22

Thank you for your attention 23