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

• J. Velstra, J. Oosterwijk and J. Groen

Impact of climate change on salinization during dry periods in Dutch polders and necessity of adaptation strategies

Human induced land subsidence and land reclamation since medieval times

2

Human induced land subsidence Land reclamation 900 1050 1250 1500

Flushing the water system

3 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%

Water shortage 2003

4

500 1000 1500 2000 2500 3000 3500 4000 jan/02 feb/02 mrt/02 apr/02 mei/02 jun/02 jul/02 aug/02 sep/02

• kt/02

nov/02 dec/02 jan/03 feb/03 mrt/03 apr/03 mei/03 jun/03 jul/03 aug/03 sep/03

• kt/03

nov/03 dec/03 Volume (Mm3/mnd) Month

IN OUT IN from river IJssel OUT Surplus -> Afsluitdijk

(Beersma, et.al 2005)

Year Description 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 Recurrence (years)

16 Mm3/d

Climate change leads to an increased

• ccurrence of periods with water shortage
• Increase of salinization

– Sea level rise – Land subsidence – Meteorological changes

• Increased evaporation
• Trend for high yielding crops
• More flushing to maintain water

quality

• Increase demand for sprinkler

irrigation

• More water needed to maintain

water levels in surface water

• Increase demand for sprinkler

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

9

• Reclamed 17th century
• Surface area (± 1900 ha)

– < 100 ha surface water – 1800 ha land

• One main inlet and

several small inlets period april – october (appr. 30.000 m3/d)

• Outlet by pumping station

(capacity 170 m3/min,

• appr. 244.000 m3/d)

inlet inlet inlet Outlet (pumping station)

Typical cross-section

• Seepage
• flux ± 0.5 mm/day
• concentration 100 - 8000 mg/l

10

Brackish /salt Peat / clay streamline groundwaterlevel

North sea Dunes Deep polder Peat area Fresh water lakes Ice pushed ridge

• Precipitation ±2.2 mm/d
• Evaporation ±1.6 mm/d
• Net Prec. ±0.6 mm/d

Water balance approach

• Fluxes and chloride balance on a daily basis

– Water – Chloride

11

Land Surface water

Drainage type Crop 1 Drainage type Crop 2 Drainage type Crop 3 Inflow from land Precipitation Seepage Evaporation Outlet Inlet Precipitation

• Ref. evaporation

Seepage Water balance

Unsaturated zone model SWAP

(Kroes, et.al. 2008)

Excel

Measurements on fresh water lens and salt accumulation

12

Sept 2009 May 2010 Pipe drain 8m brackish fresh 40 m

• Geophysical measurements (CVES) on an agricultural field

SWAP: Fresh water lens and salt accumulation

13

Rooting depth = 30cm Transp (40cm/yr)> evap(8cm/yr) Grass Rooting depth = 10-50cm Transp (15cm/yr) ~ evap(18cm/yr) Potato

SWAP: Chloride discharge from ditches and pipe drains

14

1000 2000 3000 4000 5000 6000 7000

Chloride draingae [mg/l] date

percelen greppels percelen drains

ditches pipe drains

Water balance: Calibration results

15

2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000 18000000 20000000 1-Jan-03 1-Jan-04 1-Jan-05 1-Jan-06 1-Jan-07 1-Jan-08 1-Jan-09

[m3] Date cum_uitslag WATBAL SchZ cum_gemeten Alexander

50000 100000 150000 200000 250000 300000 1-Jan-07 1-Jan-08 31-Dec-08 m3 /day

Outlet (measured) Outlet (calculated)

Measured and simulated flux at the outlet (pumping station) Measured and simulated cumulative flux

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 chloride [mg/l]

date

Waterbalance: Calibration results

16

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 chloride [mg/l]

date chloride (berekend) Cl-485307 gemaal Juliana, Sch-Z

Water balance: Origin of the surface water in the polder

17

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

Chloride concentration with different inlet amounts

18

10 20 30 40 50 60 70 80 90 100

1000 2000 3000 4000 5000 6000 jan-03 feb-03 mrt-03 apr-03 mei-03 jun-03 jul-03 aug-03 sep-03

• kt-03

nov-03 dec-03

precipitation (mm/d)

Chloride (mg/l) No flushing Actual flushing 50% of actual flushing norm crops norm grass and cattle Neerslag (mm/d)

Climate scenarios

19

2050 2100 G G+ W W+ G G+ W W+ +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% Worldwide temperature rise

• Climate scenarios made available for all meteo stations by

the Dutch Meteorological Institute

– Precipitation with daily values – Potential evaporation with monthly averages

20

Chloride concentration with different climate scenarios (no flushing)

10 20 30 40 50 60 70 80 90 100

1000 2000 3000 4000 5000 6000 7000 jan-03 feb-03 mrt-03 apr-03 mei-03 jun-03 jul-03 aug-03 sep-03 okt-03 nov-03 dec-03

precipitation (mm/d)

Chloride (mg/l)

Chloride concentration without flushing

norm crops norm grass and cattle No flushing 2003 No flushing 2003 W+2100 No flushing 2003 W+ 2050 precipitation (mm/d)

Chloride concentration with different climate scenarios (with flushing)

21

10 20 30 40 50 60 70 80 90 100

1000 2000 3000 4000 5000 6000 7000 jan-03 feb-03 mrt-03 apr-03 mei-03 jun-03 jul-03 aug-03 sep-03

• kt-03

nov-03 dec-03

precipitation (mm/d)

Chloride (mg/l) 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)

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