water and salinity dynamics in soils and...

Rien van Genuchten

U.S. Salinity Laboratory, USDA, ARSUniversity of California

Riverside, CA, USA

Water and Salinity Dynamics in Soilsand Groundwater

Kandy, Sri Lanka

September 19, 2005

Irrigation and Salinity Issues15-20% of world’s crop land is irrigated

– But provides about 40% of world’s food and fiberWorldwide, agriculture uses 70% of all water consumption

– Up to 85-95% in developing countries>10% of irrigated lands affected by salinization

– Up to 25% in arid and semi-arid regions– 45 million ha irrigated lands affected– >0.5 million ha lost annually due to salinization (1-2%)

1.5 billion people have no access to safe drinking water– 3 billion people have no access to sanitation

World’s population grows faster than increases in cultivated land– Per capita arable land decreased from 0.38 ha (1970) to 0.28 (1990) and maybe 0.15 (2050)– Irrigation must increase by 2% each year to keep up with population (now only 1%)– Urban areas now occupy 3% of world’s surface– Increased crop production requires irrigation, increased efficiency

Increased competition between agriculture and other user– Municipal, industrial, ecological, recreational, …

Long-term sustainability of many irrigation practices are at issue– Long-term implications of various actions are needed

CaliforniaFffd

Dd

Central Central Valley of Valley of CaliforniaCalifornia

San J

Sierra N(Granite salts)

San JoaquinSan Joaquin

Sacramento ValleySacramento Valley

Coastal Range(Sedimentary rock; high salts)

High saline water High saline water tables in tables in CaliforniaCalifornia’’s s San San JoaquinValleyJoaquinValley

Soil SurfaceInitial water table

Drain line Drain line

Controlling saline water tables

Reuse of Agricultural Reuse of Agricultural Drainage WaterDrainage Water: : Reduce drainage volumeReduce drainage volume

BlendingBlendingCyclicCyclicSequentialSequential

Low salinewater

Traditional crops(non-saline)

Salt-tolerant cropsAnd forages

Halophytes

Solar Evaporato

Increasing salinity

Sequential ReuseSequential Reuse

Courtesy: Daniel Hillel

OutlineIntroduction (Salinity, California, Sri Lanka)

Subsurface Flow/Transport ModelingMulticomponent Geochemical TransportColloid and Pathogen TransportRoot Water Uptake/Crop Salt ToleranceHydraulic Properties/Pedotransfer FunctionsThanks

Governing Equations

Variably-Saturated Water Flow (Richards Equation)[ ( ) ( )]hK h K h S

t z zθ∂ ∂ ∂= − −

∂ ∂ ∂

Heat Movement

Solute Transport

( )[ ( ) ]p

w w

C T T qTC C STt z z zθ

λ θ∂ ∂ ∂ ∂

= − −∂ ∂ ∂ ∂

( ) ( ) ( )s c cD qct t z zρ θ θ φ∂ ∂ ∂ ∂

+ = − −∂ ∂ ∂ ∂

The HYDRUS Software Packages

Variably-Saturated Flow (Richards Eq.)Root Water Uptake (water, salinity stress)Multiple Solutes (decay chains, ADE)Nonlinear SorptionTwo-Site Nonequilibrium SorptionMobile-Immobile Water/Preferential FlowHeat TransportPedotransfer Functions (hydraulic

properties)Parameter EstimationInteractive Graphics-Based Interface

Soil SurfaceInitial water table

Drain line Drain line

Reducing the saline water table

HYDRUS - Agricultural Applications

Irrigation and drainage managementDrip irrigation designSprinkler irrigation designTile drainage design and performanceStudies of root and crop growth Salinization and reclamation of salt-affected soilsNitrogen dynamics and leaching Transport of pesticides and degradation productsNon-point source pollutionSeasonal simulation of water flow and plant response. . .

Contaminant Plume Moving to Stream

HYDRUS - Industrial and Environmental Applications

Capillary barrier designNuclear waste disposalLandfill covers Analysis of contaminant plumes from landfillsSeepage of wastewater from land treatment systemsTunnel design - flow around buried objectsHighway design - road construction - seepageLake basin recharge analysisStream-aquifer interactionsVirus and bacteria transportHill-slope analysesTransport of TCE and its degradation productsMulticomponent geochemical transportAnalyses of riparian systemsFluid flow and chemical migration within the capillary fringeFlow and transport around land mines

OutlineIntroduction (Salinity, California, Sri Lanka)

Subsurface Flow/Transport ModelingMulticomponent Geochemical TransportColloid and Pathogen TransportRoot Water Uptake/Crop Salt ToleranceHydraulic Properties/Pedotransfer FunctionsThanks

Courtesy: Daniel Hillel

Specific Ion Toxicity

Multi-Component Geochemical Transport

Salinity dynamics in irrigated landsReclamation of sodic soilsTrace elements in agricultural drainage watersAcid mine drainageRadionuclide transportFate and transport of metal-organic mixed wastesRedox zones in organic-contaminated aquifersReactive permeable barriers. . .

Integrated Reactive Transport Codes

Models with specific chemistry (HYDRUS-1D) - physics and chemistry tightly coupled- major ion chemistry using UNSATCHEM module- restricted to certain prescribed chemical systems - constrained to very specific applications- often much easier to use- computationally much more efficient.

- General models (HP1)- physics and chemistry loosely couples- much more freedom in designing particular chemical systems- much broader range of applications

HYDRUS-1D + UNSATCHEM

H4SiO4, H3SiO4-, H2SiO4

2-3Silica species6

PCO2, H2CO3*, CO3

2-, HCO3-, H+, OH-,

H2O7CO2-H2O species 5

Ca, Mg, Na, K 4Sorbed species (exchangeable)

4

CaCO3, CaSO4⋅ 2H2O, MgCO3⋅ 3H2O, Mg5(CO3)4(OH)2⋅ 4H2O, Mg2Si3O7.5(OH) ⋅ 3H2O, CaMg(CO3)2

6Precipitated species

3

CaCO3o, CaHCO3

+, CaSO4o, MgCO3

o, MgHCO3

+, MgSO4o, NaCO3

-, NaHCO3

o, NaSO4-, KSO4

-

10

Complexed species

2

Ca2+, Mg2+, Na+, K+, SO42-, Cl-, NO3

-7Aqueous components

1

Drainage Water CompositionDrainage Water Composition(San Joaquin Valley)(San Joaquin Valley)

B, Se, MoB, Se, MoTrace ElementsTrace Elements

SOSO44 > Cl, HCO> Cl, HCO33AnionsAnions

Na > Ca, MgNa > Ca, MgCationsCations

10 to 3010 to 30SARSAR

2.0 to > 30 2.0 to > 30 dS/mdS/mECEC

Reclamation Examples [Simunek and Suarez, 1997]

0

20

40

60

80

100

0 20 40 60 80SAR

Dep

th [c

m]

A)

0

20

40

60

80

100

0 20 40 60 80SARB)

0

20

40

60

80

100

0 20 40 60 80SARC)

80

120d237.9y

234.2

200

100

50

10

00

10

2060

100

150

200d

0

20

40

60

A. Irrigation with high quality water and no amendmentsB. Irrigation with gypsum-saturatedC. Irrigation with high quality water and no gypsum incorporated in top 20 cm

Reclamation Examples [Simunek and Suarez, 1997]

0

20

40

60

80

100

0 20 40 60 80SAR

Dep

th [c

m]

D)

0

20

40

60

80

100

0 20 40 60 80SARE)

0

20

40

60

80

100

0 20 40 60 80SAR

F)

0

20

40

60

80

100d

010

2030

40

50

60

70d

02

6

10

12

14

16d

D. Irrigation with high quality water and calcite throughout the soil profileE. Irrigation with acid water at pH 2.05 and calcite throughout the soil profileF. Irrigation with acid water at pH 1.09 and calcite throughout the soil profile

Integrated Reactive Transport Codes

Models with specific chemistry (HYDRUS-1D) - physics and chemistry tightly coupled- major ion chemistry using UNSATCHEM module- restricted to certain prescribed chemical systems - constrained to very specific applications- often much easier to use- computationally much more efficient.

- General models (HP1)- physics and chemistry loosely couples- much more freedom in designing particular chemical systems- much broader range of applications

Available chemical reactions:Aqueous complexationRedox reactionsIon exchange equilibrium (Gains-Thomas)Surface complexation – diffuse double-layer model and non-electrostatic surface complexation modelPrecipitation/dissolutionChemical kineticsBiological reactions

PHREEQC (Parkhurst and Appelo, 1999)

One dimensional transport; steady-state flow

Numerical Issues– Coupling method: non-iterative sequential

approach– Within a single time step:

» solve Richards’ equation for water flow» solve ADE for element master species (inert

transport)» for each element, calculate speciation,

equilibrium reactions, kinetic reactions

Software Issues– Fortran: HYDRUS modules

C and Basic: PHREEQC

HYDRUS - PHREEQC Coupling = HP1

A Coupled Numerical Code ForVariably Saturated Flow

Solute Transport AndBiogeochemistryIn Soil Systems

• One-dimensional transient flow in partially or fully saturated media• Root water uptake as a sink for water; Root growth• One-dimensional transient convective and conductive heat transport under time-variable temperatures at the soil

surface• One-dimensional advective, dispersive and diffusive transport of multiple solutes• Effect of temperature on transport parameters, thermodynamic constants, and rate parameters• Options for different functional forms for soil hydraulic properties, including hysteresis• Physical non-equilibrium solute transport• Equilibrium aqueous speciation reactions and kinetically controlled aqueous reactions• Sequentially first-order decay/degradation reactions (forward and backward)• Multi-site cation exchange related to amount of minerals or organic matter present• Equilibrium and kinetic dissolution/precipitation of primary and secondary minerals• User-defined kinetic reactions (transition state theory for minerals, Monod or Michaelis-Menten kinetics)• Presence of simultaneous reactions (sequential and parallel kinetic reactions, equilibrium and kinetic reactions,

homogeneous and heterogeneous reactions, biogeochemical reactions)

Simulating flow, transport and bio-geochemical reactions in

environmental soil quality problems

Version 1.0November 2004

Biogeochemical modelPHREEQC-2.4

Flow and transport model

HYDRUS1D 2.0

Diederik Jacques / Dirk Mallants, SCK•CEN, Mol, BelgiumJirka Šimůnek, Dept of Environmental Sciences, UCR, Riverside, CA, Rien van Genuchten, U.S. Salinity Laboratory, Riverside, CA

OutlineIntroduction (Salinity, California, Sri Lanka)

Subsurface Flow/Transport ModelingTransport Multicomponent GeochemicalColloid and Pathogen TransportRoot Water Uptake/Crop Salt ToleranceHydraulic Properties/Pedotransfer FunctionsThanks

Prado Wetlands

Prado Dam

OCWD Forebay

San Bernardino County

RiversideCounty

Orange County

CHINO

386,000 dairy cow25,000 acre

Colloid Transport

Pathogenic Microorganisms– E. Coli and Salmonella species,

Cryptosporidium, Giardia, and enteroviruses

Bioremediation Strategies– Injection of microorganisms for

bioremediation

Facilitated-Transport of Contaminants– Organic and inorganic contaminants can be

sorbed on colloids

Colloid Transport Processes

Adsorption-DesorptionIon ExclusionAccumulation at Air-Water InterfacesSize ExclusionStraining

– Pore straining– Film straining– Textural interfaces

Decay/InactivationColloid-Facilitated TransportChemistry, ….

colloid

Straining Straining (dp/d50>0.18)

OutlineIntroduction (Salinity, California, Sri Lanka)

Subsurface Flow/Transport ModelingMulticomponent Geochemical TransportColloid and Pathogen TransportRoot Water Uptake/Crop Salt ToleranceHydraulic Properties/Pedotransfer FunctionsThanks

Rice Production in CaliforniaMore than 95% of the state’s rice is grown in Sacramento Valley (Mediterranean climate)Acreage: 300,000 - 450,000 acres in 1990sYield: 8,000 - 13,000 pounds per acre2.6% of total California water (2.23 million acre-feet) used for rice productionMarkets: Throughout North America and overseas (Pacific countries)Planting: direct water-seeding

Heritability of yield parameters under salt stress

Parameter Broad- Narrow-sense sense

Grain wt per plant 0.45 0.25

Grain wt per panicle 0.21 0.17

Tillers per plant 0.65 0.42

Genetic correlation and total phenotypic correlation

Parameter r A Phenotypic correlatio

Grain yield vs tiller no. 0.84 0.78***

Grain yield vs panicle wt 0.68 0.85***

Tiller no. vs panicle wt 0.23 0.47***

Field CropsCrop Salt Tolerance, ECw (dS/m)

7.25.03.22.5Rice

3.92.51.71.1Corn

5.04.23.73.3Soybeans

8.76.44.94.0Wheat

10.07.55.84.7Sugar Beets

12.08.46.45.1Cotton

12.08.76.75.3Barley

50%

25%

10%

0%Reduction in Yield

Vegetable CropsCrop Salt Tolerance, ECw (dS/m)

2.91.81.2.8Onions

3.52.11.4.9Lettuce

3.92.51.71.1Sweet Corn

3.92.51.71.1Potatoes

6.13.83.41.5Cantaloupes

5.03.42.31.7Tomatoes

50%

25%

10%

0%Reduction in Yield

Fruit CropsCrop Salt Tolerance, ECw (dS/m)

1.71.20.90.7Strawberries

2.41.71.20.9Avocadoes

4.52.71.71.0Grapes

3.22.21.61.0Apples

3.22.21.61.1Oranges

12.07.34.52.7Date Palms

50%

25%

10%

0%Reduction in Yield

Variably Saturated Flow Equation

[ ( ) ( )] ( , )hK h K h S ht z zθ π∂ ∂ ∂= − −

∂ ∂ ∂

Pressure head

Osmotic head

OutlineIntroduction (Salinity, California, Sri Lanka)

Subsurface Flow/Transport ModelingMulticomponent Geochemical TransportColloid and Pathogen TransportRoot Water Uptake/Crop Salt ToleranceHydraulic Properties/Pedotransfer FunctionsThanks

Thanks to CollaboratorsJirka Simunek

Scott Bradford

Diederik Jacques

Feike Leij

Marcel Schaap

Binayak Mohanty

Todd Skaggs

Peter Shouse

Jan Hopmans

. . . .

Thank You !!

Any Questions?

rvang@ussl.ars.usda.gov