water and salinity dynamics in soils and...
TRANSCRIPT
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
. . . .