DSD-INT 2014 - Symposium 'Water Quality and Ecological modelling' - Large Scale Nutrient, Wetland...
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Transcript of DSD-INT 2014 - Symposium 'Water Quality and Ecological modelling' - Large Scale Nutrient, Wetland...
Large scale nutrient, wetland vegetation and
morphodynamic modeling of the lower Mississippi
Delta and surrounding receiving basins PART 2
Ehab Meselhe and Johannes Smits
November 2014
Contents
• The modeling framework
• Wetland vegetation sub-model
• Present models, preliminary results
• Work to come
The modeling framework: Delft3D 4
Delft3D-FLOW,
SED-ONLINE Delft3D-WAQ LAVegMod
Delft3D-FLOW for transport, salinity, temperature, silt, clay and sand
Delft3D-WAQ for silt, nutrients, phytoplankton, detritus, oxygen, vegetation biomass
LAVegMod (ULL) for vegetation types (dominant species) distribution
grid, bathymetry,
flow, temperature
flow resistance
depth, salinity,
temperature,
nutrients (?)
veg. distribution
BIOMASS above/belowground
distribution
distribution
function
Delft3D-WAQ modules “layered sediment’
Processes in Delft3D-WAQ
o If water is below residual depth water quality processes except reaeration are
stopped, whereas sediment diagenesis and vegetation processes continue
o Sediment bed in open water and soil bed in wetland have the same processes
Delft3D-WAQ, processes
LAVegMod (Duke-Sylvester & Visser, ULL)
LAVegMod habitat conditions
LAVegMod for Barataria - Breton sound
Focus on 7 taxa
• Spartina alterniflora (oyster grass)
• Spartina patens (wiregrass)
• Sagittaria latifolia (arrowhead)
• Sagittaria lancifolia (bulltongue)
• Zizaniopsis miliacea (cutgrass)
• Typha spp. (cattail)
• Phragmites spp. (common reed)
Submerged Aquatic Vegetation (SAV)
• Use Delft3D-WAQ module to simulate total
biomass
• Aim to quantify nutrient store, flow resistance and
enhanced settling
VEGMOD in Delft3D-WAQ
2 of 5 biomass compartments are used for herbaceous wetland vegetation
VEGMOD, starting points for extension
• All species are in all grid cells with small biomass, but only those will
grow that are predicted by LAVegMod
• Vegetation types distribution is fixed as delivered by LAVegMod
• Biomass develops seasonally towards target biomasses (input)
• Growth is limited by available nutrients
• Mortality for scenescence, herbivory and inundation
• Nutrient (N,P,S) uptake and detritus production as in present
VEGMOD (allocated to layers)
VEGMOD extension, growth
Mass balance:
Initial biomass:
Growth rate:
Biomass incr. ≤ BMt: 𝐵𝑀𝑢𝑛𝑙 ,𝑖 = 𝐵𝑀𝑎𝑐𝑡 ,𝑖 ∗ 1 + 𝐺𝑎𝑐𝑡 ,𝑖 ∗ ∆𝑡
- Ratios of aboveground and belowground biomasses are calculated on
the basis of nutrient availability
- Ratios are determined from a look-up table or function from biomass
allocation model (ULL)
- Changing ratios require “correction” nutrient uptake fluxes due to
different nutrient content of aboveground and belowground biomasses
𝑅𝑔𝑟 𝑖 = 𝐵𝑀𝑙𝑖𝑚 ,𝑖 − 𝐵𝑀𝑎𝑐𝑡 ,𝑖
∆𝑡
VEGMOD extension, mortality
Biomass decr.:
Mortality rate:
𝐵𝑀𝑚𝑜𝑟 ,𝑖 = 𝐵𝑀𝑎𝑐𝑡 ,𝑖 × 1 − 𝑀𝑠𝑖 × ∆𝑡−𝑀𝑖𝑖 × ∆𝑡 −𝑀𝑔𝑟𝑖
𝑅𝑚 𝑖 = 𝐵𝑀𝑚𝑜𝑟 ,𝑖 − 𝐵𝑀𝑎𝑐𝑡 ,𝑖
∆𝑡
Multi-domain models
Tentative 2D test models
(7 layers)
Why aggregation? o Horizontal gradients of WQ substances in water and
sediment are relatively small compared to hydrodynamics
o Reduces computational time
Tentative results salinity
Work to come
• Implementation of new VEGMOD and the SAV module in Delft3D-WAQ
• Modification of BLOOM input
• Formulation/implementation of flow resistance output
Delft3D-WAQ-LAVegMod
• Step-wise calibration Delft3D-FLOW in combination with SED-ONLINE
and Delft3D-WAQ
• Prediction of wetland accretion, vegetation and eutrophication according
to scenarios on the timescale of decades