Wetland hydrological models – Wetland site scale

Select from the tabs below

• Overview
• Wetland site scale
• Wetland contributing catchment model
• Wetland catchment/subcatchment model

The conceptual model for the wetland site scale shows the factors influencing inputs to a wetland hydrologic model, the hydrological and nutrient processes within the wetland, the wetland components that influence water flows and processes, and the outputs from a wetland model.

The conceptual model focusses mainly on nitrogen processes within a wetland but other processes and constituents can be incorporated into a model depending on the modelling purpose.

Forcing factors – these are the factors (e.g. temperature, evaporation, rainfall intensity, duration, volume, timing and event frequency, solar radiation, wind) that influence the model inputs, including the amount and flow of water in the catchment or area of interest and the constituents (e.g. nutrients and pesticides) carried by the water.

Landscape – these factors affect the forcing factors and contribute to the resultant runoff and constituent inputs.

Wetland configuration (components) – these describe the physical components of the wetland itself, which in turn affect flow within the wetland (e.g. size, depth, shape, bathymetry, inflow configuration (controls and inlet type such as pipe, channel, rock weir)), vegetation configuration (species, shape, density).

Model inputs – these are water inputs to the wetland which can be divided into: overland flow, channelised flow, and sub-surface flow. The flow rates, volume, and timing (frequency, seasonality) of the inflows will vary depending on the forcing factors and landscape parameters (see contributing catchment conceptual model).

For a site scale wetland model the inputs may be generated from another model or dataset.

Model inflow constituents – the concentrations of pollutants such as fine sediment, dissolved inorganic nitrogen (DIN), particulate N, carbon, pesticides or other contaminants.

Wetland Processes – the nitrogen processes in wetlands vary depending on the environment:

• open water processes occur in the water column of the wetland, separate from the vegetated or benthic zones. Nitrogen processes include: nitrification, nitrogen fixing by algae, macroinvertebrate grazing and predation, algal growth and decay, stratification in terms of temperature or oxygen levels, adsorption and desorption, dissolution and flocculation of contaminants.
• benthic zone processes occur in the sediment and substrate of the wetland. Nitrogen processes include: sedimentation, and resuspension, sediment nutrient flux, nitrification, denitrification, assimilation, annamox, ammonification, litterfall, organic matter accumulation, biological uptake and filtration including biofilms at sediment water interface, and oxygenation/deoxygenation.
• vegetated zone processes occur in the vegetated zones of the wetland. Vegetation provides carbon which is used by microbes in processes such as denitrification, and biofilms which host microbes. Nitrogen processes include: denitrification, nitrification, nitrogen fixing, nitrogen assimilation, plant uptake in the root zone, litterfall, biofilm growth, decay, sloughing and scour, wetting and drying, adsorption, desorption, photosynthesis, respiration, and transpiration.

Model outputs - these are water outputs from the wetland which can be divided into: bypass or overflow, channelised flow, and sub-surface flow. The flow rates, volume, and timing (frequency, seasonality) of the outflows will vary depending on the inputs, and water flow and storage within the wetland itself.

References

1. ^ Queensland Water Modelling Network (2018), Good Modelling Practice Principles. [online], Brisbane, Queensland. Available at: https://science.des.qld.gov.au/__data/assets/pdf_file/0011/81110/qwmn-good-modelling-practice-principles.pdf.
2. ^ Weber, T, de Groot, A, Hamilton, D, Yu, S & Bayley, M (2021), QWMN Wetlands Hydrology Models Review, Alluvium Consulting Australia, Griffith University, and Australian Wetlands Consulting.

Last updated: 31 May 2023