Estimating the Water Requirements for Plants of Floodplain Wetlands

For example, changes in surface and sub-surface water and nutrientavailability are explicit controls on algae and macrophyte growth, whilemacrophytes influence surface water availability via transpiration, andsurface water movement by their contribution to surface roughness.The GEM is run as a unit model embedded in the cells of a spatialmodel. Modelling the water regime includes water-balance calculationsthat partition water into three separate stores (above surface, theunsaturated soil zone, and the saturated soil zone) and hydrauliccalculations of surface water movement. The macrophyte growthmodel predicts changes in photosynthetic carbon biomass by aproduction model limited by a multiplicative environmental controlfunction that includes light, nutrients, temperature and water. Themacrophyte model is a small part of the large and complex GEM, whichis designed for exploration of large ecosystem dynamics rather than thespecific and accurate prediction of a single component such asvegetation. Fitz et al. (1996) do not report on any attempts to validatethe models described.Finally, it should be pointed out that many complex, spatiallydistributed models have been developed: of catchment and riverhydrology; of surface and sub-surface hydraulics; and of vegetationresponse. The development, refinement and even use of such modelsare major undertakings that require considerable resources, especiallyappropriate modelling expertise. The coupling of hydrologic/hydraulicmodels adds an extra level of complexity, and while examples havebeen quoted, there are few examples for major wetland systems, noexamples for floodplain wetlands in Australia, and all examples arebetter viewed as research investigations than wetland managementapplications.90 Estimating the Water Requirements for Plants of Floodplain Wetlands