05. Other hydromorphological pressures
Other than hydromorphological pressures are beyond the scope of this review. However, there are several hydromorphological processes which in parallel also determine physico-chemical properties of the water. Thus, HYMO pressures affecting such processes will definitely also affect the related physico-chemical variables as well as potential feedbacks to hydromorphology and / or biota. Relevant other processes and potential effects have been indicated in the conceptual figures and are briefly listed here without further detailed explanation and discussion.
Effect/Impact on (including literature citations)
- Water temperature modification cold
Cooler water released by stratified reservoirs will have greater viscosity and therefore its capacity to erode channels will be reduced because it will reach lower flow velocities.
- Water temperature modification warm
Shainberg et al. (1996) concluded that high water content and high temperature (which induces high Brownian motion) during aging enhance clay-to-clay contacts and cementation of soil particles into a cohesive structure that resists rill erosion. Sidorchuk (1999), through field and laboratory experiments, found that water temperature became the main factor of gully erosion in frozen soil or in soil with the permafrost (so called thermoerosion).
- Toxic substances – pollution
The impacts of toxics on aquatic biological organisms may be increased or hidden depending on HYMO processes. Channel and bank erosion may unearth contaminants and promote their dissolution in water increasing their toxicity. On the contrary, sedimentation processes can bury pollutants at the channel bed and thereby reduce their toxicity.
- Eutrophication – nutrient enrichment
Vegetation encroachment will have a high demand on dissolved nutrients and thus, reducing eutrophication impacts on aquatic biota. Also, riparian vegetation with an extended canopy has a dense root system that filters nutrients from phreatic waters.
- Organic pollution
Excessive growth of macrophytes in eutrophic conditions and the leaf fall of riparian species in autumn, accumulate organic matter in the water. Hydraulic turbulent conditions favoring reaeration of the water column and hence the oxygen entrance which promotes the decomposition of this organic matter, reducing the impact of anoxic conditions due to organic contamination.
Case studies where this pressure is present