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Information - HS39/SSS23 Dryland hydrology (co-organized by SSS) (co-listed in GM)
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Event Information |
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In the characterisation of rivers for the EU Water Framework Directive, most of the small (10-100 km2) and some of the medium (100-1000 km2) basins in dry regions might be omitted because ephemeral or intermittent streams are considered 'not significant as water bodies for the WFD purposes' in the Provisional WFD Article 5 Report for the Jϊcar Pilot River Basin. The WFD thus would ignore approximately 30% of the area of southern Europe in assessing, managing and protecting water resources. Worldwide, over 250 million people and 100 countries suffer from degradation of soil and biodiversity in semi-arid lands, with severe consequences for water quality.
Following a successful first session in 2005, dryland hydrology remains a topic focused on improving our understanding of the distinctive hydrological processes in semi-arid areas, where Water, Sediment and Solute transfer is constrained by the absence of surface flow in the dry season, when all material is deposited on the bed or held in slow-moving subsurface waters. Because flow is less continuous than for humid areas, there are also less historic stream gauge and rainfall records for semi-arid areas, and the time required to obtain a reliable record is even longer. Coupled with storm frequency distributions that, in many areas, show more extreme behaviour in both time and space, the challenges of forecasting flash floods for both gauged and ungauged catchments is very severe.
Semi-arid areas typically have sparse vegetation cover and are consequently associated with many of the highest rates of sediment loss from the land. As the intensity of agriculture and density of population in southern Europe and other semi-arid areas continues to increase, sediment and solute loadings seem set to increase in parallel, and to accentuate existing water quality problems.
The response of dryland catchments deserves more attention from the hydrological community through the EGU. There is a less complete knowledge of semi-arid than of humid processes at all scales. Topics of particular interest within this session include:
local runoff generation which is dominated by vertical exchanges, and by the co-evolution of vegetation and soils to create patchworks of sources and sinks
connectivity of runoff pathways from hillslope to channel
dynamics of channel and flood-plain exchanges within valley bottoms.
seasonal (or rarer episodic) switches between a semi-arid and a more humid response, and the intricate dynamic of the switching transitions
modelling dryland processes at a range of time and space scales, from long term water balance to flood, sediment and solute dynamics
field and laboratory experimental data coupled to models for intra-bed transformation processes and first flush responses.
implementation of sustainable catchment management for semi-arid areas.
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Preliminary List of Solicited Speakers |
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