Temp-Qsim - Evaluation and improvement of water quality models for application to temporary waters

In the Mediterranean, temporary waters are a widespread phenomenon and they play a pivotal role for both public and agricultural water supply. The 'hydroperiod' of temporary waters, which includes duration, frequency and severity of surface drying periods, is most critical for the quality and quantity of downstream water resources including reservoirs, lagoons, and coastal areas. Temporary waters are extremely sensitive to (i) hydrological change (e.g., water abstraction, groundwater exploitation), (ii) point and nonpoint pollutions (nutrients, pesticides) and (iii) changes in catchment land use (e.g., afforestation - deforestation, urbanisation). Existing water quality models have primarily been developed for permanent streams and rivers. However, these models do not adequately consider the specific hydrological conditions and water quality dynamics in catchments containing a dense network of ephemeral and temporary waters. Increased efforts are, therefore, required to provide optimal water management tools for water agencies and decision makers in the Mediterranean and in semi-arid areas. Problems for application of water quality models in the Mediterranean arises by periods without runoff (also including numerical problems for most of the models) and extreme first flush effects with the beginning of the rain period. The natural quality of the water (sediments, solutes) is frequently poor and highly varying in time. The ongoing dynamic of processes in sediments during the period of no surface runoff and the interaction of resuspended matter and water quality is widely unconsidered in the existing models.