Low flow season river discharge boundaries definition of Greek rivers to assess the impact of hydrometeorological and climatic pressures

To assess the impact of the hydrometeorological and climatic pressures, as well as the anthropogenic activities on the Greek rivers’ hydrological regime and health, the boundary between moderate and good quality status concerning low flow season discharge was assessed. This was achieved using a discharge/ichthyofauna database and binary logistic regression models. Based on the results, the discharge boundaries between good and moderate quality during the low flow season ranged between the 22nd and 36th percentile of the low season flow duration curves across all river types. In all cases except for temporary rivers, the boundaries defined were lower than the environmental flows designated by Greek legislation. The methodology applied is highly dependent on the initial dataset validity, the sample size, the low flow season definition, and the users’ expertise. Future work should focus on the database enrichment and the sensitivity analysis of the optimum probability threshold criteria used.