Effects of climatic change on stream water quality in Spain

There is unequivocal evidence of increased air temperatures in Spain as a result of climate change Using organic matter, nitrate and soluble reactive phosphorus concentrations, we reconstructed changes in water quality in 15 montane, pristine streams between 1973 and 2005 in Spain We also measured how loading rates of these variables change as a function of shifting temperatures Almost half of tested variables were related with hypothesized trends of climatic change for air temperature Concerning extreme events, the hypothesis of climatic change matched in 33% of all relationships, which mostly occurred in Northern Spain Regional gradients of population change and soil degradation, however, did not explain the geographical distribution of climatic change effects The main reason that effects on water quality are not ubiquitous and that constraining factors are hardly detected may be that long-term signals are the outcome of several interacting processes These are still poorly known and may act at different spatial and temporal scales Hence, a case-by-case approach might prove more fruitful than a regional one when studying water quality responses to climatic change Consideration of the balance between extreme and normal events (storm- vs baseflow), catchment effects (land use and its effects on evapotranspiration and runoff) and in-stream processes (outgassing, mineralization, burial) could help increase our understanding of the responses of water quality to climatic change