Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems.

An important driver of the terrestrial hydrological cycle is atmospheric evaporative demand. Recent studies using measurements of pan evaporation have found evidence that the atmospheric evaporative demand has been declining over the second half of the 20th century. This work analyses long-term time series of pan evaporation obtained from approximately 150±30 weather stations located in Mexico with aridity indexes ranging from 0.3 to 10 for 1961-2010. The results show a consistent decline in annual pan evaporation for 1960-1990 (-3.8mmyear^-2) and for 1990-2010 (-2.6mmyear^-2) periods whereas the average change during the complete period corresponds to -3.3mmyear^-2. Statistically significant negative changes using the non-parametric Mann-Kendall test were found in 43% of the stations for the early and 27% for the recent periods, respectively. The temperature, relative humidity, radiative and aerodynamic controls attributed to the observed changes are analysed with the Noah model output from the Global Land Data Assimilation System Version 2 (GLDAS-2). Among the climatological variables extracted from GLDAS-2, it was the annual wind speed and net radiation that gave the highest statistical correlations. This work agrees with previous studies that pan evaporation rates have been in a declining trend during the second half of the 20th century though milder decline rates have been observed over the last 20years. Finally, we show that the magnitude of change in regions dominated by wind and in those dominated by radiative processes can strongly differ.