Issues and challenges in palaeohydrology are introduced in Palaeohydrology:Understanding global change (Gregory and Benito, 2003). Once the research foundations for environmental processes and Quaternary Environmental Change were established, interrelationships were explored and palaeohydrology is just one new hybrid research field generated at research frontiers where disciplinary boundaries intersect. Palaeohydrology research will continue to progress arising from the growth of palaeohydrology demonstrated in the literature data base (PHEIMS) and from subjects at Glocoph conferences; the definition of palaeohydrology which has broadened as a concomitant of rapid growth of sub branches, demonstrating the potential of palaeoflood hydrology, and the need for a more basin-based palaeohydrology; regional variations in palaeohydrology which are needed for specific global areas as the scale and rate of Late Pleistocene hydrological processes do not always have present analogues; and the potential of palaeohydrology in relation to global change is significant not only for downscaling spatially but also recognizing that the data analyzed has to be downscaled temporally.

When considering global change and recognizing that adjustments in water resources will be regional or local, potential contributions of palaeohydrology include coupling of Global Climate Change Models to hydrological models and the necessary forcing mechanisms; derivation of data to complement periods of continuous hydrological records relating to water balance, hydrological extremes, water quality; mechanics of temporal change, including the significance of thresholds; spatial contrasts identifying differences between world zones, within zones and within basins, and their synchroneity; and construction of new models of a retroductive kind. Growth areas include short term hydrological events because it has been appreciated that the most dramatic changes during glacials were succeeded by large and sometimes abrupt, natural climatic oscillations during the Holocene. A project bringing together research from six organisations with ICSU support is focusing on past hydrological events related to global change.