The IAH-CGCC and UNESCO GRAPHIC have identified three focal areas where progress is required:
Groundwater & Adaptation
Under a warming atmosphere, precipitation intensities are predicted to increase, particularly in the tropics. This projected shift in the temporal distribution of rainfall itself results in more variable river discharge and soil moisture. The former exacerbates intra-annual freshwater shortages and the risk of flooding whereas the latter threatens food security through reduced crop yields. Projected changes in the spatial distribution of mean rainfall are substantial but remain highly uncertain for most of the world. Strategies to adapt to more variable freshwater resources will, in many environments, increase dependence upon groundwater. Few climate impact models explicitly consider, however, how climate variability and change affect groundwater recharge and the sustainable development of groundwater despite its central role in enabling adaptation in domestic and agricultural water sectors.
Groundwater & Climate
The global hydrological cycle is a central component of the Earth’s climate system. Effective representation and quantification of hydrological fluxes are essential to improve climate simulations and prediction and to quantify impacts on water resources. At present, groundwater is poorly represented in the land-surface models (LSMs) incorporated in General Circulation Models (GCMs). Groundwater fluxes operating at a range of spatio-temporal scales require consideration. Indeed, the sensitivity of land-surface energy budgets to groundwater processes including feedbacks from soil-moisture and phreatophytic transpiration remains unclear.
Groundwater & monitoring
Fundamental constraints to both the representation of groundwater in climate models and analysis of climate impacts on groundwater include not only the limited coverage and duration of groundwater observations but also the continued difficulty of accessing available groundwater data. The Global Climate Observing System (GCOS) recognises groundwater as an essential climate variable but notes that data from national and regional monitoring networks are not exchanged nor managed in a centralized manner. A global initiative to rectify this situation is urgently required and key of the IAH-CGCC. The establishment of the International Groundwater Resources Assessment Centre (IGRAC) under the auspices of UNESCO and WMO and development of the Global Groundwater Monitoring Network (GGMN) are important first steps toward sharing of groundwater information on a global scale. A second major advance in groundwater observation has come through the use of satellite observations under the Gravity Recovery and Climate Experiment (GRACE). Finally, recent synthesis of groundwater mapping around the world makes available for the first time low-resolution hydrogeological maps which have the potential for integration into large–scale modelling of groundwater.