Subjects and Methods
Groundwater is not an isolated or independent resource. It is a primary component of the hydrologic cycle and is connected to the land surface and terrestrial ecosystems. Current conceptualization of terrestrial water resources incorporates groundwater and surface water as a combined resource. Thinking holistically about groundwater systems in terms of connections to the hydrologic cycle illuminates a number of interdependencies that need to be considered when assessing groundwater availability and long-term aquifer sustainability. These interdependencies can exert substantial controls on the balance of in-flows and out-flows to the groundwater system (the groundwater budget), and the controlling factors can be greatly influenced by human activities at the land surface and effects of changes in climatic conditions.
The water fluxes affecting the groundwater budget include land-surface infiltration, evapotranspiration, flow within the vadose zone, flow into and through the saturated zone, aquifer losses to deeper strata, and the many forms of groundwater discharge or abstraction. Many factors influence water movement and the chemical quality of the resource in each of these compartments. Important controlling factors include local variations in climatic conditions, hydrogeologic setting (including vadose zone processes), vegetative cover, land use, and institutional approaches to water management. A holistic assessment evaluating changes in observed groundwater budgets over time is one approach for understanding of how human stresses and climatic changes may alter the balance of components of the system and ultimately influence groundwater recharge, groundwater storage, aquifer sustainability, and socio-economic stability.
Many of these factors vary over space and time, which makes quantifying the groundwater budget complex. The more carefully the interdependencies of each aspect of this system can be measured and understood, the more clearly the effects of human and climatic influences can be identified. GRAPHIC will aid transfer of the best available technology from all participating researchers so that state of-the-art methodologies can be applied to understand the important interdependencies of the groundwater-climate-human system.
The subjects and methods GRAPHIC is focusing on include:
- Groundwater Quantity (Groundwater Recharge and Discharge, Groundwater and Soil-Water Storage)
- Groundwater Quality
- Geochemical Indicators of Climate and Linked Human Impacts on Groundwater
- Geophysical Methods (Gravity, Subsurface Temperature and Electrical /Electromagnetic Methods)
- Paleo-Indicators of Environmental Changes (Use of Proxies, Response of Hydrological Systems to Past Climate Changes, Age Dating)
- Remote Sensing Applications for Groundwater Assessment
- Information Systems
- Simulation and Modeling
- Management and Policy