Abstract
Climate change poses uncertainties to the supply and management of water resources. While climate change affects surface water resources directly through changes in the major long-term climate variables such as air temperature, precipitation, and evapotranspiration, the relationship between the changing climate variables and groundwater is more complicated and poorly understood. The greater variability in rainfall could mean more frequent and prolonged periods of high or low groundwater levels, and saline intrusion in coastal aquifers due to sea level rise and resource reduction. This chapter presents the likely impact of climate change on groundwater resources and methodology to assess the impact of climate change on groundwater resources.
TopBackground
Changes in regional temperature and precipitation have important implications for all aspects of the hydrologic cycle. Variations in these parameters determine the amount of water that reaches the surface, evaporates or transpires back to the atmosphere, becomes stored as snow or ice, infiltrates into the groundwater system, runs off the land, and ultimately becomes base flow to streams and rivers.
Temperature increases affect the hydrologic cycle by directly increasing evaporation of available surface water and vegetation transpiration. Consequently, these changes can influence precipitation amounts, timings and intensity rates, and indirectly impact the flux and storage of water in surface and subsurface reservoirs (i.e., lakes, soil moisture, groundwater). In addition, there may be other associated impacts, such as sea water intrusion, water quality deterioration, potable water shortage, etc.
Many rivers and streams that are fed by glacier runoff could be significantly impacted as a result of climate change. As glacier retreat accelerates, increased summer runoff could occur. However, when the glaciers have largely melted, the late summer and fall glacial input into streams and rivers may be lost, resulting in a significant reduction in flow in some cases.
Key Terms in this Chapter
Groundwater: Water held underground in soil pore spaces and fractures of rock formations.
MODFLOW: U.S. Geological Survey modular finite-difference flow model (computer code) that solves the groundwater flow equation to simulate the flow of groundwater through aquifers.
UnSat Suite: Software package for one-dimensional unsaturated flow and transport modeling using SESOIL, VLEACH, PESTAN, VS2DT and HELP.
IPCC: The IPCC (Intergovernmental Panel on Climate Change) is a scientific intergovernmental body which assesses the scientific, technical and socio-economic information relevant for the understanding of the risk of human-induced climate change.
Aquifer: An underground layer of permeable rock which can contain or transmit water.
Numerical Model: Mathematical model using some sort of numerical time-stepping procedure to obtain the model’s behavior over time.
Soil Moisture: The water stored in the upper soil layer.
Recharge: A hydrologic process where water moves downward from surface water to groundwater.
Seawater Intrusion: The movement of seawater into fresh water aquifers due to natural processes or human activities.
Hydrological Cycle: Describes the continuous movement of water on, above and below the surface of earth.