Christopher Barry is a doctoral researcher at the University of Birmingham. He has written for the GfGD Blog in the past – detailing his contribution to water projects in Burkina Faso and fundraising efforts to support such work. We have recently added a briefing note to our website, written by Christopher, describing the role of climate change on global groundwater resources. You can access the full briefing note here.
To help share the contents of this briefing note we are publishing a portion of it’s contents over a series of four blogs (i) Introduction to Key Impacts; (ii) Saline Intrusion, (iii) Effects for Groundwater Recharge of Temperature and Precipitation Charges, and (iv) Effects for Groundwater Recharge of Near Surface Turbidity and Parched Soil/Vegetation. At the end of each blog is a link to the full PDF, where you can read each section in its full context and find a full reference list.
Over the last two centuries, the content of the Earth’s atmosphere has changed, with certain gases, known as greenhouse gases, increasing significantly in concentration. Carbon dioxide, the most abundant of these, has increased in concentration by about 50%. They are termed “greenhouse gases” because of their effect of trapping heat in the Earth’s atmosphere rather than allowing it to be radiated into space, in the same way that a greenhouse traps heat inside of itself. This greenhouse effect, is necessary for life on Earth, because without it the Earth would be too cold to hold liquid water. However, due to the unnaturally rapid increase in greenhouse gases, the Earth’s atmosphere is heating at a rate fast enough to unbalance many of the Earth’s climates, ecosystems and ice formations, which gives rise to the term climate change. These changes have profound impacts on the Earth’s water resources. This section outlines some of the main threats posed by climate change to groundwater resources across the globe.
The effects of climate change on groundwater are slower than those on surface water. This gives an advantage for areas trying to adapt to the impacts of climate change on their water resources, in that they have more time. But groundwater is susceptible to depletion and degradation, so an awareness of the threats posed to groundwater by changing climate is important in long-term planning of water resources for communities. There are cases where people’s activities may be adjusted to minimise the potential impacts of a threat, such as disposing of waste away from water sources, in light of the increased risk of floods and high river levels. In other cases, it is useful to be able to predict where groundwater is going to come under unavoidable threat and therefore the limitations of an aquifer’s reliability in the future. For example, a coastal community relying on an aquifer which is under threat from intruding salt water due to sea-level rise would be wise to limit its development of near-coastal groundwater resources for its water supply.
2. The effects of climate change that relate to groundwater
There are two large effects of climate change that are thought to have serious implications for groundwater resources, by a number of processes.
2.1 Change in temperature
The Intergovernmental Panel on Climate Change (IPCC) in 2007 estimated that the average temperature across the globe had risen by about 0.7 °C over the 19th century, with an accelerating rate of warming (Trenberth et al., 2007). The temperature has implications for ice, at the poles and in glaciers, and evaporation of water at the surface.
2.2 Change in precipitation
Seasonal rainfall patterns have been observed to change, as a general trend. Trenberth (2011) explains that the increase of the temperature of the air increases its capacity to hold water vapour, by 7% for every 1 °C. Therefore, a greater amount of water vapour is required to form water droplets and hence precipitation and, conversely, there is more water available in the atmosphere during rainfall events, so these become more intense. The result of this is that rainfall becomes polarised, both in time and in space. That is to say that wet places and wet seasons become wetter and dry places and dry seasons become drier.
The overall effect is that wet seasons, or winters, are becoming shorter and more intense, while dry seasons are becoming more protracted. The frequency of storms, floods and conversely droughts are set to increase.