Humans, water and climate

Figure 1. Diagram illustrating the interdependence of human water use and the natural hydrologic system. Note the linkage between terrestrial (surface and subsurface) and atmospheric hydrologic cycles and the key mechanisms that provide feedbacks between the human and natural systems.

According to the 'Intergovernmental Panel on Climate Change' (IPCC), water is involved in all components of the climate system; therefore, climate change affects water through a number of mechanisms.
Climate change will significantly alter the hydrologic cycle at global and regional scales, with impacts on freshwater resources, land use, and landatmosphere feedbacks. However, the effects of climate change on the hydrologic cycle, and hence on water resources, are difficult to predict because of the complexity of the natural system, the many coupled physical processes, the scientific uncertainty, the wide range of future greenhouse gas emission scenarios, and the dependence on human factors such as government policy and public understanding of the problem. Climate change impact studies must therefore consider the full spectrum of these issues and expect to be scrutinized for their realism, sophistication, and robustness.
Recent work has demonstrated that land-atmosphere feedback and hydrologic response under climate change depend on the quantity, movement, and distribution of groundwater. These feedbacks are not only critically important to predicting hydrologic response to climate change, they also indicate any water management practices that change the depth to water tablee.g., pumping groundwater for agricultural or municipal use, or groundwater banking. Feedbacks between water management and local climate would change the scale of human-climate interactions from strictly global to highly local and could notably change the way that scientific information on climate should be communicated to the public, particularly water managers, to better inform such local policy decisions.
Therefore, there is a need to address both the scientific question of feedbacks between water management and local climate, and the sociopolitical question of understanding and improving communication between climate scientists, local decision makers and the public. Collaborative research and education will improve our understanding of the link between the human and natural systems and help to manage and adapt our water resources in a changing climate.
It is now necessary to use two fully coupled groundwater-land surface-atmosphere models to investigate the connections between global climate change, regional climate feedbacks, and local water resources practices. This will allow investigating hydrologic response and climate feedbacks over a range of scales. Furthermore, it will investigate the link between local-scale water management decisions and climate change by implementing a three-part ethnographic study of scientific communication between climate scientists, water managers and students, and the public. In particular, this will examine how modeling simulations and results can best be communicated to the stakeholders (water managers, students, and the public), explore where the most effective communication occurs, and identify existing barriers to communication. The relationship between these human and natural scales, systems and feedbacks is shown in Figure 1.
In the context of Bangladesh, any research plan related to investigating hydrologic response and climate feedbacks should include the following key questions:
* What is the effect of climate change on local hydrologic variables that impact water resources such as water table depth, stream flow, evapotranspiration, and runoff? What are the regional differences between the watersheds in the vulnerability of water resources to climate change?
* What are the effects of local water management practices, such as groundwater pumping, irrigation, and groundwater banking, on hydrologic response, land-atmosphere feedbacks, and climate change?
* How does human participation enter into local water resources management decisions and dissemination of scientific information? How can scientific research be effectively communicated to local decision makers? How does the propagation of information influence the feedback between human and natural systems?
* What role should climate scientists play in shaping policy? What kinds of alliances or relationships can climate scientists form with local policymakers, and what are the risks and ethics involved in such alliances?
* How can the results of these detailed, scientific studies be integrated into the undergraduate and graduate curricula to better educate future water engineers and managers? How can these results be shared with the public?
Dr. Rashed Chowdhury is the Principal Research Scientist of the Pacific ENSO Applications Climate Center (PEAC) and a Faculty of the Department of Urban and Regional Planning, University of Hawaii, USA; Email: [email protected]