Posted by: indiesfaves | February 24, 2011

Hydrological Cycle or the Water Cycle affected by Climate Change

Chapter 1 Hydrological Cycle or the Water Cycle affected by Climate Change

Water 101: A familiar hydrological or water cycle Figure 2

Figure 1   Hydrological Cycle source GAO report Freshwater Systems

The water cycle is a system that regulates how water is distributed and it is the that disruption of this cycle and the mismanagement of fresh water that is causing water scarcity throughout of the world affecting many level of drought and causing flooding in other areas.

The hydrology system is supposed to work like this; the wind transports water vapor over the oceans; gathering condensation through what is call evaporation. As these water vapors multiply becoming condensation, which is a heating of the atmosphere from both over land and oceans. Over land water vapor also rises through evapotranspiration. This comes from earth, plants, trees and other vegetation. The water vapors form clouds and then release precipitation. Precipitation can come in the form of rain, sleet, hail, snow. Storms bring extra moisture to specific areas. Water in the form of rain, ice and snow is a source of fresh water. This is stored in the snowpak in the winter, in the spring when the snow melts; this is what municipalities, agriculture and industry use for drinking water, irrigation and manufacturing. What water that does not evaporates, transpires or seeps into the ground as aquifer recharge forms stream and rivers. This is called surface water runoff.  Some of this surface runoff infiltrates and percolates into the soil and becomes ground water flow.  Other snowmelt run-off becomes streams and rivers and this stream flow returns to the ocean. The radiant heat from the sun and reflecting heat exchanges from the Earth’s vegetation then supports a radiative exchange in which the vegetation grows and releases water that has been moisture in the soil feeding the plants and trees allowing for growth. Droughts arise from long periods of no or low rainfall and droughts are part of a natural cycle.[ii] The hydrological cycle is made up of vast amount of oceans, glaciers, rivers, wetlands, forests and grasslands, lakes and deep aquifers and of all this, only one hundred of 1% is both fresh water and renewed by the hydrological cycle.[iii] Each part of this cycle has ocean, earth, atmosphere scientists studying the effects of the cycle of water. The benefits of clean water on society are multiple that includes landscapes that provide freshwater ecosystems, floods that recharge ground water or provides water to fields that deliver nutrients to the soils and carry off harmful salts making it a vital area for agriculture. This exchange creates watersheds, bioregions and biological ecological systems upon which all life is reliant. From time and immemorial there have been droughts when climate patterns shifted and impacts on food, energy and lifestyles were experienced.  Sandra Postel has illustrated in several writings that many previous civilizations committed “self-inflicted ecological suicide”[iv] destroying the ecosystems that supported and sustained them. The ongoing climate change is a systemic disruption that requires a change in our behavior in order for it to adjust itself. To continue with our lifestyles, as we know it will increase intensity and the cause perpetual drought. The Earth is a living organism that is ridding itself of the cause of the systemic changes. Either we will act in time to head off irreversible climate change or we will live with the consequence of technology and the Industrial Revolution.  Human beings activities have affected the world’s water patterns and our small actions (microcosm) have had consequences on the macrocosm, our Earth. [v]

What is Global Warming?

The term Global Warming describes the observed and projected increase in globally averaged temperatures over time. Because the global climate is a dynamic system, global warming has occurred in the past and will occur in the future. Using surface station temperature measurements and satellite-based measurements, researchers have identified an increasing trend in the global average surface air temperatures. The Intergovernmental Panel on Climate Change has determined that this increase can be attributed to a combination of natural climate variations and human factors. One of the leading causes under investigation is the greenhouse effect of gasses in the atmosphere.

Figure 2 The Greenhouse effect

Credit: The Science of Climate Change, Working Group 1 of the 2nd Assessment Report of the Intergovernmental Panel on Climate Change, UNEP and WMO (United Nations Environment Programme, GRID-Arendal and http://www.climateark.org)

What is the Greenhouse Effect?

The Greenhouse Effect obtained its name from the behavior of a greenhouse. A greenhouse’s glass allows shortwave radiation to enter but then prohibits outgoing long-wave radiation from exiting, thus warming the air in the greenhouse. Although the behavior of the atmosphere is different from that of a greenhouse, the result is similar and thus the warming effect was termed the Greenhouse Effect. If it wasn’t for the natural greenhouse effect, almost all radiation would be returned to space and the average surface temperature would be around 0°C. Atmospheric gasses that cause this effect include water vapor (H2O), carbon dioxide (CO2) and methane (CH4). If the amount of these gasses in the atmosphere increases, then the greenhouse effect will be magnified and warmer global temperatures would result.

The evidence of human activities effect of climate change is overwhelming. In report for the U.S. Global Change Research Program, “Water: the Potential Consequence of Climate Variability and Change of the Water Resources of the United States,” that was supported by the U.S. Department of the Interior and the U.S Geological Survey raises a wide range of concerns from circulation models.

Among the noteworthy findings in this report: ‘Problems in increased rapid runoff especially with changes of precipitation in semi-arid and arid climates. The timing and the amount of (earlier) run-off will vary by amount of snowfall. This will result in a reduction of spring and summer runoff, increases in winter run-off and earlier peak run-off are all going to be common experiences. The report warns that the management and operating rules have not been adequately assessed to meet these changes. With increased precipitation the “Intergovernmental Panel on Climate Change (IPCC) concluded in 1996, that there will be adverse impact of drought” and “ there is more evidence nor that flooding is likely to become a larger problem in many temperate regions requiring adaptations not one to droughts and chronic water shortages, but also to floods and associated damages, raising concerns about dam and levee failure.” Threshold and non-linear events are likely to occur this includes a fall in lake levels that cuts off outflows or separates a lake into parts and increases in flood intensity that passes specific damage thresholds and exceedance of water quality limits. As sea levels rise it will adversely affect groundwater aquifers and freshwater coastal ecosystems.  There will be more sea saltwater groundwater intrusions in the future. Global and regional increases in air temperature and the associated increases of water temperature are likely to lead to adverse changes in water quality, even if there is an absence of changes in precipitation.  Lakes will have variable stress including changes in lake levels and salinity, temperature range fluctuations that will result in increase nutrient cycling and productivity.  This may lower dissolved oxygen and degraded water quality. There are and will be more affects on freshwater systems depending on the nature of the change and the scope of the intentional interventions by humans. Already there is a wide range of vegetation patterns, possible extinctions of fish species already close to their thermal limits, declining area of wetlands with reductions in waterfowl populations, concerns about stream health and major habitat loss.  The report indicates that there is little known about groundwater basins or for ground water recharge and how this will effect water quality. Some studies suggest that some regional groundwater storage volumes are very sensitive to even modest changes in available recharge. [vi]’The lack of knowledge due to funding collapse of observational field studies on ecosystems which has put the United States in a poor position on making recommendations as to solutions and policies on land, water resources and existing infrastructures.[vii]


[i] Inspired by Mary Austin

[ii] Peter Gleick USGS and Pacific Institute: “Water: The Consequences of Climate Variability and Change for the Water Resources of the United States.” September, 2000; Report of the Water Sector Assessment Team of the National Assessment of the Potential Consequences of Climate Variability and Change; Pacific Institute and the US Department of the Interior through the U.S. Geological Survey.  Hydrologic cycle USGS website http://pubs.usgs.gov/circ/circ1139/htdocs/natural_processes_of_ground.htm

[iii] Sandra Postel “Liquid Assets: A critical need to safeguard freshwater systems”

[iv] Sandra Postel Liquid assets: page 10-16

[v] Gleick et al. “The World’s Water 2006-2007 the Biennial Report on Freshwater Resources,” chap 4 Scarcity Island Press Ibid

[vi] Peter H. Gleick et al U.S. Global Change Research Program, “Water: the Potential Consequence of Climate Variability and Change of the Water Resources of the United States,” that was supported by the U.S. Department of the Interior and the U.S Geological Survey.

[vii] CCSP Report, Water Resources Chapter 4 pg 149

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