Climate Change and River Systems
As mentioned on the Climate Change tab, there are several impacts that can be clearly seen. Discussing these is useful because they are easy to observe and explain the importance and impact climate change has on us and our planet. And even better are the studies that show the global impacts, like NASA GISS, because it helps show the entire picture of what is occurring across the globe. However, Earth is very diverse and not every region reacts the same way or to the same extent as others. This is true for the impacts climate change has on river systems. This makes it harder to observe the changes occurring and often individual studies have to determine the impacts present. Nevertheless, a variety of general trends that have direct impacts on river systems can be seen. These include changes in evaporation rate, altered weather patterns, altered season patterns, and increases in water temperatures (Graham, Parkinson, & Chahine, 2012).
Altered Season Patterns
Along with the increased evaporation, increases in global temperature can alter the seasons. The warming trend lengthens summer and shortens the winters (Graham, Parkinson, & Chahine, 2012). This has several impacts on river systems; first longer growing seasons during the summer with higher temperatures means more irrigation is needed. This reduces flow rates in river systems further. Another impact on river systems is with a shorter winter there is less snow accumulation and earlier melts. This releases water to the systems earlier than it is needed, resulting in wetter springs and drier summers, which leads to more water withdrawals for irrigation and drinking water
As air temperatures increase so does water temperatures. This relationship has been observed and even studied due to the importance of water temperature to aquatic organisms (Mohseni, Stefan, & Erickson, 1998). For aquatic organisms a change of one degree Celsius can mean the difference between survival and death. A clear example of this is trout. Trout require cooler, clear water, and when the water becomes too warm they must either migrate to cooler regions or die (EPA, 2012). And as native species are forced out of habitats by climate change, it makes it easier for invasive species to take over entire regions of river systems (EPA, 2012). This causes a major turn over in the structure of the ecosystem and can even lead to its destruction.
EPA. (2012, April 2). Water: Climate Change and Water. Retrieved from Water Impacts of Climate Change: http://water.epa.gov/scitech/climatechange/Water-Impacts-of-Climate-Change.cfm
Graham, S., Parkinson, C., & Chahine, M. (2012, October 1). NASA Earth Observatory. Retrieved from The Water Cycle. http://earthobservatory.nasa.gov/Features/Water/page1.php
Mohseni, O., Stefan, H. G., & Erickson, T. R. (1998). A nonlinear regression model for weekly stream temperatures. Water Resources Research, 2685-2692.
Poff, L. N., Richter, B. D., Arthington, A. H., Bunn, S. E., Naiman, R. J., Kendy, E., . . . Warner, A. (2010, January). The ecological limits of hydrologic alteration (ELOHA): a new framework for developing regional environmental flow standards. Freshwater Biology, 55(1), 147-170.
Increased Evaporation and Altered Weather
With the planet warming, more energy is available to drive the process of the water cycle, this includes evaporation. Evaporation has a duel impact on river systems. First greater evaporation rates will remove water from river systems, altering the flow rates. Altering the flows rates of rivers has a major impact on the ecosystem; often aquatic organisms are able to survive harsh conditions so long as adequate water is available (Poff, et al., 2010). In addition, increased evaporation rates lead to altered weather patterns. So regions that are warmer will have more evaporation than cooler regions, leading to shifts in the distribution of water. Regions that are already dry to become drier and regions that are wetter receive more rain (Graham, Parkinson, & Chahine, 2012). This further alters the flows within river systems disrupting the aquatic ecosystems found there.