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The Effects of Climate Change on Rivers Joe Dykema, Nolan Kriegel, Auburn Jimenez, Chase Kahn, and Jake Johnson Macalester College – St. Paul, MN Introduction Climate change is redefining earth’s natural landscape by altering air and water temperature, runoff of water, biodiversity, changes in precipitation. All of these factors play a role in how rivers will be affected by climate change. Streams will be affected differently by where they are located and what their surrounding climate already is. With temperatures expected to rise 1-8 degrees Celsius by 2050, climate change will cause a varied amount of effects on rivers. Species Diversity Ganges River • With the increase of temperature, species diversity will decrease as cold water species are outcompeted by better adapted warm water species. • Optimum habitat for most species in temperate rivers will shift northward toward colder waters. • This leads to disruption in food webs and upsets the balance of the ecosystem. • Earlier peak discharge levels resulting from increased winter precipitation, disrupts natural reproductive cycles. • Species with high flow and flood tolerance may out-compete others that could previously exist prior to climate change. Two top fish predators in the St. Croix are the Smallmouth bass and the Northern pike, both these fish influence warmer waters on the way, the Smallmouth bass who favors warmer water may be able to out compete the Northern pike that prefers cooler waters. The Ganges River is primarily fed from the Himalayan glaciers which are predicted to be entirely melted by 2035, reduced river flow will depress the dissolved oxygen content and create an anoxic environment reducing fish and macroinvertebrate species. St. Croix River http://www.travelphoto.net/a-photo-aday/wordpress/2005/04/23/ganges-riverbefore-sunrise/ Economics With a change in biodiversity, many rivers may lose some of their economic value. . With climate change affecting temperatures all over the world, states could face less income generated by fewer cold water species. In the state of Colorado, 800 million dollars are generated by sport fishing and employ over 11,000 jobs. Most of this money is generated by the cold water species the trout. -Describes increasing temperatures in the last half of the 20th century http://www.processtrends.com/pg_global_warmin g.htm Air/Water Temperature Rising air temperatures are correlated to the increase in CO2 in the atmosphere, which are predicted to raise water temperatures 3-4 degrees Celsius in the next 50 years. Atmospheric CO2 has spiked nearly 100 ppm since the 1800s from the beginning of the Industrial Revolution due in large part to the burning of fossil fuels. Increasing air temperatures are correlated to rising water temperatures and have begun to force snow-melt earlier in the year in the St. Croix River. Increasing water temperatures affect freshwater species more than marine species due to smaller bodies of water. The Ganges River dolphin have increased mortality rate due to warmer water temperatures. Increasing temperatures also alter stream metabolism, nutrient cycling and dissolved oxygen concentrations http://www.rivers.gov/wsr-st-croixlower.html Precipitation/Runoff The warmer temperatures speed up the precipitation cycle. Overland precipitation increases in temperate climates and decreases in semi-arid regions. Rivers in the North will receive more precipitation in the winter due to warmer temperatures. This will cause even more runoff and carry away even more soil from areas that could already have a topsoil deficiency. Heavier runoff and snow-melt will alter the structure of the river by limiting how much sunlight can reach the bottom due to more water laden with sand. Heavier runoff causes chemicals like Nitrogen and Phosphorus to enter the river systems. These chemicals could enter the St. Croix from surrounding agricultural plots and increase productivity to unhealthy levels. Rainfall over the Ganges River has increased dramatically and is expected to go up about 3-7 times in the next couple decades which will lead to more frequent and catastrophic floods. The Ganges River has widened in many places since 1975 due to increased erosion, which has also decreased water clarity and amplified a reduction in river productivity http://www.dnr.state.mn.us/climate/waterlevels/streams/stcr oix.html Sources Ghosh, S. K., and A. G. Ponniah. "Fresh Water Fish Habitat Science and Management in India." Aquatic Ecosystem Health & Management 4.4 (2001) Pilgrim, Fang and Stefan "Stream temperature correlations with air temperatures in Minnesota: implications for climate warming" (1998) http://www.cms.int/publications/pdf/climate_change_leaflet_cms_zsl.pdf Kaushal "Rising stream and river temperatures in the United States" (2010) Mondal, M. Shahjahan, and Saleh A. Wasimi. "Evaluation of Risk-Related Performance in Water Management for the Ganges Delta of Bangladesh." Journal of Water Resources Planning & Management 133.2 (2007)