Effects of Climate change on water resources
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Climate change will impact water resources in several ways: 1) Precipitation patterns will change and become more variable, increasing in some areas and decreasing in others, affecting water availability. 2) Rising global temperatures will cause more evaporation and affect factors like snowpack and glacial melt, altering hydrologic cycles. 3) These changes will strain water supplies, increasing risks of flooding, drought, and conflicts over scarce resources while placing stress on ecosystems and human communities. Improved management is needed to enhance resilience to such vulnerabilities.
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Effects of Climate change on water resources
- 1. Effects of Climate Change on Water Resources. 1
- 2. Objectives… By the end of the lesson, the learner should be able to; Explain the impacts of climate change on water resources in any region. Discuss the Impacts climate change on hydrology and water resources? Demonstrate the relationship between Water and Climate Change. 2
- 3. Situation now.. Global Water Crisis Over 1 billion people don't have access to clean drinking water; more than 2 billion lack access to adequate sanitation; and millions die every year due to preventable water-related diseases. 5 million people – mainly children – die every year from preventable, water-related disease is surely one of the great tragedies of our time. 3
- 4. Water and Climate Change Climate change will lead to more precipitation - but also to more evaporation Precipitation will probably increase in some areas and decline in others. Changing precipitation patterns will affect how much water can be captured. The drier the climate, the more sensitive is the local hydrology. High-latitude regions may see more runoff due to greater precipitation. The effects on the tropics are harder to predict. 4
- 5. Reservoirs and wells would be affected. New patterns of runoff and evaporation will also affect natural ecosystems. Rising seas could invade coastal freshwater supplies. Reduced water supplies would place additional stress on people, agriculture, and the environment. Conflicts could be sparked by the additional pressures. Improved water resource management can help to reduce vulnerabilities. 5
- 6. Drivers of change 6 Populatio n demand for water River flows ; groundwater quality Wealth; equity access
- 7. Measures of stress • Indicators of exposure • Numbers affected by flood / drought • Indicators of access • Numbers with access to safe water • Indicators of availability • Resources per capital 7
- 8. What to look for specifically? Precipitation amount Precipitation frequency and intensity Evaporation and transpiration Changes in average annual runoff Natural variability Snowpack Coastal zones Water quality Water storage Water demand 8
- 9. IPCC: Impacts on hydrology and water impacts (2001) • Variation in streamflow and groundwater recharge regionally and between scenarios • Early snowmelt – therefore… • Degraded water quality • Increase in flood magnitude and frequency • Increased demand for water (population. growth & economic development) globally • High vulnerability in unmanaged systems 9
- 10. • Non-climatic drivers… • Current vulnerabilities correlated with climatic variability • Particularly: precipitation variability • Particularly where? 10
- 11. Surface waters and runoff generation Changes in river flows, lake and wetland levels depend on (climatic factors): Changes in volume, timing and precipitation intensity Changes in temperature, radiation, atmospheric humidity, and wind speed: Potential evapotranspiration offset small increases in precipitation further effect of decreased precipitation on surface waters Increased atmospheric carbon dioxide [ ] Alters plant physiology affecting evapotranspiration Lake size Decreased – due to human water use + climatic factors (Lake Chad) 11
- 12. Groundwater • Respond slower than surface water systems • Correlate more strongly water precipitation than water temperature • Temperature more important for shallow aquifers • Temperature more important in warm periods 12
- 13. Floods and droughts • Climate may already have had an impact on floods • Droughts affect: • Rain-fed agriculture production • Water supply for: • Domestic • Industrial • Agricultural purposes 13
- 14. Other impacts • Climate change is killing world forests. Eg. Congo basin, Amazon forest… • With an increased rates at an average of 3% yearly. 14
- 15. Water quality Lakes and reservoirs: climate change effects primarily due to water temperature variations. (climate change or thermal pollution) Leads to diseases – via drinking water or via consuming crops irrigated with polluted water ¼ of global pop lives in coastal regions: water-scarce + rapid pop growth Leads to sea-level rise, increased saline intrusion, and reduction in freshwater availability 15
- 16. DISCUSSION •What are the impacts of climate change on water resources in any region? •Discuss the Impacts climate change on hydrology and water resources? •What is the relationship between Water and Climate Change? 16
Editor's Notes
- Climate change will lead to more precipitation - but also to more evaporation. In general, this acceleration of the hydrological cycle will result in a wetter world. The question is, how much of this wetness will end up where it is needed? Precipitation will probably increase in some areas and decline in others. Climate models are still unable to make precise regional predictions. In addition, the hydrological cycle is extremely complex: a change in precipitation may affect surface wetness, reflectivity, and vegetation, which then affect evapo-transpiration and cloud formation, which in turn affect precipitation. Meanwhile, the hydrological system is also responding to other human activities such as deforestation, urbanization, and the over-use of water supplies. Changing precipitation patterns will affect how much water can be captured. Several models suggest that downpours will become more intense. This would increase floods and runoff while reducing the ability of water to infiltrate the soil. Changes in seasonal patterns may affect the regional distribution of both ground and surface water supplies. The drier the climate, the more sensitive is the local hydrology. Relatively small changes in temperature and precipitation could cause relatively large changes in runoff. Arid and semi-arid regions will therefore be particularly sensitive to reduced rainfall and to increased evaporation and plant transpiration. High-latitude regions may see more runoff due to greater precipitation. Runoff would also be affected by a reduction in snowfall, deep snow, and glacier ice, particularly in the spring and summertime when it is traditionally used for hydroelectricity and agriculture. All climate change models show increased wintertime soil moisture in the high northern latitudes, with a reduction of moisture in some areas. Most models produce less soil moisture in summer in northern mid latitudes, including some important grain producing areas; these projections are more consistent for Europe than for North America. The effects on the tropics are harder to predict. Different climate models produce different results for the future intensity and distribution of tropical rainfall. Reservoirs and wells would be affected. Changes at the surface would influence the recharging of groundwater supplies and, in the longer term, aquifers. Water quality may also respond to changes in the amount and timing of precipitation. New patterns of runoff and evaporation will also affect natural ecosystems. Freshwater ecosystems will respond to altered flood regimes and water levels. Changes in water temperatures and in the thermal structure of fresh waters could affect the survival and growth of certain organisms, and the diversity and productivity of ecosystems. Changes in runoff, groundwater flows, and precipitation directly over lakes and streams would affect nutrients and dissolved organic oxygen, and therefore the quality and clarity of the water. Rising seas could invade coastal freshwater supplies. Coastal aquifers may be damaged by saline intrusion as salty groundwater rises. The movement of the salt-front up estuaries would affect freshwater pumping plants upriver. Reduced water supplies would place additional stress on people, agriculture, and the environment. Regional water supplies, particularly in developing countries, will come under many stresses in the 21st century. Climate change will exacerbate the stresses caused by pollution and by growing populations and economies. The most vulnerable regions are arid and semi-arid areas, some low-lying coasts, deltas, and small islands. Conflicts could be sparked by the additional pressures. The links among climate change, water availability, food production, population growth, and economic growth are many and complex. But climate change is likely to add to economic and political tensions, particularly in regions that already have scarce water resources. A number of important water systems are shared by two or more nations, and in several cases there have already been international conflicts. Improved water resource management can help to reduce vulnerabilities. New supplies must be developed and existing supplies used more efficiently. Long-term management strategies should include: regulations and technologies for directly controlling land and water use, incentives and taxes for indirectly affecting behavior, the construction of new reservoirs and pipelines to boost supplies, and improvements in water-management operations and institutions. Other adaptation measures can include removing levees to maintain flood plains, protecting waterside vegetation, restoring river channels to their natural form, and reducing water pollution.
- Disaster losses, mostly weather- and water-related, have grown much more rapidly than population or economic growth, suggesting a negative impact of climate change (Mills, 2005). However, there is no clear evidence for a climate-related trend in floods during the last decades (Table 3.1; Kundzewicz et al., 2005; Schiermeier, 2006). However, the observed increase in precipitation intensity (Table 3.1) and other observed climate changes, e.g., an increase in westerly weather patterns during winter over Europe, leading to very rainy low-pressure systems that often trigger floods (Kron and Bertz, 2007), indicate that climate might already have had an impact on floods. Globally,
- n the Sierra Nevada mountains of California, climate change is subtly eroding the health of pine and fir trees. The effect could be a portent of severe tree die-offs to come. Ecologists have been tracking the fate of more than 21,000 individual trees since 1983 as part of a project to study forest ecology at different elevations in the Californian mountains. When Phillip van Mantgem and Nathan Stephenson of the US Geological Survey in Three Rivers, California, looked at the first 22 years of this record, they noticed that mortality rates of both pine and fir trees had increased at an average of 3% a year, nearly doubling overall (Ecology Letters, DOI: 10.1111/j.1461-0248.2007.01080.x). The increased death rates were seen at all but the highest elevations. Meanwhile, the rate at which new trees established did not change.
- Increasing water temperature affects the self-purification capacity of rivers by reducing the amount of oxygen that can be dissolved and used for biodegradation.Atrend has been detected in water temperature in the Fraser River in British Columbia, Canada, for longer river sections reaching a temperature over 20°C, which is considered the threshold beyond which salmon habitats are degraded (Morrison et al., 2002). Furthermore, increases in intense rainfall result inmore nutrients, pathogens, and toxins being washed into water bodies. Chang et al. (2001) reported increased nitrogen loads from rivers of up to 50% in the Chesapeake and Delaware Bay regions due to enhanced precipitation Numerous diseases linked to climate variations can be transmitted via water, either by drinking it or by consuming crops irrigated with polluted water (Chapter 8, Section 8.2.5). The presence of pathogens in water supplies has been related to extreme rainfall events In the USA, 20 to 40% of water-borne disease outbreaks can be related to extreme precipitation (Rose et al., 2000). Effects of dry periods on water quality have not been adequately studied (Takahashi et al., 2001), although lower water availability clearly reduces dilution. Water quality problems and their effects are different in type and magnitude in developed and developing countries, particularly those stemming from microbial and pathogen content (Lipp et al., 2001; Jiménez, 2003). In developed countries, flood-related water-borne diseases are usually contained by well-maintained water and sanitation services (McMichael et al., 2003) but this does not apply in developing countries (Wisner and Adams, 2002). Regretfully, with the exception of cholera and salmonella, studies of the relationship between climate change and micro-organism content in water and wastewater do not focus on pathogens of interest in developing countries, such as specific protozoa or parasitic worms (Yarze and Chase, 2000; Rose et al., 2000; Fayer et al., 2002; Cox et al., 2003; Scott et al., 2004). One-third of urban water supplies in Africa, Latin America and the Caribbean, and more than half in Asia, are operating intermittently during periods of drought (WHO/UNICEF, 2000). This adversely affects water quality in the supply system.