303
Where total precipitation drops,
this will intensify competition among agriculture, ecosystems, settlements, industry, and
energy production, affecting regional water, energy, and food security (limited evidence,
medium to high agreement).
Three types of droughts should be recognized, each describing a significant and
sustained drop in the presence of water:
1. Meteorological drought referring to precipitation.
2. Hydrological drought referring to streams, lakes, reservoirs, and groundwater.
3. Agricultural drought referring to soil moisture.
The relationship between the three is strong but complex.
Precipitation and water flows are strongly influenced by local features such as
topography and land cover. Therefore, while it is possible to speak with high confidence about changes in precipitation averages over large areas, it is much more
difficult to speak about precise changes in specific locations.
In addition to impacts of climate change on freshwater systems, there are also
impacts on marine (saltwater) systems. The most significant are sea level rise and
changes to marine ecosystems, including fisheries.
Effective responses to water use challenges, be they rooted in natural variations
in the water cycle, or the impacts climate change are often rooted in Integrated
Water Resource Management, which coordinates different water uses with other
factors like food and energy systems, ecosystems, and socioeconomic goals.
11.4.1.2 Climate Change Impacts on Water for Human Consumption
Climate change will have an array of impacts on human consumption of water;
impacts that will depend significantly on local and regional geography, including:
• ‘Higher ambient temperatures, which reduce snow and ice volumes and increase the
evaporation rate from lakes, reservoirs, and aquifers. These changes decrease natural
storage of water, and hence, unless precipitation increases, its availability. Moreover,
higher ambient temperatures increase water demand, and with it the competition for the
resource (medium to high agreement, limited evidence).
• Shifts in the timing of river flows and possible more frequent or intense droughts, which
increase the need for artificial water storage.
• Higher water temperatures, which encourage algal blooms and increase risks from cyanotoxins and natural organic matter in water sources, requiring additional or new treatment of drinking water (high agreement, medium evidence). On the positive side,
biological water and wastewater treatment are more efficient when the water is warmer.
• Possibly drier conditions, which increase pollutant concentrations. This is a concern
especially for groundwater sources that are already of low quality, even when pollution
is natural as in India and Bangladesh, North and Latin America and Africa; here arsenic,
iron, manganese, and fluorides are often a problem.
• Increased storm runoff, which increases loads of pathogens, nutrients, and suspended
sediment.
• Sea level rise, which increases the salinity of coastal aquifers, in particular where
groundwater recharge is also expected to decrease.”
11 Climate Change
Where total precipitation drops,
this will intensify competition among agriculture, ecosystems, settlements, industry, and
energy production, affecting regional water, energy, and food security (limited evidence,
medium to high agreement).
Three types of droughts should be recognized, each describing a significant and
sustained drop in the presence of water:
1. Meteorological drought referring to precipitation.
2. Hydrological drought referring to streams, lakes, reservoirs, and groundwater.
3. Agricultural drought referring to soil moisture.
The relationship between the three is strong but complex.
Precipitation and water flows are strongly influenced by local features such as
topography and land cover. Therefore, while it is possible to speak with high confidence about changes in precipitation averages over large areas, it is much more
difficult to speak about precise changes in specific locations.
In addition to impacts of climate change on freshwater systems, there are also
impacts on marine (saltwater) systems. The most significant are sea level rise and
changes to marine ecosystems, including fisheries.
Effective responses to water use challenges, be they rooted in natural variations
in the water cycle, or the impacts climate change are often rooted in Integrated
Water Resource Management, which coordinates different water uses with other
factors like food and energy systems, ecosystems, and socioeconomic goals.
11.4.1.2 Climate Change Impacts on Water for Human Consumption
Climate change will have an array of impacts on human consumption of water;
impacts that will depend significantly on local and regional geography, including:
• ‘Higher ambient temperatures, which reduce snow and ice volumes and increase the
evaporation rate from lakes, reservoirs, and aquifers. These changes decrease natural
storage of water, and hence, unless precipitation increases, its availability. Moreover,
higher ambient temperatures increase water demand, and with it the competition for the
resource (medium to high agreement, limited evidence).
• Shifts in the timing of river flows and possible more frequent or intense droughts, which
increase the need for artificial water storage.
• Higher water temperatures, which encourage algal blooms and increase risks from cyanotoxins and natural organic matter in water sources, requiring additional or new treatment of drinking water (high agreement, medium evidence). On the positive side,
biological water and wastewater treatment are more efficient when the water is warmer.
• Possibly drier conditions, which increase pollutant concentrations. This is a concern
especially for groundwater sources that are already of low quality, even when pollution
is natural as in India and Bangladesh, North and Latin America and Africa; here arsenic,
iron, manganese, and fluorides are often a problem.
• Increased storm runoff, which increases loads of pathogens, nutrients, and suspended
sediment.
• Sea level rise, which increases the salinity of coastal aquifers, in particular where
groundwater recharge is also expected to decrease.”
11 Climate Change