rising concentrations of components due to evaporation (Mayer et al. 2010; Mosley
et al. 2012; Burt et al. 2014).
Although the IPCC fourth assessment reports that an increase in average temperatures of several degrees as a result of climate change will lead to an increase in
average global precipitation over the course of the twenty-first century, this amount
does not necessarily relate to an increase in the amount of drinking water available.
A decline in water quality can result from the increase in runoff and precipitation.
While the water will carry higher levels of nutrients, it will also contain more
pathogens and pollutants. These contaminants were originally stored in soils and in
some groundwater reservoirs but the increase in precipitation will flush them out in
the river (IPCC 2007).
Similarly, when drought conditions persist and groundwater reserves are
depleted, the residual water that remains is often of inferior quality. This is a result
of the leakage of saline or contaminated water from the land surface, the confining
layers, or the adjacent water bodies that have highly concentrated quantities of
contaminants. This occurs because decreased precipitation and runoff results in a
concentration of pollution in the water, which leads to an increased load of
microbes in waterways and drinking water reservoirs (IPCC 2007).
Water quantity and water quality are thus intrinsically related either in the case
of single or multipurpose reservoirs. Their dynamics can be complex, with implications on reservoir operation and control. In the case of the freshwater reservoir of
the Vilaine catchment in Brittany, France (Chap. 6), the operation of the locks of
the Arzal dam, an estuarine dam in the Atlantic Ocean, is one of the main aspects
that influence the quality of the water in the reservoir. The increase in salinity is
aggravated by the salt intrusions from the estuary through the opening/closing of
the boat lock of the Arzal Dam. The water quality upstream the Arzal Dam is
essential to the Drezet-Férel water plant, which provides more than 15 million m
3 of
clean drinking water per year to the surrounding population. Salt intrusion deteriorates water quality and provokes the use of siphons that pump water out of the
reservoir, back to the ocean. Freshwater is often lost, unavailable for drinking water
supply. Integrated quality–quantity management is crucial, notably during summer,
as this is the period with highest water consumption, increased number of lock
openings for touristic boats, but also the low flow period of the Vilaine River,
which is the main inflow of surface water to the reservoir.
In the case of the freshwater reservoir in Eifel-Rur managed by the WVER water
board, Germany (Chap. 4), it is mainly the increase in water temperature during
drought and low flow periods that can be a serious constraint for drinking water
supply. Water must be less than 10 °C to comply with the strict requirements of the
German Drinking Water Ordinance. Drinking water regulation limits can be
exceeded for a period of 30 days, but only under certain critical conditions. Warmer
temperatures not only increase the rate of evaporation of water from the surface of
the reservoir into the atmosphere (loss of water quantity), but may also affect water
quality, interacting with the amount of organic material in the water, the concentration of pollutants. When the water is warmer, its ability to hold oxygen decreases.
The health of a water body is dependent upon its ability to effectively self-purify
11 Cross-cutting Perspective Freshwater
219
et al. 2012; Burt et al. 2014).
Although the IPCC fourth assessment reports that an increase in average temperatures of several degrees as a result of climate change will lead to an increase in
average global precipitation over the course of the twenty-first century, this amount
does not necessarily relate to an increase in the amount of drinking water available.
A decline in water quality can result from the increase in runoff and precipitation.
While the water will carry higher levels of nutrients, it will also contain more
pathogens and pollutants. These contaminants were originally stored in soils and in
some groundwater reservoirs but the increase in precipitation will flush them out in
the river (IPCC 2007).
Similarly, when drought conditions persist and groundwater reserves are
depleted, the residual water that remains is often of inferior quality. This is a result
of the leakage of saline or contaminated water from the land surface, the confining
layers, or the adjacent water bodies that have highly concentrated quantities of
contaminants. This occurs because decreased precipitation and runoff results in a
concentration of pollution in the water, which leads to an increased load of
microbes in waterways and drinking water reservoirs (IPCC 2007).
Water quantity and water quality are thus intrinsically related either in the case
of single or multipurpose reservoirs. Their dynamics can be complex, with implications on reservoir operation and control. In the case of the freshwater reservoir of
the Vilaine catchment in Brittany, France (Chap. 6), the operation of the locks of
the Arzal dam, an estuarine dam in the Atlantic Ocean, is one of the main aspects
that influence the quality of the water in the reservoir. The increase in salinity is
aggravated by the salt intrusions from the estuary through the opening/closing of
the boat lock of the Arzal Dam. The water quality upstream the Arzal Dam is
essential to the Drezet-Férel water plant, which provides more than 15 million m
3 of
clean drinking water per year to the surrounding population. Salt intrusion deteriorates water quality and provokes the use of siphons that pump water out of the
reservoir, back to the ocean. Freshwater is often lost, unavailable for drinking water
supply. Integrated quality–quantity management is crucial, notably during summer,
as this is the period with highest water consumption, increased number of lock
openings for touristic boats, but also the low flow period of the Vilaine River,
which is the main inflow of surface water to the reservoir.
In the case of the freshwater reservoir in Eifel-Rur managed by the WVER water
board, Germany (Chap. 4), it is mainly the increase in water temperature during
drought and low flow periods that can be a serious constraint for drinking water
supply. Water must be less than 10 °C to comply with the strict requirements of the
German Drinking Water Ordinance. Drinking water regulation limits can be
exceeded for a period of 30 days, but only under certain critical conditions. Warmer
temperatures not only increase the rate of evaporation of water from the surface of
the reservoir into the atmosphere (loss of water quantity), but may also affect water
quality, interacting with the amount of organic material in the water, the concentration of pollutants. When the water is warmer, its ability to hold oxygen decreases.
The health of a water body is dependent upon its ability to effectively self-purify
11 Cross-cutting Perspective Freshwater
219