**4. Effects of climate change on water resources systems**

Climate change may impact the components on man-made water resources systems as well.

Deteoriation of reservoir water quality may cause operational problems related to equipment. Those problems are:


Increase of organic matter in raw water may increase energy and chemical consumption in water treatment systems. Possible problems are:

• Increased odour

268 Studies on Water Management Issues

Climate change may affect the ecological processes in lentic ecosystems which in turn will affect the water quality. Increase in average annual water temperature affects the primary

• Temperature changes will affect both; the photosynthesis and the respiration rates. Initially, increases in temperature will promote higher photosynthesis and respiration rates. However, for each group of primary producers, there is an optimum temperature range. If the water temperature exceeds the upper limit for optimum conditions, temperature stress will decrease photosynthesis rates and increase respiration rates. This mechanism will accelerate the nutrient recycle and making nutrients available for primary producers adapted to higher temperatures causing a shift in dominant phytoplankton group. More increase of temperature may completely suppress some phytoplankton groups and/or cause sudden breakdown of their blooms eventually

• Phytoplankton groups that can adapt to higher temperatures for example cyanobacteria will be favoured. Cyanobacteria that are generally better adapted to higher temperatures may dominate the algal community. Genera such as *Anabaena* and *Aphonizomenon* produce algal toxins, taste and odour problems. Some species of cyanobacteria are capable of nitrogen fixation and hence increase nitrogen in aquatic ecosystems through

• More days with suitable light conditions for algal blooms or longer photoperiods during a day may occur if the cloud cover changes due to the climate change. Those conditions may extend the vegetation period as well as earlier blooms may be possible. A large portion of the nutrient inputs to lotic ecosystems generally occur in late winter and early spring related to rain events and snowmelt. In this period although the nutrient concentrations increase in water, lower water temperatures limit phytoplankton growth. However, if the water temperatures increase, two factors needed for phytoplankton growth, more suitable temperature and high nutrient concentrations, will synergistically favour phytoplankton growth. If these conditions are followed by better light availability, phytoplankton blooms will be stronger and

Increase in water temperature will increase the biological activity in aquatic ecosystems, hence increase the oxygen demand. Ironically, higher temperature decreases the saturation concentration of dissolved oxygen in water as well. Combining these effects with accelerated primary production and more internal detritus loads as its conclusion, it is possible to foresee that oxygen scarcity, hypoxia or anoxia events may increase especially in deep lakes. These conditions cause stress for aquatic organisms increasing their mortality, which also means even more detritus. Those changes in internal dynamics of aquatic ecosystems are likely to decrease their capacity to assimilate external organic matter loads.

Climate change may impact the components on man-made water resources systems as well. Deteoriation of reservoir water quality may cause operational problems related to equipment.

**3.4 Deteoration of water quality in aquatic ecosystems** 

producers following ways:

internal loading.

Those problems are:

leading to decreased water quality.

more frequent and adversely affect the water quality.

**4. Effects of climate change on water resources systems** 


As stated previously, climate change is likely to increase the water demand that will increase water abstraction through the water distribution network. This situation increases the operational load on water distribution and may cause problems such as pressure drop in water distribution networks followed by urban water shortage risk and related problems listed below:

