In eastern Canada, the air temperature is expected to increase by 2˚C to 6˚C in the next 100 years [4]. Such an increase will greatly affect stream water temperatures. Higher water temperatures and changes in extreme preci- pitation events are projected to affect water quality from sediments, nutrients, dissolved organic carbon, patho- gens, pesticides and salt, with possible negative impacts on ecosystems, human health, and water system relia- bility and operating costs [5]. Many studies have looked at the impact of climate change on river water temper- atures [6]. However, the impact of climate change is difficult to predict due to a lack of long-term water temper- ature data [7]. Climate change was shown to affect water quality, potentially violating the Safe Drinking Water Act regulations [8]. Many studies have shown a decline in stream water quality under a climate change scenario [9]-[12], but very few have focused on the impact of drinking water quality. Expected impacts of climate change are flow reduction that will lower water levels in rivers and lakes, as well as an increase in water demand and higher temperatures [13]. The main impacts of the consequence of rising temperatures and heavy rainfalls would be the rise in concentration of dissolved organic matter, pollutants and pathogens [14]. Water quantity changes due to climate change have been identified as a water quality related threat to sources of drinking water [15]. In Canada, 288 outbreaks of infectious disease were linked to a drinking water source between 1974 and 2001 [16]. Flow variability was found to deteriorate water quality in general [17]-[20]. A reduction in water flow is ex- pected to increase water pollutant concentration, resulting from a lower dilution capacity, whereas an increase in water flow will increase the transport of diverse compounds from soil to water resources trough fluvial erosion [5]. Kundzewick and Krysanova [21] have presented some key consequences of declining water quality due to climate change. They cited the increase of water withdrawals from low-quantity sources. They also noted the risk of occurrence of water infrastructure malfunction, overloading the capacity of water and wastewater treat- ment plants, and greater pollutant loads from diffuse sources during extreme rainfall. An increase in waterborne disease is also expected due to insufficient supply of potable water and higher turbidity, nutrients loads, and pa- thogens transport into water supply [22] [23]. In regions where water availability is likely to decrease, water managers will need to ensure adequate water supplies, such as building new storage reservoirs or using alterna- tive water sources [24]. Low water availability could lead to groundwater over-exploitation, creating the need to pump water from deeper sources at higher costs [5].
As river temperature will increase in the future, water quality index is also expected to change under climate Change and these changes need to be quantified. The Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) as well as the Weighted Water Quality Index could be used in Canada. As such, the present paper will focus on water quality indices in New Brunswick (Canada) applied to drinking water quality and how such indices many be affected by climate change.