WEPA Outlook on Water Environmental Management in Asia 2012

Chapter 2.2Climate Change and the Water EnvironmentSummary of findings based on <strong>WEPA</strong> discussions and surveys1. BackgroundClimate change is one of the drivers of change in waterresources and poses challenges to existing watermanagement practices (Connor 2009). Climate changecan affect the water environment in complex ways (Figure2.2.1). Various direct and indirect impacts of climatechange to the water environment are expected, which willoccur in association with other socio-economic factors.The Working Group II of the Intergovernmental Panelfor Climate Change (IPCC) concluded that “higher watertemperatures, increased precipitation intensity, and longerperiods of low flows exacerbate many forms of waterpollution, with impacts on ecosystems, human health,water system reliability and operating costs (highconfidence)” (Kundzewicz et al. 2007). The impacts ofhuman induced climate change include higher watertemperatures that affect the self purification capacities ofwater bodies by reducing the amount of dissolved oxygen(DO), which consequently disrupts indigenous aquaticbiological species. In addition to direct impacts on watertemperature, the potential increase of water use in theenergy sector for cooling purposes is also considered to bean indirect cause of higher water temperatures (Kunazewiczet al. 2007). An increase in water temperatures may resultin an oxygen-deficient environment in lakes by increase inthermal stability and altered mixing patterns (Bates et al.2008).In addition to water temperature, changes inprecipitation patterns, intensity and duration also affectwater quality. Intense rainfall over short periods increasesthe amount of suspended solids, sediment, nutrients andother toxins in water bodies due to run-off. In addition,unreliable supplies of surface water caused by changes inprecipitation patterns may increase dependency ongroundwater for potable use, resulting in overexploitationof the groundwater resource, as well as increased risks tohuman health from arsenic and fluorine where they exist ingroundwater. The rising of sea water levels due to climatechange is another threat, resulting in salt water intrusion tosurface and underground freshwater systems, consequentlycausing deterioration in water quality. The impact onhuman health and water quality due to flooding of pollutedwater is also identified as a potential risk. Combined withexcessive water exploitation, problems from salt waterintrusion would be more intensified in coastal cities.Increase of wastewater due to increased demand caused byatmospheric temperature rise such as in the irrigationsector, which may provide negative impacts to waterquality. These potential adverse impacts to water qualitymay aggravate water scarcity in the region.Aquatic ecosystems are also affected by higheratmospheric and water temperatures, the changes inprecipitation and sea level rise. A warmer climate mayincrease threats to wetlands, which are one of the importanthabitats of many species. Increases in water temperaturemay favor exotic aquatic species rather than indigenousspecies. Once ecosystems are destroyed, they cannot berecovered or require tremendous time and effort to restore.Considering that climate change may render greatimpacts on the water environment in a variety of ways, andalso recognizing that the Asia-Pacific region has alreadyobserved events that are presumed to be caused by climatechange, <strong>WEPA</strong> decided to initiate information exchangeand discussions on “climate change and the waterenvironment and possible adaptation options” as one of itspriority topics in the second phase activities that started in2009.<strong>WEPA</strong> found that information on the potentialimpacts of climate change on the water environments(water quality and aquatic ecosystems) is not sufficient tofacilitate discussion among partners. Therefore <strong>WEPA</strong>activities for this topic concentrated on information andknowledge-sharing through <strong>WEPA</strong> workshops, reinforcedby literature reviews and fact-finding and perceptionsurveys. This chapter summarizes these <strong>WEPA</strong> activities inthe Japanese fiscal years 2009 to 2011 and outlines futureactions for <strong>WEPA</strong> on this topic.2. Impact of Climate Change on WaterQuality and Aquatic Ecosystems in <strong>WEPA</strong>Countries<strong>WEPA</strong> partner countries demonstrate examples of changesin the water environment that are suspected to result fromor be escalated by climate change. Figure 2.2.2 shows suchexamples from relevant literature and news articles. Acomparative study conducted in East and Southeast Asiabetween 2007 and 2008 shows that changes in precipitationvolume and patterns can affect surface water quality in East42