Climate Change can be defined as any variations in climate patterns that last for a long period of time: decades or more. The prime cause of climate change is Greenhouse Gas (GHG) Emission, typically Carbon Dioxide (CO2) and Methane (CH4), mainly caused by burning fossil fuels for energy use. Now, Climate Change is threatening the Earth and its people.
Climate Change brings negative impacts on Earth's ecosystem, the livelihood and well-being of societies through the primary medium, WATER. Climate Change causes higher temperatures and changes in water cycle, weather patterns and climate conditions which affect availability and distribution of rainfall, snowmelt, river flows and groundwater and water quality deterioration which in turn brings impacts on almost all sectors; economy (health, food production and security), domestic water supply and sanitation, energy and industry, and environmental sustainability.
Global warming, one of the impacts of Climate Change, which is caused by higher average temperatures and temperature extremes, accelerates the global hydrological cycle. This brings changes in precipitation affecting water resources availability, to meet the needs of societies and ecosystems, through changes in form, frequency, intensity and distribution of precipitation, soil moisture, glacier- and ice/snowmelt, river and groundwater flows, and leading to further deterioration of water quality and decreasing available water quantity. Global warming also results in algal bloom, an increase in toxic cyanobacteria bloom in rivers and lakes causing decreased water quality and diminished biodiversity in them.
Climate change can cause increased intensity in precipitation which results in greater peak runoffs but less groundwater recharge. Receding glaciers, melting permafrost and changes in precipitation from snow to rain, due to higher average temperature, affect seasonal flows; lower minimum flows in rivers in dry season and impact on water availability for agriculture, drinking water supply, manufacturing and energy production, thermal plant cooling and navigation, increasing soil erosion and depriving the topsoil of nutrients (due to increased intensity in rainfall, melting glacial ice and large-scale deforestation) and loss of biodiversity and damage of ecosystem (due to changes in the proper functioning of ecosystems).
Sea level rise, caused by climate change, brings negative impacts on coastal aquifers which are a substantial water supply for many cities. It has serious effects on food production in major delta regions which are food bowls for their countries, loss in estuary productivity, changes in barrier islands, loss of wetland. It also causes severe impact on people living in coastal areas by increased vulnerability to coastal erosion, flooding, and sea water intrusion to their farmlands.
Extreme weather conditions, one of the causes of Climate Change, results in an increase of water-related hazards. More and more people are being exposed to increased flooding, cyclones, and droughts. The major floods cause many deaths and cost billions of dollars in damages. The Intergovernmental Panel on Climate Change (IPCC) has forecasted that there is a 90 percent probability that the extent of drought-affected areas will increase due to higher temperatures and decreased precipitation, linking to demographic pressure.
Climate Change impacts both rain fed and irrigated agriculture, feed, and fodder for livestock. It will alter the distribution of agriculture across the globe because more frequent and severe droughts and floods will hurt subsistence agriculture in the semi-arid zones in low latitudes. It in turn brings worsen living conditions for people, depending on agriculture for their livelihood, who may face risk of crop failure or loss of livestock and fertile topsoil due to greater erosion in these areas, depending on their livelihood.
Climate Change also brings negative effects on human health through water-related impacts. Changes in the composition of aquatic ecosystems cause reduced nutrition and access to safe water for human consumption and personal hygiene, water-related vector-borne diseases due to opportunistic invaders such as cyanobacteria in lakes and reservoirs. Groundwater resources for drinking water supply can be contaminated by extreme rainfall and floods. Climate Change also reduces the benefits of obtaining clean water supply, and fisheries and coastal defences by destroying ecosystems which in turn increases impacts on vulnerability of communities.
Climate Change also causes water-related hazards: too much water (causing floods, erosion, landslides mudslides, and the like, in land-degraded areas) or too little water (causing droughts, forest fires, loss of wetlands or other habitats, saline encroachment, and the like) and from the effects of chemical and biological pollution on water quality and in-stream ecosystems.
The same Climate Change impacts on water-related sectors go for the Mekong Delta region, is the home of 20 million people in southwestern Vietnam and crucial to the country's agricultural and aquaculture production. Since 2005, the Delta's total land mass has been decreasing annually. The region also encounters more severe floods, a growing risk of drought due to decreasing rainfall and abnormal weather patterns. Agricultural production in the region is affected by changes in the Mekong River flow. A changing ecosystem along with pollution is affecting the livelihoods of the Mekong Delta population, especially in the coastal areas. Climate change increases the occurrence of large storms and inundation in the upstream provinces of the Mekong Delta in the wet season due to impact on rainfall distribution. Climate change reduces the water volume flowing from the mainstream of the Mekong River to the Delta, leading to a lack of fresh water by prolonging the dry season. Moreover, salt intrusion into the main rivers and canals affects freshwater agriculture and fisheries as well as domestic water supply in coastal provinces. In addition, changes in temperature increase diseases and environmental pollution, which directly affects the health of people and aquaculture.In conclusion, Climate Change causes worsening food security and malnutrition, increased energy shortages, spread of diseases, humanitarian emergencies, growing migration, increased risk of conflict over scarce land and water, and escalating ecosystem degradation through WATER. Innovative strategies, national-level guidelines and policies are required for Climate Change Adaptation and Mitigation through Water Resources Management.