The impact of climate change on water storage options
Climate change will increase rainfall variability and average temperatures, affecting both the supply and demand side of the irrigation equation. In some areas of the world, annual precipitation will decline, decreasing river flows and groundwater recharge. In other places, total precipitation may increase but it will fall over shorter periods with greater intensity so that dry spells are longer. Higher temperatures will increase evaporation so that crops will use more water. Although the effects will vary from place to place, farmers will generally need to adapt to less soil moisture and higher evaporation. This means larger volumes and more frequent use of supplemental water.
All storage options are potentially vulnerable to the impacts of climate change. For example, less rainfall and longer dry periods mean that conservation measures for soil water may fail to increase soil moisture sufficiently for crops. Groundwater recharge may be reduced if infiltration decreases. Many near-coast aquifers will be at risk from saltwater intrusion as a result of sea-level rise. Ponds, tanks and reservoirs may not fill enough to support agriculture, or may be at risk of damage from more extreme floods. Larger, more intense floods could also cause catastrophic failures of large dams.
The externalities created by different storage types are also likely to be affected by climate change. Forexample, water-storage tanks, ponds and reservoirs create breeding grounds for mosquitoes and can lead to increases in malaria and other waterborne diseases. The higher temperatures expected with climate change may worsen the situation. Similarly, adverse environmental impacts, arising from changes in the flow regimes of rivers, may be exacerbated by climate change. Factors such as these must be considered in the future planning, design, and operation of water-storage schemes.
The role of water storage in climate change adaptation
With increased uncertainty, higher demand and greater competition, water storage is only one component of a multipronged approach for adapting agriculture to climate change. Future water resources management must also include reallocation of water between users and increasing water productivity wherever possible. There is no doubt that providing more and diverse physical storage infrastructures is an imperative for securing reliable supplies of water for agriculture and other uses.
Each type of storage has its own niche in terms of technical feasibility, socioeconomic sustainability, impact on health and environment and institutional requirements. Each needs to be considered carefully within the context of its geographic, cultural and political location. With so much uncertainty in climate change scenarios, the best option is to focus on flexibility in storage systems wherever possible, combining a variety of types to take advantage of their unique characteristics.
Poor farmers already struggle to cope with changing and unpredictable weather patterns which will be worsened by climate change. As climate change becomes a greater threat to water systems and agriculture, variety in the types of water storage systems used will provide an important mechanism for adaptation. However, the types of storage must be tailored to the specific needs and socioeconomic conditions of an area. Planners need to start taking climate change into account when they design and manage integrated storage systems.
Water storage as an adaptation strategy to reduce climate vulnerability:
Source: McCartney, M.; Smakhtin, V. 2010. Water storage in an era of climate change: Addressing the challenge of increasing rainfall variability. Blue Paper. Colombo, Sri Lanka: International Water Management Institute.
The above content is based on:
McCartney, M.; Smakhtin, V. 2010. Water storage in an era of climate change: Addressing the challenge of increasing rainfall variability. Blue Paper. Colombo, Sri Lanka: International Water Management Institute.
International Water Management Institute (IWMI). 2009. Flexible water storage options: for adaptation to climate change. Colombo, Sri Lanka: International Water Management Institute (IWMI). 5p. (IWMI Water Policy Brief 31).
Photo Credit: IWMI