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There is a large range of possible response options for adapting to climate change. These options can be related to policies, investments, institutions, water management, farming practices and capacity development, both within the water and agriculture sectors and beyond. These options will need to be applied at different scales: on fields and farms; in irrigation schemes, particularly in large-scale schemes; in watersheds or aquifers; in subnational and transboundary river basins; and at the national level. Table 3.2 presents a list of potential response options and indicates their relevance for different scales. The list, which includes both supply-side and demand-side options, is not exhaustive, and should not be taken as a set of policy measures. To have optimal impact, these options must be used in combinations that are tailored to different contexts. Focus should be placed on major systems at risk. Their implementation depends on the local conditions and the specific climate change risks that need to be addressed (e.g. water scarcity, changes in water availability, extreme events, increased irrigation requirements, water quality).

Most of these options are not new to development programmes. Options for on-farm water conservation have long been promoted as a response to water scarcity and climate variability. Options to address increasing water scarcity through better co-management of water at the watershed, aquifer and river basin level are needed in many water-stressed areas. Although there are many areas of overlap between climate change adaptation and sustainable development, activities with an explicit focus on adaptation and climate change will be required. Box 3.2. proposes four categories of responses that cover development actions for reducing the overall vulnerability of rural communities to all types of shocks to targeted actions for adapting to the specific impacts of climate change.

Many farm-level adaptations will be spontaneous and will be done in response to changing conditions,  but they will not necessarily designed for climatic changes. Other adaptations will need to be planned, often with external financial support. Of prime importance is increasing the ability of farming systems to cope with more variable supplies of rainwater. This will require an improving the capacity to store water in the soil, surface reservoirs or underground reservoirs. Any action that increases the capacity of the farming system to access water when needed will increase the resilience of the system to climate variability. Actions in this area include on-farm water harvesting; the enhancement the soil’s capacity to hold moisture (see also module B7 on soils); on-farm water retention and enhanced infiltration; and, where possible, more systematic access to groundwater. Supplementary irrigation at critical periods of the cropping season can reduce losses and boost productivity.

Demand-side options include more efficient irrigation technologies that reduce evaporation losses and increase crop production. These actions can be combined with deficit irrigation that can help maximize productivity per volume of water applied rather than per area of land. 

Crop selection and changes in crop calendars will help farmers adapt to new temperatures and rainfall patterns. It is preferable to use crops varieties that are more resilience to dry spells. 

Increased agricultural diversification and the better integration of trees, crops, fish and livestock will reduce risk and increase the resilience of farming systems. In particular, the capture and farming of aquatic species that do not require extensive migrations and have wide environmental tolerances will help the aquaculture and fisheries sector adapt to new climatic conditions.

Farmers will also need to be more systematic in the adoption of measures to respond to increased frequency of floods and more intensive rainfalls. A combination of erosion control actions and better drainage capacities will be needed.

Actions for adapting to climate change in irrigation schemes need to be considered in the overall context of irrigation modernization. Modern irrigation systems require better water allocation mechanisms, the clear transmission of alerts about water scarcity to farmers, and the adaptation of both infrastructure and management to allow for a more flexible and reliable delivery of water (FAO, 2007). Intermediate storage within the irrigation scheme and, where possible, access to groundwater are some of the options for building the resilience and reliability of the water supply, and must be considered in adaptation plans for irrigation schemes. Water pricing and the establishment of water markets are often advocated as demand management tools for promoting better water use and reducing water wastage. While these options have proven effective in some places, they are often difficult to apply for a combination of technical, institutional and policy reasons. There are other options, such as limiting seasonal allocations to users or to groups of users, which may be simpler and more effective for fostering more productive water-use behaviour. Box 3.3, which provides an example of a climate change adaptation programme of irrigation in China, illustrates how adaptation activities are closely linked to overall irrigation modernization programmes. 

Climate change adaptation at higher levels will involve a combination of policy adjustments and investments in infrastructure and management. In river basins, increased frequency and intensity of extreme weather events will require improvements in the storage capacity and management of dams and river protection works. More than in the past, flood management plans will need to combine infrastructure upgrades with non-structural, information-intensive approaches that can better mitigate the impact of floods through a combination of land planning, early warning and insurance schemes. Similarly, there will be a need to shift from drought emergency response to drought management plans that include prevention, preparedness, relief and rehabilitation and long-term measures to mitigate the impacts of droughts (FAO and NDMC, 2008).

In all these cases, the adaptation approaches to floods and droughts used by water managers and farming communities should be considered systematically. Examples of potential options include flood mitigation through the cultivation of varieties of rice that respond differently to different levels of flooding, or the combined cropping of bean varieties with varying resistance to droughts. Habitat engineering and rehabilitation will also be needed to reduce the severity of the impacts of flood, control erosion, and provide soil nutrients, shade and oxygen. This will also create suitable environments for aquaculture and fisheries.

Integrated water resources management in river basins will become more and more important as the combination of greater water use and the occurrence of extreme events increases the interdependency of people and communities living in river basins, and as actions in one part of a basin have repercussions for downstream users. In places where climate change contributes to increased water scarcity, the whole package of supply enhancement and demand management options will need to be considered (FAO, 2012a). Improved governance of land and water use will be required to accommodate the multiple uses of water, including for livestock and fish.

Enhanced management of water under climate change requires a much better understanding of the available supply and demand. Water accounting, the systematic study of the current situation and trends in water supply, demand, accessibility and use (FAO, 2016c) will become increasingly important for providing the data and evidence that will be needed at each level of management to ensure sound water management. 

Improved weather forecasting and hydrological monitoring will also become a critical element of modern adaptation strategies (Faurès et al., 2010). Currently, reliable weather forecasting is limited to a few days. However, progressive improvements in the timing and reliability of seasonal forecasts offer new opportunities for farming communities. As efforts focus on increasing the accuracy of these forecasts, more emphasis should be given to improving the way information is conveyed to farmers and building their capacity to make the best use of climate information (Gommes et al., 2010). Monitoring and early warning during the cropping season remain a priority to help farmers make informed decisions.

Resilience to climate change is closely linked to improved access to land and water. The strengthening of land and water rights will have a positive impact on resilience as it will encourage farmers and other rural people to invest in their land and build the assets that are needed for increased productivity and diversification.

Insurance represent a potential solution that should also be considered in adaptation strategies. There has been renewed interest in various types of crop insurance, as well as aquaculture and fishing insurance schemes, that could be adapted to developing countries. National crop insurance schemes have been tested in some countries, but they face substantial challenges in terms of their cost and institutional settings. So far, few commercial insurance companies have found these schemes to be an attractive business opportunity. Roberts (2005) focused on the need to smooth tensions between insurance that is run as business for commercial profit and the protection of small farmers that is in the strategic national interest. Insurance companies need to be solid and well backed. International reinsurance could play an important stabilizing role and provide backup for emerging national companies. The role of national governments in promoting crop insurance must reflect national interests and at the same time ensure the smooth operation of private insurance companies. Efforts in this area must be based on the concept of shared risk between producers, insurance companies and governments.

A type of insurance that has recently been applied in developing countries is known as index-based insurance. In index-based products, compensation is paid to the insured if the agreed threshold of an index is exceeded. The indices must be defined in such a way that they bear a direct relationship with the performance of the product insured. Index-based insurance is difficult to apply to small-scale hazards, but appears to have good potential for hazards with regional impacts, such as hurricanes or droughts (Gommes et al., 2010).

Efforts to develop adaptation options for water management will benefit from a greater understanding of the risks and potential impacts of climate change in different agricultural systems and the vulnerability of the different groups in rural areas. 

The impact of climate change on agricultural systems and rural communities depends on a combination of the exposure to climate change and the sensitivity of the system. The adaptive capacity of these systems in relation to potential changes in water supply and demand will determine their vulnerability. The risk associated to climate change will vary substantially from one system to the other depending on the exposure and vulnerability. The table in the Annex (A.6.1) presents the main agricultural systems at risk, their exposure to climate change, their sensitivity and adaptive capacity, as well as the elements of response strategies that would be needed as part of any programme designed to strengthen adaptation to climate change. The table is based on the section, ‘Land and water systems at risk’, from the State of Land and Water Resources for Food and Agriculture (SOLAW) (FAO, 2011a).

Table A.6.1 indicates that a farming system’s vulnerability is directly related to its relative dependency on elements of the water cycle, and in particular rainfall variability. With or without climate change, agricultural communities the most at risk are those that rely exclusively on farming for their livelihoods, have little scope for diversification and are highly exposed to climate variability. Most of the responses that are needed to increase the resilience of these farmers are not necessarily specific to climate change. Actions that build resilience include enhanced conservation of soil moisture, particularly by improving the soil's capacity to retain water or increasing access to supplementary irrigation; drought preparedness strategies that improve grain storage; and better access to markets. Climate change only represents an additional justification for actions that are already needed.

The distinction between rainfed and irrigated production systems will determine the impacts and associated risks related to climate change. Rainfed systems in subtropics and semi-arid tropics will be mostly affected by changes in rainfall patterns and temperatures. These changes will lead to greater frequency of crop failures as a result of increased variations in soil moisture. In mountainous areas, rainfed farming in marginal areas will also be affected by the impact of extreme events, including intense rainfalls, floods and erosion. Pastoral areas will suffer from more frequent drying of water points and greater variability in the availability of animal feed. Irrigated systems are better protected against rainfall variability. However, these systems will increasingly require greater storage capacity to respond to more frequent droughts and floods, and changes in the annual distribution of runoff. This could affect water distribution over the entire river basin. For surface or groundwater systems already over-exploited, climate change will add an extra burden to water management and generally lead to a reduction in the availability of water and greater competition for water resources.

Production from aquaculture systems and capture fisheries will be affected by changes in quantity and quality of freshwater. Many aquatic species depend on the timing of rainfall and flood events for important migrations (e.g. spawning and feeding). Changes in precipitation may disrupt these migrations or force these species to make adaptations in their life history patterns. Integrated irrigation systems (e.g. rice and fish) could see changes in system components as climate change alters the suitability of the environment, (e.g. more or less water may require different species of fish). More or larger reservoirs could promote integration of fish farming through cage culture and enhance fisheries production.

Many governments and development partners have developed tools to assess the risks associated with climate change in relation to a given population's vulnerability (OECD, 2009). Examples of these tools include:

• Opportunities and Risks of Climate Change and Disasters (ORCHID);
• Community-based Risk Screening Tool – Adaptation and Livelihoods (CRisTAL);
• Tools developed by CARE and the International Federation of Red Cross and Red Crescent Societies;
• The Self-evaluation and Holistic Assessment of Climate Resilience of Farmers and Pastoralists (SHARP), developed by FAO, which includes specific modules on water and irrigation (FAO, 2015).
• The Climate Change Decision Tree Framework, developed by the World Bank (Ray et al., 2015)

These tools use  two types of approaches:

• The top-down approach, which focuses on potential changes in the water cycle that may result from climate change, uses different quantitative models and designs response options to anticipate and prevent the negative impacts of these changes. By nature, this approach favours long-term responses.
• The bottom-up approach seeks to understand the causes of the vulnerability of rural communities, and design solutions that help increase their resilience to external shocks. This approach, which is more generic in nature, does not specifically focus on climate change. It usually considers short- to medium-term responses. 

Both approaches are necessary when designing water management responses in relation to climate change. An impact-based approach is needed to ensure that long-term investments, such as irrigation development, take into account expected changes in water supply and demand.

Bottom-up approaches give the opportunity to address the needs of vulnerable communities in terms of resilience and development. By acknowledging that resilience is closely linked to a community's state of development, its level of economic diversification and the strength of livelihoods assets, community-based climate change response programmes offer the opportunity to progressively build capacities to reduce climate change-related risks. Most of the options that will be considered on the basis of bottom-up approaches will not differ from classical agricultural development options for reducing poverty and increasing the standard of living of rural populations. The challenge in this approach is to avoid maladaptation (i.e. designing development actions that are excessively sensitive to climate change and increase the vulnerability of beneficiaries). For instance, the SHARP tool addresses the need to gain a better understanding of the interests of family farmers and pastoralists with regard to climate resilience to ensure that their needs, including those associated with water and irrigation issues, are incorporated in decision-making processes.

Water infrastructure generally has a lifetime of 30 to 50 years. Investments for new water infrastructure or the rehabilitation of old infrastructures will be shaped by changes in climate. The changing frequency and intensity of droughts, floods, precipitation and heat waves will have a particularly significant impact on water supply and demand. Improving the resilience of water infrastructure to withstand climate change-related shocks and extreme events is a vital part of any effective water investment planning. Traditionally, climate change and disaster risks are factors that have not been assessed or integrated into plans for water investments. A World Bank study (Cervigni et al., 2015) states that the proper integration of climate change in the planning and design of infrastructure investments can considerably reduce future climate-related risks to the physical and economic performance of hydropower and irrigation. The results of the study show that not integrating climate change in the planning and design of water infrastructure could entail a loss of 10 to 20 percent in dry scenarios and a foregone gain of 1 to 4 percent in the wet scenarios for most basins.

The concept of ‘climate-proof’ investments is central to the design of programmes for reducing climate change-related risks. It is necessary to maintain a clear perspective on resilience when screening water development programmes. Governments and development agencies have prepared guidelines for incorporating climate change considerations into investment programmes. Some examples are:

• Guidelines for Climate Proofing, Investment in Agriculture, Rural Development and Food Security, developed by the Asian Development Bank (ADB, 2012)
• Incorporating climate change considerations into agricultural investment programmes, developed by FAO (FAO, 2012b)

The concept of robust decision-making in water planning (Groves, 2006) acknowledges that is it very difficult to predict the future, and makes extensive use of scenarios to work out decisions that are valid under a variety of alternative futures (see Box 3.4). In practical terms, resilient coping strategies are those that have the potential to be reasonably effective under the largest possible range of scenarios. This should be complemented with the adaptive management of existing and future water infrastructure. This approach puts the emphasis on flexible responses, and requires strong monitoring and information management systems that allow for periodic upgrading of management plans and activities (UNDP, 2004).

The combination of impact assessments, vulnerability assessments, and the screening of response options usually produces a long list of possible actions to cope with climate change. The effectiveness of an option needs to be assessed as a potential solution to a problem arising from climate change, and be measured in terms of its cost and the size of the beneficiary group. Where possible, actions that deliver benefits to many groups, with low costs per beneficiary and high levels of effectiveness should be selected. Adaptation options need to be discussed with stakeholders to ensure there is a clear understanding of possible trade-offs between costs and effectiveness.

Criteria for assessing the impacts of climate change and adaptation options must also consider social equity. Particular focus should be placed on the most vulnerable rural groups. The latest IPCC assessment makes clear that climate change will exacerbate existing gender inequalities. Women farmers represent more than half of the agricultural workforce in some low and middle-income countries, and play a crucial role in food security and natural resources management. Understanding the different adaptive strategies of men and women, including those related to water access and management, is necessary to prioritize water adaptation options. Securing water rights in a way that is both effective and equitable will also become more and more important as water scarcity increases. In irrigation schemes, ‘tail-enders’ – farmers located at the end of the irrigation canals – usually suffer more than other farmers during water shortages and floods. In river basins, downstream water users suffer from excessive water withdrawal from upstream users. Technologies and policies for climate change adaptation are not neutral in terms of equity. It is therefore important that they be analysed in terms of their impact on different groups of vulnerable people, and that actions that would increase inequalities be eliminated from climate change adaptation programmes.

The adoption of a livelihood approach to water-related adaptation strategies is a useful way to ensure that proposed actions will be beneficial to the people they are supposed to serve. Sullivan et al. (2008) consider four key dimensions of water use in rural livelihoods: 

• access to basic water services; 
• crop and livestock water security;
• a clean and healthy water environment; and
• secure and equitable entitlements to water. 

Using these entry points to screen the impact of adaptation options ensures that they will be assessed in ways that are in line with the concerns and priorities of rural populations.

An assessment of the ease of implementation considers the possible barriers to carrying out a given option that could delay or reduce its impact. These barriers could be policy-related, structural, institutional or social. Social barriers are related to the acceptability of proposed actions by local stakeholders. Specific policy or technical assistance may be required to overcome these barriers. Other relevant criteria include technical feasibility and the time frame for implementation.

The adequacy of a proposed option for the current climatic conditions is also an important criterion to consider. Possible options should be analysed in terms of their ‘level of regret’. Low-regret or no-regret options are those options that are valid whether expected climate change impacts occur or not. In general, these options increase the resilience of rural populations and reduce their vulnerability to water-related shocks. Instead, many options, in particular options dealing with infrastructure, can be considered high-regret options – they would be valid for future climate scenarios but not necessarily for the current climate situation. They would involve higher costs and have possible negative consequences under current climatic conditions, and require careful consideration in terms of risk analysis.

All options must be considered in light of the uncertainty associated with climate change predictions. Their robustness in terms of the above criteria, particularly their effectiveness and adequacy for current climatic conditions, must be assessed against different climate change scenarios and global circulation models (see module C8 on assessments).