Climate change (CC) associated with excessive CO2 emissions (IPCC 2007) will have a
profound impact on the natural resources base that agriculture is dependent upon. Climate models
generally anticipate an increase in global average precipitation, though the spatial and temporal
changes are still debated. The impacts of CC on water ? through rainfall, snowfall, soil moisture, river
flow and groundwater recharge ? will directly translate into impacts on food, livelihoods and
ecosystems. With predicted increases in the global populations, rising incomes and changing dietary
patterns, demand for food will double over the next 50-80 years ? the timeframe when most of the CC
impact will be felt. In order to keep up with this demand 60 to 90% more water will need to be
consumed by agriculture (Fraiture et al., 2007). This raises significant concerns in that currently 20%
of the world’s population lives in areas where agriculture is affected by water scarcity that will
undoubtedly be exacerbated by CC.
Agriculture consumes more than 3000 l of water per person per day to meet current food
demand. Approximately 80% of this water is directly met by rainfall and 20% is diverted from rivers,
lakes and groundwater. It is estimated that 60% of all agricultural production is derived from rainfed
systems, while 40% is generated from irrigated areas. Besides quantity, quality and the timing of water
supply through rain or irrigation is equally important and will be significantly affected by CC.
The expected effects of CC on rainfed agriculture vary regionally. In arid and semi-arid areas
the absolute amount of rain is expected to decrease but variability will likely increase substantially.
This may lead to more short term droughts and crop losses that will further limit crop choice. In
monsoon areas the amount and intensity of rain is projected to increase. Flooding in paddy areas may
increase which may prove to be beneficial because of increased water supply and fertile silt deposits.
Many irrigation schemes, particularly the smaller village level ones, divert water directly from streams
and rivers without water storage facilities. These so-called run-of-the-river schemes are particularly
vulnerable to changes in river flow in quantity and timing. Changes in rainfall quantities and intensity
will affect natural groundwater recharge and therefore the millions of smallholders depending on the
groundwater economy in South Asia Many CC mitigation measures have often unforeseen water
implications. Biofuels, promoted because they are nearly carbon neutral, in comparison to fossil fuels,
could add to pressure on water resources in areas where water is already scarce. In China and India
ambitious plans to boost biofuel production are being promotes, however, given the already overexploited
surface and groundwater resources it is unlikely that both countries can expand the irrigated
production of maize and sugarcane for ethanol production without affecting sustainable water use and
food crop production.
Improved management of water resources will be a requirement in adapting to present and
future climate variability. The main premise of previous IWMI research has been that by better
understanding and coping with existing climate variability, society will develop resilience to CC. Wise
water management can increase productivity, create higher rural incomes and smooth water supply
shocks, thus reducing fluctuations in production and associated risks. Improved water management is
an appropriate way to reduce poor people’s vulnerability by reducing water related risks and creating
buffers against often unforeseen changes in precipitation and water availability (Fraiture et al., 2007).
A key element in adaption to CC is building resilience through better water management. In this
respect IWMI advocates five key responses.
There is a need to think more creatively with respect to water storage. An obvious response to
variability in supply is to store water when it is abundant for use during dry periods. Water storage
improves the ability of rural poor to cope with climate shocks by increasing agricultural productivity
(and hence income) and by decreasing fluctuations (and hence risks). There are many proven approaches to enhancing water storage, ranging from small on-farm ponds to large reservoirs,
groundwater recharge and storage, water harvesting and soil water conservation capture that may
include in situ storage associated with conservation tillage.
Improvement of land and water productivity is important both as CC adaptation and mitigation
strategy. Improving water productivity by deriving more value from water through higher yields, crop
diversification, integrating livestock and fisheries is an important means to improve rural incomes,
alleviate poverty and reduce risks by diversifying income sources. At the global scale, improved
productivity assists in reducing greenhouse gas (GHG). Land and soil degradation are a major
constraint to increasing water productivity on much of the world’s arable lands. The needed
productivity increases will have to be achieved through enhancing current production systems, most of
which have undergone varying degrees of degradation. Soil amendments and farming practices to
enhance the productivity of rainfed production systems have resulted in dramatic increases in water
productivity, increased soil water and nutrient holding capacity and notable declines in sediment
discharge to water bodies.
A key issue in water management and allocation is the management of trans-boundary rivers i.e.
rivers that flow across international boundaries. Managing these rivers requires cooperation between
countries, a process complicated by both flow variability and potential impacts of CC. Current and
future inter- and intra-basin water transfers often insufficiently incorporate climate variability and CC.
Planning water transfers without taking adequate consideration of the likely impacts of climate change
can reduce the performance of such major investments. Clearly, adjustments in water allocation will
require both knowledge of water flows, as well as social and institutional governance mechanisms will
be a key area of research associated with adaptation to CC.
Adaptation research closely links with identification of institutional frameworks required to
support effective development and use of water, options to build ecosystem resilience to support long
term agriculture and options to build societal resilience in response to CC (such as drought early
warning systems, insurance schemes and the transition of some people out of farming). Establishing
targeted safety nets for farmers who are unable to adjust quickly enough, providing credible insurance
against catastrophic asset losses and facilitating rapid recovery will be crucial, given the expected CC
impacts.
It is also acknowledged that there will be challenges. These challenges include understanding
the impacts of anticipated increased investments in water storage on the environment and long-term
feasibility of large scale interventions; downscaling CC predictions to basin level particularly in
ungauged situations; and the impacts of mitigation measures on water availability and use.