Adaptation of water resources management to climate change

III. Measures and direct interventions:• Restoring or preserving mountain forests to reduce soil erosion and peak-flows;• Carrying out environmental flow releases and reducing water off-takes to maintain or restorefloodplains and coastal ecosystems as buffers against extreme events.Strategic Priority 3. Closing the gap between water supply and demandWater demand now exceeds or threatens to outstrip sustainable levels of supply. Conventionalstrategies to further increase water supply can no longer meet growing future needs, and areunable to cope with the uncertainty arising from increased climate variability and climate change.Sustained efforts are needed to reduce water demand and mobilise non-conventional water sourcesthrough appropriate policies, laws, incentives and technical measures.RationaleThe need for water is growing around the world. The most common strategy to meet thisincreasing demand is to further develop water supplies. Building dams to increase water storagecapacity, constructing new channels to augment water transport capacity and installing morepumps that produce water from deeper layers of the earth are the frequently-selected responses.In many areas, however, the limits for the sustainable development of water supplies for humanuse have been reached or are about to be reached. With the over-allocation of water resources,the ability of the water system to buffer extreme events and shocks, in particular droughts, hasbeen seriously compromised. People and businesses depending on these water systems are nowvulnerable to even limited climatic variability and change.As increasing the conventional water supply is no longer feasible, a greater emphasis needs tobe placed on reducing water demand. Water allocations need to be made to higher-value uses basedon a greater flexibility to allocate between competing demands. The adjustment of policies andoperational guidance will be critical to achieve this. Additional incentives such as tax breaks for dripirrigation or blocked water tariffs can assist in reducing demand. A wide range of technical measuresand know-how are now available to reduce water demand from households, industry and agriculture.Non-conventional water supplies also need to be mobilised to reduce the gap between demandand supply. The re-use of return flows and the use of wastewater can replace the conventionalwater supply for irrigation. In coastal areas, desalination of water can provide an important sourceof non-conventional fresh water supply. Increasingly, techniques and know-how are available totap non-conventional water supply sources in a sustainable manner.IN THE US, MARKET FORCES ARE AT WORK TO ADDRESS WATER SHORTAGESDURING A DROUGHTDrought stress often forces water managers to seek creative solutions for immediate water shortages.One of these solutions was the establishment of the Drought Emergency Water Bank in Californiain 1991. At the height of a six-year drought, more water was offered by water rights owners thanbuyers were willing to purchase, even though prices were reasonable at approximately US$1 percubic metre (note: the typical range of US municipal water supply is $ 0.1 – 1.4 m -3 ). 1725