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A national-scale simulation-optimization model was created to generate estimates of economic impacts associated with changes in water supply and demand as influenced by climate change. Water balances were modeled for the 99 assessment sub-regions, and are presented for 18 water resource regions in the United States. Benefit functions are developed for irrigated agriculture, municipal and domestic water use, commercial and industrial water use, and hydroelectric power generation. Environmental flows below minimal levels required for environmental needs are assessed a penalty. As a demonstration of concept for the model, future climate is projected using a climate model ensemble for two greenhouse gas (GHG) emissions scenarios: a business-as-usual (BAU) scenario in which no new GHG controls are implemented, and an exemplary mitigation policy (POL) scenario in which future GHG emissions are mitigated. Damages are projected to grow less during the 21st century under the POL scenario than the BAU scenario. The largest impacts from climate change are projected to be on non-consumptive uses (e.g., environmental flows and hydropower) and relatively lower-valued consumptive uses (e.g., agriculture), as water is reallocated during reduced water availability conditions to supply domestic, commercial, and industrial uses with higher marginal values. Lower GHG concentrations associated with a mitigation policy will result in a smaller rise in temperature and thus less extensive damage to some water resource uses. However, hydropower, environmental flow penalty, and agriculture were shown to be sensitive to the change in runoff as well., United States. Environmental Protection Agency. Office of Atmospheric Programs (Contract #EP-W-07-072)

We estimated the biological and economic impacts of climate change on freshwater fisheries in the United States (U.S.). Changes in stream temperatures, flows, and the spatial extent of suitable thermal habitats for fish guilds were modeled for the coterminous U.S. using a range of projected changes in temperature and precipitation caused by increased greenhouse gases (GHGs). Based on modeled shifts in available thermal habitat for fish guilds, we estimated potential economic impacts associated with changes in freshwater recreational fishing using a national-scale economic model of recreational fishing behavior. In general, the spatial distribution of coldwater fisheries is projected to contract, being replaced by warm/cool water and high-thermally tolerant, lower recreational priority (i.e., “rough”) fisheries. Changes in thermal habitat suitability become more pronounced under higher emissions scenarios and at later time periods. Under the highest GHG emissions scenario, by year 2100 habitat for coldwater fisheries is projected to decline by roughly 50 % and be largely confined to mountainous areas in the western U.S. and very limited areas of New England and the Appalachians. The economic model projects a decline in coldwater fishing days ranging from 1.25 million in 2030 to 6.42 million by 2100 and that the total present value of national economic losses to freshwater recreational fishing from 2009 to 2100 could range from 81 million to 6.4 billion, depending on the emissions scenario and the choice of discount rate.

Non-PR, IFPRI1, EPTD, "The increasing demand for water and limited degree of cost recovery for irrigation water delivery are important challenges for policymakers in Indonesia. To meet the increasing demand for water, it is important to reduce water use in irrigated paddy cultivation, long the dominant consumptive user, and to divert water away from agriculture to domestic and industrial sectors. Reducing water use in irrigated agriculture can be achieved through various means, including rationing, improved user management, and water markets. The appropriate method depends on the situation specific to each basin. In the Brantas Basin in East Java, rationing is already practiced, but often leaves the non-licensed, (non-paying) irrigators with insufficient supplies. Moreover, very low irrigation service fee recovery rates hamper ongoing water sector reforms, which seek to strengthen the capacity of local institutions to co-manage water resources. In the Brantas Basin the average value of water in the production of important irrigated crops substantially exceeds estimated water supply costs and current ISF. However, increased water use fees would impose a substantial burden on farm economic welfare, while water savings would be relatively modest. Therefore, to conserve water and enhance the financial autonomy of irrigators alternative management systems are proposed, including ‘Integrated Crop and Resource Management’ and a water brokerage mechanism."" -- Authors' Abstract

Non-PR, IFPRI4; Environment and Natural Resource Management, EPTD