Promoting economically efficient solutions to meet competing demands for water under uncertain and variable supplies requires knowledge about the economic value of water and costs for its scarcity. In this work, an agricultural production optimisation model was used to evaluate the marginal value of water (MVW) in an agricultural region of rice and soybean growing in southern Brazil. The results indicate a MVW of 0.02–0.09 R$/m³ (1 R$ = £0.14), which is higher than common values considered for water charges for agricultural uses in Brazilian watersheds. The total scarcity costs of two recent drought periods were also investigated – these were approximately R$138 million (£19 million) and accounted for up to 15.5% of irrigated rice and soybean agriculture net return in some of the studied regions. Finally, the potential for cropping mix changes for some regions was explored through short-term water reallocation programmes to mitigate drought impacts. The results of this work should be useful in the design of water policies in terms of improved economic water management instruments, key infrastructure investments to be prioritised by watershed plans, strategies to integrate with other sectoral policies to secure funding for new water infrastructure and strategies to reinforce local adaptation through crop mix changes and short-term water reallocation.

中文翻译：

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水在巴西南部作物生产中的经济价值和政策影响

在不确定和多变的供应情况下，推广经济高效的解决方案以满足对水的竞争需求，需要了解水的经济价值和水资源稀缺的成本。在这项工作中，使用农业生产优化模型来评估巴西南部种植水稻和大豆的农业区的水的边际价值 (MVW)。结果表明 MVW 为 0.02–0.09 R$/m ³（1 雷亚尔 = 0.14 英镑），这高于巴西流域农业用水费的常见值。还调查了最近两个干旱时期的总稀缺成本——这些成本约为 1.38 亿雷亚尔（1900 万英镑），占一些研究地区灌溉水稻和大豆农业净收益的 15.5%。最后，通过短期水资源重新分配计划探索了一些地区种植组合变化的潜力，以减轻干旱影响。这项工作的结果在改进经济水资源管理工具、流域计划优先考虑的关键基础设施投资、