Risk assessment of water allocation on water scarcity period: the case of Jaguaribe-Metropolitan System

ABSTRACT The article evaluates the transfer of risk of a water allocation policy between two user sectors: urban supply and irrigation. The allocation between uses was performed using two methods: linear apportionment and assessment with priorities (adopted in periods of water scarcity). The amount available for allocation was obtained using two reservoir operation strategies: zero inflow in the second half of the year and forecast flow. Gains and losses of the user sectors were determined through benefits functions. The two allocation scenarios pointed to lower guarantees and benefits for user sector with less priority. The priority system revealed that the water transfer infrastructures provide gains for the higher priority sector when guaranteeing water security; however, cause losses when extinguishes the right to use the demand of lower priority, indicating that the allocation of water is also a distribution process risk. The transfer risk of this sector, volumetric and monetary, can be minimized with the use of climate information. Thus, an alternative to the allocation of water in environments with water transfer systems would be an acceptable risk in order to increase the current level of benefits of irrigation and the satisfaction of the urban supply. This risk can be established based on seasonal climate prediction models.

摘要 本文评估了城市供水与灌溉两类用户部门间水资源配置政策的风险转移问题。本次研究采用两种方法进行用水配置：线性分配法（linear apportionment）与优先级评估法（assessment with priorities，该方法在水资源短缺（water scarcity）时期采用）。可配置水量通过两种水库运行调度策略（reservoir operation strategies）获取：下半年零入库流量方案与预报流量方案。用户部门的损益通过效益函数（benefits functions）进行测算。两种配置情景均显示，低优先级用户部门的保障水平与收益均更低。优先级系统表明，在保障水安全（water security）的前提下，输水基础设施（water transfer infrastructures）可为高优先级部门带来收益；但当取消低优先级需水的用水权益时，则会造成损失，这表明水资源配置同时也是一项风险分配过程。该部门的水量与经济价值维度的转移风险，可通过利用气候信息予以降低。因此，在具备输水系统的水资源配置环境中，为提升灌溉部门当前的收益水平并满足城市供水需求，可接受一定程度的风险。该风险可基于季节气候预测模型（seasonal climate prediction models）予以确定。