Stresses on water systems can be quantitatively assessed through indices that account for water demand relative to water availability, e.g., the Water Supply Stress Index (WaSSI). However, as a result of adopting deterministic supply-driven approaches, limited attention is paid to the potential impacts of climatic variability on quantifying water stresses. The current study aimed to account for the impacts of inter-annual and intra-annual variability in the WaSSI stress index and to provide insights into potential opportunities for better water management practices. The results from our analysis indicate that looking only at average stresses can substantially mask the important impacts of climate variability. Louisiana, as a typical example of humid regions in the USA, is subjected to high levels of stresses (WaSSI exceeds 1.0) with higher inter-annual variability in watersheds where thermoelectric power plants exist and extensive water is used for cooling process. In addition, intra-annual variability in some watersheds shows periodicity in terms of seasonal stress distributions due to variability in surface water supply and water demand. Our analysis indicated that the stress variability grows as the median WaSSI increases but up to a certain threshold level and then the variability decreases for very high stress levels. For the annual and monthly scales, the peak variability, quantified as the width of the 2.5–97.5 stress percentiles, reached 68% for a median annual WaSSI of 1.00 and 100% for a median monthly WaSSI of 1.15, respectively. Various decisions related to water use and management can be driven by such variability, at both annual and intra-annual scales. Hence, these results have important implications for applied water resource studies aiming to formulate water management policies and improve water system sustainability under climate variability.

供水系统的压力可以通过评估与供水相关的需水量的指数进行定量评估，例如供水压力指数（WaSSI）。但是，由于采用确定性的供应驱动方法，因此对气候变化对量化水压力的潜在影响的关注很少。当前的研究旨在说明WaSSI压力指数的年度间和年度内变化的影响，并为更好的水管理实践提供潜在机会的见解。我们的分析结果表明，仅考虑平均压力就可以充分掩盖气候变化的重要影响。路易斯安那州是美国潮湿地区的典型例子，承受着很高的压力（WaSSI超过1。0）在有热力发电厂且大量水用于冷却过程的流域，年际变化较大。此外，由于地表水供应和需水量的变化，一些流域的年内变化在季节性应力分布方面表现出周期性。我们的分析表明，应力变化率随WaSSI中位数的增加而增加，但达到一定的阈值水平，然后在非常高的应力水平时变化性降低。对于年度和月度标度，量化为2.5–97.5应力百分位数的宽度的峰值变异性分别达到，平均年WaSSI为1.00的68％和每月平均WaSSI为1.15的100％。在年度和年度范围内，与水的使用和管理有关的各种决策都可以由这种可变性决定。