Rainwater harvesting reliability, the proportion of days annually when rainwater demand is fully met, is challenging to estimate from cross-sectional household surveys that underpin international monitoring. This study investigated the use of a modelling approach that integrates household surveys with gridded precipitation data to evaluate rainwater harvesting reliability, using two local-scale household surveys in rural Siaya County, Kenya as an illustrative case study. We interviewed 234 households, administering a standard questionnaire that also identified the source of household stored drinking water. Logistic mixed effects models estimated stored rainwater availability from household and climatological variables, with random effects accounting for unobserved heterogeneity. Household rainwater availability was significantly associated with seasonality, storage capacity, and access to alternative improved water sources. Most households (95.1%) that consumed rainwater faced insufficient supply of rainwater available for potable needs throughout the year, with intermittencies during the short rains for most households with alternative improved sources. Although not significant, stored rainwater lasts longer for households whose only improved water source was rainwater (301.8 ± 40.2 days) compared to those having multiple improved sources (144.4 ± 63.7 days). Such modelling analysis could enable rainwater harvesting reliability estimation, and thereby national/international monitoring and targeted follow-up fieldwork to support rainwater harvesting.

雨水收集可靠性，即每年雨水需求得到充分满足的天数比例，很难通过支持国际监测的横断面家庭调查来估计。本研究调查了如何使用将家庭调查与网格化降水数据相结合的建模方法来评估雨水收集的可靠性，并以肯尼亚西亚亚县农村地区的两项当地规模的家庭调查作为说明性案例研究。我们采访了 234 个家庭，进行了一份标准调查问卷，其中还确定了家庭储存饮用水的来源。逻辑混合效应模型根据家庭和气候变量估计了储存雨水的可用性，并用随机效应解释了未观察到的异质性。家庭雨水的可用性与季节性、储存能力以及获得替代改良水源的机会密切相关。大多数消耗雨水的家庭（95.1%）全年都面临着饮用水供应不足的问题，对于大多数拥有替代改良水源的家庭来说，在短暂的降雨期间，雨水会出现间歇性的情况。虽然不显着，但与拥有多个改良水源的家庭（144.4 ± 63.7 天）相比，唯一改良水源是雨水的家​​庭（301.8 ± 40.2 天）储存的雨水持续时间更长。这种建模分析可以实现雨水收集可靠性估计，从而实现国家/国际监测和有针对性的后续实地工作以支持雨水收集。