Downsizing a long-term precipitation network: Using a quantitative approach to inform difficult decisions

The design of a precipitation monitoring network must balance the demand for accurate estimates with the resources needed to build and maintain the network. If there are changes in the objectives of the monitoring or the availability of resources, network designs should be adjusted. At the Hubbard Brook Experimental Forest in New Hampshire, USA, precipitation has been monitored with a network established in 1955 that has grown to 23 gauges distributed across nine small catchments. This high sampling intensity allowed us to simulate reduced sampling schemes and thereby evaluate the effect of decommissioning gauges on the quality of precipitation estimates. We considered all possible scenarios of sampling intensity for the catchments on the south-facing slope (2047 combinations) and the north-facing slope (4095 combinations), from the current scenario with 11 or 12 gauges to only 1 gauge remaining. Gauge scenarios differed by as much as 6.0% from the best estimate (based on all the gauges), depending on the catchment, but 95% of the scenarios gave estimates within 2% of the long-term average annual precipitation. The insensitivity of precipitation estimates and the catchment fluxes that depend on them under many reduced monitoring scenarios allowed us to base our reduction decision on other factors such as technician safety, the time required for monitoring, and co-location with other hydrometeorological measurements (snow, air temperature). At Hubbard Brook, precipitation gauges could be reduced from 23 to 10 with a change of

降水监测网络的设计必须在精准估算需求与构建、维护该网络所需的资源之间取得平衡。若监测目标发生变更，或是可用资源出现波动，均需对网络设计进行调整。美国新罕布什尔州哈伯德布鲁克实验林（Hubbard Brook Experimental Forest）自1955年起搭建降水监测网络，如今该网络已发展为覆盖9个小集水区的23个雨量计。得益于较高的采样密度，我们得以模拟缩减采样的方案，进而评估关停雨量计对降水估算精度的影响。我们针对南坡（共2047种组合）与北坡（共4095种组合）的集水区，梳理了从当前11或12个雨量计，到仅保留1个雨量计的所有可能采样强度场景。根据集水区的不同，不同雨量计布设方案的估算结果与基于全部雨量计得到的最优估算值之间的偏差最高可达6.0%；但95%的场景所得到的估算值与长期年平均降水量的偏差均在2%以内。在诸多缩减监测的场景下，降水估算结果以及依赖其的集水区通量均表现出不敏感性，这使得我们可以将技术员安全、监测所需时长，以及与其他水文气象测量（积雪、气温）的共址布设等其他因素作为缩减决策的依据。在哈伯德布鲁克实验林，降水雨量计的布设数量可从23台缩减至10台，其变化为