The underlining philosophical statement of this paper is that the promotion of automatic control for open-channel hydraulic systems will be greatly facilitated when simple algorithms and tuning procedures are available and adapted to this type of systems. The objective is therefore to contribute to an ``automation for hydraulic systems for dummies" approach. In this paper, we propose an automatic method to tune a series of distant downstream PI controllers for a cascade of pools. The methodology we present could also be used for local upstream controllers, with minor changes. The method is based on the Auto-Tuned Variation principle (ATV) carrying out a relay experiment. The information obtained from this experiment allows to estimate the parameters of a simplified integrator-delay model of each pool. Finally this allows tuning automatically a series of feedback PI controllers, with given gain and phase robustness margins, and a feedforward controller based on simple time delay. This relay experiment is performed for each pool of the canal or river, in sequence, with automatic activation of the previously tuned PI controllers. Different decoupling configurations, in order to reduce interactions between pools, are evaluated in simulation on the benchmark canal 2 of the ASCE Task Committee on Canal Automation Algorithms.