Replicability of an experiment holds great importance in the scientific world. Different groups of scientists ought to be able to replicate a certain experiment to achieve the same results/conclusions as the first team of scientists did. This is essential to prove that the findings are credible and did not just occur by chance, which is the case here too.
The water won't be able to penetrate the ground so can't become ground water and reservoirs are usually above ground not underground so it will become run off.
