This is excerpted from Source Elements of the Lotus Sutra.

The seven parables are those defined by Vasubandhu in his commentary on the Lotus Sutra. There are, however, many other parables in the sutra. One of the most important is the parable of digging for water in a tableland.

Traditionally, this parable has often been substituted for that of the king’s jewel to make up the seven. It is to be found in the tenth chapter, “A Teacher of the Law.” There the Buddha predicts that all those who hear a single verse or word of the Lotus Sutra, or who even by a single thought delight in it, will attain buddhahood. He speaks of the inexperienced and experienced preachers now and after his death, the sin of one who would defame those who read and recite the sutra, and the merits of those who follow the sutra. Then, speaking of the Dharma, those who receive it, and the place where it is received, he says: “Many people there are, both laymen and monks, who walk in the bodhisattva-way, without, as it were, being able to see, hear, read, recite, copy, keep, and worship this Law-Flower Sutra. Know that these people are not yet rightly walking in the bodhisattva-way; but if any of them hear this sutra, then they shall be able to walk aright in the bodhisattva-way.”

Then he indicates the effects of right action: “If any living beings who seek after the Buddha-way either see or hear this Law-Flower Sutra, and after hearing it believe and discern, receive and keep it, you may know that they are near Perfect Enlightenment.” Next he relates the parable of digging for water in a tableland.

Parable
There is a man, extremely thirsty, who searches for water by digging in a tableland. As long as he sees dry earth, he knows that the water is still far off. As he continues working, he in time sees moist earth and then gradually reaches the mire. Then he knows that water is at hand.

Correspondences Parable of Digging for Water in a Tableland
As the man who searches for water by digging in a tableland knows by seeing dry earth that the water is still far off, you may know that bodhisattvas who have not yet heard, nor understood, nor been able to observe the Lotus Sutra are still far from supreme and perfect enlightenment. In the same way that as he continues to dig, he in time sees moist earth and then gradually reaches the mire and then knows that water is at hand, if bodhisattvas hear, understand, ponder, and observe the Lotus Sutra, you may know that they are near supreme and perfect enlightenment: “The Perfect Enlightenment of every bodhisattva all belongs to this sutra. This sutra brings out the fuller meaning of the tactful . . . method in order to reveal the real truth. The [treasury] of this Law-Flower Sutra is so deep and strong, so hidden and far away that no human being has been able to reach it. Now the Buddha has revealed it for instructing and perfecting bodhisattvas.”