In the middle of the island of Java, in the mountain area of Sewu consisting of about a thousand mountains, a crowded and hard working populationlives for sixth months, every year struggling against seevere drought. No cultivation is possible. The water supply creates insuperable problems and the only known springs are tens of km away. Over the centuries the population has learnt to live with the lack of water, and yet, under the ground, there are rivers flowing.