Read the given passage and answer the questions that follow.
Both, water and energy are integral parts of the human body. By weight, about 60% of an adult's human body is water and dehydration is one of the biggest single killers of children in the modern world. Life without water is unthinkable. The human body needs its daily intake of food to meet its energy requirement which, according to the Food and Agriculture Organisation of the UN, is about 1800 kcal per day. Life without energy is equally unthinkable. The energy that we take in through food again depends, amongst other things, on water for agriculture and often that water is pumped with electrical, mechanical or other forms of energy. The interdependence of water and energy is evident. The world at large seeks water and energy security. The Worldwatch Institute estimates that about 1.1 billion are facing economic water shortage (when existing water sources cannot be used because of a lack of investment in water-related infrastructure). We will probably have a world population of 9 billion by 2050 which will put further stress on the water sourcing and supply systems. Here again, the connection between energy and water is evident. Globally, around 70% water consumption is in the agricultural sector. No water, no food, no energy.
Actions needed on the water front include reduction in water usage for agriculture (pump efficiency, drip irrigation, change in crop patterns), recycling of water, rainwater harvesting, stoppage of run-offs and water pollution.
We need to remember that the fossil-based energy we rely on so much is stored energy. And, while the sun took 150 million years to store its energy in the fossil fuels, we are busy discharging that huge solar battery in a matter of a few hundred years.
Economic water shortage occurs when ______.