Colin Chartres. Credit: International Water Management Institute

If current trends continue, global annual water usage is set to increase by more than 2 trillion cubic metres by 2030, rising to 6.9 trillion cubic metres: 40% more than can be provided by available water supplies. Without immediate action to improve the monitoring and management of existing water resources, and in particular to reform water use in agriculture, the world will face a water crisis.

But researchers at the International Water Management Institute (IWMI) in Battaramulla, Sri Lanka, have come up with plan for averting disaster1. Nature asked Colin Chartres, director of the IWMI and a co-author of the plan, how to avoid running out of water.

What is causing the crisis?

Agriculture is the biggest user of fresh water, making up 70–90% of the annual water demand for many countries. This will have to change, because global food production is going to have to double over the next 40 years to meet the needs of a growing population. Farmers will have to increase production without using any more water than they do today. If all the water in a river is used by agriculture and industry, leaving nothing for the aquatic environment, fish and plants won't be able to survive, and the river will die.

How can we change the way we use and manage water?

The water-management institutions and governance models for many nations were developed when water was plentiful. Developing countries, such as India, have traditionally used surface-irrigation systems, which use gravity to distribute water over the soil surface. But these systems are no longer adequate, and farmers are now using up groundwater supplies to irrigate their land. Governments are not regulating groundwater extraction properly, and the water tables in many regions are declining. Governments need to introduce polices that allocate water to agriculture and industry, and that will enable them to reduce those allocations when supplies become scarce or demand from other sectors increases.

So what is the hold up?

We need better data on how much water there actually is, and how demand and supply are changing. Only with those data can we make sound decisions on how to manage resources, forecast flood risks and understand variations in seasonal flow. Following the privatization of water resources during the 1980s, many countries in the West now have inadequate data because the corporate water managers cut back on information gathering and monitoring to save money. In developing countries, the problem is even greater because they never had the funds to invest in monitoring.

But there is hope on the horizon. In 3–5 years we will be able to use remote-sensing technologies such as satellites to measure and monitor water resources.

Can we prevent a catastrophe?

I don't think we will reach crisis point, because we will put in place technological solutions to help close the gap between supply and demand. For example, farmers in developing countries could save water by using sprinklers on the surface of fields to irrigate crops, rather than using up groundwater supplies or relying on surface irrigation, which wastes a lot of water.

Wastewater recycling also has an important role, but safe practices need to be developed. For example, industrial and domestic discharges should be separated and the water-supply and sanitation sectors should work more closely together.