Coping with water scarcity

Climate change will require human adaptation. Water harvesting can mitigate predicted water scarcity.

As climate change becomes the No. 1 environmental issue around the world, it presents a new framework for evaluating – and gives greater urgency to – a host of other sensitive environmental issues, such as loss of biodiversity, desertification, natural disasters, and water scarcity.

Even as policymakers debate ways to limit global warming by decreasing the emission of greenhouse gases, there is a growing sense that no level of human response can completely forestall the effects of climate change in coming decades. That's why adaptation is so critical.

Tomorrow, the United Nations' Intergovernmental Panel on Climate Change will release the second volume of its Fourth Assessment Report on global warming, titled "Impact, Adaptation, and Vulnerability." An expected key finding will examine predicted water shortages – for 1.1 billion to 3.2 billion people, according to Reuters – and the options available to cope with them.

That report comes on the heels of last month's World Water Day, which focused this year on coping with water scarcity.

Water scarcity is not just a problem in arid regions; even in the lush tropics of Costa Rica, communities experience water scarcity due to deforestation and intensive agriculture. Water quickly becomes scarce when communities, industry, agriculture, and natural ecosystems all depend on the same source. That competition is expected to intensify as climate change affects precipitation patterns around the globe, potentially depleting natural water reservoirs.

That's the bad news. The good news is that proven strategies already exist to manage this kind of water scarcity.

In the southwestern United States, climate research shows that temperatures are expected to increase. Predictions vary as to whether the Southwest will become wetter or drier. Despite the uncertainty of the amount of precipitation change, a greater variability in precipitation is expected, resulting in a higher frequency of extreme events such as droughts, high-intensity storms, and flooding.

Up to 75 percent of the water supplies for the Western United States come from snowpack. As glaciers and snowpack decrease with warming temperatures, this natural water reservoir will be depleted, threatening Western water supplies. A similar pattern is predicted in other mountainous areas, such as the Andes and the Himalayas – an area that supplies water to 1 billion people.

Governments and international bodies, of course, must devise solutions to water scarcity and climate change. Local communities can't wait for that slow, unwieldy process to conclude. But individuals can make changes immediately, community groups can start environmental education efforts, and cities and states can devise legislation that meets their specific needs.

An effective way to deal with water scarcity at the local level is to harvest a resource that is freely (if not always abundantly) available: rainwater. Rainwater is a resource we have neglected with the development of municipal water systems and storm-water systems that channel rainwater away. Instead of losing this precious resource, we can expand the use of harvesting techniques that capture rainwater on-site, allowing it to be infiltrated in landscape features or stored in cisterns for later use. Countries such as Australia and India are beginning to embrace this method. The American Southwest is, too.

In Tucson, Ariz., local consultants, small businesses, and nonprofits are leading water harvesting workshops that often have waiting lists – a healthy demand that's further boosted by a state tax credit for rainwater harvesting. The nonprofit organization that I direct, Watershed Management Group, teaches individuals how to install cisterns and shape landscape to harvest water. In dryland regions such as southern Arizona, harvested rainwater is sufficient to meet all residential landscaping needs. In a state where residents use 40 to 60 percent of their municipal water supply on outdoor uses, that's quite significant.

Water harvesting practices can benefit communities across the globe:

• When water is captured on-site, less rainwater becomes runoff – or storm water – that carries pollutants into waterways and also causes flooding.

• In areas where surface or ground-water is contaminated, rainwater may be the cleanest source of water. Rainwater can be captured, stored, and easily treated to be suitable for drinking.

• It augments available water supplies. This is crucial for areas with dropping water tables.

• Simple landscape features, such as berms, check dams, and basins can slow and infiltrate water on sloped land, which reduces erosion and increases soil moisture to establish or enhance vegetation.

• Water harvesting techniques are easy to learn, low-cost, and do not require energy input.

To be effective, water harvesting must be coupled with water conservation. Conserve water in your home by planting native landscaping, installing water-efficient appliances, and using gray water. Gray water is water from your bathroom sink, shower, or washing machine, which can be used a second time to irrigate your landscape. Conserving water also saves energy, as water purification and water delivery consumes substantial energy resources.

These approaches aren't a panacea for water scarcity. But they offer proof that each of us can take practical steps today to make our adaptation to uncertain climate change that much more certain.

• Lisa Shipek is the executive director of Watershed Management Group, Inc.