Humans have been capturing and storing rainwater for a very long time. However, the practice of rainwater harvesting is not very common in modern times because we have a network of pumps, wells, and treatment plants that transport clean drinking water to our taps. In general, many of us (in the United States) are fortunate enough to go about our daily lives without thinking about where our water comes from. Unfortunately, we as a society may no longer have that luxury. One of the consequences of climate change is widespread drought. Even as water supplies are stressed due to drought, water demand continues to increase. It is important to implement water conservation strategies to help address some of these water resource challenges.
The following blog post will describe the difference between passive and active rainwater harvesting. In addition, it will discuss the benefits of rainwater harvesting.
What is Rainwater Harvesting?
Rainwater harvesting is a general term that refers to the collection of precipitation. Rainwater harvesting can be classified as active or passive. Active rainwater harvesting systems involve capturing runoff from an impervious surface such as a rooftop for storage in a tank. This water can be used for a number of beneficial uses such as irrigating your plants, flushing toilets, or washing cars. In some parts of the world, people drink water from active rainwater harvesting systems. Passive rainwater harvesting strategies involve shaping and sculpting the earth to encourage infiltration into the soil. These strategies are aesthetically pleasing, minimize erosion, and mitigate flooding.
The following video shows a demonstration by Brad Lancaster, who is a well-known rainwater harvesting expert based in Tuscon, Arizona.
The Benefits Of Rainwater Harvesting
Rainwater harvesting systems can be simple or complex. In some cases, they require a lot of work to install. So why put in the effort? Some of the benefits of rainwater harvesting are discussed below.
Rainwater Harvesting Improves Watershed Health
The United States Environmental Protection Agency (EPA) defines a healthy watershed as one where “natural land cover supports dynamic hydrologic and geomorphic processes within their natural range of variation; habitat of sufficient size and connectivity supports native aquatic and riparian species, and water quality supports healthy biological communities.” (US EPA, 2012). This definition encompasses six characteristics of a watershed: habitat, hydrology, geomorphology, and biological condition (US EPA, 2013). As discussed in the video above, passive rainwater harvesting systems can help watersheds to act more like a sponge than pavement. This means that water can infiltrate into the soil and recharge the groundwater. Keeping water onsite also encourages the growth of native ecosystems, which promotes watershed health and enhances natural beauty. Finally, rainwater harvesting improves watershed health by reducing the amount of stormwater runoff that enters streams. In urban areas, stormwater flows across impervious areas such as streets, rooftops, and sidewalks very quickly. As a result, water enters streams and rivers more quickly than it would if the watershed was not developed. This causes the stream to become more “flashy.” Streams that experience an increase in “flashiness” will erode and widen to accommodate the increased peak flows. This erosion can adversely impact in-stream infrastructure (e.g., bridges, utilities buried beneath the stream bed) and infrastructure located adjacent to the stream. Thus, incorporating rainwater harvesting features that capture stormwater runoff improves the watershed hydrology and promotes healthy streams.
Rainwater Harvesting Reduces Flooding
As previously mentioned, a significant amount of stormwater runoff enters catch basins, pipes, and drainage channels. In many places, the stormwater infrastructure cannot adequately convey flow from intense precipitation events. This results in flooding. Active and passive rainwater harvesting systems capture and store stormwater runoff that would have otherwise entered the local stormwater infrastructure or contributed to flooding concerns. Researchers at the North Carolina State University (NCSU) Biological and Agricultural Engineering (BAE) Department designed an active rainwater harvesting system that incorporated weather data. When the smart controllers received information indicating that a storm was on the way, the system slowly drained the tanks and allowed the water to infiltrate before the storm arrived. As a result, there was more storage volume available to hold water. Creative solutions like this make rainwater harvesting systems even more effective in reducing flooding concerns.
Rainwater Harvesting Reduces Stress On The Potable Water Supply
Many areas within the United States are experiencing adverse effects of climate change. Drought has resulted in declining reservoir levels and warmer temperatures have caused increased water needs for landscaping and cooling. As a result, the water demand has increased. In many places, potable water is used to irrigate landscape plants. Using water from an active rainwater harvesting system (rainwater cistern/tank) for nonpotable water demands such as landscape irrigation decreases the stress on the potable water supply. Having access to water stored in a tank/cistern also makes your property more resilient in an era of watering restrictions.
Rainwater Harvesting: A Cost-Benefit Analysis
Rainwater harvesting, when adopted on a large scale, can have positive economic benefits such as minimizing the need for costly water infrastructure upgrades. However, individuals may not enjoy such a significant economic benefit. By using water stored in a tank to water plants, you will reduce your water bill. However, it is unlikely that the money you save on your water bill will offset the cost of a tank in any substantial way. I wish that I could say that rainwater harvesting is cheaper than tap water. Unfortunately, this is simply not the case.
This is, in part, because water is cheap in the United States of America. Some say that it is actually too cheap. Because water is a basic human need, cities subsidize the cost of water. In general, I think this is a good idea because nobody should be denied access to clean drinking water. However, the low cost of water has led many people to believe that water is basically free. Unfortunately, this is far from true. In reality, a significant amount of capital and natural resources are involved in capturing, treating, and transporting water to people’s homes and businesses. In addition, a lot of human effort is required to maintain water infrastructure.
You may be wondering if potable water is so cheap (at least in the United States of America), why invest in a rainwater capture system? Although rainwater harvesting does not make sense when comparing the cost of a tank to the cost of tap water, it does make sense when you view captured rainwater as a sort of insurance policy. Many areas, particularly in the western United States, are experiencing severe drought conditions. As a result, some cities of issued outdoor water restrictions. Reducing your dependence on municipal water will allow you to provide life-sustaining water to your favorite plants in the event of drought restrictions. In addition, water captured and stored in a tank can be useful in the event that municipal water is not accessible such as during a natural disaster.
In some areas of the United States, there are rebates available for people who purchase rain barrels or tanks. This can help offset the initial cost involved in installing an active rainwater harvesting system.