Rainwater Harvesting

Rainwater Harvesting

Rainwater harvesting is the capture, diversion, and storage of rainwater for a number of different purposes including landscape irrigation, drinking and domestic use, aquifer recharge, and stormwater abatement. In a residential or small-scale application, rainwater harvesting can be as simple as channeling rain running off an unguttered roof to a planted landscape area via contoured landscape. To prevent erosion on sloped surfaces, a bermed concave holding area down slope can store water for direct use by turfgrass or plants. More complex systems include gutters, pipes, storage tanks or cisterns, filtering, pump(s), and water treatment for potable use.

Regardless of the complexity of the system, a domestic rainwater harvesting system is commonly comprised of six basic components:

  • Catchment surface: the collection surface from which rainfall runs off, typically a roof on a home or building.
  • Gutters and downspouts: channel water from the roof to the tank
  • Leaf screens, first-flush diverters, and roof washers: components which remove debris and dust from the captured rainwater before it goes to the tank
  • One or more storage tanks, also called cisterns
  • Delivery system: gravity-fed or pumped to the end use
  • Treatment/purification: for potable systems, filters and other methods to make the water safe to drink
  • The water is free; the only cost is for collection and use.
  • The end use of harvested water is located close to the source, eliminating the need for complex and costly distribution systems.
  • Rainwater provides a water source when groundwater is unavailable, or it can augment limited groundwater supplies.
  • The zero hardness of rainwater helps prevent scale on appliances, extending their use.
  • Rainwater is superior for landscape irrigation.
  • Rainwater harvesting reduces flow to stormwater drains and also reduces non-point source pollution.
  • Rainwater harvesting helps utilities reduce the summer demand peak and delay expansion of existing water treatment plants.
  • Rainwater harvesting reduces consumers’ utility bills.

The basic rule for sizing any harvesting system is that the volume of rainwater is that can be captured (the supply) must equal or exceed the volume of water used (the demand). In theory, approximately 0.62 gallons per square foot of collection surface per inch of rainfall can be collected. In practice, however, some rainwater is lost to first flush, evaporation, splash-out overshoot from the gutters in hard rains and small leaks.

Here are two helpful resources for calculating rainwater capture amounts:

TWDB Rainwater Harvesting System Calculator

Texas AgriLife Rainwater Harvesting Calculator

Yes, there are several incentives for installing a rainwater harvesting system at your home or business. There is also statewide support for rainwater harvesting equipment.

Property Tax Exemption for Commercial Installations (statewide exemption): A constitutional amendment passed as Proposition 2 by Texas voters in November 1993 exempted pollution control equipment, including water-conserving equipment at nonresidential buildings, from property taxes. Rainwater harvesting equipment at commercial installations is considered water-conserving equipment. To qualify for the property tax exemption, (1) a facility must first receive a determination from the TCEQ that the property is used for pollution control purposes, and (2) the applicant then submits this use determination to the local tax appraisal district to obtain the property tax exemption.

Sales Tax Exemption (statewide):  Senate Bill 2 exempts rainwater harvesting equipment and supplies from sales tax.

Homeowners Associations: In Texas, HB 645, passed by the 78th Legislature in 2003, prevents homeowners associations from implementing new covenants banning outdoor water-conserving measures such as composting, water-efficient landscapes, drip irrigation, and rainwater harvesting installations. The legislation allows homeowners associations to require screening or shielding to obscure view of the tanks.

Rainwater collection systems can be as simple as collecting rain in a barrel or as elaborate as harvesting rainwater into large cisterns to supply your entire household. Rainwater storage systems and equipment can be purchased at local home improvement stores, lawn and garden stores, and even ordered online!

A good resource to find out more about rainwater harvesting in Texas is to review the Texas Water Development Board’s Texas Manual On Rainwater Harvesting.

Here is another good resource for 23 DIY Rainwater Harvesting Projects you can build at home.

Yes! The District supports rainwater harvesting as a water conservation method. Rainwater harvesting is a topic addressed in our Management Plan and Annual Report.

We also have an on-site rainwater harvesting system at our office. The District utilizes this system to irrigate the front flowerbeds and landscaping. This cistern is 11′ tall and had a 6′ diameter and has a storage capacity of 2,300 gallons. Rainwater is collected off of the barn roof through a catchment system and stored in the cistern. Rainwater is fed by a pump to water the front bushes and flower beds. The irrigation schedule runs early in the morning and late in the evening to reduce loss of water from evaporation. The system also only runs when needed to prevent overwatering and water waste. This system has potential to collect 30,605 gallons a year based on the 38” annual rainfall amount for Cleburne at 80% of precipitation captured.

Tax Exemption Resources

Application for Property Tax Exemption for Water Conservation Initiatives
Sales Tax Exemption Form for Purchasing Rainwater Harvesting Equipment