Grantee Research Project Results
Final Report: Rainwater Harvesting: A Simple Means of Supplementing California's Thirst for Water
EPA Grant Number: SU832493Title: Rainwater Harvesting: A Simple Means of Supplementing California's Thirst for Water
Investigators: Chin, Andrew , Guillen, Greg , Tam, Kawai , Matsumoto, Mark , Cusick, Roland , Ogunyoku, Temi
Institution: University of California - Riverside
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 30, 2005 through May 30, 2006
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2005) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Safe and Sustainable Water Resources , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
Rainwater harvesting is the collection and storage of precipitation for later human use. This project focuses on the design, construction and analysis of a rainwater harvesting system located at the Bourns College of Engineering at the University of California, Riverside. The information collected from this project will be used to build a template for designing a rain water harvesting system that can be placed in areas outside of the Southern California region, with a specific look at the applicability of rain water harvesting in developing regions.
A preliminary mathematical model was created using Microsoft Excel that can be used to determine the potential volume of rainwater captured from an inputted rooftop area. Besides providing the volume of water that could be potentially collected from a rain event, the Excel model outputs the estimated total cost of installation and the amount of days harvested water can be used to irrigate a given lawn area. The collected data from the Phase I design will provide an opportunity to optimize the Excel model, taking into consideration local conditions and equipment costs.
Phase I funding was used to construct a harvesting system around one drain spout located at the Bourns College site. To come up with a preliminary design of the system the Excel model was used to come up with a tank size based on local rainfall data. The system includes a catch basin connected to a roof outlet, which flows over a weir and flow meter. An auto-sampler is also connected to the system to take grab samples. The water is tested for total suspended solids and total dissolved solids.
Summary/Accomplishments (Outputs/Outcomes):
The Phase I design provided information that can be used to design a more effective full scale system for the Bourns College. The Phase I design helped in the correction of many assumptions and provided real data in which to further optimize the overall system for Phase II. The issue of whether first flush was a water quality and an equipment issue was discussed from the beginning of project; where first flush is the initial flow of water from a given surface after a rain event.
An early assumption was that first flush diversion was not necessary due to the harvested water was only to be used for non-potable uses. However, the water quality data shows a spike in total suspended and dissolved solids in first flush water, while subsequent flow of water had very low levels. This data showed that first flush diversion must be done in order to avoid build up of solids in the tank and from solid build up later in the irrigation system. In order to alleviate the solids problem, the first flush will be diverted and treated by a sand filter before being flushed out of the system.
The data used in the Excel model to calculate the necessary tank size was based on average precipitation rates for the Riverside, CA area. The rainfall for the area during the collection period was about 5 inches, with the average rainfall being 8 inches per year. The less intense rainfall rate resulted in a lower amount of water that would have been collected and this is represented by a decreased flow over the weir and read by the flow meter. The 5 inches of rain over the collection area from the roof would correlate to the collection of 18,500 gallons of water over the entire rain period. The tank size required for the entire year based on this system is 600 gallons; the tank size is lower than the total collection volume due to the daily usage for irrigation needs. The system has the ability to provide 62 days of irrigation solely on harvested rain water, while providing 90 days of irrigation using blended water; where blended water is a combination of harvested rain water and city water. The calculation assumes that there is a one inch irrigation pattern during the winter and two inches during the summer, with no irrigation occurring during days of rainfall.
Conclusions:
Rainwater harvesting is a viable option to supplement city water for non-potable human uses, such as irrigation. The overall efficiency of a rainwater harvesting system to supplement city water increases as area increases. The system would be highly effective in high commercial regions where there are warehouses and large buildings. These areas also contain less lawn area, so that the water can be used for uses beyond irrigation. In order to display the potential of the rainwater harvesting project for a heavy commercial area, Ontario, CA was chosen as a sample site. Ontario is an area with many commercial facilities, when all of the roof area is considered with the average annual rainfall at 16 inches, a total of 2,200 acre-feet per year of water can be collected, this can meet the demands of 10,000 people. In fact, the Toyota facility located in Ontario has a roof area of 380,000 square feet. When taking into consideration the average rainfall, this building has the ability to collect 3 million gallons of water. This single facility can not only meet the needs of the small patches of lawn surrounding the building, but can supply enough water for 41 people at 200 gpcpd or the water can be used to recharge groundwater levels.
The simplicity of the model and the low overall cost to install the system makes rainwater harvesting easily translatable for use in developing regions. The rainwater harvesting project was specifically chosen because of its potential to be used to help those in developing regions who do not have easy access to clean and local water sources. The water quality data shows that the water is clean for non-consumption purposes; although, a simple filtration system may have the ability to take the water into the potable range. The water collected from the harvesting system is actually cleaner than many water sources found in developing regions. In developing regions with a growing industry sector, water sources are often contaminated by outflow of waste from the facilities as many countries do not have stringent outflow laws. In areas with high populations, waterways used for drinking water are overdrawn and are used for purposes such as the cleaning of clothes and bathing. Rainwater harvesting can prevent the need to travel far distances to obtain water and can help the overall health and growth of communities.
Supplemental Keywords:
Rainwater, storm water, harvesting, best management practices, BMP, Southern California, sustainability, people, prosperity, planet, development, sustainability, irrigation, MWD, drinking water, groundwater, land, precipitation, chemical transport, health effects, ecological effects, cumulative effects, chemicals, toxics, particulates, metals, organics, DNAPL, NAPL, acid rain, effluent, discharge, dissolved solids, ecosystem, scaling, alternatives, sustainable development, clean technologies, innovative technology, renewable, waste reduction, waste minimization, public policy, community-based, observation, preferences, public good, socio-economic, conservation, environmental assets, environmental chemistry, social science, hydrology, modeling, monitoring, analytical, surveys, measurement methods, Southwest, Southern California, CA, EPA Region 4, EPA Region 7, EPA Region 8, EPA Region 9, buildings, schools, commercial, business, RFA, Scientific Discipline, Sustainable Industry/Business, Sustainable Environment, Technology for Sustainable Environment, Ecology and Ecosystems, Urban and Regional Planning, Environmental Engineering, sustainable water use, urban planning, environmental sustainability, recovery, conservation, cost benefit, sustainable urban environment, resource recovery, water conservation, rainfall harvesting, environmental cost analysis, environmental educationThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.