Using Rainfall Simulators for Water Quality Education

In Virginia, nonpoint source (NPS) pollution has been identified as the major cause of declining water quality in the Chesapeake Bay.1 As a result, the Virginia Agricultural Pollution Control Program was developed to reduce loadings of agricultural NPS pollutants in the bay and its tributaries. The program's intent is to encourage agricultural producers to voluntarily implement Best Management Practices (BMPs) through education, cost-sharing incentives, and technical help. And, the Virginia Cooperative Extension Service is playing an important role in this pollution control effort.

Implementation of BMP programs hasn't always been successful because farmers and other landowners are often unaware of the extent and impact of NPS pollution. If Virginia's voluntary approach is to be effective, land managers must be sufficiently convinced of the need for and benefits of BMPs to change their traditional methods. Although extensive pollution research using conventional water quality monitoring techniques has been conducted in recent years, this information has limited educational benefit because collected water quality data are generally difficult to interpret and relate to specific field situations.

To educate people about NPS pollution, it would be desirable to have people out in the field when rainstorms occur so they could observe this pollution phenomenon firsthand. Unfortunately, this isn't acceptable to most people nor is it possible to schedule storms for educational purposes. So, we investigated the use of rainfall simulation in demonstrating the causes, effects, and control of NPS pollution.

Rainfall simulation applies artificial rainfall to desired areas to study erosion, infiltration, runoff, and water quality. We do this by using a rainfall simulator or modified irrigation system specifically designed to reproduce the characteristics of a storm. The advantages of using rainfall simulation includes cost effectiveness, control, portability, and educational opportunities.

Rainfall simulators allow controlled rainstorms to be applied when and where they're desired. Consequently, a research/demonstration project entitled, "Rainfall Simulation for BMP Effectiveness Evaluation"2 was developed to educate the public about agricultural NPS pollution and demonstrate how it can be controlled through BMP implementation. We construct two or more adjoining runoff plots to which artificial rainfall is applied. The field plots are uniform in crop, soil, and topography, while one has a less desirable practice such as conventional till and the others include one or more BMPs, such as no-till, grass filter strips, etc. Since the outlets of the plots are adjacent, observers can readily see differences in the quantity and quality of surface runoff. While collecting water quality data to use in evaluating the effectiveness of agricultural BMPs, the rainfall simulator can also be used as an educational tool to visually demonstrate the effectiveness of BMPs for NPS pollution control to the farmers, general public, government officials, and news media.

During a given demonstration, initiation of runoff is generally delayed in the BMP plots. Data collected during past no -till versus conventional till demonstrations indicated that the no-till plots produced up to 87% less surface runoff than paired conventional till plots. Discharges from the plots using the nonrecommended practices are generally turbid, due to high soil losses, while those from the BMP plots are noticeably clearer. Measured sediment yield from no-till corn and soybean plots in previous demonstrations was 82% to 99% less than the yield from paired conventional till plots. Differences of this magnitude are visually obvious and make the soil conservation and water quality benefits of BMPs readily apparent to anyone seeing the demonstrations. Furthermore, we can readily explain how reductions in surface runoff and soil loss can also reduce nutrient and pesticide losses associated with the runoff and transported soil particles.

Since 1985, over 35 rainfall simulator demonstrations have been done to demonstrate the effectiveness of BMPs for NPS pollution control in Virginia. Nearly 5,000 people have seen the demonstrations, and thousands more have learned about NPS pollution and BMPs through dozens of newspaper and magazine articles, television reports, and documentaries on the rainfall simulator project. While the direct benefits of this and other efforts are difficult to document, indications are that agricultural producers are becoming more receptive to adopting BMP technology. If "seeing is believing," this project has been successful in visually showing the significance of the agricultural NPS pollution problem and the contribution that each individual can make towards a solution.

1. U.S. Environmental Protection Agency, Chesapeake Bay: A Framework for Action (Annapolis, Maryland: Chesapeake Bay Program, 1983).

2. This project was conducted by the Department of Agricultural Engineering, VPI & SU and supported by the Virginia Agricultural Experiment Station through funds provided by the Virginia Division of Soil and Water Conservation. Rainfall simulator demonstrations were co-sponsored by the Virginia Cooperative Extension Service, USDA Soil Conservation Service, and Virginia's Local Soil and Water Conservation Districts.